Lower tropospheric heating by Saharan dust over the tropical Atlantic Ocean
Sun Wong, Texas A&M Univ., College Station, TX; and A. E. Dessler, N. Mahowald, P. Yang, and Q. Feng
The role of Saharan dust in heating up the Saharan Air Layer (SAL) over the tropical Atlantic Ocean is investigated. We track the SAL by using the aerosol optical thickness (AOT) retrieved from the measurements taken by Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and compile the temperature and specific humidity anomalies of the SAL using the NCEP data in August-September over the North Atlantic tropical cyclone (TC) main development region (MDR). We also analyze the temperature and specific humidity anomalies of the SAL simulated in the National Center of Atmospheric Research (NCAR) community climate model (CAM3) coupled with dust radiative effect. We find that higher AOT is associated with warmer and dryer anomalies below 700 hPa. Then, we use a radiative transfer model to estimate the instantaneous heating anomalies caused by the dust alone as well as by both the dust and dry anomaly. Both the dust and dry anomaly are essential in heating or maintaining the temperature inversion in the SAL against thermal relaxation. In the eastern Atlantic, both the dust and dry anomaly in the SAL heats up the lower troposphere, and dust contributes more than 50% of the heating rate anomaly. West of 40°W, when the dust content becomes small (AOT < 0.5) in the SAL, the dry anomaly becomes essential in determining the ability of the SAL to heat up the lower troposphere.
Session 5, Aerosol direct and indirect effects
Wednesday, 14 January 2009, 8:30 AM-10:00 AM, Room 131B
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