Interannual Co-Variability of Tropical Tropopause Layer Cirrus and Temperature

The spatial and temporal distribution of cirrus cloud in the tropical tropopause layer (TTL) and its relationship to tropopause are investigated based on eight years (2006-2014) of data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements. The TTL cloud fraction and the tropical tropopause temperature both have pronounced annual cycles and are strongly negatively correlated both temporally and spatially. The interannual variability of the TTL cloud fraction and its correlation with temperature anomalies and possible dynamics processes are also discussed. The examination of the TTL cloud height relative to tropopause from collocated CALIPSO and COSMIC observations indicates that the tropopause plays a critical role in constraining the TTL cloud top height. In particular, the PDF of the highest TTL cloud top heights peaks just below the CPT height by noting that the COSMIC CPT height could be underestimated by about 100 m on average. More importantly, the highest TTL cloud top height that are above the CPT height, which is about 39% of the highest TTL cloud layers, can be largely explained by the uncertainty of the COSMIC CPT observation due to its limited vertical resolution.