Statistical Analysis of Cumulonimbus Anvil and Surrounding Aerosol Properties Retrieved by MODIS in Subtropical and Tropical Regions

In a contribution to a study of the factors controlling cumulonimbus anvil crystal size, here we present a statistical analysis of MODIS cloud and aerosol data from subtropical southern Florida (where the CRYSTAL-FACE field campaign took place in 2002) and the tropical eastern Pacific (where the TCSP field campaign will take place in 2005). We demonstrate algorithms that identify monolithic anvil shields and their more local likely core regions, where the youngest crystals are expected to be present, as well as aerosol data within a specified distance from the cloud edges. Choosing the July 2002 and June 2002 time periods for the two regions, respectively, we find that useful data from diurnal sea breeze convection over southern Florida is provided only by the Aqua platform, whereas both Aqua and Terra platforms can be used to study anvils over the eastern Pacific. Initial results indicate that predicted core regions do contain the smallest retrieved crystal effective radius over southern Florida, but not over the eastern Pacific, where the smallest retrieved effective radii in a given anvil are sometimes instead associated with the lowest optical depths. The significantly smaller anvils observed over southern Florida also exhibit a wider range of retrieved effective radius in the core regions. The greater anvil size and extent of low-cloud coverage limit successful aerosol retrievals over the eastern Pacific significantly more than over southern Florida, where aerosol data is often robust.