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1
Ceva, Lucio. "The North African campaign 1940–43: A reconsideration." Journal of Strategic Studies 13, no. 1 (March 1990): 84–104. http://dx.doi.org/10.1080/01402399008437402.
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Zolotukhina, Natalya, and Nikolay Bolgov. "Society of North Africa on the Eve of the Empire’s War with the Vandals and Its Attitude to Justinian’s Reconquista." Vestnik Volgogradskogo gosudarstvennogo universiteta. Serija 4. Istorija. Regionovedenie. Mezhdunarodnye otnoshenija, no. 6 (January 2020): 198–205. http://dx.doi.org/10.15688/jvolsu4.2019.6.16.
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Introduction. The article presents an analysis of North African society on the eve of Belisarius’s campaign against the vandals in North Africa (533–534). The campaign directed by Justinian under the leadership of Belisarius aimed to return the territory of North Africa to the Roman Empire. Methods. The methodological basis of this work is the concept of the Late Antiquity, the core of which is studying the people’s mentality, since the existing work on this issue focuses solely on socio-economic and political cause-and-effect relationships of the further confrontation between the Moorish and Roman tribes. Actually, the methods are the following: the historical-systemic method was the most important (an attempt to analyze the specifics of North African society on the eve of the war with the Vandals). Analysis. We divided North African society into three groups: the Vandals, the Libyans, the Moorish. The last two groups and their attitude towards the inclusion in the Roman Empire were of the greatest interest. Some of the tribes supported Justinian’s idea of the Reconquista and fought against the Vandals. Some supported the vandals. Nomadic tribes remained neutral. In our opinion, supporting the military campaign against the Vandals was due not only to economic reasons, but also mental ones. Thus, the research interest was caused by the transition period but not only in relation to the “Late Roman – Early Byzantium” line, but also because the region was romanized (presence of Latin culture, including the language segment), then it was part of the Vandal kingdom, after that – part of the Roman Empire (synthesis of Greek and Latin culture, with the predominance of Greek one). Results. In the course of the campaign against the vandals, North African society was represented by several social groups: the Vandals, the Libyans and the Мооrish – tribes that have their own cultural characteristics. Some tribes, who were in the Romanized zone (before the arrival of the Vandals), were on the side of Belisarius and fought against the Vandals. With extreme caution, we can say that this was due not only to socio-economic or political reasons, but also to mental ones. In our opinion, Byzantine Africa was a synthesis of Latin and Greek with the prevalence of the latter, and the Romanized population still wanted to feel part of the Roman Empire.
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Porch, Douglas. "Combat and Morale: The Eighth Army in the North African Campaign." Global War Studies 10, no. 3 (December 1, 2013): 80–85. http://dx.doi.org/10.5893/19498489.10.03.04.
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Nzongola-Ntalaja, Georges. "Putting Africa's House in Order to Deal with Developmental Challenges." African Studies Review 53, no. 2 (September 2010): 12–15. http://dx.doi.org/10.1353/arw.2010.0029.
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However proud Africans must be to have a person of African descent in the White House, they should have no illusions as to how much President Barack Hussein Obama can do for Africa. Africans must put their own house in order for purposes of dealing successfully with the major challenges facing the continent, the most important of which is that of democratic and developmental governance. Obama's priorities are not necessarily those of Africans. They have to do with the role of the United States as a superpower in a global system in which the American military and business corporations play a hegemonic role. In this context, Africa is relevant to American and Obama's global priorities when its resources are needed to strengthen this role, on the one hand, or its humanitarian crises are likely to affect them in an adverse manner, on the other.What are these global priorities, and how are they likely to affect Africa during Obama's tenure? Following is a brief examination of four major priorities. The first is limiting the spread of nuclear weapons. Operating on the premise that nuclear weapons should be limited to the few countries now possessing them (U.S., Russia, Britain, France, China, Israel, India, and Pakistan), the U.S. government has led an international campaign against the acquisition of nuclear weapons technology by other countries, particularly those deemed hostile to Western interests, such as Iran and North Korea. Since South Africa destroyed the nuclear arsenal of the former apartheid state and Libya gave up its nuclear ambitions, the only relevant issue with respect to Africa's role in the spread of nuclear weapons is the question of who has access to Africa's abundant supply of uranium. Denying access to African uranium to “rogue states” and terrorist organizations is an important foreign policy objective of any American government, including the Obama administration.
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Johnson, David. "Settler Farmers and Coerced African Labour in Southern Rhodesia, 1936–46." Journal of African History 33, no. 1 (March 1992): 111–28. http://dx.doi.org/10.1017/s002185370003187x.
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This paper contributes to a growing body of literature on the socio-economic impact of the Second World War on Africa. The focus is on the inter-relationship between the state, settler farmers and African labour in Southern Rhodesia. The war presented an opportunity for undercapitalized European farmers to enlist state support in securing African labour that they could not obtain through market forces alone. Historically, these farmers depended heavily on a supply of cheap labour from the Native Reserves and from the colonies to the north, especially Nyasaland. But the opportunities for Africans to sell their labour in other sectors of the Southern Rhodesian economy and in the Union of South Africa, or to at least determine the timing and length of their entry into wage employment, meant that settler farmers seldom obtained an adequate supply of labour. Demands for increased food production, a wartime agrarian crisis and a diminished supply of external labour all combined to ensure that the state capitulated in the face of requests for Africans to be conscripted into working for Europeans as a contribution to the Imperial war effort. The resulting mobilization of thousands of African labourers under the Compulsory Native Labour Act (1942), which emerged as the prize of the farmers' campaign for coerced labour, corrects earlier scholarship on Southern Rhodesia which asserted that state intervention in securing labour supplies was of importance only up to the 1920s. The paper also shows that Africans did not remain passive before measures aimed at coercing them into producing value for settler farmers.
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Anthony, David. "Unwritten History: African Work in the YMCA of South Africa." History in Africa 32 (2005): 435–44. http://dx.doi.org/10.1353/hia.2005.0004.
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In mid-1995, walking out of the door of my house, I received a telephone call. On the other end of the line was a distinct, well-spoken, but clearly faraway male voice. The man introduced himself, saying:My name is Vusi Kaunda, calling from Johannesburg, South Africa. I recently read an article you wrote about the YMCA, referring to events that took place some 75 years ago. I have been working for the South African YMCA for 10 years and I never knew anything about all this. Where did you get your information?Conditions did not permit us to take this conversation to its logical conclusion. I was on the way to conduct a history class; we had clearly connected at an inconvenient time. But that verbal exchange has stayed on my mind ever since. It demonstrated the power of the written word to connect people separated by thousands of miles, yet discover that they have a common purpose. Ours is to tell the story of the African voice in a new inclusive historiography of South Africa's Young Men's Christian Association.My discovery of the YMCA of South Africa came as a result of researching the life of Max Yergan, an African-American YMCA Secretary who, representing the “jim crow” “Colored Work” Department of a segregated North American YMCA, entered the Union of South Africa after considerable opposition, on the second day of January 1922. This was Yergan's third overseas posting and second African assignment, the first being in Kenya, and then Tanganyika during the East Africa campaign of World War I. He had joined the YMCA as a Shaw University sophomore in Raleigh, North Carolina in 1911, rapidly rising in its ranks to become a national figure in their Black “Y” network. Yergan became the third “non-white” YMCA Traveling Secretary in South Africa and the first to attempt to do so on a full-time basis, succeeding J. K. Bokwe and D. D. T. Jabavu.
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Webel, Mari. "MEDICAL AUXILIARIES AND THE NEGOTIATION OF PUBLIC HEALTH IN COLONIAL NORTH-WESTERN TANZANIA." Journal of African History 54, no. 3 (November 2013): 393–416. http://dx.doi.org/10.1017/s0021853713000716.
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AbstractThis article investigates the development and employment of African medical auxiliaries during the German campaign against sleeping sickness in colonial north-western Tanzania. A case study from the kingdom of Kiziba demonstrates how widespread illness and colonial public health interventions intersected with broader political and social change in the early twentieth century. Ziba auxiliaries known as gland-feelers operated within overlapping social and occupational contexts as colonial intermediaries, royal emissaries, and familiar local men. The changing fortunes of the campaign and its auxiliaries illustrate how new public health interventions became a means for the kingdom's population to engage with or avoid both royal and colonial power.
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Anthony, David Henry. "Max Yergan, Marxism and Mission during the Interwar Era." Social Sciences and Missions 22, no. 2 (2009): 257–91. http://dx.doi.org/10.1163/187489309x12537778667273.
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AbstractFrom 1922 through 1936 Max Yergan, an African-American graduate of historically Black Shaw University in Raleigh, North Carolina represented the North American YMCA in South Africa through the auspices of the Student Christian Association. A student secretary since his sophomore year in 1911, with Indian and East African experience in World War One, Yergan's star rose sufficiently to permit him entry into the racially challenging South Africa field after a protracted campaign waged on his behalf by such interfaith luminaries as Gold Coast proto nationalist J.E.K. Aggrey and the formidable Dr. W.E.B. Du Bois. Arriving on the eve of the Great Rand Mine Strike of 1922, Yergan's South African years were punctuated by political concerns. Entering the country as an Evangelical Pan-Africanist influenced by the social gospel thrust of late nineteenth and early twentieth century American Protestantism that reached the YMCA and other faith-friendly but nondenominational organizations, Yergan became favorably disposed to Marxist and Marxist-Leninist doctrine in the course of his South African posting. Against the backdrop of the labor agitation of the post World War One era and the expansion and transformation of the South African Communist Party that occurred during the mid to late nineteen twenties, Yergan's response to what he termed "the appeal of Communism" made him an avatar of a liberation theology fusing Marxist revolution and Christianity. This paper details some of the trajectory of that momentous and profound personal evolution.
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Asheeke, Toivo. "On Building a Social Movement: The North American Campaign for Southern African Liberation Revisited." Canadian Journal of African Studies / Revue canadienne des études africaines 53, no. 1 (January 2, 2019): 188–90. http://dx.doi.org/10.1080/00083968.2019.1565711.
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Lissoni, Arianna. "On building a social movement: the North American campaign for southern African liberation revisited." Review of African Political Economy 47, no. 165 (July 2, 2020): 506–8. http://dx.doi.org/10.1080/03056244.2020.1837475.
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Saunois, M., C. E. Reeves, C. Mari, J. G. Murphy, D. J. Stewart, G. P. Mills, D. E. Oram, and R. M. Purvis. "Ozone budget in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) campaign." Atmospheric Chemistry and Physics Discussions 9, no. 2 (March 16, 2009): 6979–7032. http://dx.doi.org/10.5194/acpd-9-6979-2009.
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Abstract. A bi-dimensional latitudinal-vertical meterological model coupled with O3-NOx-VOC chemistry is used to reproduce the distribution of ozone and precursors in the boundary layer over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) campaign as observed on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft. The model reproduces the increase of ozone mixing ratios in the boundary layer observed between the forested region south of 13° N and the Sahelian area northward. Sensitivity and budget analysis reveals that the intertropical convergence zone is a moderate source of O3 rich-air in the boundary layer due to convective downdrafts. Dry deposition drives the ozone minimum over the vegetated area. The combination of high NOx emissions from soil north of 13° N and northward advection by the monsoon flux of VOC-enriched air masses contributes to the ozone maximum simulated at higher latitudes. Simulated OH exhibit a well marked latitudinal gradient with minimum concentrations over the vegetated region where the reactions with biogenic compounds predominate. The model underestimates the observed OH mixing ratios, however this model discrepancy has slight effect on ozone budget and does not alter the conclusions.
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Cairncross, Sandy, Ralph Muller, and Nevio Zagaria. "Dracunculiasis (Guinea Worm Disease) and the Eradication Initiative." Clinical Microbiology Reviews 15, no. 2 (April 2002): 223–46. http://dx.doi.org/10.1128/cmr.15.2.223-246.2002.
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SUMMARY Dracunculiasis, also known as guinea worm disease, is caused by the large female of the nematode Dracunculus medinensis, which emerges painfully and slowly from the skin, usually on the lower limbs. The disease can infect animals, and sustainable animal cycles occur in North America and Central Asia but do not act as reservoirs of human infection. The disease is endemic across the Sahel belt of Africa from Mauritania to Ethiopia, having been eliminated from Asia and some African countries. It has a significant socioeconomic impact because of the temporary disability that it causes. Dracunculiasis is exclusively caught from drinking water, usually from ponds. A campaign to eradicate the disease was launched in the 1980s and has made significant progress. The strategy of the campaign is discussed, including water supply, health education, case management, and vector control. Current issues including the integration of the campaign into primary health care and the mapping of cases by using geographic information systems are also considered. Finally, some lessons for other disease control and eradication programs are outlined.
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Saunois, M., C. E. Reeves, C. H. Mari, J. G. Murphy, D. J. Stewart, G. P. Mills, D. E. Oram, and R. M. Purvis. "Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) wet season campaign." Atmospheric Chemistry and Physics 9, no. 16 (August 27, 2009): 6135–55. http://dx.doi.org/10.5194/acp-9-6135-2009.
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Abstract. Ozone and its precursors were measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the monsoon season 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) campaign. One of the main features observed in the west African boundary layer is the increase of the ozone mixing ratios from 25 ppbv over the forested area (south of 12° N) up to 40 ppbv over the Sahelian area. We employ a two-dimensional (latitudinal versus vertical) meteorological model coupled with an O3-NOx-VOC chemistry scheme to simulate the distribution of trace gases over West Africa during the monsoon season and to analyse the processes involved in the establishment of such a gradient. Including an additional source of NO over the Sahelian region to account for NO emitted by soils we simulate a mean NOx concentration of 0.7 ppbv at 16° N versus 0.3 ppbv over the vegetated region further south in reasonable agreement with the observations. As a consequence, ozone is photochemically produced with a rate of 0.25 ppbv h−1 over the vegetated region whilst it reaches up to 0.75 ppbv h−1 at 16° N. We find that the modelled gradient is due to a combination of enhanced deposition to vegetation, which decreases the ozone levels by up to 11 pbbv, and the aforementioned enhanced photochemical production north of 12° N. The peroxy radicals required for this enhanced production in the north come from the oxidation of background CO and CH4 as well as from VOCs. Sensitivity studies reveal that both the background CH4 and partially oxidised VOCs, produced from the oxidation of isoprene emitted from the vegetation in the south, contribute around 5–6 ppbv to the ozone gradient. These results suggest that the northward transport of trace gases by the monsoon flux, especially during nighttime, can have a significant, though secondary, role in determining the ozone gradient in the boundary layer. Convection, anthropogenic emissions and NO produced from lightning do not contribute to the establishment of the discussed ozone gradient.
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Janicot, S., C. D. Thorncroft, A. Ali, N. Asencio, G. Berry, O. Bock, B. Bourles, et al. "Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006." Annales Geophysicae 26, no. 9 (September 5, 2008): 2569–95. http://dx.doi.org/10.5194/angeo-26-2569-2008.
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Abstract. The AMMA (African Monsoon Multidisciplinary Analysis) program is dedicated to providing a better understanding of the West African monsoon and its influence on the physical, chemical and biological environment regionally and globally, as well as relating variability of this monsoon system to issues of health, water resources, food security and demography for West African nations. Within this framework, an intensive field campaign took place during the summer of 2006 to better document specific processes and weather systems at various key stages of this monsoon season. This campaign was embedded within a longer observation period that documented the annual cycle of surface and atmospheric conditions between 2005 and 2007. The present paper provides a large and regional scale overview of the 2006 summer monsoon season, that includes consideration of of the convective activity, mean atmospheric circulation and synoptic/intraseasonal weather systems, oceanic and land surface conditions, continental hydrology, dust concentration and ozone distribution. The 2006 African summer monsoon was a near-normal rainy season except for a large-scale rainfall excess north of 15° N. This monsoon season was also characterized by a 10-day delayed onset compared to climatology, with convection becoming developed only after 10 July. This onset delay impacted the continental hydrology, soil moisture and vegetation dynamics as well as dust emission. More details of some less-well-known atmospheric features in the African monsoon at intraseasonal and synoptic scales are provided in order to promote future research in these areas.
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Baillot, Hélène. "A Well-Adjusted Debt: How the International Anti-Debt Movement Failed to Delink Debt Relief and Structural Adjustment." International Review of Social History 66, S29 (March 9, 2021): 215–38. http://dx.doi.org/10.1017/s0020859021000146.
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AbstractThis article analyses the process by which the issues of debt and structural adjustment were redefined by a plurality of actors, from institutional experts to activists, during the 1980s and 1990s. Although it mainly focuses on the 1990s, when the Jubilee 2000 campaign emerged, blossomed, and died, it takes into account the institutional mobilization preceding it. It then points to the need to think about the dynamics of competition and the division of labour among international players. While the leading Jubilee 2000 coalition in the Global North opposed debt on economic and religious grounds, African anti-structural adjustment programme (SAP) activists who joined the Jubilee Afrika campaign promoted an alternative framework: according to them, debt was not just economically “unsustainable”; it was first and foremost “illegitimate”, as were any conditions attached to its reduction, beginning with the implementation of SAPs. The story of the anti-debt campaign is the story of their failure.
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ANDERSON, DAVID, and NEIL CARRIER. "KHAT IN COLONIAL KENYA: A HISTORY OF PROHIBITION AND CONTROL." Journal of African History 50, no. 3 (November 2009): 377–97. http://dx.doi.org/10.1017/s0021853709990752.
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ABSTRACTEfforts to institute a system for the control and prohibition of khat in Kenya are examined in this article. Prohibition was introduced in the 1940s after an advocacy campaign led by prominent colonial officials. The legislation imposed a racialized view of the effect of khat, seeking to protect an allegedly ‘vulnerable’ community in the north of the country while allowing khat to be consumed and traded in other areas, including Meru where ‘traditional’ production and consumption was permitted. Colonial policy took little account of African opinion, although African agency was evident in the failure and ultimate collapse of the prohibition in the face of widespread smuggling and general infringement. Trade in khat became ever more lucrative, and in the final years of colonial rule economic arguments overcame the prohibition lobby. The imposition of prohibition and control indicates the extent to which colonial attitudes towards and beliefs about cultural behaviour among Africans shaped policies, but the story also illustrates the fundamental weakness of the colonial state in its failure to uphold the legislation.
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Olatoye, Tolulope Ayodeji, Sonwabo Perez Mazinyo, Akinwunmi Sunday Odeyemi, Israel Ropo Orimoloye, and Emmanuel Tolulope Busayo. "Forest Systems Services Provisioning in Africa: Case of Gambari Forest Reserve, Ibadan, Nigeria." International Journal of Forestry Research 2021 (July 6, 2021): 1–6. http://dx.doi.org/10.1155/2021/8823826.
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This study, therefore, which is focused on forest systems services provisioning in Africa, case of Gambari Forest Reserve, Ibadan, Nigeria, provides policy makers, decision makers, ecologists, environmentalists, the academia, and other stakeholders with a document geared towards promoting national development through sustainable forest products utilization practices. In this study, a total of 200 key respondents participated in it, out of which 194 copies were returned and distributed among the seven main communities in the study area, namely, Ibusogbora, Oloowa, Daley north and south, Onipe, Mamu, Olubi, and Onipanu, respectively. The respondents stated that moringa 164 (84.5%), mint leaf (166 (85.6%), bitter kola 143 (73.7%), and shea tree accounts for 176 (90.7%), and the wood species utilized by producers in the study area include Leucaena leucocephala, Leucaena glauca, Gliricidia sepium, Tectona grandis, and Gmelina arborea, among others. The study recommends that there is need for African governments to restore public awareness campaign in the area of timber planting initiatives and sustainable forest resource management and increase allocation to fund forestry research in the African continent.
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Johnson, Wray R. "Christopher M. Rein. The North African Air Campaign: U.S. Army Air Forces from El Alamein to Salerno." American Historical Review 119, no. 3 (June 2014): 922. http://dx.doi.org/10.1093/ahr/119.3.922.
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Chouza, Fernando, Oliver Reitebuch, Angela Benedetti, and Bernadett Weinzierl. "Saharan dust long-range transport across the Atlantic studied by an airborne Doppler wind lidar and the MACC model." Atmospheric Chemistry and Physics 16, no. 18 (September 20, 2016): 11581–600. http://dx.doi.org/10.5194/acp-16-11581-2016.
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Abstract. A huge amount of dust is transported every year from north Africa into the Caribbean region. This paper presents an investigation of this long-range transport process based on airborne Doppler wind lidar (DWL) measurements conducted during the SALTRACE campaign (June–July 2013), as well as an evaluation of the ability of the MACC (Monitoring Atmospheric Composition and Climate) global aerosol model to reproduce it and its associated features. Although both the modeled winds from MACC and the measurements from the DWL show a generally good agreement, some differences, particularly in the African easterly jet (AEJ) intensity, were noted. The observed differences between modeled and measured wind jet speeds are between 5 and 10 m s−1. The vertical aerosol distribution within the Saharan dust plume and the marine boundary layer is investigated during the June–July 2013 period based on the MACC aerosol model results and the CALIOP satellite lidar measurements. While the modeled Saharan dust plume extent shows a good agreement with the measurements, a systematic underestimation of the marine boundary layer extinction is observed. Additionally, three selected case studies covering different aspects of the Saharan dust long-range transport along the west African coast, over the North Atlantic Ocean and the Caribbean are presented. For the first time, DWL measurements are used to investigate the Saharan dust long-range transport. Simultaneous wind and backscatter measurements from the DWL are used, in combination with the MACC model, to analyze different features associated with the long-range transport, including an African easterly wave trough, the AEJ and the intertropical convergence zone.
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Schepanski, Kerstin, Bernd Heinold, and Ina Tegen. "Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic." Atmospheric Chemistry and Physics 17, no. 17 (September 1, 2017): 10223–43. http://dx.doi.org/10.5194/acp-17-10223-2017.
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Abstract. The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are predominantly activated during the second half of the day, when downdrafts associated with deep moist convection are the major atmospheric driver. Complementary to the satellite-based analysis on dust source activations and implications from their diurnal cycle, simulations on atmosphere and dust life cycle were performed using the mesoscale atmosphere–dust model system COSMO-MUSCAT (COSMO: COnsortium for Small-scale MOdelling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Fields from this simulation were analysed regarding the variability of the harmattan, the Saharan heat low, and the monsoon circulation as well as their impact on the variability of the Saharan dust outflow towards the North Atlantic. This study illustrates the complexity of the interaction among the three major circulation regimes and their modulation of the North African dust outflow. Enhanced westward dust fluxes frequently appear following a phase characterized by a deep SHL. Ultimately, findings from this study contribute to the quantification of the interannual variability of the atmospheric dust burden.
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Fennell, Jonathan. "Courage and Cowardice in the North African Campaign: The Eighth Army and Defeat in the Summer of 1942." War in History 20, no. 1 (January 2013): 99–122. http://dx.doi.org/10.1177/0968344512454251.
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High rates of desertion and surrender during the battles in North Africa in the summer of 1942 were a major factor in Eighth Army’s poor combat performance. At the time, some suggested that these problems were symptomatic of a lack of courage or even of cowardice. There are two broad strands to the conceptualization of courage and cowardice. One focuses on the willingness of the person to fight; the other puts emphasis on how actions express an individual’s ability to cope with fear. Whichever conceptualization is used, high morale motivates the soldier to fight and shields the ordinary recruit from his fear, preventing it from overcoming him in battle. Where morale fails, the soldier is left demotivated and burdened with his terror and, therefore, and is therefore prone to desertion or surrender. Because it is extremely difficult to maintain morale at a continuously high level in an environment governed by chance and managed by humans, all soldiers can find themselves in situations where their actions may be judged as cowardly. Alternatively, if they are properly motivated to fight and prepared by the state and military to deal with the unavoidable fear of combat, all soldiers can be labelled courageous. Accordingly, emotive terms should be avoided when attempting to describe rationally explainable outcomes. The undoubtedly negative connotations attached to cowardice in battle and the positive ones attached to courage are, therefore, arguably unhelpful in understanding Eighth Army’s performance in the summer of 1942 and the human dimension in warfare more generally.
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Barret, B., P. Ricaud, C. Mari, J. L. Attié, N. Bousserez, B. Josse, E. Le Flochmoën, et al. "Transport pathways of CO in the African upper troposphere during the monsoon season: a study based upon the assimilation of spaceborne observations." Atmospheric Chemistry and Physics 8, no. 12 (June 26, 2008): 3231–46. http://dx.doi.org/10.5194/acp-8-3231-2008.
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Abstract. The transport pathways of carbon monoxide (CO) in the African Upper Troposphere (UT) during the West African Monsoon (WAM) is investigated through the assimilation of CO observations by the Aura Microwave Limb Sounder (MLS) in the MOCAGE Chemistry Transport Model (CTM). The assimilation setup, based on a 3-D First Guess at Assimilation Time (3-D-FGAT) variational method is described. Comparisons between the assimilated CO fields and in situ airborne observations from the MOZAIC program between Europe and both Southern Africa and Southeast Asia show an overall good agreement around the lowermost pressure level sampled by MLS (~215 hPa). The 4-D assimilated fields averaged over the month of July 2006 have been used to determine the main dynamical processes responsible for the transport of CO in the African UT. The studied period corresponds to the second AMMA (African Monsoon Multidisciplinary Analyses) aircraft campaign. At 220 hPa, the CO distribution is characterized by a latitudinal maximum around 5° N mostly driven by convective uplift of air masses impacted by biomass burning from Southern Africa, uplifted within the WAM region and vented predominantly southward by the upper branch of the winter hemisphere Hadley cell. Above 150 hPa, the African CO distribution is characterized by a broad maximum over northern Africa. This maximum is mostly controlled by the large scale UT circulation driven by the Asian Summer Monsoon (ASM) and characterized by the Asian Monsoon Anticyclone (AMA) centered at 30° N and the Tropical Easterly Jet (TEJ) on the southern flank of the anticyclone. Asian pollution uplifted to the UT over large region of Southeast Asia is trapped within the AMA and transported by the anticyclonic circulation over Northeast Africa. South of the AMA, the TEJ is responsible for the tranport of CO-enriched air masses from India and Southeast Asia over Africa. Using the high time resolution provided by the 4-D assimilated fields, we give evidence that the variability of the African CO distribution above 150 hPa and north of the WAM region is mainly driven by the synoptic dynamical variability of both the AMA and the TEJ.
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Barret, B., P. Ricaud, C. Mari, J. L. Attié, N. Bousserez, B. Josse, E. Le Flochmoën, et al. "Transport pathways of CO in the African upper troposphere during the monsoon season: a study based upon the assimilation of spaceborne observations." Atmospheric Chemistry and Physics Discussions 8, no. 1 (February 13, 2008): 2863–902. http://dx.doi.org/10.5194/acpd-8-2863-2008.
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Abstract. The transport pathways of carbon monoxide (CO) in the African Upper Troposphere (UT) during the West African Monsoon (WAM) is investigated through the assimilation of CO observations by the Aura Microwave Limb Sounder (MLS) in the MOCAGE Chemistry Transport Model (CTM). The assimilation setup, based on a 3-D First Guess at Assimilation Time (3-D-FGAT) variational method is described. Comparisons between the assimilated CO fields and in situ airborne observations from the MOZAIC program between Europe and both Southern Africa and Southeast Asia show an overall good agreement around the lowermost pressure level sampled by MLS (~215 hPa). The 4-D assimilated fields averaged over the month of July 2006 have been used to determine the main dynamical processes responsible for the transport of CO in the African UT. The studied period corresponds to the second AMMA (African Monsoon Multidisciplinary Analyses) aircraft campaign. At 220 hPa, the CO distribution is characterized by a latitudinal maximum around 5° N mostly driven by convective uplift of air masses impacted by biomass burning from Southern Africa, uplifted within the WAM region and vented predominantly southward by the upper branch of the winter hemisphere Hadley cell. Above 150 hPa, the African CO distribution is characterized by a broad maximum over northern Africa. This maximum is mostly controlled by the large scale UT circulation driven by the Asian Summer Monsoon (ASM) and characterized by the Asian Monsoon Anticyclone (AMA) centered at 30° N and the Tropical Easterly Jet (TEJ) on the southern flank of the anticyclone. Asian pollution uplifted to the UT over large region of Southeast Asia is trapped within the AMA and transported by the anticyclonic circulation over Northeast Africa. South of the AMA, the TEJ is responsible for the tranport of CO-enriched air masses from India and Southeast Asia over Africa. Using the high time resolution provided by the 4-D assimilated fields, we give evidence that the variability of the African CO distribution above 150 hPa and north of the WAM region is mainly driven by the synoptic dynamical variability of both the AMA and the TEJ.
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Oldfield, J. R. "The London Committee and mobilization of public opinion against the slave trade." Historical Journal 35, no. 2 (June 1992): 331–43. http://dx.doi.org/10.1017/s0018246x00025826.
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AbstractDuring the late eighteenth century organized anti-slavery, in the shape of the campaign to end the African slave trade (1787–1807), became an unavoidable feature of political life in Britain. Drawing on previously unpublished material in the Josiah Wedgwood Papers, the following article seeks to reassess this campaign and, in particular, the part played in it by the (London) Committee for the Abolition of the Slave Trade. So far from being a low-level lobby, as historians like Seymour Drescher have suggested, it is argued here that the Committee's activities, both in terms of opinion-building and arranging for petitions to be sent to the house of commons, were central to the success of the early abolitionist movement. Thus while the provinces and public opinion at the grass roots level were undoubtedly important, not least in the industrial north, it was the metropolis and the London Committee which gave political shape and significance to popular abolitionism.
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Knippertz, Peter, Andreas H. Fink, Adrien Deroubaix, Eleanor Morris, Flore Tocquer, Mat J. Evans, Cyrille Flamant, et al. "A meteorological and chemical overview of the DACCIWA field campaign in West Africa in June–July 2016." Atmospheric Chemistry and Physics 17, no. 17 (September 14, 2017): 10893–918. http://dx.doi.org/10.5194/acp-17-10893-2017.
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Abstract. In June and July 2016 the Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa (DACCIWA) project organised a major international field campaign in southern West Africa (SWA) including measurements from three inland ground supersites, urban sites in Cotonou and Abidjan, radiosondes, and three research aircraft. A significant range of different weather situations were encountered during this period, including the monsoon onset. The purpose of this paper is to characterise the large-scale setting for the campaign as well as synoptic and mesoscale weather systems affecting the study region in the light of existing conceptual ideas, mainly using objective and subjective identification algorithms based on (re-)analysis and satellite products. In addition, it is shown how the described synoptic variations influence the atmospheric composition over SWA through advection of mineral dust, biomass burning and urban pollution plumes.The boreal summer of 2016 was characterised by Pacific La Niña, Atlantic El Niño and warm eastern Mediterranean conditions, whose competing influences on precipitation led to an overall average rainy season. During the relatively dusty pre-onset Phase 1 (1–21 June 2016), three westward-propagating coherent cyclonic vortices between 4 and 13° N modulated winds and rainfall in the Guinea coastal area. The monsoon onset occurred in connection with a marked extratropical trough and cold surge over northern Africa, leading to a breakdown of the Saharan heat low and African easterly jet and a suppression of rainfall. During this period, quasi-stationary low-level vortices associated with the trough transformed into more tropical, propagating disturbances resembling an African easterly wave (AEW). To the east of this system, moist southerlies penetrated deep into the continent. The post-onset Phase 2 (22 June–20 July 2016) was characterised by a significant increase in low-level cloudiness, unusually dry conditions and strong northeastward dispersion of urban pollution plumes in SWA as well as rainfall modulation by westward-propagating AEWs in the Sahel. Around 12–14 July 2016 an interesting and so-far undocumented cyclonic–anticyclonic vortex couplet crossed SWA. The anticyclonic centre had its origin in the Southern Hemisphere and transported unusually dry air filled with aged aerosol into the region. During Phase 3 (21–26 July 2016), a similar vortex couplet slightly farther north created enhanced westerly moisture transports into SWA and extraordinarily wet conditions, accompanied by a deep penetration of the biomass burning plume from central Africa. Finally, a return to more undisturbed monsoon conditions took place during Phase 4 (27–31 July 2016). The in-depth synoptic analysis reveals that several significant weather systems during the DACCIWA campaign cannot be attributed unequivocally to any of the tropical waves and disturbances described in the literature and thus deserve further study.
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MOORE-COLYER, R. J. "The Call to the Land: British and European Adult Voluntary Farm Labour; 1939–49." Rural History 17, no. 1 (March 16, 2006): 83–101. http://dx.doi.org/10.1017/s0956793305001615.
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As the armed forces continued to siphon away labour from the land following the outbreak of the war, the Ministry of Agriculture's County War Agricultural Executive Committees were hard put to meet the demand for labour to sustain the plough-up campaign. While schoolchildren made a major contribution, there were few prisoners-of-war before the North African campaign and volunteers from all walks of life were sought to attend harvest camps, weekend farm clubs and other land-based activities. At the end of the war the Ministry of Agriculture turned to mainland Europe for volunteers to work towards the solution of the British and pan-European food shortages. They were supplemented by members of the Polish Resettlement Corps, German prisoners who had opted to defer repatriation and volunteers from the British zones of Austria and Germany. The article raises the issue of how far the enterprise promoted international understanding as was assumed at the time or, indeed, whether the home volunteer experience narrowed the so-called rural-urban divide as opposed to reinforcing entrenched prejudices.
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Todman, D. "Combat and Morale in the North African Campaign: The Eighth Army and the Path to El Alamein. By Jonathan Fennell." Twentieth Century British History 24, no. 1 (December 6, 2011): 164–66. http://dx.doi.org/10.1093/tcbh/hwr059.
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Cross, Graham. "Book Review: The North African Air Campaign: U.S. Army Air Forces from El Alamein to Salerno by Christopher M. Rein." War in History 21, no. 2 (April 2014): 264–65. http://dx.doi.org/10.1177/0968344513516553i.
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Kitchen, J. "Combat and Morale in the North African Campaign: The Eighth Army and the Path to El Alamein, by Jonathan Fennell." English Historical Review 128, no. 531 (March 26, 2013): 485–87. http://dx.doi.org/10.1093/ehr/cet019.
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Lyons, Maryinez. "From ‘Death Camps’ toCordon Sanitaire: The Development of Sleeping Sickness Policy in the Uele District of the Belgian Congo, 1903–1914." Journal of African History 26, no. 1 (January 1985): 69–91. http://dx.doi.org/10.1017/s0021853700023094.
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SummaryWhen sleeping sickness was discovered to be epidemic in the Congo Free State in 1904, the administration responded by attempting to implement public health measures which had evolved in Europe in relation to plague and cholera epidemics. These measures were to identify and isolate victims and suspected victims of the disease and to map out the infected and uninfected zones. This article describes the early sleeping-sickness campaign of the Belgian authorities in the Uele District of Province Orientale between 1904 and 1914, focusing on the formation of isolation camps or lazarets. Uele district had been identified as a potentially rich and uninfected zone to be protected from contamination by the establishment of acordon sanitaire. Public health policy and practice during this period provides an example of attempted ‘social engineering’ on the part of a colonial authority. While sleeping sickness provided the major impetus for the gradual development of the colonial medical service by the 1920s, the early period between 1903 and World War I was particularly onerous for the African populations in the north-east. The public health policy was perceived by many Africans as one more element in the on-going conquest and exploitation of the region. Examples are provided to demonstrate the ways in which numerous sleeping-sickness regulations affected African societies in Uele.
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Sparks, Randy J. "Blind Justice: The United States's Failure to Curb the Illegal Slave Trade." Law and History Review 35, no. 1 (February 2017): 53–79. http://dx.doi.org/10.1017/s0738248016000535.
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On March 2, 1807, President Thomas Jefferson signed a bill outlawing the African slave trade. Opponents of the traffic rejoiced that the bill was passed at almost the same time as a similar anti-slave-trade bill in Britain. As one Philadelphia newspaper put it, “Thus, will terminate, on the same day, in two countries of the civilized world, a traffic which has hitherto stained the history of all countries who made it a practice to deal in the barter ofhuman flesh.” Efforts to end the African slave trade in the British colonies of North America dated back to the 1760s, proceeded in fits and starts, and resulted from a wide range of motives. In contrast to Great Britain, the United States 1807 bill was not the result of a long, hard-won, popular abolition campaign. However, despite a series of laws intended to curb the trade, eventually making the United States laws the world's toughest, smugglers continued to bring enslaved Africans into the South after 1808, and, more significantly, American vessels played a crucial role in the massive illegal slave trade to Cuba and Brazil during the nineteenth century. The impact on the United States economy was not inconsequential, but even more important was the trade's impact on the Atlantic economy, fueling the rapid economic growth of Cuba and Brazil in the decades that followed.
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Fink, A. H., D. G. Vincent, and V. Ermert. "Rainfall Types in the West African Sudanian Zone during the Summer Monsoon 2002." Monthly Weather Review 134, no. 8 (August 1, 2006): 2143–64. http://dx.doi.org/10.1175/mwr3182.1.
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Abstract Enhanced surface and upper-air observations from the field campaign of the Integrated Approach to the Efficient Management of Scarce Water Resources in West Africa (IMPETUS) project are used to partition rainfall amounts over the West African Sudanian zone during the 2002 summer monsoon season into several characteristic types and subtypes of precipitating systems. The most prominent rainfall subtype was fast-moving, long-lived, and extensive cloud clusters that often developed far upstream over the central Nigerian highlands in the afternoon hours and arrived at the Upper Ouémé Valley (UOV) after midnight. These organized convective systems (advective OCSs, subtype Ia) accounted for 50% of the total rain amount in the UOV catchment in Benin. Subtypes Ia and IIa (i.e., locally developing OCSs) were found to pass by or organize when a highly sheared environment with deep and dry midtropospheric layers was present over the UOV. These systems were most frequent outside the peak of the monsoon season. The second major type of organized convection, termed mesoscale convective systems (subtypes Ib, IIb, and IIIb) in the present study, contributed 26% to the annual UOV precipitation. They occurred in a less-sheared and moister tropospheric environment mainly around the height of the rainy season. A third distinct class of rainfall events occurred during an unusual synoptic situation in which a cyclonic vortex to the north of the UOV led to deep westerly flow. During these periods, the African easterly jet was lacking. The so-called vortex-type rainfalls (subtypes IIIa, IIIb, and IIIc) contributed about 9% to the annual rainfall totals.
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Real, E., E. Orlandi, K. S. Law, F. Fierli, D. Josset, F. Cairo, H. Schlager, et al. "Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production." Atmospheric Chemistry and Physics Discussions 9, no. 4 (August 20, 2009): 17385–427. http://dx.doi.org/10.5194/acpd-9-17385-2009.
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Abstract. Pollutant plumes with enhanced levels of trace gases and aerosols were observed over the southern coast of West Africa during August 2006 as part of the AMMA wet season field campaign. Plumes were observed both in the mid and upper troposphere. In this study we examined both the origin of these pollutant plumes and their potential to produce O3 downwind over the Atlantic Ocean. Runs using the BOLAM mesoscale model including biomass burning CO tracers were used to confirm an origin from central African fires. The plumes in the mid troposphere had significantly higher pollutant concentrations due to the fact that transport occurred from a region nearer or even over the fire region. In contrast, plumes transported into the upper troposphere over West Africa had been transported to the north-east of the fire region before being uplifted. Modelled tracer results showed that pollutants resided for between 9 and 12 days over Central Africa before being transported for 4 days, in the case of the mid-troposphere plume and 2 days in the case of the upper tropospheric plume to the measurement location over the southern part of West Africa. Around 35% of the biomass burning tracer was transported into the upper troposphere compared to that remaining in the mid troposphere. Runs using a photochemical trajectory model, CiTTyCAT, were used to estimate the net photochemical O3 production potential of these plumes. The mid tropospheric plume was still very photochemically active (up to 7 ppbv/day) especially during the first few days of transport westward over the Atlantic Ocean. The upper tropospheric plume was also still photochemically active, although at a slower rate (1–2 ppbv/day). Trajectories show this plume being recirculated around an upper tropospheric anticyclone back towards the African continent (around 20° S). The potential of theses plumes to produce O3 supports the hypothesis that biomass burning pollutants are contributing to the observed O3 maxima over the southern Atlantic at this time of year.
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Ferreira, J., C. E. Reeves, J. G. Murphy, L. Garcia-Carreras, D. J. Parker, and D. E. Oram. "Isoprene emissions modelling for West Africa using MEGAN." Atmospheric Chemistry and Physics Discussions 10, no. 3 (March 11, 2010): 6923–53. http://dx.doi.org/10.5194/acpd-10-6923-2010.
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Abstract. Isoprene emissions are the largest source of reactive carbon to the atmosphere, with the tropics being a major source region. These natural emissions are expected to change with changing climate and human impact on land use. As part of the African Monsoon Multidisciplinary Analyses (AMMA) project the Model of Emissions of Gases and Aerosols from Nature (MEGAN) has been used to estimate the spatial and temporal distribution of isoprene emissions over the West African region. During the AMMA field campaign, carried out in July and August 2006, isoprene mixing ratios were measured on board the FAAM BAe-146 aircraft. These data have been used to evaluate the model performance. MEGAN was firstly applied to a large area covering much of West Africa from the Gulf of Guinea in the south to the desert in the north and was able to capture the large scale spatial distribution of isoprene emissions as inferred from the observed isoprene mixing ratios. In particular the model captures the transition from the forested area in the south to the bare soils in the north, but some discrepancies have been identified over the bare soil, mainly due to the emission factors used. Sensitivity analyses were performed to assess the model response to changes in driving parameters, namely Leaf Area Index (LAI), Emission Factors (EF), temperature and solar radiation. A high resolution simulation was made of a limited area south of Niamey, Niger, where the higher concentrations of isoprene were observed. This is used to evaluate the model's ability to simulate smaller scale spatial features and to examine the influence of the driving parameters on an hourly basis through a case study of a flight on 17 August 2006. This study highlights the complex interactions between land surface processes and the meteorological dynamics and chemical composition of the PBL. This has implications for quantifying the impact of biogenic emissions on the atmospheric composition over West Africa and any changes that may occur with changing climate.
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Ferreira, J., C. E. Reeves, J. G. Murphy, L. Garcia-Carreras, D. J. Parker, and D. E. Oram. "Isoprene emissions modelling for West Africa: MEGAN model evaluation and sensitivity analysis." Atmospheric Chemistry and Physics 10, no. 17 (September 7, 2010): 8453–67. http://dx.doi.org/10.5194/acp-10-8453-2010.
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Abstract. Isoprene emissions are the largest source of reactive carbon to the atmosphere, with the tropics being a major source region. These natural emissions are expected to change with changing climate and human impact on land use. As part of the African Monsoon Multidisciplinary Analyses (AMMA) project the Model of Emissions of Gases and Aerosols from Nature (MEGAN) has been used to estimate the spatial and temporal distribution of isoprene emissions over the West African region. During the AMMA field campaign, carried out in July and August 2006, isoprene mixing ratios were measured on board the FAAM BAe-146 aircraft. These data have been used to make a qualitative evaluation of the model performance. MEGAN was firstly applied to a large area covering much of West Africa from the Gulf of Guinea in the south to the desert in the north and was able to capture the large scale spatial distribution of isoprene emissions as inferred from the observed isoprene mixing ratios. In particular the model captures the transition from the forested area in the south to the bare soils in the north, but some discrepancies have been identified over the bare soil, mainly due to the emission factors used. Sensitivity analyses were performed to assess the model response to changes in driving parameters, namely Leaf Area Index (LAI), Emission Factors (EF), temperature and solar radiation. A high resolution simulation was made of a limited area south of Niamey, Niger, where the higher concentrations of isoprene were observed. This is used to evaluate the model's ability to simulate smaller scale spatial features and to examine the influence of the driving parameters on an hourly basis through a case study of a flight on 17 August 2006. This study highlights the complex interactions between land surface processes and the meteorological dynamics and chemical composition of the PBL. This has implications for quantifying the impact of biogenic emissions on the atmospheric composition over West Africa and any changes that may occur with changing climate.
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Pey, Jorge, Jesús Revuelto, Natalia Moreno, Esteban Alonso-González, Miguel Bartolomé, Jesús Reyes, Simon Gascoin, and Juan Ignacio López-Moreno. "Snow Impurities in the Central Pyrenees: From Their Geochemical and Mineralogical Composition towards Their Impacts on Snow Albedo." Atmosphere 11, no. 9 (September 2, 2020): 937. http://dx.doi.org/10.3390/atmos11090937.
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The aim of this work is to understand aerosol transfers to the snowpack in the Spanish Pyrenees (Southern Europe) by determining their episodic mass-loading and composition, and to retrieve their regional impacts regarding optical properties and modification of snow melting. Regular aerosol monitoring has been performed during three consecutive years. Complementarily, short campaigns have been carried out to collect dust-rich snow samples. Atmospheric samples have been chemically characterized in terms of elemental composition and, in some cases, regarding their mineralogy. Snow albedo has been determined in different seasons along the campaign, and temporal variations of snow-depth from different observatories have been related to concentration of impurities in the snow surface. Our results noticed that aerosol flux in the Central Pyrenees during cold seasons (from November to May, up to 12–13 g m−2 of insoluble particles overall accumulated) is much higher than the observed during the warm period (from June to October, typically around 2.1–3.3 g m−2). Such high values observed during cold seasons were driven by the impact of severe African dust episodes. In absence of such extreme episodes, aerosol loadings in cold and warm season appeared comparable. Our study reveals that mineral dust particles from North Africa are a major driver of the aerosol loading in the snowpack in the southern side of the Central Pyrenees. Field data revealed that the heterogeneous spatial distribution of impurities on the snow surface led to differences close to 0.2 on the measured snow albedo within very short distances. Such impacts have clear implications for modelling distributed energy balance of snow and predicting snow melting from mountain headwaters.
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Cobbing, Julian. "The Mfecane as Alibi: Thoughts on Dithakong and Mbolompo." Journal of African History 29, no. 3 (November 1988): 487–519. http://dx.doi.org/10.1017/s0021853700030590.
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The ‘mfecane’ is a characteristic product of South African liberal history used by the apartheid state to legitimate South Africa's racially unequal land division. Some astonishingly selective use or actual invention of evidence produced the myth of an internally-induced process of black-on-black destruction centring on Shaka's Zulu. A re-examination of the ‘battles’ of Dithakong and Mbolompo suggests very different conclusions and enables us to decipher the motives of subsequent historiographical amnesias. After about 1810 the black peoples of southern Africa were caught between intensifying and converging imperialistic thrusts: one to supply the Cape Colony with labour; another, at Delagoa Bay, to supply slaves particularly to the Brazilian sugar plantations. The flight of the Ngwane from the Mzinyathi inland to the Caledon was, it is argued, a response to slaving. But they ran directly into the colonial raiding-grounds north of the Orange. The (missionary-led) raid on the still unidentified ‘Mantatees’ (not a reference to MaNtatisi) at Dithakong in 1823 was one of innumerable Griqua raids for slaves to counter an acute shortage of labour among Cape settlers after the British expansionist wars of 1811–20. Similar Griqua raids forced the Ngwane south from the Caledon into the Transkei. Here, at Mbolompo in 1828, the Ngwane were attacked yet again, this time by a British army seeking ‘free’ labour after the reorganisation of the Cape's labour-procurement system in July 1828. The British claim that they were parrying a Zulu invasion is exposed as propaganda, and the connexions between the campaign and the white-instigated murder of Shaka are shown. In short, African societies did not generate the regional violence on their own. Rather, caught within the European net, they were transformed over a lengthy period in reaction to the attentions of external plunderers. The core misrepresentations of ‘the mfecane’ are thereby revealed; the term, and the concept, should be abandoned.
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Yus-Díez, Jesús, Marina Ealo, Marco Pandolfi, Noemí Perez, Gloria Titos, Griša Močnik, Xavier Querol, and Andrés Alastuey. "Aircraft vertical profiles during summertime regional and Saharan dust scenarios over the north-western Mediterranean basin: aerosol optical and physical properties." Atmospheric Chemistry and Physics 21, no. 1 (January 14, 2021): 431–55. http://dx.doi.org/10.5194/acp-21-431-2021.
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Abstract. Accurate measurements of the horizontal and vertical distribution of atmospheric aerosol particle optical properties are key for a better understanding of their impact on the climate. Here we present the results of a measurement campaign based on instrumented flights over north-eastern Spain. We measured vertical profiles of size-segregated atmospheric particulate matter (PM) mass concentrations and multi-wavelength scattering and absorption coefficients in the western Mediterranean basin (WMB). The campaign took place during typical summer conditions, characterized by the development of a vertical multi-layer structure, under both summer regional pollution episodes (REGs) and Saharan dust events (SDEs). REG patterns in the region form under high insolation and scarce precipitation in summer, favouring layering of highly aged fine-PM strata in the lower few kma.s.l. The REG scenario prevailed during the entire measurement campaign. Additionally, African dust outbreaks and plumes from northern African wildfires influenced the study area. The vertical profiles of climate-relevant intensive optical parameters such as single-scattering albedo (SSA); the asymmetry parameter (g); scattering, absorption and SSA Ångström exponents (SAE, AAE and SSAAE); and PM mass scattering and absorption cross sections (MSC and MAC) were derived from the measurements. Moreover, we compared the aircraft measurements with those performed at two GAW–ACTRIS (Global Atmosphere Watch–Aerosol, Clouds and Trace Gases) surface measurement stations located in north-eastern Spain, namely Montseny (MSY; regional background) and Montsec d'Ares (MSA; remote site). Airborne in situ measurements and ceilometer ground-based remote measurements identified aerosol air masses at altitudes up to more than 3.5 kma.s.l. The vertical profiles of the optical properties markedly changed according to the prevailing atmospheric scenarios. During SDE the SAE was low along the profiles, reaching values < 1.0 in the dust layers. Correspondingly, SSAAE was negative, and AAE reached values up to 2.0–2.5, as a consequence of the UV absorption increased by the presence of the coarse dust particles. During REG, the SAE increased to > 2.0, and the asymmetry parameter g was rather low (0.5–0.6) due to the prevalence of fine PM, which was characterized by an AAE close to 1.0, suggesting a fossil fuel combustion origin. During REG, some of the layers featured larger AAE (> 1.5), relatively low SSA at 525 nm (< 0.85) and high MSC (> 9 m2 g−1) and were associated with the influence of PM from wildfires. Overall, the SSA and MSC near the ground ranged around 0.85 and 3 m2 g−1, respectively, and increased at higher altitudes, reaching values above 0.95 and up to 9 m2 g−1. The PM, MSC and MAC were on average larger during REG compared to SDE due to the larger scattering and absorption efficiency of fine PM compared with dust. The SSA and MSC had quite similar vertical profiles and often both increased with height indicating the progressive shift toward PM with a larger scattering efficiency with altitude. This study contributes to our understanding of regional-aerosol vertical distribution and optical properties in the WMB, and the results will be useful for improving future climate projections and remote sensing or satellite retrieval algorithms.
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Chen, G., L. D. Ziemba, D. A. Chu, K. L. Thornhill, G. L. Schuster, E. L. Winstead, G. S. Diskin, et al. "Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign." Atmospheric Chemistry and Physics Discussions 10, no. 5 (May 26, 2010): 13445–93. http://dx.doi.org/10.5194/acpd-10-13445-2010.
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Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, nephelometer, and Particle Soot Absorption Photometer. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions were well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The absorption coefficient measurements exhibited a strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97±0.02. Closure analyses showed that observed scattering and absorption coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. These values are generally consistent with literature values.
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Chen, G., L. D. Ziemba, D. A. Chu, K. L. Thornhill, G. L. Schuster, E. L. Winstead, G. S. Diskin, et al. "Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign." Atmospheric Chemistry and Physics 11, no. 2 (January 26, 2011): 723–40. http://dx.doi.org/10.5194/acp-11-723-2011.
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Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in-situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, a nephelometer, and a Particle Soot Absorption Photometer. The NAAMA sampling inlet has a size cut (i.e., 50% transmission efficiency size) of approximately 4 μm in diameter for dust particles, which limits the representativeness of the NAMMA observational findings. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions can be well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The Ångström Exponent assessments exhibited strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97 ± 0.02. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. Closure analysis showed that observed scattering coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. These values are generally consistent with literature values reported from studies with similar particle sampling size range.
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Ridder, T., C. Gerbig, J. Notholt, M. Rex, O. Schrems, T. Warneke, and L. Zhang. "Ship-borne FTIR measurements of CO and O<sub>3</sub> in the Western Pacific from 43° N to 35° S: an evaluation of the sources." Atmospheric Chemistry and Physics Discussions 11, no. 8 (August 15, 2011): 22951–85. http://dx.doi.org/10.5194/acpd-11-22951-2011.
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Abstract. Carbon monoxide (CO) and ozone (O3) have been measured in the Western Pacific (43° N to 35° S) during a ship campaign with Research Vessel Sonne in fall 2009. Observations have been performed using ship-based solar absorption Fourier Transform infrared spectrometry, flask sampling, balloon sounding, and in-situ Fourier Transform infrared analysis. The obtained results are compared to the GEOS-Chem global 3-D chemistry transport model for atmospheric composition. In general, a very good agreement is found between the GEOS-Chem model and all instruments. The CO and O3 distributions show a comparable variability suggesting an impact from the same source regions. Tagged-CO simulations implemented in the GEOS-Chem model allow to differentiate between different sources and source regions. The sources are verified with HYSPLIT backward trajectory calculations. In the Northern Hemisphere fossil fuel combustion in Asia is the dominant source. European and North American fossil fuel combustion also contribute to Northern Hemispheric CO pollution. In the Southern Hemisphere contributions from biomass burning and fossil fuel combustion are dominant; African biomass burning has a significant impact on Western Pacific CO pollution. Furthermore, in the tropical Western Pacific enhanced upper tropospheric CO within the tropical tropopause layer mainly originates from Indonesian fossil fuel combustion and can be transported into the stratosphere. The sources and source regions of the measured O3 pollution are simulated with a tagged-O3 simulation implemented in the GEOS-Chem model. Similar source regions compared to the tagged-CO simulations are identified by the model. In the Northern Hemisphere contributions from Asia, Europe, and North America are significant. In the Southern Hemisphere the impact of emissions from South America, South-East Africa, and Oceania is important.
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Ridder, T., C. Gerbig, J. Notholt, M. Rex, O. Schrems, T. Warneke, and L. Zhang. "Ship-borne FTIR measurements of CO and O<sub>3</sub> in the Western Pacific from 43° N to 35° S: an evaluation of the sources." Atmospheric Chemistry and Physics 12, no. 2 (January 18, 2012): 815–28. http://dx.doi.org/10.5194/acp-12-815-2012.
Full textAbstract:
Abstract. Carbon monoxide (CO) and ozone (O3) have been measured in the Western Pacific (43° N to 35° S) during a ship campaign with Research Vessel Sonne in fall 2009. Observations have been performed using ship-based solar absorption Fourier Transform infrared spectrometry, flask sampling, balloon sounding, and in-situ Fourier Transform infrared analysis. The results obtained are compared to the GEOS-Chem global 3-D chemistry transport model for atmospheric composition. In general, a very good agreement is found between the GEOS-Chem model and all instruments. The CO and O3 distributions show a comparable variability suggesting an impact from the same source regions. Tagged-CO simulations implemented in the GEOS-Chem model make it possible to differentiate between different source processes and source regions. The source regions are verified with HYSPLIT backward trajectory calculations. In the Northern Hemisphere fossil fuel combustion in Asia is the dominant source. European and North American fossil fuel combustion also contribute to Northern Hemispheric CO pollution. In the Southern Hemisphere contributions from biomass burning and fossil fuel combustion are dominant; African biomass burning has a significant impact on Western Pacific CO pollution. Furthermore, in the tropical Western Pacific enhanced upper tropospheric CO within the tropical tropopause layer mainly originates from Indonesian fossil fuel combustion and can be transported into the stratosphere. The source regions of the measured O3 pollution are simulated with a tagged-O3 simulation implemented in the GEOS-Chem model. Similar source regions compared to the tagged-CO simulations are identified by the model. In the Northern Hemisphere contributions from Asia, Europe, and North America are significant. In the Southern Hemisphere emissions from South America, south-east Africa, and Oceania significantly contribute to the measured O3 pollution.
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Real, E., E. Orlandi, K. S. Law, F. Fierli, D. Josset, F. Cairo, H. Schlager, et al. "Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production." Atmospheric Chemistry and Physics 10, no. 6 (March 30, 2010): 3027–46. http://dx.doi.org/10.5194/acp-10-3027-2010.
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Abstract. Pollutant plumes with enhanced concentrations of trace gases and aerosols were observed over the southern coast of West Africa during August 2006 as part of the AMMA wet season field campaign. Plumes were observed both in the mid and upper troposphere. In this study we examined the origin of these pollutant plumes, and their potential to photochemically produce ozone (O3) downwind over the Atlantic Ocean. Their possible contribution to the Atlantic O3 maximum is also discussed. Runs using the BOLAM mesoscale model including biomass burning carbon monoxide (CO) tracers were used to confirm an origin from central African biomass burning fires. The plumes measured in the mid troposphere (MT) had significantly higher pollutant concentrations over West Africa compared to the upper tropospheric (UT) plume. The mesoscale model reproduces these differences and the two different pathways for the plumes at different altitudes: transport to the north-east of the fire region, moist convective uplift and transport to West Africa for the upper tropospheric plume versus north-west transport over the Gulf of Guinea for the mid-tropospheric plume. Lower concentrations in the upper troposphere are mainly due to enhanced mixing during upward transport. Model simulations suggest that MT and UT plumes are 16 and 14 days old respectively when measured over West Africa. The ratio of tracer concentrations at 600 hPa and 250 hPa was estimated for 14–15 August in the region of the observed plumes and compares well with the same ratio derived from observed carbon dioxide (CO2) enhancements in both plumes. It is estimated that, for the period 1–15 August, the ratio of Biomass Burning (BB) tracer concentration transported in the UT to the ones transported in the MT is 0.6 over West Africa and the equatorial South Atlantic. Runs using a photochemical trajectory model, CiTTyCAT, initialized with the observations, were used to estimate in-situ net photochemical O3 production rates in these plumes during transport downwind of West Africa. The mid-troposphere plume spreads over altitude between 1.5 and 6 km over the Atlantic Ocean. Even though the plume was old, it was still very photochemically active (mean net O3 production rates over 10 days of 2.6 ppbv/day and up to 7 ppbv/day during the first days) above 3 km especially during the first few days of transport westward. It is also shown that the impact of high aerosol loads in the MT plume on photolysis rates serves to delay the peak in modelled O3 concentrations. These results suggest that a significant fraction of enhanced O3 in mid-troposphere over the Atlantic comes from BB sources during the summer monsoon period. According to simulated occurrence of such transport, BB may be the main source for O3 enhancement in the equatorial south Atlantic MT, at least in August 2006. The upper tropospheric plume was also still photochemically active, although mean net O3 production rates were slower (1.3 ppbv/day). The results suggest that, whilst the transport of BB pollutants to the UT is variable (as shown by the mesoscale model simulations), pollution from biomass burning can make an important contribution to additional photochemical production of O3 in addition to other important sources such as nitrogen oxides (NOx) from lightning.
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Jung, Eunsil, Bruce A. Albrecht, Graham Feingold, Haflidi H. Jonsson, Patrick Chuang, and Shaunna L. Donaher. "Aerosols, clouds, and precipitation in the North Atlantic trades observed during the Barbados aerosol cloud experiment – Part 1: Distributions and variability." Atmospheric Chemistry and Physics 16, no. 13 (July 15, 2016): 8643–66. http://dx.doi.org/10.5194/acp-16-8643-2016.
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Abstract. Shallow marine cumulus clouds are by far the most frequently observed cloud type over the Earth's oceans; but they are poorly understood and have not been investigated as extensively as stratocumulus clouds. This study describes and discusses the properties and variations of aerosol, cloud, and precipitation associated with shallow marine cumulus clouds observed in the North Atlantic trades during a field campaign (Barbados Aerosol Cloud Experiment- BACEX, March–April 2010), which took place off Barbados where African dust periodically affects the region. The principal observing platform was the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter (TO) research aircraft, which was equipped with standard meteorological instruments, a zenith pointing cloud radar and probes that measured aerosol, cloud, and precipitation characteristics.The temporal variation and vertical distribution of aerosols observed from the 15 flights, which included the most intense African dust event during all of 2010 in Barbados, showed a wide range of aerosol conditions. During dusty periods, aerosol concentrations increased substantially in the size range between 0.5 and 10 µm (diameter), particles that are large enough to be effective giant cloud condensation nuclei (CCN). The 10-day back trajectories showed three distinct air masses with distinct vertical structures associated with air masses originating in the Atlantic (typical maritime air mass with relatively low aerosol concentrations in the marine boundary layer), Africa (Saharan air layer), and mid-latitudes (continental pollution plumes). Despite the large differences in the total mass loading and the origin of the aerosols, the overall shapes of the aerosol particle size distributions were consistent, with the exception of the transition period.The TO was able to sample many clouds at various phases of growth. Maximum cloud depth observed was less than ∼ 3 km, while most clouds were less than 1 km deep. Clouds tend to precipitate when the cloud is thicker than 500–600 m. Distributions of cloud field characteristics (depth, radar reflectivity, Doppler velocity, precipitation) were well identified in the reflectivity–velocity diagram from the cloud radar observations. Two types of precipitation features were observed for shallow marine cumulus clouds that may impact boundary layer differently: first, a classic cloud-base precipitation where precipitation shafts were observed to emanate from the cloud base; second, cloud-top precipitation where precipitation shafts emanated mainly near the cloud tops, sometimes accompanied by precipitation near the cloud base. The second type of precipitation was more frequently observed during the experiment. Only 42–44 % of the clouds sampled were non-precipitating throughout the entire cloud layer and the rest of the clouds showed precipitation somewhere in the cloud, predominantly closer to the cloud top.
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Mari, C. H., G. Cailley, L. Corre, M. Saunois, J. L. Attié, V. Thouret, and A. Stohl. "Tracing biomass burning plumes from the Southern Hemisphere during the AMMA 2006 wet season experiment." Atmospheric Chemistry and Physics 8, no. 14 (July 24, 2008): 3951–61. http://dx.doi.org/10.5194/acp-8-3951-2008.
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Abstract. The Lagrangian particle dispersion model FLEXPART coupled with daily active fire products provided by the MODIS instrument was used to forecast the intrusions of the southern hemispheric fire plumes in the Northern Hemisphere during the AMMA (African Monsoon Multidisciplinary Analysis) fourth airborne campaign from 25 July to 31 August 2006 (Special Operation Period SOP2_a2). The imprint of the biomass burning plumes over the Gulf of Guinea showed a well marked intraseasonal variability which is controlled by the position and strength of the southern hemispheric African Easterly Jet (AEJ-S). Three different periods were identified which correspond to active and break phases of the AEJ-S: 25 July–2 August (active phase), 3 August–8 August (break phase) and 9 August–31 August (active phase). During the AEJ-S active phases, the advection of the biomass burning plumes out over the Atlantic ocean was efficient in the mid-troposphere. During the AEJ-S break phases, pollutants emitted by fires were trapped over the continent where they accumulated. The continental circulation increased the possibility for the biomass burning plumes to reach the convective regions located further north. As a consequence, biomass burning plumes were found in the upper troposphere over the Gulf of Guinea during the AEJ-S break phase. Observational evidences from the ozonesounding network at Cotonou and the carbon monoxide measured by MOPITT confirmed the alternation of the AEJ-S phases with low ozone and CO in the mid-troposphere over the Gulf of Guinea during the break phase.
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Desboeufs, K., E. Journet, J. L. Rajot, S. Chevaillier, S. Triquet, P. Formenti, and A. Zakou. "Chemical properties of rain events during the AMMA campaign: an evidence of dust and biogenic influence in the convective systems." Atmospheric Chemistry and Physics Discussions 10, no. 6 (June 21, 2010): 15263–93. http://dx.doi.org/10.5194/acpd-10-15263-2010.
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Abstract. This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June–July 2006) of the African Monsoon Multidisciplinary Analyses (AMMA) experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-Eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3−), sulphate (SO42−) and chloride (Cl−). However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate) associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.
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Hepach, H., B. Quack, F. Ziska, S. Fuhlbrügge, E. L. Atlas, I. Peeken, K. Krüger, and D. W. R. Wallace. "Drivers of diel and regional variations of halocarbon emissions from the tropical North East Atlantic." Atmospheric Chemistry and Physics Discussions 13, no. 7 (July 25, 2013): 19701–50. http://dx.doi.org/10.5194/acpd-13-19701-2013.
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Abstract. Methyl iodide (CH3I}, bromoform (CHBr3) and dibromomethane (CH2Br2), which are produced naturally in the oceans, take part in ozone chemistry both in the troposphere and the stratosphere. The significance of oceanic upwelling regions for emissions of these trace gases in the global context is still uncertain although they have been identified as important source regions. To better quantify the role of upwelling areas in current and future climate, this paper analyzes major factors that influenced halocarbon emissions from the tropical North East Atlantic including the Mauritanian upwelling during the DRIVE expedition. Diel and regional variability of oceanic and atmospheric CH3I, CHBr3 and CH2Br2 was determined along with biological and meteorological parameters at six 24 h-stations. Low oceanic concentrations of CH3I from 0.1–5.4 pmol L-1 were equally distributed throughout the investigation area. CHBr3 of 1.0–42.4 pmol L-1 and CH2Br2 of 1.0–9.4 pmol L-1 were measured with maximum concentrations close to the Mauritanian coast. Atmospheric mixing rations of CH3I of up to 3.3, CHBr3 to 8.9 and CH2Br2 to 3.1 ppt above the upwelling and 1.8, 12.8, respectively 2.2 ppt at a Cape Verdean coast were detected during the campaign. While diel variability in CH3I emissions could be mainly ascribed to oceanic non-biological production, no main driver was identified for its emissions in the entire study region. In contrast, oceanic bromocarbons resulted from biogenic sources which were identified as regional drivers of their sea-to-air fluxes. The diel impact of wind speed on bromocarbon emissions increased with decreasing distance to the coast. The height of the marine atmospheric boundary layer (MABL) was determined as an additional factor influencing halocarbon emissions. Oceanic and atmospheric halocarbons correlated well in the study region and in combination with high oceanic CH3I, CHBr3 and CH2Br2 concentrations, local hot spots of atmospheric halocarbons could solely be explained by marine sources. This conclusion is in contrast with previous studies that hypothesized the occurrence of elevated atmospheric halocarbons over the eastern tropical Atlantic mainly originating from the West-African continent.
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Immler, F., and O. Schrems. "Vertical profiles, optical and microphysical properties of Saharan dust layers determined by a ship-borne lidar." Atmospheric Chemistry and Physics Discussions 3, no. 3 (May 21, 2003): 2707–37. http://dx.doi.org/10.5194/acpd-3-2707-2003.
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Abstract. A unique data set of ship-borne lidar measurements of Saharan dust layers above the Atlantic ocean has been collected aboard the research vessel Polarstern with a mobile Aerosol Raman Lidar (MARL) during the LIMPIDO-campaign in June 2000. Extended Saharan dust layers have been observed in the region between 8.5° N and 34° N in an altitude range between 2 and 6 km. The continental, North African origin of the probed air masses is confirmed by 8-day backward trajectories. The Saharan dust is characterized by an optical depth in the range of 0.1 and 0.3, a depolarization around 10\\% and high lidar ratios of 45 sr at 532 nm and 75 sr at 355 nm. The backscattering by the dust particles at the UV-wavelength is relatively weak, resulting in a negative color index. From the measured optical properties the effective radius and the refractive index of the dust particles are derived using a new approach based on Mie Theory and non-spherical scattering calculations. The low backscatter coefficient observed at 355 nm is due to significant absorption which increases with decreasing wavelength. This finding agrees very well with results from satellite and sun photometer measurements. The effective radii decrease from about 3 mm base to 0.6 mm at the top of the dust plumes. The non-spherical shapes of the dust particles are responsible for the high values of the lidar ratios.
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Immler, F., and O. Schrems. "Vertical profiles, optical and microphysical properties of Saharan dust layers determined by a ship-borne lidar." Atmospheric Chemistry and Physics 3, no. 5 (September 15, 2003): 1353–64. http://dx.doi.org/10.5194/acp-3-1353-2003.
Full textAbstract:
Abstract. A unique data set of ship-borne lidar measurements of Saharan dust layers above the Atlantic ocean has been collected aboard the research vessel Polarstern with a mobile Aerosol Raman Lidar (MARL) during the LIMPIDO-campaign in June 2000. Extended Saharan dust layers have been observed in the region between 8.5º N and 34º N in an altitude range between 2 and 6 km. The continental, North African origin of the probed air masses is confirmed by 8-day backward trajectories. The Saharan dust is characterized by an optical depth in the range of 0.1 and 0.3, a depolarization around 10% and high lidar ratios of 45 sr at 532 nm and 75 sr at 355 nm. The backscattering by the dust particles at the UV-wavelength is relatively weak, resulting in a negative color index. From the measured optical properties the effective radius and the refractive index of the dust particles are derived using a new approach based on Mie Theory and non-spherical scattering calculations. The low backscatter coefficient observed at 355 nm is due to significant absorption which increases with decreasing wavelength. This finding agrees very well with results from satellite and sun photometer measurements. The effective radii decrease from about 3 mm at the base to 0.6 mm at the top of the dust plumes. The non-spherical shapes of the dust particles are responsible for the high values of the lidar ratios.
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Mari, C. H., G. Cailley, L. Corre, M. Saunois, J. L. Attié, V. Thouret, and A. Stohl. "Tracing biomass burning plumes from the Southern Hemisphere during the AMMA 2006 wet season experiment." Atmospheric Chemistry and Physics Discussions 7, no. 6 (November 28, 2007): 17339–66. http://dx.doi.org/10.5194/acpd-7-17339-2007.
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Abstract. The Lagrangian particle dispersion model FLEXPART coupled with daily active fire products provided by the MODIS instrument was used to forecast the intrusions of the southern hemispheric fire plumes in the Northern Hemisphere during the AMMA fourth airborne campaign from 25 July to 31 August 2006 (Special Operation Period SOP2_a2). The imprint of the biomass burning plumes over the Gulf of Guinea showed a well marked intraseasonal variability which is controlled by the position and strength of the southern hemispheric African Easterly Jet (AEJ-S). Three different periods were identified which correspond to active and break phases of the AEJ-S: 25 July–2 August (active phase), 3 August–8 August (break phase) and 9 August–31 August (active phase). During the AEJ-S active phases, the advection of the biomass burning plumes out over the Atlantic ocean was efficient in the mid-troposphere. During the AEJ-S break phases, pollutants emitted by fires were trapped over the continent where they accumulated. The continental circulation increased the possibility for the biomass burning plumes to reach the convective regions located further north. As a consequence, biomass burning plumes were found in the upper troposphere over the Gulf of Guinea during the AEJ-S break phase. Observational evidences from the ozonesounding network at Cotonou and the carbon monoxide measured by MOPITT confirmed the alternation of the AEJ-S phases with low ozone and CO in the mid-troposphere over the Gulf of Guinea during the break phase.