Abstract
Abstract. A daytime climatological spatio-temporal distribution of high opaque ice cloud (HOIC) classes over the Indian subcontinent (0–40° N, 60° E–100° E) is presented using 25-year data from the Advanced Very High Resolution Radiometers (AVHRRs) for the summer monsoon months. The HOICs are important for regional radiative balance, precipitation and troposphere-stratosphere exchange. In this study, HOICs are sub-divided into three classes based on their cloud top brightness temperatures (BT). Class I represents very deep convection (BT<220 K). Class II represents deep convection (220 K
Highlights
During summer monsoon months the Indian subcontinent and surrounding oceanic areas experience strong presence of very high convectively formed clouds
This study presents in finest spatial resolution (0.1×0.1 degrees) the long-term climatology of such cloud classes from the Advanced Very High Resolution Radiometers (AVHRRs) to date over the Indian subcontinent
Since most of the monsoonal rainfall occurs through convective clouds, the footprints of the movement of monsoon over the Indian subcontinent could be seen in the high opaque ice cloud (HOIC) classes
Summary
During summer monsoon months the Indian subcontinent and surrounding oceanic areas experience strong presence of very high convectively formed clouds (mainly deep convective cores, stratiform clouds and anvil cirrus). The Advanced Very High Resolution Radiometer (AVHRR) sensors onboard series of National Oceanic and Atmospheric Administration (NOAA) satellites offer the longest and continuous data to study clouds These more than 25 years of data provide a wealth of information, which can be exploited to characterize clouds during monsoon. Devasthale and Grassl (2009) compared brightness temperatures derived from 11 and 12 micrometer channels of AVHRRs for June, July and August months (coldest months and minimal atmospheric influence) of 25-year period from 1982–2006 at five stations in Antarctica with the insitu measurements and found very good correlation among them They found no significant deviations in the derived surface temperatures due to the change of satellite platform suggesting consistent calibration and intercalibration of the thermal channels. The cloud amount is calculated as the ratio of number of pixels qualifying criteria for the particular cloud class to the total number of pixels in a scene
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