Wavelet-Based Technique to Extract Convective Clouds From Infrared Satellite Images

Extraction of all cumuliform clouds from infrared satellite images is important for cloud studies. Existing methods have focused on extracting only the cumulonimbus clouds. Over monsoon Asia, warm cumulus and cumulus congestus clouds are a large fraction of total cumuliform clouds and are covered by cirrus. An extraction method based only on brightness temperatures (BT) is not sufficient for the detection of these cumuliform clouds. In this letter, a new cloud extraction technique based on spatial characteristics of the convective clouds is presented. The À trous wavelet transform (ATWT) is shown here to successfully extract both shallow and deep convective clouds. The depression in BT caused by the cold cloud tops corresponds to negative wavelet components found by the ATWT.