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Anne M Thompson - One of the best experts on this subject based on the ideXlab platform.

  • Insights into Tropospheric Ozone from the INTEX Ozonesonde Network Study (IONS)
    2020
    Co-Authors: Anne M Thompson, S.j. Oltmans, F J Schmidlin, Michael J. Newchurch, J C Witte, Tom Kucsera, John T. Merrill, G. Morris, D. Tarasick
    Abstract:

    Ozone profile data from soundings integrate models, aircraft and other ground-based measurements for better interpretation of atmospheric chemistry and dynamics. A well-designed network of ozonesonde stations, with consistent sampling, can answer questions not possible with short campaigns or current satellite technology. The SHADOZ (Southern Hemisphere Additional Ozonesondes) project, for example, has led to these findings about tropical ozone: definition of the zonal tropospheric wave-one pattern in equatorial ozone, characterization of the "Atlantic ozone paradox" and establishment of a link between tropical Atlantic and Indian Ocean pollution. Building on the SHADOZ concept, a short-term ozone network was formed in July-August 2004 to coordinate ozonesonde launches during the ICARTT/INTEX/NEAQS (International Consortium on Atmospheric Research on Transport and Transformation)/Intercontinental Transport Experiment/New England Air Quality Study. In IONS (INTEX Ozonesonde Network Study), more than 250 soundings, with daily frequency at half the sites, were launched from eleven North American stations and an oceanographic ship in the Gulf of Maine. Although the goal was to examine pollution influences under stable high-pressure systems and transport associated with "warm conveyor belt" flows, the INTEX study region was dominated by a series of weak frontal system that mixed aged pollution with stratospheric ozone in the middle troposphere. Deconvoluting ozone sources provides new insights into ozone in the transition between mid-latitude and polar air.

  • A Characterization of Vertical Ozonesonde Measurements at the Equatorial Locations of SHADOZ
    2020
    Co-Authors: F J Schmidlin, Anne M Thompson, Volker W J H Kirchhoff, Bruno Hoegger, S. Oltmans, John C. Gerlach
    Abstract:

    Beginning in 1997 ozonesonde observations have been obtained from Equatorial locations participating in SHADOZ (Southern Hemisphere Additional Ozone) Project. Vertical ozone profiles are available from the western Pacific eastward to Kenya. Presently 10 stations provide vertical ECC ozonesonde measurements at least weekly. Statistical analysis shows the variation that occurs in the level of maximum ozone, the difference between integrated total ozone overburden from ECC and EP-TOMS observations, and with Dobson Spectrophotometers, when data are available.

  • quantifying stratosphere troposphere transport of ozone using balloon borne Ozonesondes radar windprofilers and trajectory models
    Atmospheric Environment, 2019
    Co-Authors: D W Tarasick, B. J. Johnson, Anne M Thompson, S.j. Oltmans, T K Careysmith, W K Hocking, O Moeini, H He, M Osman, John T. Merrill
    Abstract:

    Abstract In a series of 10-day campaigns in Ontario and Quebec, Canada, between 2005 and 2007, Ozonesondes were launched twice daily in conjunction with continuous high-resolution wind-profiling radar measurements. Windprofilers can measure rapid changes in the height of the tropopause, and in some cases follow stratospheric intrusions. Observed stratospheric intrusions were studied with the aid of a Lagrangian particle dispersion model and the Canadian operational weather forecast system. Definite stratosphere-troposphere transport (STT) events occurred approximately every 2–3 days during the spring and summer campaigns, whereas during autumn and winter, the frequency was reduced to every 4–5 days. Although most events reached the lower troposphere, only three events appear to have significantly contributed to ozone amounts in the surface boundary layer. Detailed calculations find that STT, while highly variable, is responsible for an average, over the seven campaigns, of 3.1% of boundary layer ozone (1.2 ppb), but 13% (5.4 ppb) in the lower troposphere and 34% (22 ppb) in the middle and upper troposphere, where these layers are defined as 0–1 km, 1–3 km, and 3–8 km respectively. Estimates based on counting laminae in ozonesonde profiles, with judicious choices of ozone and relative humidity thresholds, compare moderately well, on average, with these values. The lamina detection algorithm is then applied to a large dataset from four summer ozonesonde campaigns at 18 North American sites between 2006 and 2011. The results show some site-to-site and year-to-year variability, but stratospheric ozone contributions average 4.6% (boundary layer), 15% (lower troposphere) and 26% (middle/upper troposphere). Calculations were also performed based on the TOST global 3D trajectory-mapped ozone data product. Maps of STT in the same three layers of the troposphere suggest that the STT ozone flux is greater over the North American continent than Europe, and much greater in winter and spring than in summer or fall. When averaged over all seasons, magnitudes over North America show similar ratios between levels to the previous calculations, but are overall 3–4 times smaller. This may be because of limitations (trajectory length and vertical resolution) to the current TOST-based calculation.

  • Homogenizing and estimating the uncertainty in NOAA's long-term vertical ozone profile records measured with the electrochemical concentration cell ozonesonde
    Atmospheric Measurement Techniques, 2018
    Co-Authors: C. W. Sterling, Samuel J. Oltmans, Anne M Thompson, Herman G J Smit, Bryan J. Johnson, A. F. Jordan, P. Cullis, E. Hall, Jacquelyn C. Witte
    Abstract:

    NOAA’s program of long term monitoring of the vertical distribution of ozone with Electrochemical Concentration Cell (ECC) Ozonesondes has undergone a number of changes over the 50 year record. In order to produce a homogenous data set, these changes must be documented and where necessary, appropriate corrections applied. This is the first comprehensive and consistent reprocessing of NOAA’s ozonesonde data records that corrects for these changes using the rawest form of the data (cell current and pump temperature) in native resolution as well as a point by point uncertainty calculation that is unique to each sounding. The reprocessing is carried out uniformly at all eight ozonesonde sites in NOAA’s network with differences in sensing solution and ozonesonde types accounted for in the same way at all sites. The corrections used to homogenize the NOAA ozonesonde data records greatly improve the ozonesonde measurements with an average one sigma uncertainty of ±4–6 % in the stratosphere and ±5–20 % in the troposphere. A comparison of the integrated column ozone from the ozonesonde profile with co-located Dobson spectrophotometers total column ozone measurements shows agreement within ±5 % for > 70 % of the profiles. Very good agreement is also found in the stratosphere between ozonesonde profiles and profiles retrieved from the Solar Backscatter Ultraviolet Instruments (SBUV).

  • the southern hemisphere additional Ozonesondes shadoz 1998 2002 tropical ozone climatology
    2018
    Co-Authors: F J Schmidlin, B. J. Johnson, J C Witte, Herman G J Smit, Volker W J H Kirchhoff, S.j. Oltmans, Anne M Thompson
    Abstract:

    Abstract: Since 1998 the Southern Hemisphere ADditional Ozonesondes (SHADOZ) project has collected more than 2000 ozone profiles from a dozen tropical and subtropical sites using balloon-borne electrochemical concentration cell (ECC) Ozonesondes. The data (with accompanying pressure-temperature-humidity soundings) are archived. Analysis of ozonesonde imprecision within the SHADOZ dataset revealed that variations in ozonesonde technique could lead to station-to-station biases in the measurements. In this paper imprecisions and accuracy in the SHADOZ dataset are examined in light of new data. When SHADOZ total ozone column amounts are compared to version 8 TOMS (2004 release), discrepancies between sonde and satellite datasets decline 1-2 percentage points on average, compared to version 7 TOMS. Variability among stations is evaluated using total ozone normalized to TOMS and results of laboratory tests on Ozonesondes (JOSE-2O00, Julich Ozonesonde Intercomparison Experiment). Ozone deviations from a standard instrument in the JOSE flight simulation chamber resemble those of SHADOZ station data relative to a SHADOZ-defined climatological reference. Certain systematic variations in SHADOZ ozone profiles are accounted for by differences in solution composition, data processing and instrument (manufacturer). Instrument bias leads to a greater ozone measurement above 25 km over Nairobi and to lower total column ozone at three Pacific sites compared to other SHADOZ stations at 0-20 deg.S.

J C Witte - One of the best experts on this subject based on the ideXlab platform.

  • Insights into Tropospheric Ozone from the INTEX Ozonesonde Network Study (IONS)
    2020
    Co-Authors: Anne M Thompson, S.j. Oltmans, F J Schmidlin, Michael J. Newchurch, J C Witte, Tom Kucsera, John T. Merrill, G. Morris, D. Tarasick
    Abstract:

    Ozone profile data from soundings integrate models, aircraft and other ground-based measurements for better interpretation of atmospheric chemistry and dynamics. A well-designed network of ozonesonde stations, with consistent sampling, can answer questions not possible with short campaigns or current satellite technology. The SHADOZ (Southern Hemisphere Additional Ozonesondes) project, for example, has led to these findings about tropical ozone: definition of the zonal tropospheric wave-one pattern in equatorial ozone, characterization of the "Atlantic ozone paradox" and establishment of a link between tropical Atlantic and Indian Ocean pollution. Building on the SHADOZ concept, a short-term ozone network was formed in July-August 2004 to coordinate ozonesonde launches during the ICARTT/INTEX/NEAQS (International Consortium on Atmospheric Research on Transport and Transformation)/Intercontinental Transport Experiment/New England Air Quality Study. In IONS (INTEX Ozonesonde Network Study), more than 250 soundings, with daily frequency at half the sites, were launched from eleven North American stations and an oceanographic ship in the Gulf of Maine. Although the goal was to examine pollution influences under stable high-pressure systems and transport associated with "warm conveyor belt" flows, the INTEX study region was dominated by a series of weak frontal system that mixed aged pollution with stratospheric ozone in the middle troposphere. Deconvoluting ozone sources provides new insights into ozone in the transition between mid-latitude and polar air.

  • first reprocessing of southern hemisphere additional Ozonesondes profile records 3 uncertainty in ozone profile and total column
    Journal of Geophysical Research, 2018
    Co-Authors: J C Witte, Françoise Posny, Anne M Thompson, Herman G J Smit, Holger Vomel, René Stübi
    Abstract:

    Reprocessed ozonesonde data from eight SHADOZ (Southern Hemisphere ADditional Ozonesondes) sites have been used to derive the first analysis of uncertainty estimates for both profile and total column ozone (TCO). The ozone uncertainty is a composite of the uncertainties of the individual terms in the ozone partial pressure (PO3) equation, those being the ozone sensor current, background current, internal pump temperature, pump efficiency factors, conversion efficiency, and flow-rate. Overall, PO3 uncertainties (ΔPO3) are within 15% and peak around the tropopause (15±3km) where ozone is a minimum and ΔPO3 approaches the measured signal. The uncertainty in the background and sensor currents dominate the overall ΔPO3 in the troposphere including the tropopause region, while the uncertainties in the conversion efficiency and flow-rate dominate in the stratosphere. Seasonally, ΔPO3 is generally a maximum in the March-May, with the exception of SHADOZ sites in Asia, for which the highest ΔPO3 occurs in September-February. As a first approach, we calculate sonde TCO uncertainty (ΔTCO) by integrating the profile ΔPO3 and adding the ozone residual uncertainty, derived from the McPeters and Labow [2012] 1-σ ozone mixing ratios. Overall, ΔTCO are within ±15 DU, representing ~5-6% of the TCO. TOMS and OMI satellite overpasses are generally within the sonde ΔTCO. However, there is a discontinuity between TOMS v8.6 (1998-2004/09) and OMI (2004/10-2016) TCO on the order of 10DU that accounts for the significant 16DU overall difference observed between sonde and TOMS. By comparison, the sonde-OMI absolute difference for the eight stations is only ~4DU.

  • first reprocessing of southern hemisphere additional Ozonesondes shadoz profile records 1998 2015 1 methodology and evaluation
    Journal of Geophysical Research, 2017
    Co-Authors: J C Witte, B. J. Johnson, Françoise Posny, Masatomo Fujiwara, Anne M Thompson, Herman G J Smit, Gert J R Coetzee, Edward T Northam, C W Sterling
    Abstract:

    Electrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long-term data records for deriving O3 trends, model development, satellite validation, and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reporting, and instrument changes that have resulted in inhomogeneities within individual station data records. A major milestone is the first reprocessing of seven Southern Hemisphere ADditional Ozonesondes (SHADOZ) station ozonesonde records to account for errors and biases in operating/processing procedures. Ascension Island, Hanoi, Irene, Kuala Lumpur, La Reunion, Natal, and Watukosek station records all show an overall increase in O3 after reprocessing. Watukosek shows the largest increase of 9.0 ± 2.1 Dobson Units (DU) in total column O3; Irene and Hanoi show a 5.5 ± 2.5 DU increase, while remaining sites show statistically insignificant enhancements. Negligible to modest O3 enhancements are observed after reprocessing in the troposphere (up to 8%) and stratosphere (up to 6%), except at La Reunion for which the application of background currents reduces tropospheric O3 (−2.1 ± 1.3 DU). Inhomogeneities due to ozonesonde/solution-type changes at Ascension, Natal, and La Reunion are resolved with the application of transfer functions. Comparisons with EP-TOMS, Aura's Ozone Monitoring Instrument and Microwave Limb Sounder (MLS) satellite O3 overpasses show an overall improvement in agreement after reprocessing. Most reprocessed data sets show a significant reduction in biases with MLS at the ozone maximum region (50–10 hPa). Changes in radiosonde/ozonesonde system and nonstandard solution types can account for remaining discrepancies observed at several sites when compared to satellites.

  • tropospheric ozone sources and wave activity over mexico city and houston during milagro intercontinental transport experiment intex b ozonesonde network study 2006 ions 06
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: Anne M Thompson, Gary A. Morris, J C Witte, J. E. Yorks, S. K. Miller, K. M. Dougherty, D. Baumgardner, L. Ladino, B Rappengluck
    Abstract:

    During the INTEX-B (Intercontinental Chemical Transport Experiment)/ MILAGRO (Megacities Initiative: Local and Global Research Observations) experiments in March 2006 and the associated IONS-06 (INTEX Ozonesonde Network Study; http://croc.gsfc.nasa.gov/intexb/ions06.html ), regular ozonesonde launches were made over 15 North American sites. The soundings were strategically positioned to study inter-regional flows and meteorological interactions with a mixture of tropospheric O 3 sources: local pollution; O 3 associated with convection and lightning; stratosphere-troposphere exchange. The variability of tropospheric O 3 over the Mexico City Basin (MCB; 19° N, 99° W) and Houston (30° N, 95° W) is reported here. MCB and Houston profiles displayed a double tropopause in most soundings and a subtropical tropopause layer with frequent wave disturbances, identified through O 3 laminae as gravity-wave induced. Ozonesondes launched over both cities in August and September 2006 (IONS-06, Phase 3) displayed a thicker tropospheric column O 3 (~7 DU or 15–20%) than in March 2006; nearly all of the increase was in the free troposphere. In spring and summer, O 3 laminar structure manifested mixed influences from the stratosphere, convective redistribution of O 3 and precursors, and O 3 from lightning NO. Stratospheric O 3 origins were present in 39% (MCB) and 60% (Houston) of the summer sondes. Comparison of summer 2006 O 3 structure with summer 2004 sondes (IONS-04) over Houston showed 7% less tropospheric O 3 in 2006. This may reflect a sampling contrast, August to mid-September 2006 instead of July-mid August 2004.

  • Tropospheric ozone sources and wave activity over Mexico City and Houston during MILAGRO/Intercontinental Transport Experiment (INTEX-B) Ozonesonde Network Study, 2006 (IONS-06)
    Atmospheric Chemistry and Physics Discussions, 2008
    Co-Authors: A M Thompson, J C Witte, J. E. Yorks, S. K. Miller, K. M. Dougherty, G. A. Morris, D. Baumgardner, L. Ladino, B. Rappenglueck
    Abstract:

    During the INTEX-B (Intercontinental Chemical Transport Experiment)/MILAGRO (Megacities Initiative: Local and Global Research Observations) experiments in March 2006 and the associated IONS-06 (INTEX Ozonesonde Network Study; http://croc.gsfc.nasa.gov/intexb/ions06.html), regular ozonesonde launches were made over 15 North American sites. The soundings were strategically positioned to study inter-regional flows and meteorological interactions with a mixture of tropospheric O3 sources: local pollution; O3 associated with convection and lightning; stratosphere-troposphere exchange. The variability of tropospheric O3 over the Mexico City Basin (MCB; 19 N, 99 W) and Houston (30 N, 95 W) is reported here. MCB and Houston profiles displayed a double tropopause in most soundings and a subtropical tropopause layer with frequent wave disturbances, identified through O3 laminae as gravity-wave induced. Ozonesondes launched over both cities in August and September~2006 (IONS-06, Phase 3) displayed a thicker tropospheric column O3 (~7 DU or 15?20%) than in March 2006; nearly all of the increase was in the free troposphere. In spring and summer, O3 laminar structure manifested mixed influences from the stratosphere, convective redistribution of O3 and precursors, and O3 from lightning NO. Stratospheric O3 origins were present in 39% (MCB) and 60% (Houston) of the summer sondes. Comparison of summer 2006 O3 structure with summer 2004 sondes (IONS-04) over Houston showed 7% less tropospheric O3 in 2006. This may reflect a sampling contrast, August to mid-September 2006 instead of July?mid August 2004.

Françoise Posny - One of the best experts on this subject based on the ideXlab platform.

  • first reprocessing of southern hemisphere additional Ozonesondes profile records 3 uncertainty in ozone profile and total column
    Journal of Geophysical Research, 2018
    Co-Authors: J C Witte, Françoise Posny, Anne M Thompson, Herman G J Smit, Holger Vomel, René Stübi
    Abstract:

    Reprocessed ozonesonde data from eight SHADOZ (Southern Hemisphere ADditional Ozonesondes) sites have been used to derive the first analysis of uncertainty estimates for both profile and total column ozone (TCO). The ozone uncertainty is a composite of the uncertainties of the individual terms in the ozone partial pressure (PO3) equation, those being the ozone sensor current, background current, internal pump temperature, pump efficiency factors, conversion efficiency, and flow-rate. Overall, PO3 uncertainties (ΔPO3) are within 15% and peak around the tropopause (15±3km) where ozone is a minimum and ΔPO3 approaches the measured signal. The uncertainty in the background and sensor currents dominate the overall ΔPO3 in the troposphere including the tropopause region, while the uncertainties in the conversion efficiency and flow-rate dominate in the stratosphere. Seasonally, ΔPO3 is generally a maximum in the March-May, with the exception of SHADOZ sites in Asia, for which the highest ΔPO3 occurs in September-February. As a first approach, we calculate sonde TCO uncertainty (ΔTCO) by integrating the profile ΔPO3 and adding the ozone residual uncertainty, derived from the McPeters and Labow [2012] 1-σ ozone mixing ratios. Overall, ΔTCO are within ±15 DU, representing ~5-6% of the TCO. TOMS and OMI satellite overpasses are generally within the sonde ΔTCO. However, there is a discontinuity between TOMS v8.6 (1998-2004/09) and OMI (2004/10-2016) TCO on the order of 10DU that accounts for the significant 16DU overall difference observed between sonde and TOMS. By comparison, the sonde-OMI absolute difference for the eight stations is only ~4DU.

  • first reprocessing of southern hemisphere additional Ozonesondes shadoz profile records 1998 2015 1 methodology and evaluation
    Journal of Geophysical Research, 2017
    Co-Authors: J C Witte, B. J. Johnson, Françoise Posny, Masatomo Fujiwara, Anne M Thompson, Herman G J Smit, Gert J R Coetzee, Edward T Northam, C W Sterling
    Abstract:

    Electrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long-term data records for deriving O3 trends, model development, satellite validation, and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reporting, and instrument changes that have resulted in inhomogeneities within individual station data records. A major milestone is the first reprocessing of seven Southern Hemisphere ADditional Ozonesondes (SHADOZ) station ozonesonde records to account for errors and biases in operating/processing procedures. Ascension Island, Hanoi, Irene, Kuala Lumpur, La Reunion, Natal, and Watukosek station records all show an overall increase in O3 after reprocessing. Watukosek shows the largest increase of 9.0 ± 2.1 Dobson Units (DU) in total column O3; Irene and Hanoi show a 5.5 ± 2.5 DU increase, while remaining sites show statistically insignificant enhancements. Negligible to modest O3 enhancements are observed after reprocessing in the troposphere (up to 8%) and stratosphere (up to 6%), except at La Reunion for which the application of background currents reduces tropospheric O3 (−2.1 ± 1.3 DU). Inhomogeneities due to ozonesonde/solution-type changes at Ascension, Natal, and La Reunion are resolved with the application of transfer functions. Comparisons with EP-TOMS, Aura's Ozone Monitoring Instrument and Microwave Limb Sounder (MLS) satellite O3 overpasses show an overall improvement in agreement after reprocessing. Most reprocessed data sets show a significant reduction in biases with MLS at the ozone maximum region (50–10 hPa). Changes in radiosonde/ozonesonde system and nonstandard solution types can account for remaining discrepancies observed at several sites when compared to satellites.

  • First reprocessing of Southern Hemisphere ADditional Ozonesondes (SHADOZ) profile records (1998–2015): 1. Methodology and evaluation
    Journal of Geophysical Research, 2017
    Co-Authors: Jacquelyn C. Witte, Françoise Posny, Masatomo Fujiwara, Anne M Thompson, Herman G J Smit, Bryan J. Johnson, Gert J R Coetzee, Edward T Northam, C W Sterling, Maznorizan Mohamad
    Abstract:

    Electrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long-term data records for deriving O3 trends, model development, satellite validation, and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reporting, and instrument changes that have resulted in inhomogeneities within individual station data records. A major milestone is the first reprocessing of seven Southern Hemisphere ADditional Ozonesondes (SHADOZ) station ozonesonde records to account for errors and biases in operating/processing procedures. Ascension Island, Hanoi, Irene, Kuala Lumpur, La Reunion, Natal, and Watukosek station records all show an overall increase in O3 after reprocessing. Watukosek shows the largest increase of 9.0 ± 2.1 Dobson Units (DU) in total column O3; Irene and Hanoi show a 5.5 ± 2.5 DU increase, while remaining sites show statistically insignificant enhancements. Negligible to modest O3 enhancements are observed after reprocessing in the troposphere (up to 8%) and stratosphere (up to 6%), except at La Reunion for which the application of background currents reduces tropospheric O3 (−2.1 ± 1.3 DU). Inhomogeneities due to ozonesonde/solution-type changes at Ascension, Natal, and La Reunion are resolved with the application of transfer functions. Comparisons with EP-TOMS, Aura's Ozone Monitoring Instrument and Microwave Limb Sounder (MLS) satellite O3 overpasses show an overall improvement in agreement after reprocessing. Most reprocessed data sets show a significant reduction in biases with MLS at the ozone maximum region (50–10 hPa). Changes in radiosonde/ozonesonde system and nonstandard solution types can account for remaining discrepancies observed at several sites when compared to satellites.

  • tropospheric ozone climatology at two southern hemisphere tropical subtropical sites reunion island and irene south africa from Ozonesondes lidar and in situ aircraft measurements
    Atmospheric Chemistry and Physics, 2009
    Co-Authors: Gaëlle Clain, Robert Delmas, Roseanne Diab, Jean-marc Metzger, Jean-luc Baray, Françoise Posny, Philippe Keckhut, Jimmy Leclair De Bellevue, Jean-pierre Cammas
    Abstract:

    This paper presents a climatology and trends of tropospheric ozone in the Southwestern Indian Ocean (Reunion Island) and South Africa (Irene and Johannesburg). This study is based on a multi-instrumental dataset: PTU-O3 Ozonesondes, DIAL LIDAR and MOZAIC airborne instrumentation. The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets: Ozonesondes and LIDAR. The two climatological profiles are similar, except in austral summer when the LIDAR profiles show greater values in the free troposphere, and in the upper troposphere when the LIDAR profiles show lower values during all seasons. These results show that the climatological value of LIDAR profiles must be discussed with care since LIDAR measurements can be performed only under clear sky conditions, and the upper limit of the profile depends on the signal strength. In addition, linear trends have been calculated from ozonesonde data at Reunion and Irene. Considering the whole tropospheric column, the trend is slightly positive for Reunion, and more clearly positive for Irene. Trend calculations have also been made separating the troposphere into three layers, and separating the dataset into seasons. Results show that the positive trend for Irene is governed by the lower layer that is affected by industrial pollution and biomass burning. On the contrary, for Reunion Island, the strongest trends are observed in the upper troposphere, and in winter when stratosphere-troposphere exchange is more frequently expected.

  • Tropospheric ozone climatology at two Southern Hemisphere tropical/subtropical sites, (Reunion Island and Irene, South Africa) from Ozonesondes, LIDAR, and in situ aircraft measurements
    Atmospheric Chemistry and Physics, 2009
    Co-Authors: Gaëlle Clain, Robert Delmas, Roseanne Diab, Jimmy Leclair De Bellevue, Jean-marc Metzger, Jean-luc Baray, Françoise Posny, Philippe Keckhut, Jean-pierre Cammas
    Abstract:

    This paper presents a climatology and trends of tropospheric ozone in the Southwestern Indian Ocean (Reunion Island) and South Africa (Irene and Johannesburg). This study is based on a multi-instrumental dataset: PTU-O3 Ozonesondes, DIAL LIDAR and MOZAIC airborne instrumentation. The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets: Ozonesondes and LIDAR. The two climatological profiles are similar, except in austral summer when the LIDAR profiles show greater values in the free troposphere, and in the upper troposphere when the LIDAR profiles show lower values during all seasons. These results show that the climatological value of LIDAR profiles must be discussed with care since LIDAR measurements can be performed only under clear sky conditions, and the upper limit of the profile depends on the signal strength. In addition, linear trends have been calculated from ozonesonde data at Reunion and Irene. Considering the whole tropospheric column, the trend is slightly positive for Reunion, and more clearly positive for Irene. Trend calculations have also been made separating the troposphere into three layers, and separating the dataset into seasons. Results show that the positive trend for Irene is governed by the lower layer that is affected by industrial pollution and biomass burning. On the contrary, for Reunion Island, the strongest trends are observed in the upper troposphere, and in winter when stratosphere-troposphere exchange is more frequently expected.

Herman G J Smit - One of the best experts on this subject based on the ideXlab platform.

  • Homogenizing and estimating the uncertainty in NOAA's long-term vertical ozone profile records measured with the electrochemical concentration cell ozonesonde
    Atmospheric Measurement Techniques, 2018
    Co-Authors: C. W. Sterling, Samuel J. Oltmans, Anne M Thompson, Herman G J Smit, Bryan J. Johnson, A. F. Jordan, P. Cullis, E. Hall, Jacquelyn C. Witte
    Abstract:

    NOAA’s program of long term monitoring of the vertical distribution of ozone with Electrochemical Concentration Cell (ECC) Ozonesondes has undergone a number of changes over the 50 year record. In order to produce a homogenous data set, these changes must be documented and where necessary, appropriate corrections applied. This is the first comprehensive and consistent reprocessing of NOAA’s ozonesonde data records that corrects for these changes using the rawest form of the data (cell current and pump temperature) in native resolution as well as a point by point uncertainty calculation that is unique to each sounding. The reprocessing is carried out uniformly at all eight ozonesonde sites in NOAA’s network with differences in sensing solution and ozonesonde types accounted for in the same way at all sites. The corrections used to homogenize the NOAA ozonesonde data records greatly improve the ozonesonde measurements with an average one sigma uncertainty of ±4–6 % in the stratosphere and ±5–20 % in the troposphere. A comparison of the integrated column ozone from the ozonesonde profile with co-located Dobson spectrophotometers total column ozone measurements shows agreement within ±5 % for > 70 % of the profiles. Very good agreement is also found in the stratosphere between ozonesonde profiles and profiles retrieved from the Solar Backscatter Ultraviolet Instruments (SBUV).

  • the southern hemisphere additional Ozonesondes shadoz 1998 2002 tropical ozone climatology
    2018
    Co-Authors: F J Schmidlin, B. J. Johnson, J C Witte, Herman G J Smit, Volker W J H Kirchhoff, S.j. Oltmans, Anne M Thompson
    Abstract:

    Abstract: Since 1998 the Southern Hemisphere ADditional Ozonesondes (SHADOZ) project has collected more than 2000 ozone profiles from a dozen tropical and subtropical sites using balloon-borne electrochemical concentration cell (ECC) Ozonesondes. The data (with accompanying pressure-temperature-humidity soundings) are archived. Analysis of ozonesonde imprecision within the SHADOZ dataset revealed that variations in ozonesonde technique could lead to station-to-station biases in the measurements. In this paper imprecisions and accuracy in the SHADOZ dataset are examined in light of new data. When SHADOZ total ozone column amounts are compared to version 8 TOMS (2004 release), discrepancies between sonde and satellite datasets decline 1-2 percentage points on average, compared to version 7 TOMS. Variability among stations is evaluated using total ozone normalized to TOMS and results of laboratory tests on Ozonesondes (JOSE-2O00, Julich Ozonesonde Intercomparison Experiment). Ozone deviations from a standard instrument in the JOSE flight simulation chamber resemble those of SHADOZ station data relative to a SHADOZ-defined climatological reference. Certain systematic variations in SHADOZ ozone profiles are accounted for by differences in solution composition, data processing and instrument (manufacturer). Instrument bias leads to a greater ozone measurement above 25 km over Nairobi and to lower total column ozone at three Pacific sites compared to other SHADOZ stations at 0-20 deg.S.

  • first reprocessing of southern hemisphere additional Ozonesondes profile records 3 uncertainty in ozone profile and total column
    Journal of Geophysical Research, 2018
    Co-Authors: J C Witte, Françoise Posny, Anne M Thompson, Herman G J Smit, Holger Vomel, René Stübi
    Abstract:

    Reprocessed ozonesonde data from eight SHADOZ (Southern Hemisphere ADditional Ozonesondes) sites have been used to derive the first analysis of uncertainty estimates for both profile and total column ozone (TCO). The ozone uncertainty is a composite of the uncertainties of the individual terms in the ozone partial pressure (PO3) equation, those being the ozone sensor current, background current, internal pump temperature, pump efficiency factors, conversion efficiency, and flow-rate. Overall, PO3 uncertainties (ΔPO3) are within 15% and peak around the tropopause (15±3km) where ozone is a minimum and ΔPO3 approaches the measured signal. The uncertainty in the background and sensor currents dominate the overall ΔPO3 in the troposphere including the tropopause region, while the uncertainties in the conversion efficiency and flow-rate dominate in the stratosphere. Seasonally, ΔPO3 is generally a maximum in the March-May, with the exception of SHADOZ sites in Asia, for which the highest ΔPO3 occurs in September-February. As a first approach, we calculate sonde TCO uncertainty (ΔTCO) by integrating the profile ΔPO3 and adding the ozone residual uncertainty, derived from the McPeters and Labow [2012] 1-σ ozone mixing ratios. Overall, ΔTCO are within ±15 DU, representing ~5-6% of the TCO. TOMS and OMI satellite overpasses are generally within the sonde ΔTCO. However, there is a discontinuity between TOMS v8.6 (1998-2004/09) and OMI (2004/10-2016) TCO on the order of 10DU that accounts for the significant 16DU overall difference observed between sonde and TOMS. By comparison, the sonde-OMI absolute difference for the eight stations is only ~4DU.

  • Homogenizing and Estimating the Uncertainty in NOAA’s Long Term Vertical Ozone Profile Records Measured with the Electrochemical Concentration Cell Ozonesonde
    2017
    Co-Authors: C. W. Sterling, Samuel J. Oltmans, Anne M Thompson, Herman G J Smit, Bryan J. Johnson, A. F. Jordan, P. Cullis, Emrys G. Hall, Jacquelyn C. Witte
    Abstract:

    <p><strong>Abstract.</strong> NOAA’s program of long term monitoring of the vertical distribution of ozone with Electrochemical Concentration Cell (ECC) Ozonesondes has undergone a number of changes over the 50 year record. In order to produce a homogenous data set, these changes must be documented and where necessary, appropriate corrections applied. This is the first comprehensive and consistent reprocessing of NOAA’s ozonesonde data records that corrects for these changes using the rawest form of the data (cell current and pump temperature) in native resolution as well as a point by point uncertainty calculation that is unique to each sounding. The reprocessing is carried out uniformly at all eight ozonesonde sites in NOAA’s network with differences in sensing solution and ozonesonde types accounted for in the same way at all sites. The corrections used to homogenize the NOAA ozonesonde data records greatly improve the ozonesonde measurements with an average one sigma uncertainty of ±4–6 % in the stratosphere and ±5–20 % in the troposphere. A comparison of the integrated column ozone from the ozonesonde profile with co-located Dobson spectrophotometers total column ozone measurements shows agreement within ±5 % for > 70 % of the profiles. Very good agreement is also found in the stratosphere between ozonesonde profiles and profiles retrieved from the Solar Backscatter Ultraviolet Instruments (SBUV).</p>

  • first reprocessing of southern hemisphere additional Ozonesondes shadoz profile records 1998 2015 1 methodology and evaluation
    Journal of Geophysical Research, 2017
    Co-Authors: J C Witte, B. J. Johnson, Françoise Posny, Masatomo Fujiwara, Anne M Thompson, Herman G J Smit, Gert J R Coetzee, Edward T Northam, C W Sterling
    Abstract:

    Electrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long-term data records for deriving O3 trends, model development, satellite validation, and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reporting, and instrument changes that have resulted in inhomogeneities within individual station data records. A major milestone is the first reprocessing of seven Southern Hemisphere ADditional Ozonesondes (SHADOZ) station ozonesonde records to account for errors and biases in operating/processing procedures. Ascension Island, Hanoi, Irene, Kuala Lumpur, La Reunion, Natal, and Watukosek station records all show an overall increase in O3 after reprocessing. Watukosek shows the largest increase of 9.0 ± 2.1 Dobson Units (DU) in total column O3; Irene and Hanoi show a 5.5 ± 2.5 DU increase, while remaining sites show statistically insignificant enhancements. Negligible to modest O3 enhancements are observed after reprocessing in the troposphere (up to 8%) and stratosphere (up to 6%), except at La Reunion for which the application of background currents reduces tropospheric O3 (−2.1 ± 1.3 DU). Inhomogeneities due to ozonesonde/solution-type changes at Ascension, Natal, and La Reunion are resolved with the application of transfer functions. Comparisons with EP-TOMS, Aura's Ozone Monitoring Instrument and Microwave Limb Sounder (MLS) satellite O3 overpasses show an overall improvement in agreement after reprocessing. Most reprocessed data sets show a significant reduction in biases with MLS at the ozone maximum region (50–10 hPa). Changes in radiosonde/ozonesonde system and nonstandard solution types can account for remaining discrepancies observed at several sites when compared to satellites.

F J Schmidlin - One of the best experts on this subject based on the ideXlab platform.

  • A Characterization of Vertical Ozonesonde Measurements at the Equatorial Locations of SHADOZ
    2020
    Co-Authors: F J Schmidlin, Anne M Thompson, Volker W J H Kirchhoff, Bruno Hoegger, S. Oltmans, John C. Gerlach
    Abstract:

    Beginning in 1997 ozonesonde observations have been obtained from Equatorial locations participating in SHADOZ (Southern Hemisphere Additional Ozone) Project. Vertical ozone profiles are available from the western Pacific eastward to Kenya. Presently 10 stations provide vertical ECC ozonesonde measurements at least weekly. Statistical analysis shows the variation that occurs in the level of maximum ozone, the difference between integrated total ozone overburden from ECC and EP-TOMS observations, and with Dobson Spectrophotometers, when data are available.

  • Insights into Tropospheric Ozone from the INTEX Ozonesonde Network Study (IONS)
    2020
    Co-Authors: Anne M Thompson, S.j. Oltmans, F J Schmidlin, Michael J. Newchurch, J C Witte, Tom Kucsera, John T. Merrill, G. Morris, D. Tarasick
    Abstract:

    Ozone profile data from soundings integrate models, aircraft and other ground-based measurements for better interpretation of atmospheric chemistry and dynamics. A well-designed network of ozonesonde stations, with consistent sampling, can answer questions not possible with short campaigns or current satellite technology. The SHADOZ (Southern Hemisphere Additional Ozonesondes) project, for example, has led to these findings about tropical ozone: definition of the zonal tropospheric wave-one pattern in equatorial ozone, characterization of the "Atlantic ozone paradox" and establishment of a link between tropical Atlantic and Indian Ocean pollution. Building on the SHADOZ concept, a short-term ozone network was formed in July-August 2004 to coordinate ozonesonde launches during the ICARTT/INTEX/NEAQS (International Consortium on Atmospheric Research on Transport and Transformation)/Intercontinental Transport Experiment/New England Air Quality Study. In IONS (INTEX Ozonesonde Network Study), more than 250 soundings, with daily frequency at half the sites, were launched from eleven North American stations and an oceanographic ship in the Gulf of Maine. Although the goal was to examine pollution influences under stable high-pressure systems and transport associated with "warm conveyor belt" flows, the INTEX study region was dominated by a series of weak frontal system that mixed aged pollution with stratospheric ozone in the middle troposphere. Deconvoluting ozone sources provides new insights into ozone in the transition between mid-latitude and polar air.

  • An Automated Method for Ozonesonde Calibration: New Insights
    2008
    Co-Authors: F J Schmidlin, Gilbert Levrat, Bruno Hoegger, Tony Baldwin
    Abstract:

    An automated method for preparation of the electrochemical concentration cell (ECC) ozonesonde is presented. Development of a computer-controlled system for preparation and calibration of the ECC is an improvement over the manual preparation method, and reduces subjectivity considerably. Preparation measurements in digital form aids analysis of the ECC before release and enhances post-flight data certification. Calibration of Ozonesondes over a range of ozone concentrations between 0 mPA and 30 mPA is discussed. This presentation describes the automatic system, gives examples of calibrations. The automated system enables comparison of varying potassium iodide (KI) concentrations that should allow adjustment of earlier ozonesonde data obtained with different KT concentrations used since 1970, i.e., 2, 1.5, 1, and 0.5 percent. Preliminary results indicate ECC accuracy has a strong dependence on the electrolyte concentration and should not be considered linear with altitude.

  • in flight comparison of brewer mast and electrochemical concentration cell Ozonesondes
    Journal of Geophysical Research, 2008
    Co-Authors: René Stübi, Gilbert Levrat, Bruno Hoegger, P Viatte, J Staehelin, F J Schmidlin
    Abstract:

    [1] The analysis of 140 dual flights between two types of Ozonesondes, namely, the Brewer-Mast (BM) and the electrochemical concentration cell (ECC), is presented in this study. These dual flights were performed before the transition from BM to ECC as the operational ozonesonde for the Payerne Aerological Station, Switzerland. The different factors of the ozonesonde data processing are considered and their influences on the profile of the difference are evaluated. The analysis of the ozone difference between the BM and the ECC ozonesonde data shows good agreement between the two sonde types. The profile of the ozone difference is limited to ±5% (±0.3 mPa) from the ground to 32 km. The analysis confirms the appropriateness of the standard BM data processing method and the usefulness of the normalization of the ozonesonde data. The conclusions of the extended dual flight campaigns are corroborated by the analysis of the time series of the Payerne soundings for the periods of 5 years before and after the change from BM to ECC which occurred in September 2002. No significant discontinuity can be identified in 2002 attributable to the change of sonde.

  • southern hemisphere additional Ozonesondes shadoz 1998 2000 tropical ozone climatology 1 comparison with total ozone mapping spectrometer toms and ground based measurements
    Journal of Geophysical Research, 2003
    Co-Authors: Anne M Thompson, Françoise Posny, Masatomo Fujiwara, Volker W J H Kirchhoff, S.j. Oltmans, F J Schmidlin, R D Mcpeters, Jennifer A Logan, J C Witte, Gert J R Coetzee
    Abstract:

    [1] A network of 10 southern hemisphere tropical and subtropical stations, designated the Southern Hemisphere Additional Ozonesondes (SHADOZ) project and established from operational sites, provided over 1000 ozone profiles during the period 1998–2000. Balloon-borne electrochemical concentration cell (ECC) Ozonesondes, combined with standard radiosondes for pressure, temperature, and relative humidity measurements, collected profiles in the troposphere and lower to midstratosphere at: Ascension Island; Nairobi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; and Natal, Brazil. The archived data are available at: 〈http://croc.gsfc.nasa.gov/shadoz〉.1 In this paper, uncertainties and accuracies within the SHADOZ ozone data set are evaluated by analyzing: (1) imprecisions in profiles and in methods of extrapolating ozone above balloon burst; (2) comparisons of column-integrated total ozone from sondes with total ozone from the Earth-Probe/Total Ozone Mapping Spectrometer (TOMS) satellite and ground-based instruments; and (3) possible biases from station to station due to variations in ozonesonde characteristics. The key results are the following: (1) Ozonesonde precision is 5%. (2) Integrated total ozone column amounts from the sondes are usually to within 5% of independent measurements from ground-based instruments at five SHADOZ sites and overpass measurements from the TOMS satellite (version 7 data). (3) Systematic variations in TOMS-sonde offsets and in ground-based-sonde offsets from station to station reflect biases in sonde technique as well as in satellite retrieval. Discrepancies are present in both stratospheric and tropospheric ozone. (4) There is evidence for a zonal wave-one pattern in total and tropospheric ozone, but not in stratospheric ozone.

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