Assessing the potential of the Atmospheric Infrared Sounder (AIRS) surface temperature and specific humidity in turbulent heat flux estimates in the southern Ocean

Abstract

Surface air temperature (TA), sea surface temperature (TO), and surface specific humidity (qa) satellite retrievals from the Atmospheric Infrared Sounder (AIRS) are compared with shipboard measurements across Drake Passage for the period from September 2002 to June 2007. The objective is to evaluate whether AIRS retrievals, in conjunction with microwave sea surface temperatures from the Advanced Microwave Scanning Radiometer (AMSRE), can provide sufficiently accurate parameters to estimate sensible and latent heat fluxes in the data-limited Southern Ocean. The collocated data show that both AIRS T A and TO are colder than those from shipboard measurements, with a time mean bias of -2.03°C for TAand -0.22°C for TO. Results show that air-sea temperature difference (TA - TO), qa, and relative humidity (RH) are the major factors contributing to the differences between satellite and shipboard temperature measurements. Differ nces in AIRS and shipboard T A (ΔTA) decrease with increasing TA - TO, and ΔTA increases with increasing RH, whereas differences in AIRS and shipboard TO (ΔTO) increase with both increasing TA - TO and increasing qa. The time mean qa from AIRS is lower than the shipboard qa by 0.69 g/kg. Statistical analyses suggest that TA - TO, cloud, and qa are the major contributors to the qa difference (Δqa). Δqa becomes more negative with increasing TA - TO and increasing cloud fraction. Δqa also becomes more negative as qa increases. Compared with TA, TO, and TA - TO, from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis (NCEP), AIRS-derived and AMSRE-derived variables show more small-scale spatial structure, as is lso typical of the ship observations. Although AIRSqa gives a better representation of the full range of values of shipboard qa, its deviation from shipboard qa is relatively large compared to NCEP qa. Compared with several existing gridded flux products, turbulent fluxes estimated from AIRS and AMSRE data using bulk algorithms are better able to represent the full range of flux values estimated from shipboard parameters. Copyright 2010 by the American Geophysical Union.