Radiometric Stability Validation of 17 Years of AIRS Data Using Sea Surface Temperatures

Aumann, Hartmut H.; Broberg, Steven E.; Manning, Evan; Pagano, T. S.

doi:10.1029/2019gl085098

Cited by 23 publications

(23 citation statements)

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“…As the Aqua spacecraft drifts away from the A-Train, 1:30 PM mean local crossing time, additional data valuable to weather and process studies are expected to be acquired for another 3 to 4 years. The AIRS radiances at the 1231 cm -1 window channel show excellent stability relative to independent SST estimates, with a drift of less than 0.2-0.3 mK/decade, from 2002 to 2019 [13]. Using retrievals of trace gases from AIRS compared to in situ measurements allows the estimation of radiance trends of several AIRS channels to as good as 0.02-0.03 mK/decade [14].…”

Section: Introductionmentioning

confidence: 90%

“…Rigorous quantification of the uncertainties relative to SI standards will enable the benchmarking of the AIRS radiances, enabling trends over long periods, in the event of a break in continuity of similar IR sounder measurements.The AIRS instrument meets the three primary elements identified in the Guidelines for Radiometric Calibration of Electro-Optical Instruments for Remote Sensing [24] as the foundation of an effective calibration: (1) traceability, (2) measurement uncertainty, and (3) verification and validation. Verification and validation of AIRS Level 1B radiances using vicarious calibration of the Earth scene can be found in the literature [13,14]. The SI-traceability, as defined in the Joint Committee for Guides in Metrology (JCGM) the Vocabulaire international de métrologie (VIM) [25] and the Guide to the expression of Uncertainty of Measurement (GUM) [26], requires an unbroken chain of calibrations, each contributing measurement uncertainty.…”

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confidence: 99%

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SI-Traceability and Measurement Uncertainty of the Atmospheric Infrared Sounder Version 5 Level 1B Radiances

et al. 2020

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The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on 4 May 2002. The AIRS is designed to measure atmospheric temperature and water vapor profiles and has demonstrated exceptional radiometric and spectral accuracy and stability in orbit. The International System of Units (SI)-traceability of the derived radiances is achieved by transferring the calibration from the Large Area Blackbody (LABB) with SI traceable temperature sensors, to the On-Board Calibrator (OBC) blackbody during preflight testing. The AIRS views the OBC blackbody and four full aperture space views every scan. A recent analysis of pre-flight and on-board data has improved our understanding of the measurement uncertainty of the Version 5 AIRS L1B radiance product. For temperatures greater than 260 K, the measurement uncertainty is better than 250 mK 1-sigma for most channels. SI-traceability and quantification of the radiometric measurement uncertainty is critical to reducing biases in reanalysis products and radiative transfer models (RTMs) that use AIRS data, as well as establishing the suitability of AIRS as a benchmark for radiances established in the early 2000s.Remote Sens. 2020, 12, 1338 2 of 25 measure surface temperature and emissivity, cloud top height, cloud liquid water and cloud fraction. The data from the IR sounders assimilated into Numerical Weather Prediction (NWP) models have demonstrated amongst the highest forecast improvement in NWP models of all data types. The data are regularly used in studies of processes affecting weather [7] and climate as well as the validation of weather and climate models [8]. The data are also used in applications including volcano alerts [9], drought prediction [10], and air quality and pollution transport [11]. The AIRS instrument has shown exceptional radiometric stability to date, making it a valuable tool for climate trending and model validation [12]. Remote Sens. 2019, 11, x FOR PEER REVIEW 2 of 25 models have demonstrated amongst the highest forecast improvement in NWP models of all data types. The data are regularly used in studies of processes affecting weather [7] and climate as well as the validation of weather and climate models [8]. The data are also used in applications including volcano alerts [9], drought prediction [10], and air quality and pollution transport [11]. The AIRS instrument has shown exceptional radiometric stability to date, making it a valuable tool for climate trending and model validation [12]. Remote Sens. 2020, 12, 1338 3 of 25The AIRS is a reference sensor in the Global Space-Based Intercalibration of Sensors (GSICS) [17,18]. AIRS is used operationally by the Japan Meteorological Agency (JMA) for comparison to Himawari 8/9 AHI JM [19], the Korean Meteorological Administration (KMA) for comparison to COMS [20], and NOAA for comparison to CrIS [21] and GOES [22], and EUMETSAT for comparison to IASI [23]. The results show that the AIRS compares with IASI and CrIS to better than 0.2 K (1-sigma) in most cases. The long record of AIRS, com...

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Section: Introductionmentioning

confidence: 90%

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confidence: 99%

SI-Traceability and Measurement Uncertainty of the Atmospheric Infrared Sounder Version 5 Level 1B Radiances

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“…A recent study (Aumann et al, 2019) addressed the stability of a single AIRS channel by comparisons to sea surface temperatures (SSTs). Some limitations of that study are ad-L. L. Strow and S. DeSouza-Machado: AIRS stability dressed below, but its major limitation is that it evaluates only one channel.…”

Section: Introductionmentioning

confidence: 99%

“…Some limitations of that study are ad-L. L. Strow and S. DeSouza-Machado: AIRS stability dressed below, but its major limitation is that it evaluates only one channel. AIRS retrievals use 400+ AIRS channels, and there is no guarantee that the AIRS stability in one channel applies to all channels, as acknowledged in Aumann et al (2019).…”

Section: Introductionmentioning

confidence: 99%

Establishment of AIRS climate-level radiometric stability using radiance anomaly retrievals of minor gases and sea surface temperature

Strow

DeSouza‐Machado

2020

Atmos. Meas. Tech.

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Abstract. Temperature, H2O, and O3 profiles, as well as CO2, N2O, CH4, chlorofluorocarbon-12 (CFC-12), and sea surface temperature (SST) scalar anomalies are computed using a clear subset of AIRS observations over ocean for the first 16 years of NASA's Earth-Observing Satellite (EOS) Aqua Atmospheric Infrared Sounder (AIRS) operation. The AIRS Level-1c radiances are averaged over 16 d and 40 equal-area zonal bins and then converted to brightness temperature anomalies. Geophysical anomalies are retrieved from the brightness temperature anomalies using a relatively standard optimal estimation approach. The CO2, N2O, CH4, and CFC-12 anomalies are derived by applying a vertically uniform multiplicative shift to each gas in order to obtain an estimate for the gas mixing ratio. The minor-gas anomalies are compared to the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) in situ values and used to estimate the radiometric stability of the AIRS radiances. Similarly, the retrieved SST anomalies are compared to the SST values used in the ERA-Interim reanalysis and to NOAA's Optimum Interpolation SST (OISST) product. These intercomparisons strongly suggest that many AIRS channels are stable to better than 0.02 to 0.03 K per decade, well below climate trend levels, indicating that the AIRS blackbody is not drifting. However, detailed examination of the anomaly retrieval residuals (observed – computed) shows various small unphysical shifts that correspond to AIRS hardware events (shutdowns, etc.). Some examples are given highlighting how the AIRS radiance stability could be improved, especially for channels sensitive to N2O and CH4. The AIRS shortwave channels exhibit larger drifts that make them unsuitable for climate trending, and they are avoided in this work. The AIRS Level 2 surface temperature retrievals only use shortwave channels. We summarize how these shortwave drifts impacts recently published comparisons of AIRS surface temperature trends to other surface climatologies.

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“…Overall the excellent agreement of these two extremely independent assessments (CO 2 versus SST) to within 0.02K/decade is very encouraging given the complexity of the CO 2 measurement and the uncertainties in the SST product trends. Aumann (Aumann et al, 2019) recently compared the 1231 cm -1 AIRS channel trends to RTGSST, a precursor to OISST.…”

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confidence: 99%

Establishment of AIRS Climate-Level Radiometric Stability using Radiance Anomaly Retrievals of Minor Gases and SST

Strow

DeSouza‐Machado

2020

Preprint

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Abstract. Temperature, H2O, and O3 profiles, as well as CO2, N2O, CH4, CFC12, and SST scalar anomalies are computed using a clear subset of AIRS observations over ocean for the first 16-years of NASA's EOS-AQUA AIRS operation. The AIRS Level 1c radiances are averaged over 16 days and 40 equal-area zonal bins and then converted to brightness temperature anomalies. Geophysical anomalies are retrieved from the brightness temperature anomalies using a relatively standard optimal estimation approach. The CO2, N2O, CH4, and CFC12 anomalies are derived by applying a vertically uniform multiplicative shift to each gas in order to obtain an estimate for the ngas mixing ratio. The minor gas anomalies are compared to the NOAA ESRL in-situ values and used to estimate the radiometric stability of the AIRS radiances. Similarly the retrieved SST anomalies are compared to the SST values used in the ERA-Interim reanalysis and to NOAA's OISST SST product. These inter-comparisons strongly suggest that many AIRS channels are stable to better than 0.02 to 0.03 K/Decade, well below climate trend levels, indicating that the AIRS blackbody is not drifting. However, detailed examination of the anomaly retrieval residuals (observed minus computed) show various small unphysical shifts that correspond to AIRS hardware events (shutdowns, etc.). Some examples are given highlighting how the AIRS radiances stability could be improved, especially for channels sensitive to N2O and CH4. The AIRS short wave channels exhibit larger drifts that make them unsuitable for climate trending, and they are avoided in this work. The AIRS Level 2 surface temperature retrievals only use short wave channels. We summarize how these short wave drifts impacts recently published comparisons of AIRS surface temperature trends to other surface climatologies.

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Radiometric Stability Validation of 17 Years of AIRS Data Using Sea Surface Temperatures

Cited by 23 publications

References 13 publications

SI-Traceability and Measurement Uncertainty of the Atmospheric Infrared Sounder Version 5 Level 1B Radiances

SI-Traceability and Measurement Uncertainty of the Atmospheric Infrared Sounder Version 5 Level 1B Radiances

Establishment of AIRS climate-level radiometric stability using radiance anomaly retrievals of minor gases and sea surface temperature

Establishment of AIRS Climate-Level Radiometric Stability using Radiance Anomaly Retrievals of Minor Gases and SST

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