Jet Propulsion Labratory

AIRS - Improving Weather Forecasting and Providing New Data on Greenhouse Gases

Chahine, et al. The Atmospheric Infrared Sounder (AIRS), and its two companion microwave instruments, the Advanced Microwave Sounding Unit and the Humidity Sounder for Brazil, form the integrated atmospheric sounding system flying on the Earth Observing System Aqua spacecraft since its launch in May 2002.1 The primary scientific achievement of AIRS has been to improve weather prediction and to study the water and energy cycle. AIRS also provides information on several greenhouse gases. The measurement goal of AIRS is the retrieval of temperature and precipitable-water vapor profiles with accuracies approaching those of conventional radiosondes. 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.

Moustafa T. Chahine, Thomas S. Pagano, Hartmut H. Aumann, Robert Atlas, Christopher Barnet, John Blaisdell, Luke Chen, Murty Divakarla, Eric J. Fetzer, Mitch Goldberg, Catherine Gautier, Stephanie Granger, Scott Hannon, Fredrick W. Irion, Ramesh Kakar, Eugenia Kalnay, Bjorn H. Lambrigtsen, Sung-Yung Lee, John Le Marshall, W. Wallace McMillan, Larry McMillin, Edward T. Olsen, Henry Revercomb, Philip Rosenkranz, William L. Smith, David Staelin, L. Larrabee Strow, Joel Susskind, David Tobin, Walter Wolf and Lihang Zhou. 2006: AIRS: Improving Weather Forecasting and Providing New Data on Greenhouse Gases. Bulletin of the American Meteorological Society: Vol. 87, No. 7, pp. 911-926.

Three-dimensional tropospheric water vapor in coupled climate models compared with observations from the AIRS satellite system

Pierce et al. (2006) find that six coupled models are drier than AIRS measurements by 10%-25% in tropics below 800mb and are more moist by 25%-100% between 300-600mb, especially in the extra-tropics. They conclude "analysis of the accuracy and sampling biases of the AIRS measurements suggest that these differences are due to systematic model errors, which might affect the model estimated range of climate warming anticipated over the next century.

Pierce D. W., T. P. Barnett, E. J. Fetzer, P. J. Gleckler (2006),Three-dimensional tropospheric water vapor in coupled climate models compared with observations from the AIRS satellite system, Geophys. Res. Lett., 33, L21701, doi:10.1029/2006GL027060.

Climatology of Upper-Tropospheric Relative Humidity from the Atmospheric Infrared Sounder and Implications for Climate, J. Climate

Gettelman et al. (2006) analyze the NCAR CAM3 water vapor climatology and find that the model only succeeds in reproducing the mean observed water vapor, missing many scales of variability apparent in AIRS profiles. They also find that "AIRS provides insight on climate forcing, e.g. the greenhouse effect appears to increase with SST and that although the water vapor feedback is positive, it is not as positive as a constant relative humidity profile would produce and the differences in humidity imply global differences in the TOA atmosphere fluxes of ~1 W/m2.

Gettelman, Collins, Fetzer, Eldering, Irion (2006), Climatology of Upper-Tropospheric Relative Humidity from the Atmospheric Infrared Sounder and Implications for Climate, J. Climate, 19, 6104-6121. DOI: 10.1175/JCLI3956.1

Vertical moist thermodynamic structure and spatial-temporal evolution of the MJO in AIRS observations

Tian et al., (2006) study the vertical moist thermodynamic structure and spatial-temporal evolution of the Madden-Julian Oscillation (MJO). They find significant differences in the lower troposphere moisture and temperature between AIRS measurements and the NCEP reanalysis over the Indian and Pacific Oceans. "Specifically, the anomalous lower-troposphere temperature structure is much less well defined in NCEP than in AIRS for the western Pacific,...

Tian, B., D. E. Waliser, E. J. Fetzer, B. H. Lambrigtsen, Y. Yung, and B. Wang (2006), Vertical moist thermodynamic structure and spatial-temporal evolution of the MJO in AIRS observations,. J. Atmos. Sci., 63, 2462-2485 (2006). DOI: 10.1175/JAS3782.1

On the determination of atmospheric minor gases by the method of vanishing partial derivatives with application to CO2

Chahine et al. (2005) demonstrate the first retrieval of mid-tropospheric CO2 directly from AIRS cloudy radiance spectra. They compared their results to the aircraft flask CO2 measurements obtained by Matsueda over the Western Pacific and demonstrate skill in tracking the measured 5 ppmv seasonal variation with an accuracy of 0.43 +/- 1.20 ppmv.

Chahine M., C. Barnet, E. T. Olsen, L. Chen, E. Maddy (2005), On the determination of atmospheric minor gases by the method of vanishing partial derivatives with application to CO 2, Geophys. Res. Lett., 32, L22803, doi:10.1029/2005GL024165.

Improving global analysis and forecasting with AIRS: Bulletin Of The American Meteorological Society

Le Marshall et al. (2006) report that assimilation into NCEP of thinned AIRS data improves the global analysis and forecasting by 6 hours in 6 days in both the Northern and the Southern hemispheres. They conclude: "AIRS hyperspectral data (from one orbital instrument), used within current stringent operational constraints, show significant positive impact in forecast skill over both the Northern and Southern Hemisphere for January 2004. The results indicate a considerable opportunity to improve operational analyses and forecasts with hyperspectral data. The AIRS data are now used operationally within NCEP, with imminent system upgrades expected to further increase the impact of the AIRS data."

Le Marshall, J., Jung, J., Derber, J., Chahine, M., Treadon, R., Lord, S.J., Goldberg, M., Wolf, W., Liu, H.C., Joiner, J., Woollen, J., Todling, R., van Delst, P., and Tahara, Y., 2006, Improving global analysis and forecasting with AIRS: Bulletin Of The American Meteorological Society, v. 87, no. 7, p. 891-894, DOI: 10.1175/BAMS-87-7-891.

Satellite data reveal the 3-D moisture structure of Tropical Intraseasonal Oscillation and it's coupling with underlying ocean

Fu et al. (2006) use AIRS water vapor profiles to document the 3-D moisture structure of the boreal-summer TISO over the Indo-western Pacific region in their investigation of the interaction between the TISO and the underlying ocean. They find the AIRS data reveal much larger tropospheric moisture perturbations than those depicted in previous NCAR/NCEP reanalysis and ECMWF analysis data sets, both of which have been widely used as observations to validate models. They conclude: "If the AIRS data are closer to the ground truth, many state-of-the-art GCMs may considerably underestimate the tropospheric moisture perturbations associated with the TISO convection. The AIRS data also reveal a drying atmospheric boundary layer associated with the convection. This feature doesn't exist in the previous analysis and reanalysis data sets, but appears in some sounding observations. This may suggest that the impact of convection-induced downdrafts on the ABL is significantly underestimated in both ECMWF and NCEP reanalysis data sets."

Fu X., B. Wang, L. Tao (2006), Satellite data reveal the 3-D moisture structure of Tropical Intraseasonal Oscillation and it's coupling with underlying ocean, Geophys. Res. Lett., 33, L03705, doi:10.1029/2005GL025074.

Daily global maps of carbon monoxide from NASA's Atmospheric Infrared Sounder

Employing AIRS retrieved mid-tropospheric CO, McMillan et al. (2005) report that the AIRS sensitivity to mid-tropospheric CO is similar to that of MAPS and MOPITT, but that its unique daily global view provides nearly an order of magnitude as many retrievals per day as MOPITT. This dense coverage enables process studies of phenomena on daily timescales. They present maps of daily changes in the globe-encircling transport of biomass burning emissions heretofore seen only in computer models, and state that "Never before have such detailed views of a tropospheric trace gas (other than water) been available on a daily basis. ...we expect the routine global CO maps will lead to a more complete understanding of the CO budget, and along with future AIRS CO2 and CH4 retrievals, will provide unique insights into the global carbon cycle and global climate change."

McMillan W. W., C. Barnet, L. Strow, M. T. Chahine, M. L. McCourt, J. X. Warner, P. C. Novelli, S. Korontzi, E. S. Maddy, S. Datta (2005), Daily global maps of carbon monoxide from NASA's Atmospheric Infrared Sounder, Geophys. Res. Lett., 32, L11801, doi:10.1029/2004GL021821.

Deep convective influence on the Asian summer monsoon anticyclone and associated tracer variability observed with Atmospheric Infrared Sounder (AIRS)

Randel and Park (2006) employ AIRS data to analyze the deep convective influence on the Asian summer monsoon anticyclone and associated tracer variability. The find that "AIRS data show that the transient convective events are associated with the vertical transport of low ozone and high water vapor into the UTLS region,..."

Randel W. J., M. Park (2006), Deep convective influence on the Asian summer monsoon anticyclone and associated tracer variability observed with Atmospheric Infrared Sounder (AIRS), J. Geophys. Res., 111, D12314, doi:10.1029/2005JD006490.

Simulating the formation of Hurricane Isabel (2003) with AIRS data

Wu et al. (2006) evaluate the impact of relaxing the MM5 model to the AIRS retrieved temperature and humidity profiles in regions uncontaminated by clouds on tropical cyclone development. The inclusion of AIRS data allowed them to "...show that the SAL may have delayed the formation of Hurricane Isabel and inhibited the development of another tropical disturbance to the East." They suggest "the AIRS Level 2 products are useful for investigating the influence of the SAL on tropical cyclones."

Wu L., S. A. Braun, J. J. Qu, X. Hao (2006), Simulating the formation of Hurricane Isabel (2003) with AIRS data, Geophys. Res. Lett., 33, L04804, doi:10.1029/2005GL024665.