To see the other types of publications on this topic, follow the link: Ozone calibration.
Journal articles on the topic 'Ozone calibration'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Ozone calibration.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Birks, John W., Andrew A. Turnipseed, Peter C. Andersen, et al. "Portable calibrator for NO based on the photolysis of N<sub>2</sub>O and a combined NO<sub>2</sub>∕NO∕O<sub>3</sub> source for field calibrations of air pollution monitors." Atmospheric Measurement Techniques 13, no. 2 (2020): 1001–18. http://dx.doi.org/10.5194/amt-13-1001-2020.
Full textAbstract:
Abstract. A highly portable calibration source of nitric oxide (NO) based on the photolysis of nitrous oxide (N2O) supplied by 8 or 16 g disposable cartridges is demonstrated to serve as an accurate and reliable transfer standard for the calibration of NO monitors in the field. The instrument provides output mixing ratios in the range 0–1000 ppb with a precision and accuracy better than the greater of 3 ppb or 3 % of the target NO mixing ratio over a wide range of environmental conditions of ambient temperature (8.5–35.0 ∘C), pressure (745–1015 mbar corresponding to 2.7–0.0 km of elevation), and relative humidity (0 %–100 % RH). The combination of the NO calibration source with a previously described ozone calibration source based on the photolysis of oxygen in air provides a new instrument capable of outputting calibrated mixing ratios of NO, ozone (O3), and nitrogen dioxide (NO2), where the NO2 is produced by the stoichiometric gas-phase reaction of NO with O3. The portable NO2/NO/O3 calibration source requires no external gas cylinders and can be used for calibrations of NO, NO2, and O3 instruments for mixing ratios up to 1000, 500, and 1000 ppb, respectively. This portable calibrator may serve as a convenient transfer standard for field calibrations of ozone and NOx air pollution monitors.
2
Redondas, Alberto, Saulius Nevas, Alberto Berjón, et al. "Wavelength calibration of Brewer spectrophotometer using a tunable pulsed laser and implications to the Brewer ozone retrieval." Atmospheric Measurement Techniques 11, no. 6 (2018): 3759–68. http://dx.doi.org/10.5194/amt-11-3759-2018.
Full textAbstract:
Abstract. In this contribution we present the wavelength calibration of the travelling reference Brewer spectrometer of the Regional Brewer Calibration Center for Europe (RBCC-E) at PTB in Braunschweig, Germany. The wavelength calibration is needed for the calculation of the ozone absorption coefficients used by the Brewer ozone algorithm. In order to validate the standard procedure for determining Brewer's wavelength scale, a calibration has been performed by using a tunable laser source at PTB in the framework of the EMRP project ENV59 ATMOZ “Traceability for the total column ozone”. Here we compare these results to those of the standard procedure for the wavelength calibration of the Brewer instrument. Such a comparison allows validating the standard methodology used for measuring the ozone absorption coefficient with respect to several assumptions. The results of the laser-based calibrations reproduces those obtained by the standard operational methodology and shows that there is an underestimation of 0.8 % of the ozone absorption coefficients due to the use of the parametrized slit functions.
3
Dobber, M. R., R. J. Dirksen, P. F. Levelt, et al. "Ozone monitoring instrument calibration." IEEE Transactions on Geoscience and Remote Sensing 44, no. 5 (2006): 1209–38. http://dx.doi.org/10.1109/tgrs.2006.869987.
Full text
4
Bluvshtein, Nir, J. Michel Flores, Quanfu He, et al. "Calibration of a multi-pass photoacoustic spectrometer cell using light-absorbing aerosols." Atmospheric Measurement Techniques 10, no. 3 (2017): 1203–13. http://dx.doi.org/10.5194/amt-10-1203-2017.
Full textAbstract:
Abstract. The multi-pass photoacoustic spectrometer (PAS) is an important tool for the direct measurement of light absorption by atmospheric aerosol. Accurate PAS measurements heavily rely on accurate calibration of their signal. Ozone is often used for calibrating PAS instruments by relating the photoacoustic signal to the absorption coefficient measured by an independent method such as cavity ring down spectroscopy (CRD-S), cavity-enhanced spectroscopy (CES) or an ozone monitor. We report here a calibration method that uses measured absorption coefficients of aerosolized, light-absorbing organic materials and offer an alternative approach to calibrate photoacoustic aerosol spectrometers at 404 nm. To implement this method, we first determined the complex refractive index of nigrosin, an organic dye, using spectroscopic ellipsometry and then used this well-characterized material as a standard material for PAS calibration.
5
Mauersberger, K., D. Hanson, and J. Morton. "Precision ozone calibration system based on vapor pressures of ozone." Review of Scientific Instruments 58, no. 6 (1987): 1063–66. http://dx.doi.org/10.1063/1.1139608.
Full text
6
Barcelo-Ordinas, Jose M., Pau Ferrer-Cid, Jorge Garcia-Vidal, Anna Ripoll, and Mar Viana. "Distributed Multi-Scale Calibration of Low-Cost Ozone Sensors in Wireless Sensor Networks." Sensors 19, no. 11 (2019): 2503. http://dx.doi.org/10.3390/s19112503.
Full textAbstract:
New advances in sensor technologies and communications in wireless sensor networks have favored the introduction of low-cost sensors for monitoring air quality applications. In this article, we present the results of the European project H2020 CAPTOR, where three testbeds with sensors were deployed to capture tropospheric ozone concentrations. One of the biggest challenges was the calibration of the sensors, as the manufacturer provides them without calibrating. Throughout the paper, we show how short-term calibration using multiple linear regression produces good calibrated data, but instead produces biases in the calculated long-term concentrations. To mitigate the bias, we propose a linear correction based on Kriging estimation of the mean and standard deviation of the long-term ozone concentrations, thus correcting the bias presented by the sensors.
7
Dandocsi, Alexandru, Anca Nemuc, Doina Nicolae, Livio Belegante, Alexander Cede, and Martin Tiefengraber. "Aerosol Field Influence on the Retrieval of the Ozone Vertical Column Densities from Pandora 2S Measurements." EPJ Web of Conferences 237 (2020): 03002. http://dx.doi.org/10.1051/epjconf/202023703002.
Full textAbstract:
Total ozone and other trace gases are measured and reported regularly due to the increased interest started with the ozone hole discovery but the new satellites dedicated to worldwide observations of these species need both short-and long-term well calibrated ground based observation for validation procedures. The ESA/NASA Pandora network established a sophisticated, automatic calibration procedure that utilizes a variety of narrow-line and broadband emission lamps with temperature control for their UV-Vis-NIR spectroradiometers. In this study, we describe additional calibration efforts for ozone retrievals. In this paper we explore the local aerosol field influence on the retrieval of the ozone spectra from PANDORA 2S measurements using collocated lidar and sunphotometer measurements and proposed a methodology to be implemented in the calibration procedure of the instruments.
8
DeLand, M. T., S. L. Taylor, L. K. Huang, and B. L. Fisher. "Calibration of the SBUV version 8.6 ozone data product." Atmospheric Measurement Techniques 5, no. 11 (2012): 2951–67. http://dx.doi.org/10.5194/amt-5-2951-2012.
Full textAbstract:
Abstract. This paper describes the calibration process for the Solar Backscatter Ultraviolet (SBUV) Version 8.6 (V8.6) ozone data product. Eight SBUV instruments have flown on NASA and NOAA satellites since 1970, and a continuous data record is available since November 1978. The accuracy of ozone trends determined from these data depends on the calibration and long-term characterization of each instrument. V8.6 calibration adjustments are determined at the radiance level, and do not rely on comparison of retrieved ozone products with other instruments. The primary SBUV instrument characterization is based on prelaunch laboratory tests and dedicated on-orbit calibration measurements. We supplement these results with "soft" calibration techniques using carefully chosen subsets of radiance data and information from the retrieval algorithm output to validate each instrument's calibration. The estimated long-term uncertainty in albedo is approximately ±0.8–1.2% (1σ) for most of the instruments. The overlap between these instruments and the Shuttle SBUV (SSBUV) data allows us to intercalibrate the SBUV instruments to produce a coherent V8.6 data set covering more than 32 yr. The estimated long-term uncertainty in albedo is less than 3% over this period.
9
DeLand, M. T., S. L. Taylor, L. K. Huang, and B. L. Fisher. "Calibration of the SBUV version 8.6 ozone data product." Atmospheric Measurement Techniques Discussions 5, no. 4 (2012): 5151–203. http://dx.doi.org/10.5194/amtd-5-5151-2012.
Full textAbstract:
Abstract. This paper describes the calibration process for the Solar Backscatter Ultraviolet (SBUV) Version 8.6 (V8.6) ozone data product. Eight SBUV instruments have flown on NASA and NOAA satellites since 1970, and a continuous data record is available since November 1978. The accuracy of ozone trends determined from these data depends on the calibration and long-term characterization of each instrument. V8.6 calibration adjustments are determined at the radiance level, and do not rely on comparison of retrieved ozone products with other instruments. The primary SBUV instrument characterization is based on prelaunch laboratory tests and dedicated on-orbit calibration measurements. We supplement these results with "soft" calibration techniques using carefully chosen subsets of radiance data and information from the retrieval algorithm output to validate each instrument's calibration. The estimated long-term uncertainty in albedo is approximately ±0.8–1.2% (1σ) for most of the instruments. The overlap between these instruments and the Shuttle SBUV (SSBUV) data allows us to intercalibrate the SBUV instruments to produce a coherent V8.6 data set covering more than 32 yr. The estimated long-term uncertainty in albedo is less than 3% over this period.
10
Davies, Nicholas W., Michael I. Cotterell, Cathryn Fox, Kate Szpek, Jim M. Haywood, and Justin M. Langridge. "On the accuracy of aerosol photoacoustic spectrometer calibrations using absorption by ozone." Atmospheric Measurement Techniques 11, no. 4 (2018): 2313–24. http://dx.doi.org/10.5194/amt-11-2313-2018.
Full textAbstract:
Abstract. In recent years, photoacoustic spectroscopy has emerged as an invaluable tool for the accurate measurement of light absorption by atmospheric aerosol. Photoacoustic instruments require calibration, which can be achieved by measuring the photoacoustic signal generated by known quantities of gaseous ozone. Recent work has questioned the validity of this approach at short visible wavelengths (404 nm), indicating systematic calibration errors of the order of a factor of 2. We revisit this result and test the validity of the ozone calibration method using a suite of multipass photoacoustic cells operating at wavelengths 405, 514 and 658 nm. Using aerosolised nigrosin with mobility-selected diameters in the range 250–425 nm, we demonstrate excellent agreement between measured and modelled ensemble absorption cross sections at all wavelengths, thus demonstrating the validity of the ozone-based calibration method for aerosol photoacoustic spectroscopy at visible wavelengths.
11
Birks, John W., Craig J. Williford, Peter C. Andersen, Andrew A. Turnipseed, Stanley Strunk, and Christine A. Ennis. "Portable ozone calibration source independent of changes in temperature, pressure and humidity for research and regulatory applications." Atmospheric Measurement Techniques 11, no. 8 (2018): 4797–807. http://dx.doi.org/10.5194/amt-11-4797-2018.
Full textAbstract:
Abstract. A highly portable ozone (O3) calibration source that can serve as a U.S. EPA level 4 transfer standard for the calibration of ozone analyzers is described and evaluated with respect to analytical figures of merit and effects of ambient pressure and humidity. Reproducible mixing ratios of ozone are produced by the photolysis of oxygen in O3-scrubbed ambient air by UV light at 184.9 nm light from a low-pressure mercury lamp. By maintaining a constant volumetric flow rate (thus constant residence time within the photolysis chamber), the mixing ratio produced is independent of both pressure and temperature and can be varied by varying the lamp intensity. Pulse width modulation of the lamp with feedback from a photodiode monitoring the 253.7 nm emission line is used to maintain target ozone mixing ratios in the range 30–1000 ppb. In order to provide a constant ratio of intensities at 253.7 and 184.9 nm, the photolysis chamber containing the lamp is regulated at a temperature of 40 ∘C. The resulting O3 calibrator has a response time for step changes in output ozone mixing ratio of < 30 s and precision (σp) of 0.4 % of the output mixing ratio for 10 s measurements (e.g., σp=±0.4 ppb for 100 ppb of O3). Ambient humidity was found to affect the output mixing ratio of ozone primarily by dilution of the oxygen precursor. This potential humidity interference could be up to a few percent in extreme cases but is effectively removed by varying the lamp intensity to compensate for the reduced oxygen concentration based on feedback from a humidity sensor.
12
Ziemke, J. R., S. Chandra, L. D. Oman, and P. K. Bhartia. "A new ENSO index derived from satellite measurements of column ozone." Atmospheric Chemistry and Physics 10, no. 8 (2010): 3711–21. http://dx.doi.org/10.5194/acp-10-3711-2010.
Full textAbstract:
Abstract. Column Ozone measured in tropical latitudes from Nimbus 7 total ozone mapping spectrometer (TOMS), Earth Probe TOMS, solar backscatter ultraviolet (SBUV), and Aura ozone monitoring instrument (OMI) are used to derive an El Nino-Southern Oscillation (ENSO) index. This index, which covers a time period from 1979 to the present, is defined as the "Ozone ENSO Index" (OEI) and is the first developed from atmospheric trace gas measurements. The OEI is constructed by first averaging monthly mean column ozone over two broad regions in the western and eastern Pacific and then taking their difference. This differencing yields a self-calibrating ENSO index which is independent of individual instrument calibration offsets and drifts in measurements over the long record. The combined Aura OMI and MLS ozone data confirm that zonal variability in total column ozone in the tropics caused by ENSO events lies almost entirely in the troposphere. As a result, the OEI can be derived directly from total column ozone instead of tropospheric column ozone. For clear-sky ozone measurements a +1 K change in Nino 3.4 index corresponds to +2.9 Dobson Unit (DU) change in the OEI, while a +1 hPa change in SOI coincides with a −1.7 DU change in the OEI. For ozone measurements under all cloud conditions these numbers are +2.4 DU and −1.4 DU, respectively. As an ENSO index based upon ozone, it is potentially useful in evaluating climate models predicting long term changes in ozone and other trace gases.
13
Schmidlin, Francis J., and Bruno A. Hoegger. "An automated method for preparing and calibrating electrochemical concentration cell (ECC) ozonesondes." Atmospheric Measurement Techniques 13, no. 3 (2020): 1157–66. http://dx.doi.org/10.5194/amt-13-1157-2020.
Full textAbstract:
Abstract. In contrast to the legacy manual method used to prepare, condition, and calibrate the electrochemical concentration cell (ECC) ozonesonde, an automated digital calibration bench similar to one developed by MeteoSwiss at Payerne, Switzerland, was established at NASA's Wallops Flight Facility and provides reference measurements of the same ozone partial pressure as measured by the ECC. The purpose of an automated system is to condition and calibrate ECCs before launching on a balloon. Operation of the digital calibration bench is simple and real-time graphs and summaries are available to the operator; all information is archived. The parameters of interest include ozone partial pressure, airflow, temperature, background current, response, and time (real and elapsed). ECCs, prepared with 1.0 % solution of potassium iodide (KI) and full buffer, show increasing partial pressure values when compared to the reference as partial pressures increase. Differences of approximately 5–6 % are noted at 20.0 mPa. Additional tests with different concentrations revealed the Science Pump Corp. (SPC) 6A ECC with 0.5 % KI solution and one-half buffer agreed closer to the reference than the 1.0 % cells. The information gained from the automated system allows a compilation of ECC characteristics, as well as calibrations. The digital calibration bench is recommended for ECC studies as it conserves resources.
14
Bak, Juseon, Xiong Liu, Jae-Hwan Kim, et al. "Characterization and correction of OMPS nadir mapper measurements for ozone profile retrievals." Atmospheric Measurement Techniques 10, no. 11 (2017): 4373–88. http://dx.doi.org/10.5194/amt-10-4373-2017.
Full textAbstract:
Abstract. This paper verifies and corrects the Ozone Mapping and Profiler Suite (OMPS) nadir mapper (NM) level 1B v2.0 measurements with the aim of producing accurate ozone profile retrievals using an optimal-estimation-based inversion method to fit measurements in the spectral range 302.5–340 nm. The evaluation of available slit functions demonstrates that preflight-measured slit functions represent OMPS measurements well compared to derived Gaussian slit functions. Our initial OMPS fitting residuals contain significant wavelength and cross-track-dependent biases, resulting in serious cross-track striping errors in the tropospheric ozone retrievals. To eliminate the systematic component of the fitting residuals, we apply soft calibration to OMPS radiances. With the soft calibration the amplitude of fitting residuals decreases from ∼ 1 to 0.2 % over low and middle latitudes, and thereby the consistency of tropospheric ozone retrievals between OMPS and the Ozone Monitoring Instrument (OMI) is substantially improved. A common mode correction is also implemented for additional radiometric calibration; it improves retrievals especially at high latitudes where the amplitude of fitting residuals decreases by a factor of ∼ 2. We estimate the noise floor error of OMPS measurements from standard deviations of the fitting residuals. The derived error in the Huggins band ( ∼ 0.1 %) is twice the OMPS L1B measurement error. OMPS noise floor errors constrain our retrievals better, leading to improving information content of ozone and reducing fitting residuals. The final precision of the fitting residuals is less than 0.1 % in the low and middle latitudes, with ∼ 1 degrees of freedom for signal for the tropospheric ozone, meeting the general requirements for successful tropospheric ozone retrievals.
15
Mandel, P., D. Wolbert, P. Roche, H. H. Pham, and P. Bréant. "A modelling procedure for on-site ozonation steps in potable water treatment." Water Supply 9, no. 4 (2009): 459–67. http://dx.doi.org/10.2166/ws.2009.581.
Full textAbstract:
This article presents a calibration procedure for a model describing the role of NOM during ozonation. Calibration has been conceived as practical tool for engineering purpose. Using a single-phase batch protocol, two waters were investigated following experimental plans comprising 32 and 14 experiments. Results of the simulations show that the calibration procedure enables the model, for both waters, to predict well changes in ozone dose, temperature and pH, even when a radical scavenger, tert-butanol, is added. More than 70% of the experiments could thus be modelled satisfactorily (predictions statistically classified as “good” or “very good”), having used only 26% of the experiments in calibrating the model. Results obtained for experiments performed at low NOM concentration are more contrasted, however the model is able to account for most changes in sub listed experimental parameters.
16
Vaziri Zanjani, Zahra, Omid Moeini, Tom McElroy, David Barton, and Vladimir Savastiouk. "A calibration procedure which accounts for non-linearity in single-monochromator Brewer ozone spectrophotometer measurements." Atmospheric Measurement Techniques 12, no. 1 (2019): 271–79. http://dx.doi.org/10.5194/amt-12-271-2019.
Full textAbstract:
Abstract. It is now known that single-monochromator Brewer spectrophotometer ozone and sulfur dioxide measurements suffer from non-linearity at large ozone slant column amounts due to the presence of instrumental stray light caused by scattering within the optics of the instrument. Because of the large gradient in the ozone absorption spectrum in the near-ultraviolet, the atmospheric spectra measured by the instrument possess a very large gradient in intensity in the 300 to 325 nm wavelength region. This results in a significant sensitivity to stray light when there is more than 1000 Dobson units (DU) of ozone in the light path. As the light path (air mass) through ozone increases, the stray-light effect on the measurements also increases. The measurements can be of the order of 10 %, low for an ozone column of 600 DU and an air mass factor of 3 (1800 DU slant column amount), which is an example of conditions that produce large slant column amounts. Primary calibrations for the Brewer instrument are carried out at Mauna Loa Observatory in Hawaii and Izana Observatory in Tenerife. They are done using the Langley plot method to extrapolate a set of measurements made under a constant ozone vertical column to an extraterrestrial calibration constant. Since the effects of a small non-linearity at moderate ozone paths may still be important, a better calibration procedure should account for the non-linearity of the instrument response. Studies involving the scanning of a laser source have been used to characterize the stray-light response of the Brewer (Fioletov et al., 2000), but until recently these data have not been used to elucidate the relationship between the stray-light response and the ozone measurement non-linearity. In a study done by Karppinen et al. (2015), a method for correcting stray light has been presented that uses an additive correction, which is determined via instrument slit characterization and a radiative transfer model simulation and is then applied to the single Brewer data (Karppinen et al., 2015). The European Brewer Network is also applying stray-light corrections, which includes an iterative process that results in correcting the single Brewer data to agree with double Brewer data (Rimmer et al., 2018; Redondas et al., 2018). The first model requires measurements of the slit function and the latter method relies on a calibrated instrument, such as a double Brewer, to characterize the instrument and to determine a correction for stray light. This paper presents a simple and practical method to correct for the effects of stray light, which includes a mathematical model of the instrument response and a non-linear retrieval approach that calculates the best values for the model parameters. The model can then be used in reverse to provide more accurate ozone values up to a defined maximum ozone slant path. The parameterization used was validated using an instrument physical model simulation. This model can be applied independently to any Brewer instrument and correct for the effects of stray light.
17
Marno, Daniel, Cheryl Ernest, Korbinian Hens, et al. "Calibration of an airborne HO<sub><i>x</i></sub> instrument using the All Pressure Altitude-based Calibrator for HO<sub><i>x</i></sub> Experimentation (APACHE)." Atmospheric Measurement Techniques 13, no. 5 (2020): 2711–31. http://dx.doi.org/10.5194/amt-13-2711-2020.
Full textAbstract:
Abstract. Laser-induced fluorescence (LIF) is a widely used technique for both laboratory-based and ambient atmospheric chemistry measurements. However, LIF instruments require calibrations in order to translate instrument response into concentrations of chemical species. Calibration of LIF instruments measuring OH and HO2 (HOx) typically involves the photolysis of water vapor by 184.9 nm light, thereby producing quantitative amounts of OH and HO2. For ground-based HOx instruments, this method of calibration is done at one pressure (typically ambient pressure) at the instrument inlet. However, airborne HOx instruments can experience varying cell pressures, internal residence times, temperatures, and humidity during flight. Therefore, replication of such variances when calibrating in the lab is essential to acquire the appropriate sensitivities. This requirement resulted in the development of the APACHE (All Pressure Altitude-based Calibrator for HOx Experimentation) chamber to characterize the sensitivity of the airborne LIF-FAGE (fluorescence assay by gas expansion) HOx instrument, HORUS, which took part in an intensive airborne campaign, OMO-Asia 2015. It utilizes photolysis of water vapor but has the additional ability to alter the pressure at the nozzle of the HORUS instrument. With APACHE, the HORUS instrument sensitivity towards OH (26.1–7.8 cts s−1 pptv−1 mW−1, ±22.6 % 1σ; cts stands for counts by the detector) and HO2 (21.2–8.1 cts s−1 pptv−1 mW−1, ±22.1 % 1σ) was characterized to the external pressure range at the instrument nozzle of 227–900 mbar. Measurements supported by a computational fluid dynamics model, COMSOL Multiphysics, revealed that, for all pressures explored in this study, APACHE is capable of initializing a homogenous flow and maintaining near-uniform flow speeds across the internal cross section of the chamber. This reduces the uncertainty regarding average exposure times across the mercury (Hg) UV ring lamp. Two different actinometrical approaches characterized the APACHE UV ring lamp flux as 6.37×1014(±1.3×1014) photons cm−2 s−1. One approach used the HORUS instrument as a transfer standard in conjunction with a calibrated on-ground calibration system traceable to NIST standards, which characterized the UV ring lamp flux to be 6.9(±1.1)×1014 photons cm−2 s−1. The second approach involved measuring ozone production by the UV ring lamp using an ANSYCO O3 41 M ozone monitor, which characterized the UV ring lamp flux to be 6.11(±0.8)×1014 photons cm−2 s−1. Data presented in this study are the first direct calibrations of an airborne HOx instrument, performed in a controlled environment in the lab using APACHE.
18
Foster, Katie, Rudra Pokhrel, Matthew Burkhart, and Shane Murphy. "A novel approach to calibrating a photoacoustic absorption spectrometer using polydisperse absorbing aerosol." Atmospheric Measurement Techniques 12, no. 6 (2019): 3351–63. http://dx.doi.org/10.5194/amt-12-3351-2019.
Full textAbstract:
Abstract. A new technique for calibrating photoacoustic aerosol absorption spectrometers with multiple laser passes in the acoustic cavity (multi-pass PAS) has been developed utilizing polydisperse and highly absorbing aerosol. This is the first calibration technique for multi-pass PAS instruments that utilizes particles instead of reactive gases and does not require knowledge of the exact size or refractive index of the absorbing aerosol. In this new method, highly absorbing materials are aerosolized into a polydisperse distribution and measured simultaneously with a multi-pass PAS and a cavity-attenuated phase shift particulate matter single-scattering albedo (CAPS PMSSA, Aerodyne Inc.) instrument. The CAPS PMSSA measures the bulk absorption coefficient through the subtraction of the scattering coefficient from the extinction coefficient. While this approach can have significant errors in ambient aerosol, the accuracy and precision of the CAPS PMSSA are high when the measured aerosol has a low single-scattering albedo (SSA) and particles are less than 300 nm in size, in which case truncation errors are small. To confirm the precision and accuracy of the new calibration approach, a range of aerosol concentrations were sent to the multi-pass PAS and CAPS PMSSA instruments using three different absorbing substances: Aquadag, Regal Black, and Nigrosin. Six repetitions with each of the three substances produced stable calibrations, with the standard deviation of the calibration slopes being less than 2 % at 660 nm and less than 5 % at 405 nm for a given calibration substance. Calibrations were also consistent across the different calibration substances (standard deviation of 2 % at 660 nm and 10 % at 405 nm) except for Nigrosin at 405 nm. The accuracy of the calibration approach is dependent on the SSA of the calibration substance but is roughly 6 % for the calibration substances used here, which all have an SSA near 0.4 at 405 nm. This calibration technique is easily deployed in the field as it involves no toxic or reactive gases and it does not require generation of a monodisperse aerosol. Advantages to this particle-based calibration technique versus techniques based on ozone or nitrogen dioxide absorption include no reactive losses or impact from carrier gases and the broad absorption characteristics of the particles, which eliminate potentially significant errors in calibration that come with small errors in the peak wavelength of the laser light when utilizing gas-phase standards.
19
McPeters, Richard, Stacey Frith, Natalya Kramarova, Jerry Ziemke, and Gordon Labow. "Trend quality ozone from NPP OMPS: the version 2 processing." Atmospheric Measurement Techniques 12, no. 2 (2019): 977–85. http://dx.doi.org/10.5194/amt-12-977-2019.
Full textAbstract:
Abstract. A version 2 processing of data from two ozone monitoring instruments on Suomi NPP, the OMPS nadir ozone mapper and the OMPS nadir ozone profiler, has now been completed. The previously released data were useful for many purposes but were not suitable for use in ozone trend analysis. In this processing, instrument artifacts have been identified and corrected, an improved scattered light correction and wavelength registration have been applied, and soft calibration techniques were implemented to produce a calibration consistent with data from the series of SBUV/2 instruments. The result is a high-quality ozone time series suitable for trend analysis. Total column ozone data from the OMPS nadir mapper now agree with data from the SBUV/2 instrument on NOAA 19 with a zonal average bias of −0.2 % over the 60∘ S to 60∘ N latitude zone. Differences are somewhat larger between OMPS nadir profiler and N19 total column ozone, with an average difference of −1.1 % over the 60∘ S to 60∘ N latitude zone and a residual seasonal variation of about 2 % at latitudes higher than about 50∘. For the profile retrieval, zonal average ozone in the upper stratosphere (between 2.5 and 4 hPa) agrees with that from NOAA 19 within ±3 % and an average bias of −1.1 %. In the lower stratosphere (between 25 and 40 hPa) agreement is within ±3 % with an average bias of +1.1 %. Tropospheric ozone produced by subtracting stratospheric ozone measured by the OMPS limb profiler from total column ozone measured by the nadir mapper is consistent with tropospheric ozone produced by subtracting stratospheric ozone from MLS from total ozone from the OMI instrument on Aura. The agreement of tropospheric ozone is within 10 % in most locations.
20
Gómez-Amo, J. L., V. Estellés, A. di Sarra, et al. "Operational considerations to improve total ozone measurements with a Microtops II ozone monitor." Atmospheric Measurement Techniques 5, no. 4 (2012): 759–69. http://dx.doi.org/10.5194/amt-5-759-2012.
Full textAbstract:
Abstract. A Microtops II "ozone monitor" with UV channels centered at 305.5, 312.5, and 320 nm has been used routinely in six experimental campaigns carried out in several geographic locations and seasons, covering latitudes from 35 to 68° N during the last ten years (2001–2011). The total ozone content is retrieved by Microtops II by using different combinations (Channel I, 305.5/312.5 nm; Channel II, 312.5/320 nm; and Channel III, 305.5/312.5/320 nm) of the signals at the three ultraviolet wavelengths. The long-term performance of the total ozone content determination has been studied taking into account the sensitivities to the calibration, airmass, temperature and aerosols. When a calibration was used and the airmass limit was fixed to 3, the root mean square deviations of the relative differences produced by Microtops II with respect to several Brewers are 0.9, 2, and 2% respectively for the Channel I, Channel II, and Channel III retrieval. The performance of the Microtops retrieval has been stable during the last ten years. Channel I represents the best option to determine the instantaneous total ozone content. Channels II and III values appear weakly sensitive to temperature, ozone content, and aerosols. Channel II is more stable than Channel I for airmasses larger than 2.6. The conclusions do not show any dependence on latitude and season.
21
Ziemke, J. R., S. Chandra, L. D. Oman, and P. K. Bhartia. "A new ENSO index derived from satellite measurements of column ozone." Atmospheric Chemistry and Physics Discussions 10, no. 2 (2010): 2859–87. http://dx.doi.org/10.5194/acpd-10-2859-2010.
Full textAbstract:
Abstract. Column Ozone measured in tropical latitudes from Nimbus 7 TOMS, Earth Probe TOMS, NOAA SBUV, and Aura OMI satellite instruments are used to derive an El Niño-Southern Oscillation (ENSO) index. This index, which covers a time period from 1979 to the present, is defined as the Ozone ENSO Index (OEI) and is the first developed from atmospheric trace gas measurements. Using a data mining technique with existing ENSO indices of surface pressure and sea-surface temperature, the OEI is constructed by first averaging monthly mean column ozone over two broad regions in the western and eastern Pacific and taking their difference. This differencing yields a self-calibrating ENSO index which is independent of individual instrument calibration offsets and drifts in measurements over the long record. The combined Aura OMI and MLS ozone data confirm that zonal variability in total column ozone in the tropics caused by ENSO events lies almost entirely in the troposphere. As a result, the OEI can be derived directly from total column ozone instead of tropospheric column ozone. For clear-sky ozone measurements a +1 K change in Nino 3.4 index corresponds to +2.9 DU (Dobson Unit) change in the OEI, while a +1 hPa change in SOI coincides with a −1.7 DU change in the OEI. For ozone measurements under all cloud conditions these numbers are +2.4 DU and −1.4 DU, respectively. As an ENSO index based upon ozone, it is potentially useful in evaluating climate models predicting long term changes in ozone and other trace gases.
22
Cotterell, Michael I., Andrew J. Orr-Ewing, Kate Szpek, Jim M. Haywood, and Justin M. Langridge. "The impact of bath gas composition on the calibration of photoacoustic spectrometers with ozone at discrete visible wavelengths spanning the Chappuis band." Atmospheric Measurement Techniques 12, no. 4 (2019): 2371–85. http://dx.doi.org/10.5194/amt-12-2371-2019.
Full textAbstract:
Abstract. Photoacoustic spectroscopy is a sensitive in situ technique for measuring the absorption coefficient for gas and aerosol samples. Photoacoustic spectrometer (PAS) instruments require accurate calibration by comparing the measured photoacoustic response with a known level of absorption for a calibrant. Ozone is a common calibrant of PAS instruments, yet recent work by Bluvshtein et al. (2017) has cast uncertainty on the validity of ozone as a calibrant at a wavelength of 405 nm. Moreover, Fischer and Smith (2018) demonstrate that a low O2 mass fraction in the bath gas can bias the measured PAS calibration coefficient to lower values for wavelengths in the range 532–780 nm. In this contribution, we present PAS sensitivity measurements at wavelengths of 405, 514 and 658 nm using ozone-based calibrations with variation in the relative concentrations of O2 and N2 bath gases. We find excellent agreement with the results of Fischer and Smith at the 658 nm wavelength. However, the PAS sensitivity decreases significantly as the bath gas composition tends to pure oxygen for wavelengths of 405 and 514 nm, which cannot be rationalised using arguments presented in previous studies. To address this, we develop a model to describe the variation in PAS sensitivity with both wavelength and bath gas composition that considers Chappuis band photodynamics and recognises that the photoexcitation of O3 leads rapidly to the photodissociation products O(3P) and O2(X, v > 0). We show that the rates of two processes are required to model the PAS sensitivity correctly. The first process involves the formation of vibrationally excited O3(X̃) through the reaction of the nascent O(3P) with bath gas O2. The second process involves the quenching of vibrational energy from the nascent O2(X, v > 0) to translational modes of the bath gas. Both of these processes proceed at different rates in collisions with N2 or O2 bath gas species. Importantly, we show that the PAS sensitivity is optimised for our PAS instruments when the ozone-based calibration is performed in a bath gas with a similar composition to ambient air and conclude that our methods for measuring aerosol absorption using an ozone-calibrated PAS are accurate and without detectable bias. We emphasise that the dependence of PAS sensitivity on bath gas composition is wavelength-dependent, and we recommend strongly that researchers characterise the optimal bath gas composition for their particular instrument.
23
Shah, Sweta, Olaf N. E. Tuinder, Jacob C. A. van Peet, Adrianus T. J. de Laat, and Piet Stammes. "Evaluation of SCIAMACHY Level-1 data versions using nadir ozone profile retrievals in the period 2003–2011." Atmospheric Measurement Techniques 11, no. 4 (2018): 2345–60. http://dx.doi.org/10.5194/amt-11-2345-2018.
Full textAbstract:
Abstract. Ozone profile retrieval from nadir-viewing satellite instruments operating in the ultraviolet–visible range requires accurate calibration of Level-1 (L1) radiance data. Here we study the effects of calibration on the derived Level-2 (L2) ozone profiles for three versions of SCanning Imaging Absorption spectroMeter for Atmospheric ChartograpHY (SCIAMACHY) L1 data: version 7 (v7), version 7 with m-factors (v7mfac) and version 8 (v8). We retrieve nadir ozone profiles from the SCIAMACHY instrument that flew on board Envisat using the Ozone ProfilE Retrieval Algorithm (OPERA) developed at KNMI with a focus on stratospheric ozone. We study and assess the quality of these profiles and compare retrieved L2 products from L1 SCIAMACHY data versions from the years 2003 to 2011 without further radiometric correction. From validation of the profiles against ozone sonde measurements, we find that the v8 performs better than v7 and v7mfac due to correction for the scan-angle dependency of the instrument's optical degradation. Validation for the years 2003 and 2009 with ozone sondes shows deviations of SCIAMACHY ozone profiles of 0.8–15 % in the stratosphere (corresponding to pressure range ∼ 100–10 hPa) and 2.5–100 % in the troposphere (corresponding to pressure range ∼ 1000–100 hPa), depending on the latitude and the L1 version used. Using L1 v8 for the years 2003–2011 leads to deviations of ∼ 1–11 % in stratospheric ozone and ∼ 1–45 % in tropospheric ozone. The SCIAMACHY L1 v8 data can still be improved upon in the 265–330 nm range used for ozone profile retrieval. The slit function can be improved with a spectral shift and squeeze, which leads to a few percent residue reduction compared to reference solar irradiance spectra. Furthermore, studies of the ratio of measured to simulated reflectance spectra show that a bias correction in the reflectance for wavelengths below 300 nm appears to be necessary.
24
Fischer, D. Al, and Geoffrey D. Smith. "Can ozone be used to calibrate aerosol photoacoustic spectrometers?" Atmospheric Measurement Techniques 11, no. 12 (2018): 6419–27. http://dx.doi.org/10.5194/amt-11-6419-2018.
Full textAbstract:
Abstract. Photoacoustic spectroscopy (PAS) has become a popular technique for measuring absorption of light by atmospheric aerosols in both the laboratory and field campaigns. It has low detection limits, measures suspended aerosols, and is insensitive to scattering. But PAS requires rigorous calibration to be applied quantitatively. Often, a PAS instrument is either filled with a gas of known concentration and absorption cross section, such that the absorption in the cell can be calculated from the product of the two, or the absorption is measured independently with a technique such as cavity ring-down spectroscopy. Then, the PAS signal can be regressed upon the known absorption to determine a calibration slope that reflects the sensitivity constant of the cell and microphone. Ozone has been used for calibrating PAS instruments due to its well-known UV–visible absorption spectrum and the ease with which it can be generated. However, it is known to photodissociate up to approximately 1120 nm via the O3 + hν(>1.1eV)→O2(3Σg-) + O(3P) pathway, which is likely to lead to inaccuracies in aerosol measurements. Two recent studies have investigated the use of O3 for PAS calibration but have reached seemingly contradictory conclusions with one finding that it results in a sensitivity that is a factor of 2 low and the other concluding that it is accurate. The present work is meant to add to this discussion by exploring the extent to which O3 photodissociates in the PAS cell and the role that the identity of the bath gas plays in determining the PAS sensitivity. We find a 5 % loss in PAS signal attributable to photodissociation at 532 nm in N2 but no loss in a 5 % mixture of O2 in N2. Furthermore, we discovered a dramatic increase of more than a factor of 2 in the PAS sensitivity as we increased the O2 fraction in the bath gas, which reached an asymptote near 100 % O2 that nearly matched the sensitivity measured with both NO2 and nigrosin particles. We interpret this dependence with a kinetic model that suggests the reason for the observed results is a more efficient transfer of energy from excited O3 to O2 than to N2 by a factor of 22–55 depending on excitation wavelength. Notably, the two prior studies on this topic used different bath gas compositions, and although the results presented here do not fully resolve the differences in their results, they may at least partially explain them.
25
Hilsenrath, E., P. K. Bhartia, R. P. Cebula, and C. G. Wellemeyer. "Calibration and intercalibration of backscatter ultraviolet (BUV) satellite ozone data." Advances in Space Research 19, no. 9 (1997): 1345–53. http://dx.doi.org/10.1016/s0273-1177(97)00243-3.
Full text
26
Bhangar, Seema, Brett C. Singer, and William W. Nazaroff. "Calibration of the Ogawa passive ozone sampler for aircraft cabins." Atmospheric Environment 65 (February 2013): 21–24. http://dx.doi.org/10.1016/j.atmosenv.2012.10.012.
Full text
27
Redondas, A., R. Evans, R. Stuebi, U. Köhler, and M. Weber. "Evaluation of the use of five laboratory determined ozone absorption cross sections in brewer and dobson retrieval algorithms." Atmospheric Chemistry and Physics Discussions 13, no. 9 (2013): 22979–3021. http://dx.doi.org/10.5194/acpd-13-22979-2013.
Full textAbstract:
Abstract. The primary ground-based instruments used to report total column ozone (TOC) are Brewer and Dobson Spectrophotometers, in separate networks. These instruments make measurements of the UV irradiances, and through a well-defined process a TOC value is produced. Inherent in the algorithm is the use of a laboratory determined cross-section data set. We used five ozone cross section data sets: three Bass and Paur, Daumont, Malicet and Brion (DMB) and a new Institute of Environmental Physics (IUP), University of Bremen, set. The three Bass and Paur (1985) sets are: quadratic temperature coefficients from IGACO web page (IGQ4), the Brewer network operational calibration set (BOp), and the set used by Bernhard et al. (2005), in the reanalysis of the Dobson absorption coefficient values (B05). The ozone absorption coefficients for Brewer and Dobson are then calculated using the normal Brewer operative method which is essentially the same as used on Dobson. Considering the standard TOC algorithm for the Brewer instruments and comparing to the Brewer standard operational calibration data set, using the slit functions for the individual instruments: we find the UIP data set changes the calculated TOC by −0.5%, the DBM data set changes the calculate TOC by −3.2%, and the IGQ4 data set at −45 °C changes the calculated TOC by +1.3%. Considering the standard algorithm for the Dobson instruments, and comparing to results using the official 1992 ozone absorption coefficients values and the single set of slit functions defined for all Dobson instruments, the calculated TOC changes by +1%, with little variation depending on which data set is used We applied the changes to the European Dobson and Brewer reference instruments during the Izaña 2012 Absolute Calibration Campaign. The application of a common Langley calibration and the IUP cross section the differences between Brewer and Dobson vanish whereas using Bass and Paur and DBM produce differences of 1.5% and 2% respectively. A study of temperature dependence of these cross section (XS) data sets is presented using the Arosa, Switzerland total ozone record of 2003–2006, obtained from two Brewer instrument types and a Dobson instrument, combined with the stratospheric ozone and temperature profiles from the Payerne soundings in the same period. The seasonal dependence of the differences between the results from the various instruments is greatly reduced with the application of temperature dependent absorption coefficients, with the greatest reduction obtained using the IUP data set.
28
Zhao, Xiaoyi, Vitali Fioletov, Michael Brohart, et al. "The world Brewer reference triad – updated performance assessment and new double triad." Atmospheric Measurement Techniques 14, no. 3 (2021): 2261–83. http://dx.doi.org/10.5194/amt-14-2261-2021.
Full textAbstract:
Abstract. The Brewer ozone spectrophotometer (the Brewer) was designed at Environment and Climate Change Canada (ECCC) in the 1970s to make accurate automated total ozone column measurements. Since the 1980s, the Brewer instrument has become a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) standard ozone monitoring instrument. Now, more than 230 Brewers have been produced. To assure the quality of the Brewer measurements, a calibration chain is maintained, i.e., first, the reference instruments are independently absolutely calibrated, and then the calibration is transferred from the reference instrument to the travelling standard, and subsequently from the travelling standard to field instruments. ECCC has maintained the world Brewer reference instruments since the 1980s to provide transferable calibration to field instruments at monitoring sites. Three single-monochromator (Mark II) type instruments (serial numbers 008, 014, and 015) formed this world Brewer reference triad (BrT) and started their service in Toronto, Canada, in 1984. In the 1990s, the Mark III type Brewer (known as the double Brewer) was developed, which has two monochromators to reduce the internal instrumental stray light. The double-Brewer world reference triad (BrT-D) was formed in 2013 (serial numbers 145, 187 and 191), co-located with the BrT. The first assessment of the BrT's performance was made in 2005, covering the period between 1984 and 2004 (Fioletov et al., 2005). The current work provides an updated assessment of the BrT's performance (from 1999 to 2019) and the first comprehensive assessment of the BrT-D. The random uncertainties of individual reference instruments are within the WMO/GAW requirement of 1 % (WMO, 2001): 0.49 % and 0.42 % for BrT and BrT-D, respectively, as estimated in this study. The long-term stability of the reference instruments is also evaluated in terms of uncertainties of the key instrument characteristics: the extraterrestrial calibration constant (ETC) and effective ozone absorption coefficients (both having an effect of less than 2 % on total column ozone). Measurements from a ground-based instrument (Pandora spectrometer), satellites (11 datasets, including the most recent high-resolution satellite, TROPOspheric Monitoring Instrument), and reanalysis model (the second Modern-Era Retrospective analysis for Research and Applications, MERRA-2) are used to further assess the performance of world Brewer reference instruments and to provide a context for the requirements of stratospheric ozone observations during the last two decades.
29
Carlund, Thomas, Natalia Kouremeti, Stelios Kazadzis, and Julian Gröbner. "Aerosol optical depth determination in the UV using a four-channel precision filter radiometer." Atmospheric Measurement Techniques 10, no. 3 (2017): 905–23. http://dx.doi.org/10.5194/amt-10-905-2017.
Full textAbstract:
Abstract. The determination of aerosol properties, especially the aerosol optical depth (AOD) in the ultraviolet (UV) wavelength region, is of great importance for understanding the climatological variability of UV radiation. However, operational retrievals of AOD at the biologically most harmful wavelengths in the UVB are currently only made at very few places. This paper reports on the UVPFR (UV precision filter radiometer) sunphotometer, a stable and robust instrument that can be used for AOD retrievals at four UV wavelengths. Instrument characteristics and results of Langley calibrations at a high-altitude site were presented. It was shown that due to the relatively wide spectral response functions of the UVPFR, the calibration constants (V0) derived from Langley plot calibrations underestimate the true extraterrestrial signals. Accordingly, correction factors were introduced. In addition, the instrument's spectral response functions also result in an apparent air-mass-dependent decrease in ozone optical depth used in the AOD determinations. An adjusted formula for the calculation of AOD, with a correction term dependent on total column ozone amount and ozone air mass, was therefore introduced. Langley calibrations performed 13–14 months apart resulted in sensitivity changes of ≤ 1.1 %, indicating good instrument stability. Comparison with a high-accuracy standard precision filter radiometer, measuring AOD at 368–862 nm wavelengths, showed consistent results. Also, very good agreement was achieved by comparing the UVPFR with AOD at UVB wavelengths derived with a Brewer spectrophotometer, which was calibrated against the UVPFR at an earlier date. Mainly due to non-instrumental uncertainties connected with ozone optical depth, the total uncertainty of AOD in the UVB is higher than that reported from AOD instruments measuring in UVA and visible ranges. However, the precision can be high among instruments using harmonized algorithms for ozone and Rayleigh optical depth as well as for air mass terms. For 4 months of comparison measurements with the UVPFR and a Brewer, the root mean squared AOD differences were found < 0.01 at all the 306–320 nm Brewer wavelengths.
30
Fernandez, S., A. Murk, and N. Kämpfer. "GROMOS-C, a novel ground based microwave radiometer for ozone measurement campaigns." Atmospheric Measurement Techniques Discussions 8, no. 3 (2015): 3001–48. http://dx.doi.org/10.5194/amtd-8-3001-2015.
Full textAbstract:
Abstract. Stratospheric ozone is of major interest as it absorbs most of harmful UV radiation from the sun, allowing life on Earth. Ground based microwave remote sensing is the only method that allows to measure ozone profiles up to the mesopause, 24 h and under different weather conditions with high time resolution. In this paper a novel ground based microwave radiometer is presented. It is called GROMOS-C (GRound based Ozone MOnitoring System for Campaigns), and it has been designed to measure the vertical profile of ozone distribution in the middle atmosphere, by observing ozone emission spectra at a frequency of 110.836 GHz. The instrument is designed in a compact way which makes it transportable and suitable for outdoor use in campaigns, an advantageous feature that is lacking in present day ozone radiometers. It is operated through remote control. GROMOS-C is a total power radiometer which uses a preamplified heterodyne receiver, and a digital Fast Fourier Transform spectrometer for the spectral analysis. Among its main new features stands out the incorporation of different calibration loads, including a noise diode and a new type of blackbody target specifically designed for this instrument, based on Peltier elements. The calibration scheme does not depend on the use of liquid nitrogen, therefore GROMOS-C can be operated at remote places with no maintenance requirements. In addition the instrument can be switched in frequency to observe the CO line at 115 GHz. A description of the main characteristics of GROMOS-C is included in this paper, as well as the results of a first campaign at the High Altitude Research Station in Jungfraujoch (HFSJ), Switzerland. The validation is performed by comparison of the retrieved profiles against equivalent profiles from MLS satellite data, ECMWF model data, as well as our nearby NDACC ozone radiometer measuring at Bern.
31
Puckrin, E., and W. F. J. Evans. "The calibration of instruments for atmospheric ozone measurement with a sealed ozone cell: The OSIRIN/ODIN spectrograph." Advances in Space Research 32, no. 11 (2003): 2153–58. http://dx.doi.org/10.1016/s0273-1177(03)90537-0.
Full text
32
Redondas, A., R. Evans, R. Stuebi, U. Köhler, and M. Weber. "Evaluation of the use of five laboratory-determined ozone absorption cross sections in Brewer and Dobson retrieval algorithms." Atmospheric Chemistry and Physics 14, no. 3 (2014): 1635–48. http://dx.doi.org/10.5194/acp-14-1635-2014.
Full textAbstract:
Abstract. The primary ground-based instruments used to report total column ozone (TOC) are Brewer and Dobson spectrophotometers in separate networks. These instruments make measurements of the UV irradiances, and through a well-defined process, a TOC value is produced. Inherent to the algorithm is the use of a laboratory-determined cross-section data set. We used five ozone cross-section data sets: three data sets that are based on measurements of Bass and Paur; one derived from Daumont, Brion and Malicet (DBM); and a new set determined by Institute of Experimental Physics (IUP), University of Bremen. The three Bass and Paur (1985) sets are as follows: quadratic temperature coefficients from the IGACO (a glossary is provided in Appendix A) web page (IGQ4), the Brewer network operational calibration set (BOp), and the set used by Bernhard et al. (2005) in the reanalysis of the Dobson absorption coefficient values (B05). The ozone absorption coefficients for Brewer and Dobson instruments are then calculated using the normal Brewer operative method, which is essentially the same as that used for Dobson instruments. Considering the standard TOC algorithm for the Brewer instruments and comparing to the Brewer standard operational calibration data set, using the slit functions for the individual instruments, we find the IUP data set changes the calculated TOC by −0.5%, the DBM data set changes the calculated TOC by −3.2%, and the IGQ4 data set at −45 °C changes the calculated TOC by +1.3%. Considering the standard algorithm for the Dobson instruments, and comparing to results using the official 1992 ozone absorption coefficients values and the single set of slit functions defined for all Dobson instruments, the calculated TOC changes by +1%, with little variation depending on which data set is used. We applied the changes to the European Dobson and Brewer reference instruments during the Izaña 2012 Absolute Calibration Campaign. With the application of a common Langley calibration and the IUP cross section, the differences between Brewer and Dobson data sets vanish, whereas using those of Bass and Paur and DBM produces differences of 1.5 and 2%, respectively. A study of the temperature dependence of these cross-section data sets is presented using the Arosa, Switzerland, total ozone record of 2003–2006, obtained from two Brewer-type instruments and one Dobson-type instrument, combined with the stratospheric ozone and temperature profiles from the Payerne soundings in the same period. The seasonal dependence of the differences between the results from the various instruments is greatly reduced with the application of temperature-dependent absorption coefficients, with the greatest reduction obtained using the IUP data set.
33
Newchurch, Michael J., Raul J. Alvarez, Timothy A. Berkoff, et al. "TOLNet ozone lidar intercomparison during the discover-aq and frappé campaigns." EPJ Web of Conferences 176 (2018): 10007. http://dx.doi.org/10.1051/epjconf/201817610007.
Full textAbstract:
The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure atmospheric profiles of ozone and aerosols, to contribute to air-quality studies, atmospheric modeling, and satellite validation efforts. The accurate characterization of these lidars is of critical interest, and is necessary to determine cross-instrument calibration uniformity. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the “Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality” (DISCOVER-AQ) mission and the “Front Range Air Pollution and Photochemistry Éxperiment” (FRAPPÉ) to measure sub-hourly ozone variations from near the surface to the top of the troposphere. Although large differences occur at few individual altitudes in the near field and far field range, the TOLNet lidars agree with each other within ±4%. These results indicate excellent measurement accuracy for the TOLNet lidars that is suitable for use in air-quality and ozone modeling efforts.
34
ZHANG Zhuo, 张. 卓., 王维和 WANG Wei-he, 王后茂 WANG Hou-mao, and 王咏梅 WANG Yong-mei. "On-board vicarious calibration of FY-3C UV total ozone unit." Optics and Precision Engineering 27, no. 2 (2019): 326–33. http://dx.doi.org/10.3788/ope.20192702.0326.
Full text
35
Fernandez, S., A. Murk, and N. Kämpfer. "GROMOS-C, a novel ground-based microwave radiometer for ozone measurement campaigns." Atmospheric Measurement Techniques 8, no. 7 (2015): 2649–62. http://dx.doi.org/10.5194/amt-8-2649-2015.
Full textAbstract:
Abstract. Stratospheric ozone is of major interest as it absorbs most harmful UV radiation from the sun, allowing life on Earth. Ground-based microwave remote sensing is the only method that allows for the measurement of ozone profiles up to the mesopause, over 24 hours and under different weather conditions with high time resolution. In this paper a novel ground-based microwave radiometer is presented. It is called GROMOS-C (GRound based Ozone MOnitoring System for Campaigns), and it has been designed to measure the vertical profile of ozone distribution in the middle atmosphere by observing ozone emission spectra at a frequency of 110.836 GHz. The instrument is designed in a compact way which makes it transportable and suitable for outdoor use in campaigns, an advantageous feature that is lacking in present day ozone radiometers. It is operated through remote control. GROMOS-C is a total power radiometer which uses a pre-amplified heterodyne receiver, and a digital fast Fourier transform spectrometer for the spectral analysis. Among its main new features, the incorporation of different calibration loads stands out; this includes a noise diode and a new type of blackbody target specifically designed for this instrument, based on Peltier elements. The calibration scheme does not depend on the use of liquid nitrogen; therefore GROMOS-C can be operated at remote places with no maintenance requirements. In addition, the instrument can be switched in frequency to observe the CO line at 115 GHz. A description of the main characteristics of GROMOS-C is included in this paper, as well as the results of a first campaign at the High Altitude Research Station at Jungfraujoch (HFSJ), Switzerland. The validation is performed by comparison of the retrieved profiles against equivalent profiles from MLS (Microwave Limb Sounding) satellite data, ECMWF (European Centre for Medium-Range Weather Forecast) model data, as well as our nearby NDACC (Network for the Detection of Atmospheric Composition Change) ozone radiometer measuring at Bern.
36
Gómez-Amo, J. L., V. Estellés, A. di Sarra, et al. "Operational considerations to improve total ozone measurements with a Microtops II ozone monitor." Atmospheric Measurement Techniques Discussions 4, no. 6 (2011): 7529–58. http://dx.doi.org/10.5194/amtd-4-7529-2011.
Full textAbstract:
Abstract. A Microtops II "ozone monitor" with UV channels centered at 305.5, 312.5, and 320 nm has been used routinely in six experimental campaigns carried out in several geographic locations and seasons, covering latitudes from 35 to 68° N during the last ten years (2001–2011). The total ozone content is retrieved by Microtops II by using different combinations (Channel I, 305.5/312.5 nm; Channel II, 312.5/320 nm; and Channel III, 305.5/312.5/320 nm) of the signals at the three ultraviolet wavelengths. When a calibration was used and the airmass limit was fixed to 3, Microtops II produce mean relative deviations with respect to the Brewer of 0.1, −11, and 8% respectively for the Channel I, Channel II, and Channel III retrieval. The performance of the Microtops retrieval has been stable during the last ten years. Channel I represents the best option to determine the instantaneous total ozone content. Channel II and III values appear weakly sensitive to temperature, ozone content, and aerosols. Channel II is more stable than Channel I for airmasses larger than 2.6. The conclusions do not show any dependence on latitude and season.
37
Wagner, T., S. Beirle, S. Dörner, et al. "A new method for the absolute radiance calibration for UV–vis measurements of scattered sunlight." Atmospheric Measurement Techniques 8, no. 10 (2015): 4265–80. http://dx.doi.org/10.5194/amt-8-4265-2015.
Full textAbstract:
Abstract. Absolute radiometric calibrations are important for measurements of the atmospheric spectral radiance. Such measurements can be used to determine actinic fluxes, the properties of aerosols and clouds, and the shortwave energy budget. Conventional calibration methods in the laboratory are based on calibrated light sources and reflectors and are expensive, time consuming and subject to relatively large uncertainties. Also, the calibrated instruments might change during transport from the laboratory to the measurement sites. Here we present a new calibration method for UV–vis instruments that measure the spectrally resolved sky radiance, for example zenith sky differential optical absorption spectroscopy (DOAS) instruments or multi-axis (MAX)-DOAS instruments. Our method is based on the comparison of the solar zenith angle dependence of the measured zenith sky radiance with radiative transfer simulations. For the application of our method, clear-sky measurements during periods with almost constant aerosol optical depth are needed. The radiative transfer simulations have to take polarisation into account. We show that the calibration results are almost independent from the knowledge of the aerosol optical properties and surface albedo, which causes a rather small uncertainty of about < 7 %. For wavelengths below about 330 nm it is essential that the ozone column density during the measurements be constant and known.
38
Wagner, T., S. Beirle, S. Dörner, et al. "A new method for the absolute radiance calibration for UV/vis measurements of scattered sun light." Atmospheric Measurement Techniques Discussions 8, no. 5 (2015): 5329–62. http://dx.doi.org/10.5194/amtd-8-5329-2015.
Full textAbstract:
Abstract. Absolute radiometric calibrations are important for measurements of the atmospheric spectral radiance. Such measurements can be used to determine actinic fluxes, the properties of aerosols and clouds and the short wave energy budget. Conventional calibration methods in the laboratory are based on calibrated light sources and reflectors and are expensive, time consuming and subject to relatively large uncertainties. Also, the calibrated instruments might change during transport from the laboratory to the measurement sites. Here we present a new calibration method for UV/vis instruments that measure the spectrally resolved sky radiance, like for example zenith sky Differential Optical Absorption Spectroscopy (DOAS-) instruments or Multi-AXis (MAX-) DOAS instruments. Our method is based on the comparison of the solar zenith angle dependence of the measured zenith sky radiance with radiative transfer simulations. For the application of our method clear sky measurements during periods with almost constant aerosol optical depth are needed. The radiative transfer simulations have to take polarisation into account. We show that the calibration results are almost independent from the knowledge of the aerosol optical properties and surface albedo, which causes a rather small uncertainty of about <7%. For wavelengths below about 330 nm it is essential that the ozone column density during the measurements is constant and known.
39
Gilge, S., C. Plass-Duelmer, W. Fricke, et al. "Ozone, carbon monoxide and nitrogen oxides time series at four alpine GAW mountain stations in central Europe." Atmospheric Chemistry and Physics 10, no. 24 (2010): 12295–316. http://dx.doi.org/10.5194/acp-10-12295-2010.
Full textAbstract:
Abstract. Long-term, ground based in-situ observations of ozone (O3) and its precursor gases nitrogen dioxide (NO2) and carbon monoxide (CO) from the four sites Hohenpeissenberg and Zugspitze (D), Sonnblick (A) and Jungfraujoch (CH) are presented for the period 1995–2007. These Central European alpine mountain observatories cover an altitude range of roughly 1000 to 3500 m. Comparable analytical methods and common quality assurance (QA) procedures are used at all sites. For O3 and CO, calibration is linked to primary calibrations (O3) or CO standards provided by the Central Calibration Laboratory (CCL) at NOAA/ESRL. All stations have been audited by the World Calibration Centre (WCC) for CO and O3 (WCC-Empa; CH). Data from long-term measurements of NO2 and CO are only available from Hohenpeissenberg and Jungfraujoch. Both sites show slightly decreasing mixing ratios of the primarily emitted NO2 and the partly anthropogenically emitted CO between 1995 and 2007. The findings are generally consistent with shorter observation periods at Zugspitze and Sonnblick and thus are considered to represent regional changes in Central European atmospheric composition at this altitude range. Over the same period, 1995–2007, the O3 mixing ratios have slightly increased at three of the four sites independent of wind sector. Trends are often more pronounced in winter and less in summer; highest declines of NO2 and CO are observed in winter and the lowest in summer, whereas the strongest O3 increase was detected in winter and lowest or even decline in summer, respectively. Weekly cycles demonstrate anthropogenic impact at all elevations with enhanced NO2 on working days compared to weekends. Enhanced O3 values on working days indicating photochemical production from anthropogenic precursors are only observed in summer, whereas in all other seasons anti-correlation with NO2 was found due to reduced O3 values on working days. Trends are discussed with respect to anthropogenic impacts and vertical mixing. The observed trends for NO2 at the alpine mountain sites are less pronounced than trends estimated based on emission inventories.
40
Wang, Lihua, Michael J. Newchurch, Raul J. Alvarez II, et al. "Quantifying TOLNet ozone lidar accuracy during the 2014 DISCOVER-AQ and FRAPPÉ campaigns." Atmospheric Measurement Techniques 10, no. 10 (2017): 3865–76. http://dx.doi.org/10.5194/amt-10-3865-2017.
Full textAbstract:
Abstract. The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure high-resolution atmospheric profiles of ozone. The accurate characterization of these lidars is necessary to determine the uniformity of the network calibration. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission and the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) to measure ozone variations from the boundary layer to the top of the troposphere. This study presents the analysis of the intercomparison between the TROPOZ, TOPAZ, and LMOL lidars, along with comparisons between the lidars and other in situ ozone instruments including ozonesondes and a P-3B airborne chemiluminescence sensor. The TOLNet lidars measured vertical ozone structures with an accuracy generally better than ±15 % within the troposphere. Larger differences occur at some individual altitudes in both the near-field and far-field range of the lidar systems, largely as expected. In terms of column average, the TOLNet lidars measured ozone with an accuracy better than ±5 % for both the intercomparison between the lidars and between the lidars and other instruments. These results indicate that these three TOLNet lidars are suitable for use in air quality, satellite validation, and ozone modeling efforts.
41
Coldewey-Egbers, Melanie, Sander Slijkhuis, Bernd Aberle, Diego Loyola, and Angelika Dehn. "The Global Ozone Monitoring Experiment: review of in-flight performance and new reprocessed 1995–2011 level 1 product." Atmospheric Measurement Techniques 11, no. 9 (2018): 5237–59. http://dx.doi.org/10.5194/amt-11-5237-2018.
Full textAbstract:
Abstract. The Global Ozone Monitoring Experiment (GOME) on-board the second European Remote Sensing satellite provided measurements of atmospheric constituents such as ozone and other trace gases for the 16-year period from 1995 to 2011. In this paper we present a detailed analysis of the long-term performance of the sensor and introduce the new homogenised and fully calibrated level 1 product that has been generated using the recently developed GOME Data Processor level-0-to-1b (GDP-L1) Version 5.1. By means of the various in-flight calibration parameters, we monitor the behaviour and stability of the instrument during the entire mission. Severe degradation of the optical components has led to a significant decrease in intensity, in particular in channels 1 and 2, which cover the spectral ranges of 240–316 and 311–405 nm, respectively. Thus, a soft correction based on using the Sun as a stable calibration source is applied. Revision and optimisation of other calibration algorithms such as the wavelength assignment, polarisation correction, and dark current correction resulted in an improved and homogeneous level 1 product that can be regarded as the European satellite reference data for successor atmospheric composition sensors and that provides an excellent prerequisite for further exploitation of GOME measurements.
42
Sadighi, Kira, Evan Coffey, Andrea Polidori, et al. "Intra-urban spatial variability of surface ozone in Riverside, CA: viability and validation of low-cost sensors." Atmospheric Measurement Techniques 11, no. 3 (2018): 1777–92. http://dx.doi.org/10.5194/amt-11-1777-2018.
Full textAbstract:
Abstract. Sensor networks are being more widely used to characterize and understand compounds in the atmosphere like ozone (O3). This study employs a measurement tool, called the U-Pod, constructed at the University of Colorado Boulder, to investigate spatial and temporal variability of O3 in a 200 km2 area of Riverside County near Los Angeles, California. This tool contains low-cost sensors to collect ambient data at non-permanent locations. The U-Pods were calibrated using a pre-deployment field calibration technique; all the U-Pods were collocated with regulatory monitors. After collocation, the U-Pods were deployed in the area mentioned. A subset of pods was deployed at two local regulatory air quality monitoring stations providing validation for the collocation calibration method. Field validation of sensor O3 measurements to minute-resolution reference observations resulted in R2 and root mean squared errors (RMSEs) of 0.95–0.97 and 4.4–5.9 ppbv, respectively. Using the deployment data, ozone concentrations were observed to vary on this small spatial scale. In the analysis based on hourly binned data, the median R2 values between all possible U-Pod pairs varied from 0.52 to 0.86 for ozone during the deployment. The medians of absolute differences were calculated between all possible pod pairs, 21 pairs total. The median values of those median absolute differences for each hour of the day varied between 2.2 and 9.3 ppbv for the ozone deployment. Since median differences between U-Pod concentrations during deployment are larger than the respective root mean square error values, we can conclude that there is spatial variability in this criteria pollutant across the study area. This is important because it means that citizens may be exposed to more, or less, ozone than they would assume based on current regulatory monitoring.
43
Alhasa, Kemal, Mohd Mohd Nadzir, Popoola Olalekan, et al. "Calibration Model of a Low-Cost Air Quality Sensor Using an Adaptive Neuro-Fuzzy Inference System." Sensors 18, no. 12 (2018): 4380. http://dx.doi.org/10.3390/s18124380.
Full textAbstract:
Conventional air quality monitoring systems, such as gas analysers, are commonly used in many developed and developing countries to monitor air quality. However, these techniques have high costs associated with both installation and maintenance. One possible solution to complement these techniques is the application of low-cost air quality sensors (LAQSs), which have the potential to give higher spatial and temporal data of gas pollutants with high precision and accuracy. In this paper, we present DiracSense, a custom-made LAQS that monitors the gas pollutants ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). The aim of this study is to investigate its performance based on laboratory calibration and field experiments. Several model calibrations were developed to improve the accuracy and performance of the LAQS. Laboratory calibrations were carried out to determine the zero offset and sensitivities of each sensor. The results showed that the sensor performed with a highly linear correlation with the reference instrument with a response-time range from 0.5 to 1.7 min. The performance of several calibration models including a calibrated simple equation and supervised learning algorithms (adaptive neuro-fuzzy inference system or ANFIS and the multilayer feed-forward perceptron or MLP) were compared. The field calibration focused on O3 measurements due to the lack of a reference instrument for CO and NO2. Combinations of inputs were evaluated during the development of the supervised learning algorithm. The validation results demonstrated that the ANFIS model with four inputs (WE OX, AE OX, T, and NO2) had the lowest error in terms of statistical performance and the highest correlation coefficients with respect to the reference instrument (0.8 < r < 0.95). These results suggest that the ANFIS model is promising as a calibration tool since it has the capability to improve the accuracy and performance of the low-cost electrochemical sensor.
44
Dusanter, S., D. Vimal, and P. S. Stevens. "Technical Note: Measuring tropospheric OH and HO<sub>2</sub> by laser-induced fluorescence at low pressure – a comparison of calibration techniques." Atmospheric Chemistry and Physics Discussions 7, no. 5 (2007): 12877–926. http://dx.doi.org/10.5194/acpd-7-12877-2007.
Full textAbstract:
Abstract. The hydroxyl radical (OH) is one of the most important oxidants in the atmosphere, as it is involved in many reactions that affect regional air quality and global climate change. Because of its high reactivity, measurements of OH radical concentrations in the atmosphere are difficult, and often require careful calibrations that rely on the production of a known concentration of OH at atmospheric pressure. The Indiana University OH instrument, based on the Fluorescence Assay by Gas Expansion technique (FAGE), has been calibrated in the laboratory using two different approaches: the production of OH from the UV-photolysis of water-vapor, and the steady-state production of OH from the reaction of ozone with alkenes. Both techniques are shown to agree within their experimental uncertainties, although the sensitivities derived from the ozone-alkene technique were systematically lower than those derived from the water-vapor UV-photolysis technique. The agreement between the two different methods improves the confidence of the water-vapor photolysis method as an accurate calibration technique for HOx instruments. Because several aspects of the mechanism of the gas phase ozonolysis of alkenes are still uncertain, this technique should be used with caution to calibrate OH instruments.
45
de Laat, A. T. J., R. J. van der A, and M. van Weele. "Evaluation of tropospheric ozone columns derived from assimilated GOME ozone profile observations." Atmospheric Chemistry and Physics Discussions 9, no. 3 (2009): 11811–41. http://dx.doi.org/10.5194/acpd-9-11811-2009.
Full textAbstract:
Abstract. Tropospheric O3 column estimates are produced and evaluated from spaceborne O3 observations by the subtraction of assimilated O3 profile observations from total column observations, the so-called Tropospheric O3 ReAnalysis or TORA method. Here we apply the TORA method to six years (1996–2001) of ERS-2 GOME/TOMS total O3 and ERS-2 GOME O3 profile observations using the TM5 global chemistry-transport model with a linearized O3 photochemistry parameterization scheme. Free running TM5 simulations show good agreement with O3 sonde observations in the upper-tropospheric and lower stratospheric (UTLS). Assimilation of GOME O3 profile observations improves the comparisons in the tropical UTLS region but slightly degrades the model-to-sonde comparisons in the extra-tropical UTLS for both short day-do-day variability as well as for monthly means. We suggest that this degradation is related to the large ground pixel size of the GOME O3 measurements (960×100 km) in combination with retrieval and calibration errors. The assimilation of GOME O3 profile observations does counter the gradual multiyear mid-latitude stratospheric O3 accumulation caused by the overstrong stratospheric meridional circulation in TM5. The evaluation of daily and monthly tropospheric O3 columns obtained from total column observations and using the TORA methodology shows realistic residuals within the tropics but unrealistically large deviations outside of the tropics, although average biases remain small for the monthly means. The findings of this paper suggest that improvements can be expected by using O3 observations from present-day instruments like MetOp/GOME-2 and EOS-AURA/OMI.
46
Frith, Stacey M., Richard S. Stolarski, Natalya A. Kramarova, and Richard D. McPeters. "Estimating uncertainties in the SBUV Version 8.6 merged profile ozone data set." Atmospheric Chemistry and Physics 17, no. 23 (2017): 14695–707. http://dx.doi.org/10.5194/acp-17-14695-2017.
Full textAbstract:
Abstract. The combined record of total and profile ozone measurements from the solar backscatter ultraviolet (SBUV) and SBUV/2 series of instruments, known as the SBUV Merged Ozone Data (MOD) product, constitutes the longest satellite-based ozone time series from a single instrument type and as such plays a key role in ozone trend analyses.Following the approach documented in Frith et al. (2014) to analyze the merging uncertainties in the MOD total ozone record, we use Monte Carlo simulations to estimate the potential for uncertainties in the calibration and drift of individual instruments in the profile ozone merged data set. We focus our discussion on the trends and associated merging uncertainty since 2001 in an effort to verify the start of ozone recovery as predicted by chemistry climate models. We find that merging uncertainty dominates the overall estimated uncertainty when considering only the 15 years of data since 2001. We derive trends versus pressure level for the MOD data set that are positive in the upper stratosphere as expected for ozone recovery. These trends appear to be significant when only statistical uncertainties are included but become not significant at the 2σ level when instrument uncertainties are accounted for. However, when we use the entire data set from 1979 through 2015 and fit to the EESC (equivalent effective stratospheric chlorine) we find statistically significant fits throughout the upper stratosphere at all latitudes. This implies that the ozone profile data remain consistent with our expectation that chlorine is the dominant ozone forcing term.
47
Veres, P. R., J. M. Roberts, R. J. Wild, et al. "Peroxynitric acid (HO<sub>2</sub>NO<sub>2</sub>) measurements during the UBWOS 2013 and 2014 studies using iodide ion chemical ionization mass spectrometry." Atmospheric Chemistry and Physics 15, no. 14 (2015): 8101–14. http://dx.doi.org/10.5194/acp-15-8101-2015.
Full textAbstract:
Abstract. In this paper laboratory work is documented establishing iodide ion chemical ionization mass spectrometry (I- CIMS) as a sensitive method for the unambiguous detection of peroxynitric acid (HO2NO2; PNA). A dynamic calibration source for HO2NO2, HO2, and HONO was developed and calibrated using a novel total NOy cavity ring-down spectroscopy (CaRDS) detector. Photochemical sources of these species were used for the calibration and validation of the I- CIMS instrument for detection of HO2NO2. Ambient observations of HO2NO2 using I- CIMS during the 2013 and 2014 Uintah Basin Wintertime Ozone Study (UBWOS) are presented. Strong inversions leading to a build-up of many primary and secondary pollutants as well as low temperatures drove daytime HO2NO2 as high as 1.5 ppbv during the 2013 study. A comparison of HO2NO2 observations to mixing ratios predicted using a chemical box model describing an ozone formation event observed during the 2013 wintertime shows agreement in the daily maxima HO2NO2 mixing ratio, but a differences of several hours in the timing of the observed maxima. Observations of vertical gradients suggest that the ground snow surface potentially serves as both a net sink and source of HO2NO2 depending on the time of day. Sensitivity tests using a chemical box model indicate that the lifetime of HO2NO2 with respect to deposition has a non-negligible impact on ozone production rates on the order of 10 %.
48
Snow, Martin, Francis G. Eparvier, Jerald Harder, et al. "Ultraviolet Solar Spectral Irradiance Variation on Solar Cycle Timescales." Proceedings of the International Astronomical Union 13, S340 (2018): 203–8. http://dx.doi.org/10.1017/s1743921318001278.
Full textAbstract:
AbstractUltraviolet (UV) Solar spectral Irradiance (SSI) has been measured from orbit on a regular basis since the beginning of the space age. These observations span four Solar Cycles, and they are crucial for our understanding of the Sun-Earth connection and space weather. SSI at these wavelengths are the main drivers for the upper atmosphere including the production and destruction of ozone in the stratosphere. The instruments that measure UV SSI not only require good preflight calibration, but also need a robust method to maintain that calibration on orbit. We will give an overview of the catalog of current and former UV SSI measurements along with the calibration philosophy of each instrument and an estimation of the uncertainties in the published irradiances.
49
Dusanter, S., D. Vimal, and P. S. Stevens. "Technical note: Measuring tropospheric OH and HO<sub>2</sub> by laser-induced fluorescence at low pressure. A comparison of calibration techniques." Atmospheric Chemistry and Physics 8, no. 2 (2008): 321–40. http://dx.doi.org/10.5194/acp-8-321-2008.
Full textAbstract:
Abstract. The hydroxyl radical (OH) is one of the most important oxidants in the atmosphere, as it is involved in many reactions that affect regional air quality and global climate change. Because of its high reactivity, measurements of OH radical concentrations in the atmosphere are difficult, and often require careful calibrations that rely on the production of a known concentration of OH at atmospheric pressure. The Indiana University OH instrument, based on the Fluorescence Assay by Gas Expansion technique (FAGE), has been calibrated in the laboratory using two different approaches: the production of OH from the UV-photolysis of water-vapor, and the steady-state production of OH from the reaction of ozone with alkenes. The former technique relies on two different actinometric methods to measure the product of the lamp flux at 184.9 nm and the photolysis time. This quantity derived from N2O actinometry was found to be 1.5 times higher than that derived from O2 actinometry. The water photolysis and ozone-alkene techniques are shown to agree within their experimental uncertainties (respectively 17% and 44%), although the sensitivities derived from the ozone-alkene technique were systematically lower by 40% than those derived from the water-vapor UV- photolysis technique using O2 actinometry. The agreement between the two different methods improves the confidence of the water-vapor photolysis method as an accurate calibration technique for HOx instruments. Because several aspects of the mechanism of the gas phase ozonolysis of alkenes are still uncertain, this technique should be used with caution to calibrate OH instruments.
50
Gilge, S., C. Plass-Duelmer, W. Fricke, A. Kaiser, L. Ries, and B. Buchmann. "Ozone, Carbon monoxide and Nitrogen oxides time series at four Alpine GAW mountain stations in Central Europe." Atmospheric Chemistry and Physics Discussions 10, no. 8 (2010): 19071–127. http://dx.doi.org/10.5194/acpd-10-19071-2010.
Full textAbstract:
Abstract. Long-term, ground based in-situ observations of Ozone (O3) and its precursor gases Nitrogen dioxide (NO2) and Carbon monoxide (CO) from the four sites Hohenpeissenberg and Zugspitze (D), Sonnblick (A) and Jungfraujoch (CH) are presented for the period 1995–2007. These Central European alpine mountain observatories cover an altitude range of roughly 1000 to 3500 m. Comparable analytical methods and common quality assurance (QA) procedures are used at all sites. For O3 and CO, calibration is linked to primary calibrations (O3) or CO standards provided by the Central Calibration Laboratory (CCL) at NOAA/ESRL. All stations have been audited by the World Calibration Centre (WCC) for CO and O3 (WCC-Empa; CH). Data from long-term measurements of NO2 and CO are only available from Hohenpeissenberg and Jungfraujoch. Both sites show slightly decreasing mixing ratios of the primarily emitted NO2 and the partly anthropogenically emitted CO between 1995 and 2007. The findings are generally consistent with shorter observation periods at Zugspitze and Sonnblick and thus are considered to represent regional changes in Central European atmospheric composition at this altitude range. Over the same period 1995–2007, the O3 mixing ratios have slightly increased at three of the four sites. This was observed independent of wind sector and for most seasons, with a tendency to higher positive trends in winter and lower and partly negative trends in summer. Trends are often more pronounced in winter and less in summer; highest declines of NO2 and CO are observed in winter and the lowest in summer, whereas the highest rate of O3 increase was detected in winter and lowest in summer, respectively. Weekly cycles demonstrate anthropogenic impact at all elevations with enhanced NO2 on working days compared to weekends. Enhanced O3 values on working days indicating photochemical production from anthropogenic precursors are only observed in summer, whereas in all other seasons anti-correlation with NO2, was found due to reduced O3 values on working days. Trends are discussed with respect to anthropogenic impacts and vertical mixing. The observed trends for NO2 at the alpine mountain sites are less pronounced than trends estimated based on emission inventories.