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L Froidevaux,
Y B Jiang,
A Lambert,
N J Livesey,
W G Read,
J W Waters,
E V Browell,
J W Hair,
M A Avery,
T J Mcgee, [......],
B J Drouin, R E Cofield,
D T Cuddy,
R F Jarnot,
B W Knosp,
V S Perun,
W V Snyder,
P C Stek,
R P Thurstans,
P A Wagner
[show abstract]
[hide abstract]
ABSTRACT: 1] The Earth Observing System (EOS) Microwave Limb Sounder (MLS) aboard the Aura satellite has provided essentially daily global measurements of ozone (O 3) profiles from the upper troposphere to the upper mesosphere since August of 2004. This paper focuses on validation of the MLS stratospheric standard ozone product and its uncertainties, as obtained from the 240 GHz radiometer measurements, with a few results concerning mesospheric ozone. We compare average differences and scatter from matched MLS version 2.2 profiles and coincident ozone profiles from other satellite instruments, as well as from aircraft lidar measurements taken during Aura Validation Experiment (AVE) campaigns. Ozone comparisons are also made between MLS and balloon-borne remote and in situ sensors. We provide a detailed characterization of random and systematic uncertainties for MLS ozone. We typically find better agreement in the comparisons using MLS version 2.2 ozone than the version 1.5 data. The agreement and the MLS uncertainty estimates in the stratosphere are often of the order of 5%, with values closer to 10% (and occasionally 20%) at the lowest stratospheric altitudes, where small positive MLS biases can be found. There is very good agreement in the latitudinal distributions obtained from MLS and from coincident profiles from other satellite instruments, as well as from aircraft lidar data along the MLS track.
J. Geophys. Res. 01/2008; 113:15-20.
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L Froidevaux,
Y B Jiang,
A Lambert,
N J Livesey,
W G Read,
J W Waters,
R A Fuller,
T P Marcy,
P J Popp,
R S Gao, [......],
B J Drouin, R E Cofield,
D T Cuddy,
R F Jarnot,
B W Knosp,
V S Perun,
W V Snyder,
P C Stek,
R P Thurstans,
P A Wagner
[show abstract]
[hide abstract]
ABSTRACT: 1] The Earth Observing System (EOS) Microwave Limb Sounder (MLS) aboard the Aura satellite has provided daily global HCl profiles since August 2004. We provide a characterization of the resolution, random and systematic uncertainties, and known issues for the version 2.2 MLS HCl data. The MLS sampling allows for comparisons with many ($1500 to more than 3000) closely matched profiles from the Halogen Occultation Experiment (HALOE) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). These data sets provide HCl latitudinal distributions that are, overall, very similar to those from (coincident) MLS profiles, although there are some discrepancies in the upper stratosphere between the MLS and HALOE gradients. As found in previous work, MLS and ACE HCl profiles agree very well (within $5%, on average), but the MLS HCl abundances are generally larger (by 10–20%) than HALOE HCl. The bias versus HALOE is unlikely to arise mostly from MLS, as a similar systematic bias (of order 15%) is not observed between average MLS and balloon-borne measurements of HCl, obtained over Fort Sumner, New Mexico, in 2004 and 2005. At the largest pressure (147 hPa) for MLS HCl, a high bias ($0.2 ppbv) is apparent in analyses of low to midlatitude data versus in situ aircraft chemical ionization mass spectrometry (CIMS) HCl measurements from the Aura Validation Experiment (AVE) campaigns in 2004, 2005, and 2006; this bias is also observed in comparisons of MLS and aircraft HCl/O 3 correlations. Good agreement between MLS and CIMS HCl is obtained at 100 to 68 hPa. The recommended pressure range for MLS HCl is from 100 to 0.15 hPa.
J. Geophys. Res. 01/2008; 113:15-25.
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A Lambert,
W G Read,
N J Livesey,
M L Santee,
G L Manney,
L Froidevaux,
D L Wu,
M J Schwartz,
H C Pumphrey,
C Jimenez, [......],
K W Jucks,
G C Toon,
R A Stachnik,
P F Bernath,
C D Boone,
K A Walker,
J Urban,
D Murtagh,
J W Elkins,
E Atlas
[show abstract]
[hide abstract]
ABSTRACT: 1] The quality of the version 2.2 (v2.2) middle atmosphere water vapor and nitrous oxide measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System (EOS) Aura satellite is assessed. The impacts of the various sources of systematic error are estimated by a comprehensive set of retrieval simulations. Comparisons with correlative data sets from ground-based, balloon and satellite platforms operating in the UV/visible, infrared and microwave regions of the spectrum are performed. Precision estimates are also validated, and recommendations are given on the data usage. The v2.2 H 2 O data have been improved over v1.5 by providing higher vertical resolution in the lower stratosphere and better precision above the stratopause. The single-profile precision is $0.2–0.3 ppmv (4–9%), and the vertical resolution is $3–4 km in the stratosphere. The precision and vertical resolution become worse with increasing height above the stratopause. Over the pressure range 0.1–0.01 hPa the precision degrades from 0.4 to 1.1 ppmv (6–34%), and the vertical resolution degrades to $12–16 km. The accuracy is estimated to be 0.2–0.5 ppmv (4–11%) for the pressure range 68–0.01 hPa. The scientifically useful range of the H 2 O data is from 316 to 0.002 hPa, although only the 82–0.002 hPa pressure range is validated here. Substantial improvement has been achieved in the v2.2 N 2 O data over v1.5 by reducing a significant low bias in the stratosphere and eliminating unrealistically high biased mixing ratios in the polar regions. The single-profile precision is $13–25 ppbv (7–38%), the vertical resolution is $4–6 km and the accuracy is estimated to be 3–70 ppbv (9–25%) for the pressure range 100–4.6 hPa. The scientifically useful range of the N 2 O data is from 100 to 1 hPa.
J. Geophys. Res. 01/2007; 112:24-36.
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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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L. J. Kovalenko,
N. L. Livesey,
R. J. Salawitch,
C. Camy-Peyret,
M. P. Chipperfield, R. E. Cofield,
M. Dorf,
B. J. Drouin,
L. Froidevaux,
R. A. Fuller, [......],
J.-P. Pommereau,
W. G. Read,
M. L. Santee,
M. J. Schwartz,
W. V. Snyder,
R. Stachnik,
P. C. Stek,
P. A. Wagner,
K. Pfeilsticker,
J. W. Water
Journal of Geophysical Research 01/2007; 112(D24S41). · 3.02 Impact Factor
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J.W. Waters,
L. Froidevaux,
R.S. Harwood,
R.F. Jarnot,
H.M. Pickett,
W.G. Read,
P.H. Siegel, R.E. Cofield,
M.J. Filipiak,
D.A. Flower, [......],
D. Miller,
J.E. Oswald,
N.C. Patel,
D.M. Pukala,
O. Quintero,
D.M. Scaff,
W. Van Snyder,
M.C. Tope,
P.A. Wagner,
M.J. Walch
[show abstract]
[hide abstract]
ABSTRACT: The Earth Observing System Microwave Limb Sounder measures several atmospheric chemical species (OH, HO<sub>2</sub>, H<sub>2</sub>O, O<sub>3</sub>, HCl, ClO, HOCl, BrO, HNO<sub>3</sub>, N<sub>2</sub>O, CO, HCN, CH<sub>3</sub>CN, volcanic SO<sub>2</sub>), cloud ice, temperature, and geopotential height to improve our understanding of stratospheric ozone chemistry, the interaction of composition and climate, and pollution in the upper troposphere. All measurements are made simultaneously and continuously, during both day and night. The instrument uses heterodyne radiometers that observe thermal emission from the atmospheric limb in broad spectral regions centered near 118, 190, 240, and 640 GHz, and 2.5 THz. It was launched July 15, 2004 on the National Aeronautics and Space Administration's Aura satellite and started full-up science operations on August 13, 2004. An atmospheric limb scan and radiometric calibration for all bands are performed routinely every 25 s. Vertical profiles are retrieved every 165 km along the suborbital track, covering 82°S to 82°N latitudes on each orbit. Instrument performance to date has been excellent; data have been made publicly available; and initial science results have been obtained.
IEEE Transactions on Geoscience and Remote Sensing 06/2006; · 2.89 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: This paper describes the optics design and field-of-view (FOV) calibration for five radiometers covering 114-660 GHz which share a common antenna in the Microwave Limb Sounder instrument on the National Aeronautics and Space Administration's Aura satellite. Details of near-field pattern measurements are presented. Estimated systematic scaling uncertainties (3σ) on calibrated limb emissions, due to FOV calibration uncertainties, are below 0.4%. 3σ uncertainties in beamwidth and relative pointing of radiometer boresights are 0.006° and 0.003°, respectively. The uncertainty in modeled instrument response, due to the scan dependence of FOV patterns, is less than ±0.24 K equivalent black-body temperature. Refinements to the calibration using in-flight data are presented.
IEEE Transactions on Geoscience and Remote Sensing 06/2006; · 2.89 Impact Factor
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L. Froidevaux,
W. G. Read,
T. A. Lungu, R. E. Cofield,
E. F. Fishbein,
D. A. Flower,
R. F. Jarnot,
B. P. Ridenoure,
Z. Shippony,
J. W. Waters,
J. J. Margitan,
I. S. McDermid,
R. A. Stachnik,
G. E. Peckham,
G. Braathen,
T. Deshler,
J. Fishman,
D. J. Hofmann,
S. J. Oltmans
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the validation of ozone data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz. Analyses described here focus on the MLS Version 3 data (the first set of files made publicly available). We describe results of simulations performed to assess the quality of the retrieval algorithms, in terms of both mixing ratio and radiance closure. From actual MLS observations, the 205-GHz ozone retrievals give better closure (smaller radiance residuals) than that from the 183-GHz measurements and should be considered more accurate from the calibration aspects. However, the 183-GHz data are less noise limited in the mesosphere and can provide the most useful scientific results in that region. We compare the retrieved 205-GHz ozone profiles in the middle-to lower stratosphere to ozonesonde measurements at a wide range of latitudes and seasons. Ground-based lidar data from Table Mountain, California, provide a good reference for comparisons at higher altitudes. Based on these analyses, comparisons with balloon-borne measurements and others, as well as a detailed budget of estimated uncertainties, MLS results appear to be generally of high quality, with some biases worth mentioning. Results for the lowermost stratosphere (approx. 50 to 100 bPa) are still in need of improvement. A set of estimated precision and accuracy values is derived for the MLS ozone data sets. We also comment on recent updates in the retrieval algorithms and their impact on ozone values.
05/1996;
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E. F. Fishbein, R. E. Cofield,
L. Froidevaux,
R. F. Jarnot,
T. Lungu,
W. G. Read,
Z. Shippony,
J. W. Waters,
I. S. McDermid,
T. J. Mcgee,
U. Singh,
M. Gross,
A. Hauchecorne,
P. Keckhut,
M. E. Gelman,
R. M. Nagatani
[show abstract]
[hide abstract]
ABSTRACT: The accuracy and precision of the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) atmospheric temperature and tangent-point pressure measurements are described. Temperatures and tangent- point pressure (atmospheric pressure at the tangent height of the field of view boresight) are retrieved from a 15-channel 63-GHz radiometer measuring O2 microwave emissions from the stratosphere and mesosphere. The Version 3 data (first public release) contains scientifically useful temperatures from 22 to 0.46 hPa. Accuracy estimates are based on instrument performance, spectroscopic uncertainty and retrieval numerics, and range from 2.1 K at 22 hPa to 4.8 K at 0.46 hPa for temperature and from 200 m (equivalent log pressure) at 10 hPa to 300 m at 0.1 hPa. Temperature accuracy is limited mainly by uncertainty in instrument characterization, and tangent-point pressure accuracy is limited mainly by the accuracy of spectroscopic parameters. Precisions are around 1 K and 100 m. Comparisons are presented among temperatures from MLS, the National Meteorological Center (NMC) stratospheric analysis and lidar stations at Table Mountain, California, Observatory of Haute Provence (OHP), France, and Goddard Spaceflight Center, Maryland. MLS temperatures tend to be 1-2 K lower than NMC and lidar, but MLS is often 5 - 10 K lower than NMC in the winter at high latitudes, especially within the northern hemisphere vortex. Winter MLS and OHP (44 deg N) lidar temperatures generally agree and tend to be lower than NMC. Problems with Version 3 MLS temperatures and tangent-point pressures are identified, but the high precision of MLS radiances will allow improvements with better algorithms planned for the future.
Journal of Geophysical Research 05/1996; · 3.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The Microwave Limb Sounder (MLS) is a three-radiometer, passive, limb emission instrument onboard the Upper Atmosphere Research Satellite (UARS). Radiometric, spectral and field-of-view calibrations of the MLS instrument are described in this paper. In-orbit noise performance, gain stability, spectral baseline and dynamic range are described, as well as use of in-flight data for validation and refinement of prelaunch calibrations. Estimated systematic scaling uncertainties (3 sigma) on calibrated limb radiances from prelaunch calibrations are 2.6% in bands 1 through 3, 3.4% in band 4, and 6% in band 5. The observed systematic errors in band 6 are about 15%, consistent with prelaunch calibration uncertainties. Random uncertainties on individual limb radiance measurements are very close to the levels predicted from measured radiometer noise temperature, with negligible contribution from noise and drifts on the regular in-flight gain calibration measurements.
05/1996;
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J. W. Waters,
W. G. Read,
L. Froidevaux,
T. A. Lungu,
V. S. Perun,
R. A. Stachnik,
R. F. Jarnot, R. E. Cofield,
E. F. Fishbein,
D. A. Flower,
J. R. Burke,
J. C. Hardy,
L. L. Nakamura,
B. P. Ridenoure,
Z. Shippony,
R. P. Thurstans,
L. M. Avallone,
D. W. Toohey,
R. L. DeZafra,
D. T. Shindell
[show abstract]
[hide abstract]
ABSTRACT: Validation of stratospheric ClO measurements by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is described. Credibility of the measurements is established by (1) the consistency of the measured ClO spectral emission line with the retrieved ClO profiles and (2) comparisons of ClO from MLS with that from correlative measurements by balloon-based, ground-based, and aircraft-based instruments. Values of "noise" (random), "scaling" (multiplicative), and "bias" (additive) uncertainties are determined for the Version 3 data, in the first version public release of the known artifacts in these data are identified. Comparisons with correlative measurements indicate agreement to within the combined uncertainties expected for MLS and the other measurements being compared. It is concluded that MLS Version 3 ClO data, with proper consideration of the uncertainties and "quality" parameters produced with these data, can be used for scientific analyses at retrieval surfaces between 46 and 1 hPa (approximately 20-50 km in height). Future work is planned to correct known problems in the data and improve their quality.
05/1996;
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G. E. Peckham,
J. W. Waters,
R. S. Harwood, R. E. Cofield,
D. A. Flower,
M.A. Frerking,
L. Froidevaux,
R. F. Jarnot,
C. L. Lau,
G.K. Lau,
B.J. Maddison,
H. M. Pickett,
H. C. Pumphrey,
W. G. Read,
M. L. Santee,
R. A. Suttie,
W.J. Wilson
[show abstract]
[hide abstract]
ABSTRACT: A first airborne mission, using the high altitude aircraft M-55 Geophysika, to study polar stratospheric clouds and background aerosols is described. By means of such an aircraft equipped with in-situ and remote sensing instrumentation, more insight into the microphysics and chemistry of PSCs will be possible
Geoscience and Remote Sensing Symposium, 1995. IGARSS '95. 'Quantitative Remote Sensing for Science and Applications', International; 08/1995
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R.E. Cofield
[show abstract]
[hide abstract]
ABSTRACT: Describes the field-of-view (FOV) calibration of the Microwave
Limb Sounder (MLS) on board NASA's Upper Atmosphere Research Satellite
(UARS). Calibration data are derived from measurements and analytical
models, combined with in flight data. Particular emphasis is given to
pointing calibration and estimation of far sidelobe levels and radiance
offsets, using both the Moon and the residual signals when the FOV is
pointed high above Earth's atmosphere
Geoscience and Remote Sensing Symposium, 1994. IGARSS '94. Surface and Atmospheric Remote Sensing: Technologies, Data Analysis and Interpretation., International; 09/1994
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[show abstract]
[hide abstract]
ABSTRACT: The microwave limb sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is the first satellite experiment using limb sounding techniques at microwave frequencies. Primary measurement objectives are stratospheric ClO, O3, H2O, temperature, and pressure. Measurements are of thermal emission: all are performed simultaneously and continuously and are not degraded by ice clouds or volcanic aerosols. The instrument has a 1.6-m mechanically scanning antenna system and contains heterodyne radiometers in spectral bands centred near 63, 183, and 205 GHz. The radiometers operate at ambient temperature and use Schottky-diode mixers with local oscillators derived from phase-locked Gunn oscillators. Frequency tripling by varactor multipliers generates the 183- and 205-GHz local oscillators, and quasi-optical techniques inject these into the mixers. Six 15-channel filter banks spectrally resolve stratospheric thermal emission lines and produce an output spectrum every 2 s. Thermal stability is sufficient for 'total power' measurements which do not require fast chopping. Radiometric calibration, consisting of measurements of cold space and an internal target, is performed every 65-s limb scan. Instrument in-orbit performance has been excellent, and all objectives are being met.
07/1993;
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M. L. Santee,
A. Lambert,
W. G. Read,
N. J. Livesey, R. E. Cofield,
D. T. Cuddy,
W. H. Daffer,
B. J. Drouin,
L. Froidevaux,
R. A. Fuller, [......],
V. S. Perun,
W. V. Snyder,
P. C. Stek,
R. P. Thurstans,
P. A. Wagner,
J. W. Waters,
Istituto Nazionale di Geofisica e Vulcanologia,
Sezione Roma,
Roma,
Italia
[show abstract]
[hide abstract]
ABSTRACT: We assess the quality of the version 2.2 (v2.2) HNO3 measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS HNO3 product has been greatly improved over that in the previous version (v1.5), with smoother profiles, much more realistic behavior at the lowest retrieval levels, and correction of a high bias caused by an error in one of the spectroscopy files used in v1.5 processing. The v2.2 HNO3 data are scientifically useful over the range 215 to 3.2 hPa, with single-profile precision of 0.7 ppbv throughout. Vertical resolution is 3–4 km in the upper troposphere and lower stratosphere, degrading to 5 km in the middle and upper stratosphere. The impact of various sources of systematic uncertainty has been quantified through a comprehensive set of retrieval simulations. In aggregate, systematic uncertainties are estimated to induce in the v2.2 HNO3 measurements biases that vary with altitude between ±0.5 and ±2 ppbv and multiplicative errors of ±5–15% throughout the stratosphere, rising to ±30% at 215 hPa. Consistent with this uncertainty analysis, comparisons with correlative data sets show that relative to HNO3 measurements from ground-based, balloon-borne, and satellite instruments operating in both the infrared and microwave regions of the spectrum, MLS v2.2 HNO3 mixing ratios are uniformly low by 10–30% throughout most of the stratosphere. Comparisons with in situ measurements made from the DC-8 and WB-57 aircraft in the upper troposphere and lowermost stratosphere indicate that the MLS HNO3 values are low in this region as well, but are useful for scientific studies (with appropriate averaging). published D24S40 1.7. Osservazioni di alta e media atmosfera JCR Journal
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M. L. Santee,
A. Lambert,
W. G. Read,
N. J. Livesey,
G. L. Manney, R. E. Cofield,
D. T. Cuddy,
W. H. Daffer,
B. J. Drouin,
L. Froidevaux, [......],
J. Urban,
D. Murtagh,
P. Ricaud,
B. Barret,
A. Kleinböhl,
J. Kuttippurath,
H. Küllmann,
M. Von Hobe,
G. C. Toon,
R. A. Stachnik
[show abstract]
[hide abstract]
ABSTRACT: We assess the quality of the version 2.2 (v2.2) ClO measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS v2.2 ClO data are scientifically useful over the range 100 to 1 hPa, with a single-profile precision of ~0.1 ppbv throughout most of the vertical domain. Vertical resolution is ~3–4 km. Comparisons with climatology and correlative measurements from a variety of different platforms indicate that both the amplitude and the altitude of the peak in the ClO profile in the upper stratosphere are well determined by MLS. The latitudinal and seasonal variations in the ClO distribution in the lower stratosphere are also well determined, but a substantial negative bias is present in both daytime and nighttime mixing ratios at retrieval levels below (i.e., pressures larger than) 22 hPa. Outside of the winter polar vortices, this negative bias can be eliminated by subtracting gridded or zonal mean nighttime values from the individual daytime measurements. In studies for which knowledge of lower stratospheric ClO mixing ratios inside the winter polar vortices to better than a few tenths of a ppbv is needed, however, day − night differences are not recommended and the negative bias must be corrected for by subtracting the estimated value of the bias from the individual measurements at each affected retrieval level.
Journal of Geophysical Research D: Atmospheres.
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N. J. Livesey,
M. J. Filipiak,
L. Froidevaux,
W. G. Read,
A. Lambert,
M. L. Santee,
J.H. Jiang,
H. C. Pumphrey,
J. W. Waters, R. E. Cofield, [......],
L. E. Christensen,
G. S. Diskin,
R. S. Gao,
H. J. Jost,
M. Loewenstein,
J.D. Lopez,
P. Nedelec,
G. B. Osterman,
G. W. Sachse,
R. C. Webster
[show abstract]
[hide abstract]
ABSTRACT: Global satellite observations of ozone and carbon monoxide from the Microwave Limb Sounder (MLS) on the EOS Aura spacecraft are discussed with emphasis on those observations in the 215–100 hPa region (the upper troposphere and lower stratosphere). The precision, resolution and accuracy of the data produced by the MLS “version 2.2” processing algorithms are discussed and quantified. O3 accuracy is estimated at ~40 ppbv +5% (~20 ppbv +20% at 215 hPa) while the CO accuracy is estimated at ~30 ppbv +30% for pressures of 147 hPa and less. Comparisons with expectations and other observations show good agreements for the O3 product, generally consistent with the systematic errors quoted above. In the case of CO, a persistent factor of ~2 high bias is seen at 215 hPa. However, the morphology is shown to be realistic, consistent with raw MLS radiance data, and useful for scientific study. The MLS CO data at higher altitudes are shown to be consistent with other observations.
Journal of Geophysical Research D: Atmospheres.
