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[show abstract]
[hide abstract]
ABSTRACT: Recognizing the importance of water vapor in the upper troposphere and lower strato-sphere (UT/LS) and the scarcity of high-quality, long-term measurements, JPL began the development of a powerful Raman lidar in 2005 to try to meet these needs. This development was endorsed by the Network for the Detection of Atmospheric Compo-5 sition Change (NDACC) and the validation program for the EOS-Aura satellite. In this paper we review the stages in the instrumental development of the lidar and the con-clusions from three validation campaigns: MOHAVE, MOHAVE-II, and MOHAVE 2009 (Measurements of Humidity in the Atmosphere and Validation Experiments). The data analysis, profile retrieval and calibration procedures, as well as additional results from 10 MOHAVE-2009 are presented in detail in a companion paper (Leblanc et al., 2011a). Ultimately the lidar has demonstrated capability to measure water vapor profiles from ∼1 km above the ground to the lower stratosphere, reaching 14 km for 1-h integrated profiles and 21 km for 6-h integrated profiles, with a precision of 10 % or better near 13 km and below, and an estimated accuracy of 5 %.
Meas. Tech. Discuss. 01/2011; 4:5079-5109.
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O R Cooper,
D D Parrish,
A Stohl,
M Trainer,
P Nédélec,
V Thouret,
J P Cammas,
S J Oltmans,
B J Johnson,
D Tarasick,
T Leblanc, I S McDermid,
D Jaffe,
R Gao,
J Stith,
T Ryerson,
K Aikin,
T Campos,
A Weinheimer,
M A Avery
[show abstract]
[hide abstract]
ABSTRACT: In the lowermost layer of the atmosphere-the troposphere-ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases. High concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity. Moreover, tropospheric ozone itself acts as an effective greenhouse gas. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors resulting in widespread increases in ozone concentrations since the late 1800s. At present, east Asia has the fastest-growing ozone precursor emissions. Much of the springtime east Asian pollution is exported eastwards towards western North America. Despite evidence that the exported Asian pollution produces ozone, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995-2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes, with western North America being particularly sensitive to rising Asian emissions. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA's compliance with its ozone air quality standard.
Nature 01/2010; 463(7279):344-8. · 36.28 Impact Factor
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J. A. E. van Gijsel,
D. P. J. Swart,
Jean-Luc Baray,
Hassan Bencherif,
H. Claude,
T. Fehr,
Sophie Godin-Beekmann,
G. H. Hansen,
Philippe Keckhut,
Thierry Leblanc, I. S. McDermid,
Y. J. Meijer,
H. Nakane,
E. J. Quel,
K. Stebel,
W. Steinbrecht,
K. B. Strawbridge,
B. I. Tatarov,
A. E. Wolfram
[show abstract]
[hide abstract]
ABSTRACT: The validation of ozone profiles retrieved by satellite instruments through comparison with data from ground-based instruments is important to monitor the evolution of the satellite instrument, to assist algorithm development and to allow multi-mission trend analyses. In this study we compare ozone profiles derived from GOMOS night-time observations with measurements from lidar, microwave radiometer and balloon sonde. Collocated pairs are analysed for dependence on several geophysical and instrument observational parameters. Validation results are presented for the operational ESA level 2 data (GOMOS version 5.00) obtained during nearly seven years of observations and a comparison using a smaller dataset from the previous processor (version 4.02) is also included. The profiles obtained from dark limb measurements (solar zenith angle >107°) when the provided processing flag is properly considered match the ground-based measurements within ±2 percent over the altitude range 20 to 40 km. Outside this range, the pairs start to deviate more and there is a latitudinal dependence: in the polar region where there is a higher amount of straylight contamination, differences start to occur lower in the mesosphere than in the tropics, whereas for the lower part of the stratosphere the opposite happens: the profiles in the tropics reach less far down as the signal reduces faster because of the higher altitude at which the maximum ozone concentration is found compared to the mid and polar latitudes. Also the bias is shifting from mostly negative in the polar region to more positive in the tropics Profiles measured under "twilight" conditions are often matching the ground-based measurements very well, but care has to be taken in all cases when dealing with "straylight" contaminated profiles. For the selection criteria applied here (data within 800 km, 3 degrees in equivalent latitude, 20 h (5 h above 50 km) and a relative ozone error in the GOMOS data of 20% or less), no dependence was found on stellar magnitude, star temperature, nor the azimuth angle of the line of sight. No evidence of a temporal trend was seen either in the bias or frequency of outliers, but a comparison applying less strict data selection criteria might show differently.
Atmospheric Chemistry and Physics. 01/2010;
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Dupuy E,
K. A. Walker,
Kar J,
C. D. Boone,
C. T. McElroy,
P. F. Bernath,
J. R. Drummond,
Skelton R,
S. D. McLeod,
R. C. Hughes, [......],
Urban J,
Vanhellemont F,
Vigouroux C,
T. von Clarmann,
P. von der Gathen,
C. von Savigny,
J. W. Waters,
J. C. Witte,
Wolff M,
J. M. Zawodny
[show abstract]
[hide abstract]
ABSTRACT: This paper presents extensive {bias determination} analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (45–60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about +20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within ±10% (average values within ±6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (~35–55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 45–55 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements.
Atmospheric Chemistry and Physics 01/2009; · 4.88 Impact Factor
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W Steinbrecht,
H Claude,
F Schoenenborn, I S McDermid,
T Leblanc,
S Godin-Beekmann,
P Keckhut,
A Hauchecorne,
J A E Van Gijsel,
D P J Swart, [......],
I S Boyd,
N Kaempfer,
K Hocke,
R S Stolarski,
S M Frith,
L W Thomason,
E E Remsberg,
C Von Savigny,
A Rozanov,
J P Burrows
[show abstract]
[hide abstract]
ABSTRACT: Upper stratospheric ozone anomalies from the satellite-borne Solar Backscatter Ultra-Violet (SBUV), Stratospheric Aerosol and Gas Experiment II (SAGE II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments agree within 5% or better with ground-based data from lidars and microwave radiometers at five stations of the Network for the Detection of Atmospheric Composition Change (NDACC), from 45 degrees S to 48 degrees N. From 1979 until the late 1990s, all available data show a clear decline of ozone near 40 km, by 10%-15%. This decline has not continued in the last 10 years. At some sites, ozone at 40 km appears to have increased since 2000, consistent with the beginning decline of stratospheric chlorine. The phaseout of chlorofluorocarbons after the International Montreal Protocol in 1987 has been successful, and is now showing positive effects on ozone in the upper stratosphere. Temperature anomalies near 40 km altitude from European Centre for Medium Range Weather Forecast reanalyses (ERA-40), from National Centers for Environmental Prediction (NCEP) operational analyses, and from HALOE and lidar measurements show good consistency at the five stations, within about 3 K. Since about 1985, upper stratospheric temperatures have been fluctuating around a constant level at all five NDACC stations. This non-decline of upper stratospheric temperatures is a significant change from the more or less linear cooling of the upper stratosphere up until the mid-1990s, reported in previous trend assessments. It is also at odds with the almost linear 1 K per decade cooling simulated over the entire 1979-2010 period by chemistry-climate models (CCMs). The same CCM simulations, however, track the historical ozone anomalies quite well, including the change of ozone tendency in the late 1990s.
International Journal of Remote Sensing 01/2009; 30(15-16):3875-3886. · 1.12 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The Jet Propulsion Laboratory operates lidar systems at Table Mountain Facility (TMF), California (34.4 degrees N, 117.7 degrees W) and Mauna Loa Observatory, Hawaii (19.5 degrees N, 155.6 degrees W) under the framework of the Network for the Detection of Atmospheric Composition Change. To complement these systems a new Raman lidar has been developed at TMF with particular attention given to optimizing water vapor profile measurements up to the tropopause and lower stratosphere. The lidar has been designed for accuracies of 5% up to 12 km in the free troposphere and a detection capability of <5 ppmv. One important feature of the lidar is a precision alignment system using range resolved data from eight Licel transient recorders, allowing fully configurable alignment via a LABVIEW/C++ graphical user interface (GUI). This allows the lidar to be aligned on any channel while simultaneously displaying signals from other channels at configurable altitude/bin combinations. The general lidar instrumental setup and the details of the alignment control system, data acquisition, and GUI alignment software are described. Preliminary validation results using radiosonde and lidar intercomparisons are briefly presented.
The Review of scientific instruments 10/2008; 79(9):094502. · 1.52 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Analyses and results of the radiometric calibration accuracy and measurement characteristics of the first Defense Meteorological Satellite Program (DMSP)'s Special Sensor Microwave Imager/Sounder (SSMIS) upper atmosphere sounding (UAS) channels are presented herein. Launched on October 18, 2003, aboard the DMSP F-16 spacecraft in a sun-synchronous orbit, the SSMIS UAS channels provide the first operational measurements of microwave radiation emitted by the Earth's atmosphere at mesospheric altitudes. The analysis of the SSMIS radiometer absolute calibration and stability is based upon extensive comparisons with a fully polarimetric radiative transfer model (RTM) that solves for all four Stokes parameters using coincident atmospheric temperature profiles derived from collocated Rayleigh lidar observations merged with the European Centre for Medium-Range Weather Forecasting temperature analyses and climatological data sets. The resulting merged profiles provide a physically consistent temperature profile from the surface to 100 km, as needed by the RTMs. The results presented herein of the SSMIS instrument show that significant hardware and scientific technical challenges arise from microwave temperature sounding of the mesosphere. These include the following: 1) addressing the impact of large noise-equivalent temperature difference associated with narrow channel bandwidths; 2) achieving high channel center-frequency stability; 3) compensation of large spacecraft-induced Doppler shift; 4) better characterization of the Zeeman splitting of the oxygen absorption lines; 5) development of a fast polarimetric RTM; and 6) designing stable and accurate on-orbit radiometric calibration targets. Results to date show that the uncertainties of the calibration accuracy of the SSMIS UAS channels are consistent and in agreement with the limits derived for the SSMIS UAS channels and with the simulated radiances derived from the merged lidar profiles.
IEEE Transactions on Geoscience and Remote Sensing 05/2008; · 2.89 Impact Factor
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R. J. Sica,
M. R. M. Izawa,
K. A. Walker,
Boone C,
S. V. Petelina,
P. S. Argall,
Bernath P,
G. B. Burns,
Catoire V,
R. L. Collins, [......],
Murayama Y,
Piccolo C,
Raspollini P,
Ridolfi M,
Robert C,
Steinbrecht W,
K. B. Strawbridge,
Strong K,
Stübi R,
Thurairajah B
[show abstract]
[hide abstract]
ABSTRACT: An ensemble of space-borne and ground-based instruments has been used to evaluate the quality of the version 2.2 temperature retrievals from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The agreement of ACE-FTS temperatures with other sensors is typically better than 2 K in the stratosphere and upper troposphere and 5 K in the lower mesosphere. There is evidence of a systematic high bias (roughly 3–6 K) in the ACE-FTS temperatures in the mesosphere, and a possible systematic low bias (roughly 2 K) in ACE-FTS temperatures near 23 km. Some ACE-FTS temperature profiles exhibit unphysical oscillations, a problem fixed in preliminary comparisons with temperatures derived using the next version of the ACE-FTS retrieval software. Though these relatively large oscillations in temperature can be on the order of 10 K in the mesosphere, retrieved volume mixing ratio profiles typically vary by less than a percent or so. Statistical comparisons suggest these oscillations occur in about 10% of the retrieved profiles. Analysis from a set of coincident lidar measurements suggests that the random error in ACE-FTS version 2.2 temperatures has a lower limit of about ±2 K.
Atmospheric Chemistry and Physics. 01/2008;
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Dupuy E,
K. A. Walker,
Kar J,
C. D. Boone,
C. T. McElroy,
P. F. Bernath,
J. R. Drummond,
Skelton R,
S. D. McLeod,
R. C. Hughes, [......],
M. B. Tully,
Urban J,
Vanhellemont F,
T. von Clarmann,
P. von der Gathen,
C. von Savigny,
J. W. Waters,
J. C. Witte,
Wolff M,
J. M. Zawodny
[show abstract]
[hide abstract]
ABSTRACT: This paper presents extensive validation analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. The ACE satellite instruments operate in the mid-infrared and ultraviolet-visible-near-infrared spectral regions using the solar occultation technique. In order to continue the long-standing record of solar occultation measurements from space, a detailed quality assessment is required to evaluate the ACE data and validate their use for scientific purposes. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the mean differences range generally between 0 and +10% with a slight but systematic positive bias (typically +5%). At higher altitudes (45–60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments by up to ~40% (typically +20%). For the ACE-MAESTRO version 1.2 ozone data product, agreement within ±10% (generally better than ±5%) is found between 18 and 40 km for the sunrise and sunset measurements. At higher altitudes (45–55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (by as much as −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS and indicate a large positive bias (+10 to +30%) in this altitude range. In contrast, there is no significant difference in bias found for the ACE-FTS sunrise and sunset measurements. These systematic effects in the ozone profiles retrieved from the measurements of ACE-FTS and ACE-MAESTRO are being investigated. This work shows that the ACE instruments provide reliable, high quality measurements from the tropopause to the upper stratosphere and can be used with confidence in this vertical domain.
Atmospheric Chemistry and Physics Discussions. 01/2008;
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Cortesi U,
J C Lambert,
C De Clercq,
Bianchini G,
Blumenstock T,
Bracher A,
Castelli E,
Catoire V,
K. V. Chance,
M. De Mazière, [......],
J. J. Remedios,
Sembhi H,
Smale D,
Steck T,
Taddei A,
Varotsos C,
Vigouroux C,
Waterfall A,
Wetzel G,
Wood S
[show abstract]
[hide abstract]
ABSTRACT: The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on-board the European ENVIronmental SATellite (ENVISAT) launched on 1 March 2002, is a middle infrared Fourier Transform spectrometer measuring the atmospheric emission spectrum in limb sounding geometry. The instrument is capable to retrieve the vertical distribution of temperature and trace gases, aiming at the study of climate and atmospheric chemistry and dynamics, and at applications to data assimilation and weather forecasting. MIPAS operated in its standard observation mode for approximately two years, from July 2002 to March 2004, with scans performed at nominal spectral resolution of 0.025 cm−1 and covering the altitude range from the mesosphere to the upper troposphere with relatively high vertical resolution (about 3 km in the stratosphere). Only reduced spectral resolution measurements have been performed subsequently. MIPAS data were re-processed by ESA using updated versions of the Instrument Processing Facility (IPF v4.61 and v4.62) and provided a complete set of level-2 operational products (geo-located vertical profiles of temperature and volume mixing ratio of H2O, O3, HNO3, CH4, N2O and NO2) with quasi continuous and global coverage in the period of MIPAS full spectral resolution mission. In this paper, we report a detailed description of the validation of MIPAS-ENVISAT operational ozone data, that was based on the comparison between MIPAS v4.61 (and, to a lesser extent, v4.62) O3 VMR profiles and a comprehensive set of correlative data, including observations from ozone sondes, ground-based lidar, FTIR and microwave radiometers, remote-sensing and in situ instruments on-board stratospheric aircraft and balloons, concurrent satellite sensors and ozone fields assimilated by the European Center for Medium-range Weather Forecasting. A coordinated effort was carried out, using common criteria for the selection of individual validation data sets, and similar methods for the comparisons. This enabled merging the individual results from a variety of independent reference measurements of proven quality (i.e. well characterized error budget) into an overall evaluation of MIPAS O3 data quality, having both statistical strength and the widest spatial and temporal coverage. Collocated measurements from ozone sondes and ground-based lidar and microwave radiometers of the Network for the Detection Atmospheric Composition Change (NDACC) were selected to carry out comparisons with time series of MIPAS O3 partial columns and to identify groups of stations and time periods with a uniform pattern of ozone differences, that were subsequently used for a vertically resolved statistical analysis. The results of the comparison are classified according to synoptic and regional systems and to altitude intervals, showing a generally good agreement within the comparison error bars in the upper and middle stratosphere. Significant differences emerge in the lower stratosphere and are only partly explained by the larger contributions of horizontal and vertical smoothing differences and of collocation errors to the total uncertainty. Further results obtained from a purely statistical analysis of the same data set from NDACC ground-based lidar stations, as well as from additional ozone soundings at middle latitudes and from NDACC ground-based FTIR measurements, confirm the validity of MIPAS O3 profiles down to the lower stratosphere, with evidence of larger discrepancies at the lowest altitudes. The validation against O3 VMR profiles using collocated observations performed by other satellite sensors (SAGE II, POAM III, ODIN-SMR, ACE-FTS, HALOE, GOME) and ECMWF assimilated ozone fields leads to consistent results, that are to a great extent compatible with those obtained from the comparison with ground-based measurements. Excellent agreement in the full vertical range of the comparison is shown with respect to collocated ozone data from stratospheric aircraft and balloon instruments, that was mostly obtained in very good spatial and temporal coincidence with MIPAS scans. This might suggest that the larger differences observed in the upper troposphere and lowermost stratosphere with respect to collocated ground-based and satellite O3 data are only partly due to a degradation of MIPAS data quality. They should be rather largely ascribed to the natural variability of these altitude regions and to other components of the comparison errors. By combining the results of this large number of validation data sets we derived a general assessment of MIPAS v4.61 and v4.62 ozone data quality. A clear indication of the validity of MIPAS O3 vertical profiles is obtained for most of the stratosphere, where the mean relative difference with the individual correlative data sets is always lower than ±10%. Furthermore, these differences always fall within the combined systematic error (from 1 hPa to 50 hPa) and the standard deviation is fully consistent with the random error of the comparison (from 1 hPa to ~30–40 hPa). A degradation in the quality of the agreement is generally observed in the lower stratosphere and upper troposphere, with biases up to 25% at 100 hPa and standard deviation of the global mean differences up to three times larger than the combined random error in the range 50–100 hPa. The larger differences observed at the bottom end of MIPAS retrieved profiles can be associated, as already noticed, to the effects of stronger atmospheric gradients in the UTLS that are perceived differently by the various measurement techniques. However, further components that may degrade the results of the comparison at lower altitudes can be identified as potentially including cloud contamination, which is likely not to have been fully filtered using the current settings of the MIPAS cloud detection algorithm, and in the linear approximation of the forward model that was used for the a priori estimate of systematic error components. The latter, when affecting systematic contributions with a random variability over the spatial and temporal scales of global averages, might result in an underestimation of the random error of the comparison and add up to other error sources, such as the possible underestimates of the p and T error propagation based on the assumption of a 1 K and 2% uncertainties, respectively, on MIPAS temperature and pressure retrievals. At pressure lower than 1 hPa, only a small fraction of the selected validation data set provides correlative ozone data of adequate quality and it is difficult to derive quantitative conclusions about the performance of MIPAS O3 retrieval for the topmost layers.
Atmospheric Chemistry and Physics 09/2007; 7:4807-4867. · 4.88 Impact Factor
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Yong Jiang,
L Froidevaux,
A Lambert,
N J Livesey,
W G Read,
J W Waters,
B Bojkov,
T Leblanc, I S McDermid,
S Godin-Beekmann, [......],
P Skrivankova,
R Stubi,
D Tarasick,
A Thompson,
V Thouret,
P Viatte,
H Vömel,
Peter Gathen,
M Yela,
G Zablocki
Journal of Geophysical Research, 112, D24S34. 01/2007;
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Rozanov A,
Eichmann K.-U,
C. von Savigny,
Bovensmann H,
J. P. Burrows,
A. Von Bargen,
Doicu A,
Hilgers S,
Godin-Beekmann S,
Leblanc T, I. S. McDermid
[show abstract]
[hide abstract]
ABSTRACT: This paper is devoted to an intercomparison of ozone vertical profiles retrieved from the measurements of scattered solar radiation performed by the SCIAMACHY instrument in the limb viewing geometry. Three different inversion algorithms including the prototype of the operational Level 1 to 2 processor to be operated by the European Space Agency are considered. The intercomparison was performed for 5 selected orbits of SCIAMACHY showing a good overall agreement of the results in the middle stratosphere, whereas considerable discrepancies were identified in the lower stratosphere and upper troposphere altitude region. Additionally, comparisons with ground-based lidar measurements are shown for selected profiles demonstrating an overall correctness of the retrievals.
Atmospheric Chemistry and Physics Discussions. 01/2007;
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E. J. Brinksma,
Bracher A,
D. E. Lolkema,
A. J. Segers,
I. S. Boyd,
Bramstedt K,
Claude H,
Godin-Beekmann S,
Hansen G,
Kopp G,
Leblanc T, I. S. McDermid,
Y. J. Meijer,
Nakane H,
Parrish A,
C. von Savigny,
Stebel K,
D. P. J. Swart,
Taha G,
A. J. M. Piters
[show abstract]
[hide abstract]
ABSTRACT: We discuss the quality of the two available SCIAMACHY limb ozone profile products. They were retrieved with the University of Bremen IFE's algorithm version 1.61 (hereafter IFE), and the official ESA offline algorithm (hereafter OL) versions 2.4 and 2.5. The ozone profiles were compared to a suite of correlative measurements from ground-based lidar and microwave, sondes, SAGE II and SAGE III (Stratospheric Aerosol and Gas Experiment). To correct for the expected Envisat pointing errors, which have not been corrected implicitly in either of the algorithms, we applied a constant altitude shift of -1.5 km to the SCIAMACHY ozone profiles. The IFE ozone profile data between 16 and 40 km are biased low by 3-6%. The average difference profiles have a typical standard deviation of 10% between 20 and 35 km. We show that more than 20% of the SCIAMACHY official ESA offline (OL) ozone profiles version 2.4 and 2.5 have unrealistic ozone values, most of these are north of 15° S. The remaining OL profiles compare well to correlative instruments above 24 km. Between 20 and 24 km, they underestimate ozone by 15±5%.
Atmospheric Chemistry and Physics. 01/2006;
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O. R. Cooper,
A. Stohl,
M. Trainer,
A. M. Thompson,
J. C. Witte,
S. J. Oltmans,
G. Morris,
K. E. Pickering,
J. H. Crawford,
G. Chen, [......],
S. Turquety,
S. L. Baughcum,
X. Ren,
F. C. Fehsenfeld,
J. F. Meagher,
N. Spichtinger,
C. C. Brown,
S. A. McKeen, I. S. McDermid,
T. Leblanc
Journal of Geophysical Research-Atmospheres. 01/2006; 111(D24).
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[show abstract]
[hide abstract]
ABSTRACT: Limb scattering retrievals of atmospheric minor constituent profiles require highly accurate knowledge of the tangent heights during the measurements. The limb scattering measurements of the Scanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) on Envisat are affected by tangent height errors of up to 2 km. This contribution provides a summary of the temporal and spatial variation of the SCIAMACHY limb pointing errors during the first three years of the SCIAMACHY mission. The tangent height errors are retrieved from the limb measurements in the UV-B spectral range. A seasonal modulation of the monthly mean tangent height offsets is identified with amplitudes of 800m (220m) before (after) the improvement of the Envisat orbit propagator model in December 2003. Even after the December 2003 orbit model improvement a constant offset component of about 1km is present. Furthermore, pointing discontinuities are identified that coincide with the daily updates of the on-board orbit propagator model. In order to reduce the errors in ozone profile retrievals caused by pointing errors to less than 5%, the tangent heights have to be known to within 250m.
Atmospheric Chemistry and Physics. 01/2005;
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Y. J. Meijer,
D. P. J. Swart,
M. Allaart,
S. B. Andersen,
G. Bodeker,
I. Boyd,
G. Braathen,
Y. Calisesi,
H. Claude,
V. Dorokhov, [......],
G. Kopp,
J.-C. Lambert,
T. Leblanc, I. S. McDermid,
S. Pal,
H. Schets,
R. Stubi,
T. Suortti,
G. Visconti,
M. Yela
[show abstract]
[hide abstract]
ABSTRACT: In March 2002 the European Space Agency (ESA) launched the polar-orbiting
environmental satellite Envisat. One of its nine instruments is the Global Ozone
Monitoring by Occultation of Stars (GOMOS) instrument, which is a medium-resolution
stellar occultation spectrometer measuring vertical profiles of ozone. In the first year after
launch a large group of scientists performed additional measurements and validation
activities to assess the quality of Envisat observations. In this paper, we present validation
results of GOMOS ozone profiles from comparisons to microwave radiometer, balloon
ozonesonde, and lidar measurements worldwide. Thirty-one instruments/launch sites at
twenty-five stations ranging from the Arctic to the Antarctic joined in this activity. We
identified 6747 collocated observations that were performed within an 800-km radius and
a maximum 20-hour time difference of a satellite observation, for the period between
1 July 2002 and 1 April 2003. The GOMOS data analyzed here have been generated with
a prototype processor that corresponds to version 4.02 of the operational GOMOS
processor. The GOMOS data initially contained many obviously unrealistic values, most
of which were successfully removed by imposing data quality criteria. Analyzing the
effect of these criteria indicated, among other things, that for some specific stars, only less
than 10% of their occultations yield an acceptable profile. The total number of useful
collocated observations was reduced to 2502 because of GOMOS data unavailability, the
imposed data quality criteria, and lack of altitude overlap. These collocated profiles were
compared, and the results were analyzed for possible dependencies on several geophysical
(e.g., latitude) and GOMOS observational (e.g., star characteristics) parameters. We
find that GOMOS data quality is strongly dependent on the illumination of the limb
through which the star is observed. Data measured under bright limb conditions, and to a
certain extent also in twilight limb, should be used with caution, as their usability is
doubtful. In dark limb the GOMOS data agree very well with the correlative data, and
between 14- and 64-km altitude their differences only show a small (2.5–7.5%)
Journal of Geophysical Research 12/2004; · 3.02 Impact Factor
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Y J Meijer,
D P J Swart,
M. Allaart,
S. B. Andersen,
G. Bodeker,
I. Boyd,
G. Braathen,
Y. Calisesi,
H. Claude,
V. Dorokhov, [......],
J.-C. Lambert,
T. Leblanc, I. S. McDermid,
S. Pal,
G. Kopp,
H. Schets,
R. Stubi,
T. Suortti,
G. Visconti,
M. Yela
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ABSTRACT: 6) Norwegian Institute for Air Research, Kjeller, Norway, geir@nilu.no (7) Institute of Applied Physics, Bern, Switzerland, yasmine.calisesi@issi.unibe.ch (8) Deutscher Wetterdienst, Hohenpeissenberg, Germany, Hans.Claude@dwd.de (9) Central Aerological Observatory, Moscow, Russia, vdor@caomsk.mipt.ru (10) Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany, gathen@awi-potsdam.de (11 (14) Norwegian Institute for Air Research, Tromso, Norway, ghh@nilu.no (15) Finnish Meteorological Institute, Sodankylä, Finland, alex.karpetchko@fmi.fi; tuomo.suortti@fmi.fi (16) Institute of Meteorology and Water Management, Warsaw, Poland, bogdan.kois@imgw.pl (17) ESA-ESRIN, Via Galileo Galilei, I-00044 Frascati, Italy, Rob.Koopman@esa.int (18) Belgian Inst. for Space Aeronomy (BIRA), Avenue Circulaire 3, Bruxelles, Belgium, j-c.lambert@iasb.be (19) Jet Propulsion Laboratory, Wrightwood (CA), USA (22) Royal Meteorological Institute (RMI), Ringlaan 3, Brussels B-1180, Belgium, henk.schets@oma.be (23) Meteo Swiss, Payerne, Switzerland, rsi@meteoswiss.ch (24 ABSTRACT One of the nine instruments on-board the polar-orbiting environmental satellite ENVISAT is the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument. This paper presents validation results of GOMOS ozone profiles (v6.0a) from comparisons to microwave radiometer, balloon ozonesonde and lidar measurements worldwide. Thirty-one instruments/ launch-sites at twenty-five stations ranging from the Arctic to the Antarctic joined in this activity. We identified 3,713 useful collocated observations that were performed within an 800-km radius and a maximum 20-hours time difference of a satellite observation, for the period June 2002 and March 2003. These collocated profiles were compared and the results were analyzed for possible dependencies on several geophysical (e.g., latitude) and GOMOS observational (e.g., star characteristics) parameters. In a dark atmospheric limb the GOMOS data agree very well with the correlative data and between 20-to 61-km altitude their differences only show a small (2.5%) insignificant negative bias with a standard deviation of about 14%. This conclusion is demonstrated to be independent of the star temperature and magnitude, and the latitudinal region of the GOMOS observation.
ACVE-2 (Atmospheric Chemstry Validation of Envisat; 01/2004
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ABSTRACT: Using more than 1600 nighttime profiles obtained by the JPL differential absorption lidars (DIAL) located at Table Mountain Facility (TMF, 34.4 N) and Mauna Loa Observatory (MLO, 19.5 N) is presented in this paper. These two systems have been providing high-resolution vertical profiles of ozone number density between 15-50 km, several nights a week since 1989 (TMF) and 1993 (MLO). The climatology presented here is typical of early night ozone values with only a small influence of the Pinatubo aerosols and the 11-year solar cycle. The observed seasonal and vertical structure of the ozone concentration at TMF is consistent with that typical of mid- to subtropical latitudes. A clear annual cycle in opposite phase below and above the ozone concentration peak is observed. The observed winter maximum below the ozone peak is associated with a maximum day-to-day variability, typical of a dynamically driven lower stratosphere. The maximum concentration observed in summer above the ozone peak emphasizes the more dominant role of photochemistry. Unlike TMF, the ozone concentration observed at MLO tends to be higher during the summer months and lower during the winter months throughout the entire stratospheric ozone layer. Only a weak signature of the extra-tropical latitudes is observed near 19-20 km, with a secondary maximum in late winter. The only large variability observed at MLO is associated with the natural variability of the tropical tropopause.
02/2000;
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S Godin,
A I Carswell,
D P Donovan,
H Claude,
W Steinbrecht, I S McDermid,
T J McGee,
M R Gross,
H Nakane,
D P Swart,
H B Bergwerff,
O Uchino,
P von der Gathen,
R Neuber
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ABSTRACT: An intercomparison of ozone differential absorption lidar algorithms was performed in 1996 within the framework of the Network for the Detection of Stratospheric Changes (NDSC) lidar working group. The objective of this research was mainly to test the differentiating techniques used by the various lidar teams involved in the NDSC for the calculation of the ozone number density from the lidar signals. The exercise consisted of processing synthetic lidar signals computed from simple Rayleigh scattering and three initial ozone profiles. Two of these profiles contained perturbations in the low and the high stratosphere to test the vertical resolution of the various algorithms. For the unperturbed profiles the results of the simulations show the correct behavior of the lidar processing methods in the low and the middle stratosphere with biases of less than 1% with respect to the initial profile to as high as 30 km in most cases. In the upper stratosphere, significant biases reaching 10% at 45 km for most of the algorithms are obtained. This bias is due to the decrease in the signal-to-noise ratio with altitude, which makes it necessary to increase the number of points of the derivative low-pass filter used for data processing. As a consequence the response of the various retrieval algorithms to perturbations in the ozone profile is much better in the lower stratosphere than in the higher range. These results show the necessity of limiting the vertical smoothing in the ozone lidar retrieval algorithm and questions the ability of current lidar systems to detect long-term ozone trends above 40 km. Otherwise the simulations show in general a correct estimation of the ozone profile random error and, as shown by the tests involving the perturbed ozone profiles, some inconsistency in the estimation of the vertical resolution among the lidar teams involved in this experiment.
Applied Optics 11/1999; 38(30):6225-36. · 1.41 Impact Factor
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ABSTRACT: A method is described for the empirical determination of altitude range resolutions of ozone profiles obtained by differential absorption lidar (DIAL) analysis. The algorithm is independent of the implementation of the DIAL analysis, in particular of the type and order of the vertical smoothing filter applied. An interpretation of three definitions of altitude range resolution is given on the basis of simulations carried out with the Jet Propulsion Laboratory ozone DIAL analysis program, SO3ANL. These definitions yield altitude range resolutions that differ by as much as a factor of 2. It is shown that the altitude resolution calculated by SO3ANL, and reported with all Jet Propulsion Laboratory lidar ozone profiles, corresponds closely to the full width at half-maximum of a retrieved ozone profile if an impulse function is used as the input ozone profile.
Applied Optics 03/1999; 38(6):924-7. · 1.41 Impact Factor
