The Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), and the Humidity Sounder for Brazil (HSB) form an integrated cross-track scanning temperature and humidity sounding system on the Aqua satellite of the Earth Observing System (EOS). AIRS is an infrared spectrometer/radiometer that covers the 3.7-15.4-/spl mu/m spectral range with 2378 spectral channels. AMSU is a 15-channel microwave radiometer operating between 23 and 89 GHz. HSB is a four-channel microwave radiometer that makes measurements between 150 and 190 GHz. In addition to supporting the National Aeronautics and Space Administration's interest in process study and climate research, AIRS is the first hyperspectral infrared radiometer designed to support the operational requirements for medium-range weather forecasting of the National Ocean and Atmospheric Administration's National Centers for Environmental Prediction (NCEP) and other numerical weather forecasting centers. AIRS, together with the AMSU and HSB microwave radiometers, will achieve global retrieval accuracy of better than 1 K in the lower troposphere under clear and partly cloudy conditions. This paper presents an overview of the science objectives, AIRS/AMSU/HSB data products, retrieval algorithms, and the ground-data processing concepts. The EOS Aqua was launched on May 4, 2002 from Vandenberg AFB, CA, into a 705-km-high, sun-synchronous orbit. Based on the excellent radiometric and spectral performance demonstrated by AIRS during prelaunch testing, which has by now been verified during on-orbit testing, we expect the assimilation of AIRS data into the numerical weather forecast to result in significant forecast range and reliability improvements.

http://www.atmos.berkeley.edu/~inez/MSRI-NCAR_CarbonDA/papers/barnet_refs/Aumann_IEEE8big15aug02.pdf

AIRS/AMSU/HSB on the Aqua mission: design, science objectives, data products, and processing systems

We consider the problem of reconstructing remotely obtained images from image-plane detector arrays. Although the individual detectors may be larger than the blur spot of the imaging optics, high-resolution reconstructions can be obtained by scanning or rotating the image with respect to the detector. As an alternative to matrix inversion or least-squares estimation [Appl. Opt. 26, 3615 (1987)], the method of convex projections is proposed. We show that readily obtained prior knowledge can be used to obtain good-quality imagery with reduced data. The effect of noise on the reconstruction process is considered.

High-resolution image recovery from image-plane arrays, using convex projections.

This paper discusses the performance of AIRS and examines how it is meeting its operational and research objectives based on the experience of more than 2 yr with AIRS data. We describe the science background and the performance of AIRS in terms of the accuracy and stability of its observed spectral radiances. We examine the validation of the retrieved temperature and water vapor profiles against collocated operational radiosondes, and then we assess the impact thereof on numerical weather forecasting of the assimilation of the AIRS spectra and the retrieved temperature. We close the paper with a discussion on the retrieval of several minor tropospheric constituents from AIRS spectra.

AIRS: Improving Weather Forecasting and Providing New Data on Greenhouse Gases.

Errors in the simulation of clouds in general circulation models (GCMs) remain a long-standing issue in climate projections, as discussed in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. This highlights the need for developing new analysis techniques to improve our knowledge of the physical processes at the root of these errors. The Cloud Feedback Model Intercomparison Project (CFMIP) pursues this objective, and under that framework the CFMIP Observation Simulator Package (COSP) has been developed. COSP is a flexible software tool that enables the simulation of several satellite-borne active and passive sensor observations from model variables. The flexibility of COSP and a common interface for all sensors facilitates its use in any type of numerical model, from high-resolution cloud-resolving models to the coarser-resolution GCMs assessed by the IPCC, and the scales in between used in weather forecast and regional models. The diversity of model parameterization techniques makes the comparison between model and observations difficult, as some parameterized variables (e.g., cloud fraction) do not have the same meaning in all models. The approach followed in COSP permits models to be evaluated against observations and compared against each other in a more consistent manner. This permits a more detailed diagnosis of the physical processes that govern the behavior of clouds and precipitation in numerical models. The World Climate Research Programme (WCRP) Working Group on Coupled Modelling has recommended the use of COSP in a subset of climate experiments that will be assessed by the next IPCC report. In this article we describe COSP, present some results from its application to numerical models, and discuss future work that will expand its capabilities.

https://hal.archives-ouvertes.fr/hal-01117353/document

COSP: Satellite simulation software for model assessment

Tropospheric aqueous-phase chemistry: kinetics, mechanisms, and its coupling to a changing gas phase.

Recent breakthroughs in IR detector array and cryocooler technology have made it possible to convert the concepts of optimum, passive, IR sounding to a practical satellite-borne instrument: the Atmospheric Infrared Sounder (AIRS), a grating array IR spectrometer
temperature sounder. AIRS, together with the Advanced Microwave Sounding Unit and the Microwave Humidity Sounder, will form a complementary sounding system for the Earth Observing System to be
launched in the year 2000. The three instruments are expected to become the new operational sounding system for the National Oceanic and Atmospheric Administration.

Atmospheric Infrared Sounder on the Earth Observing System

The Atmospheric Infrared Sounder (AIRS) has been developed for the NASA Earth Observing System (EOS) program for a scheduled launch on the EOS PM-1 spacecraft in December 2000. AIRS, working in concert with complementary microwave instrumentation on EOS PM-1, is designed to provide both new and more accurate data about the atmosphere, land and oceans for application to climate studies and weather prediction. Among the important parameters to be derived from AIRS observations are atmospheric temperature profiles with an average accuracy of 1 K in 1 kilometer (km) layers in the troposphere, humidity profiles to 10% accuracy and surface temperatures with an average accuracy of 0.5 K. The AIRS measurement technique is based on passive IR remote sensing using a precisely calibrated grating spectrometer operating in the 3.7 - 15.4 micrometer region. The instrument concept uses a passively cooled array spectrometer approach in combination with advanced state of the art focal plan and cryogenic refrigerator technology to achieve high performance in a practical long life configuration. The AIRS instrument has successfully completed a comprehensive performance verification program conducted at the Lockheed Martin IR Imaging Systems (LMIRIS) AIRS Test and Calibration Facility (ATCF), which was specially designed for precise spectroradiometric testing of space instrumentation. This paper provides a brief overview of the AIRS mission and instrument design, ATCF test capabilities, along with key results.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Development and test of the Atmospheric Infrared Sounder (AIRS) for the NASA Earth Observing System (EOS)

The creation of multi-decadal data sets for climate research requires better than 100 mK absolute calibration accuracy for the full range of spectral temperatures encountered under global conditions Validation that this accuracy is achieved by the operational hyperspectral sounders from polar orbit is facilitated by comparing data from two instruments Extreme radiometric calibration stability is critical to allow a long time series of noisy, but presumably long-term accurate truth measurements to be used for the validation of absolute accuracy at the 100 mK level We use the RTGSST in the tropical oceans as ground truth The difference between the AIRS derived sst2616 and the RTGSST based on six years of data shows a systematic cold bias of about 250 mK, but better than 4 mK/year stability The double difference between AIRS and the RTGSST and IASI and the RTGSST with less than one year of data already allows statements at the 100 mK absolute level It shows a 60 mK difference between the AIRS and the IASI calibration at 2616 cm-(sup 1) and 300 K, with a statistically insignificant 20 mK shift in six months

Using AIRS and IASI data to evaluate absolute radiometric accuracy and stability for climate applications

The comparison of global sea surface skin temperatures derived from cloud-free AIRS super window channel at 2616 cm-1 (sst2616) with the Real-Time Global Sea Surface Temperature (RTG.SST) for September 2002 shows a surprisingly small standard deviation of 0.44 K; however, sst2616 is colder than the RTG.SST by 0.67 K. About 0.35 K of the cold bias is due the expected bulk-skin gradient and the effect of using the day/night average RTG.SST for a nighttime comparison. The other 0.32 K is due to an absorbing layer in the atmosphere. There are large areas of the oceans where this absorbing layer is absent, and other areas where it is as large at 1.5 K. The layers persist regionally on a months timescale and might be related to some form of aerosol or marine haze. A correlation with major weather events, like the Monsoon season in the Indian ocean and, possibly, El Nino events is suspected, but has not been demonstrated. AIRS was lauched into polar orbit on the EOS Aqua spacecraft on May 4, 2002.

Hartmut H. Aumann

Papers

AIRS: Improving Weather Forecasting and Providing New Data on Greenhouse Gases.

Atmospheric Infrared Sounder on the Earth Observing System

Development and test of the Atmospheric Infrared Sounder (AIRS) for the NASA Earth Observing System (EOS)

Using AIRS and IASI data to evaluate absolute radiometric accuracy and stability for climate applications

Sea surface temperature measurements with AIRS: RTG.SST comparison