Recorded presentation3.4
Five-year climatology of dry air intrusions as viewed by AIRS/Aqua
Sean P. F. Casey, Texas A&M University, College Station, TX; and A. E. Dessler and C. Schumacher
Many studies have commented on the presence of mid-troposphere (400-600 hPa) dry air intrusions into normally moist areas of the warm pool region in the tropical western Pacific. In this study, we analyze five years of relative humidity (RH) observations from the Atmospheric Infrared Sounder (AIRS) instrument aboard the Aqua satellite to identify areas of anomalously dry air between 600 and 400 hPa over deep convective regions of the tropical oceans. A dry air intrusion is defined when RH < 20%, accounting for the lowest 10% of RH observations. Intrusions appear to be more frequent over the Indian and Pacific Oceans than over the Atlantic. Large seasonal differences in the locations of dry air intrusions are apparent in each ocean basin.Back trajectories are then calculated for each observed parcel. The origin, or location of dehydration, is identified as the point along each trajectory where the RH of the parcel is greater than or equal to 100%. An analysis of the time between dehydration and dry air observation by AIRS suggests that dry air intrusions in June-August (JJA) tend to last one to two days longer than those observed in other seasons. While more dry air intrusions are observed to come from each hemisphere in its respective winter, most sources of dry air intrusions are subtropical and contribute anomalously dry air year-round. Other meteorological features are noted in the back-trajectories, such as the eastward/westward wind transition from the subtropics to the tropics and the effects of the Indian monsoon on dry air distribution paths.
Session 3, Special Session on Latest Developments in Hyperspectral Remote Sensing
Thursday, 15 January 2009, 3:30 PM-5:00 PM, Room 126BC
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