Cloud Properties over the Bay of Bengal Derived from NOAA-9 Split Window Data and the TRMM PR Product

Abstract

We studied the features of convective activity over the Bay of Bengal (BoB) in terms of cloud type and rainfall. In this paper, six cloud types were classified over the tropics using split window (11 and 12 µm) data measured by the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA-9. The spatiotemporal structure of Dense Cirrus (D-Ci) and Cumulonimbus (Cb) type clouds is surveyed in this study. As for the summer monsoon season, D-Ci-type clouds higher than 10% can be seen over the entire BoB. The spatiotemporal structure of the D-Ci-type cloudiness coincides with those of outgoing longwave radiation (OLR) value of less than 230 W/m ² over the BoB. The Cb-type cloudiness, which is less than D-Ci-type, concentrates over the northeastern part of the BoB in the boreal summer. The enhanced precipitation, derived from Tropical Rainfall Measurements Mission (TRMM) Precipitation Rader (PR), coincides with the D-Ci-type clouds area higher than 20% and the low OLR value less than 190 W/m ² as well as large amount of Cb-type cloudiness in the boreal summer.