부산대학교 도서관

Tropical convection regimes range from deep organized to shallow convective systems. Mesoscale processes such as cold pools within tropical convective systems can play a significant role in the evolution of convection over land and open ocean. Although cold pools are widely observed, their diurnal properties are not well understood over tropical oceans and land. The oceanic cold pool identification metric applied herein uses the gradient feature (GF) technique and is compared with diurnally resolved buoy-identified thermal cold pools. This study provides a first-ever diurnal climatology of GF number, area, and attributed TRMM 3B42 precipitation using a spaceborne scatterometer (RapidSCAT). Buoy data over the Pacific, Atlantic, and Indian Oceans have been used to validate and examine the RapidSCAT-identified diurnal cycle of GF number and precipitation. Buoy-observed cold pool duration, precipitation, temperature, and wind speed is analyzed to understand the in situ cold pool properties over tropical oceans. GF- and buoy-observed cold pool number and precipitation exhibits a similar bimodal diurnal variability with morning and afternoon maxima, thus establishing confidence in using GF as a proxy to observe cold pools over tropical oceans. The morning peak is attributed to cold pools associated with deep moist convection while the afternoon peak is related to shallower clouds in relatively drier environments resulting in smaller cold pools over global tropical oceans. Significance Statement: The global diurnal cycle of oceanic convectively generated cold pools (cool outflows from convection) is observed for the first time using the gradient feature method—revealing a bimodal distribution of cold pools organized by deep, organized convective systems in the early morning and afternoon cold pools predominated by shallower, more isolated convection. This analysis will provide a reference for high-resolution climate models to mimic in order to accurately represent key processes that organize convection and govern air–sea interactions. [ABSTRACT FROM AUTHOR]