Detecting tropical convection using AVHRR satellite data

A new method is introduced to identify active convective cloud regions in h igh-resolution AVHRR satellite data. This method is developed to overcome s everal limitations of existing visible/infrared techniques. Steep temperatu re gradients between the convective overshoots of cumulonimbus clouds and t he surrounding cirrus are used to identify the edges of active convective r egions. The limitations of previous methods are shown using up to 1.1 km re solution AVHRR data of the NOAA-11 and NOAA-12 satellites collected during the Central Equatorial Pacific Experiment (CEPEX), a measurement campaign t hat took place over the central Pacific Ocean between March 7 and April 6, 1993. Differences in the identification of convection between the new algor ithm and the existing algorithms are clarified by a case study and further illustrated by three collocations between NOAA-11 and NOAA-12 overpasses an d observations made with the Massachusetts Institute of Technology (MIT) 5 cm Doppler radar onboard the research vessel RN Vickers.