Detecting tropical convection using AVHRR satellite data

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