PNNL

Abstract

Tropical Tropopause Layer cirrus (TTLC) profiles identified from CALIPSO LIDAR measurements are grouped into cloud objects and classified according to whether or not they are connected to deep convection. TTLC objects connected to deep convection are optically and physically thicker than isolated objects, consistent with what would be expected if connected objects were formed from convective detrainment and isolated objects formed in situ. In the tropics (±20 Latitude), 36% of TTLC profiles are classified as connected to deep convection, 43% as isolated, and the remaining 21% are part of lower, thicker cirrus clouds. Regions with higher occurence of deep convection also have higher occurrence of TTLC, and a greater percentage of those TTLC are connected to deep convection. Cloud top heights of both isolated and connected clouds are distributed similarly with respect to the height of the cold point tropopause. No difference in thickness or optical depth was found between TTLC above deep convection or above clear sky, though both cloud base and top heights are higher over deep convection than over clear sky.