Temperature Control of the Variability of Tropical Tropopause Layer Cirrus Clouds

We examine the temperature control of variability of tropical tropopause layer (TTL) cirrus clouds (i.e., clouds with bases higher than 14.5 km) by using 8 years (2006–2014) of observations of clouds from the CALIPSO and temperatures from COSMIC. It is found that the temporal variability of vertical structure of TTL cirrus cloud fraction averaged between 15°N and 15°S can be well explained by the vertical temperature gradient for both seasonal and interannual time scales. For the interannual variations, it is shown that the El Niño–Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO) are the leading factors in controlling the spatial variability of the TTL cirrus clouds while their spatial averages between 15°N and 15°S are dominated by the QBO and the Brewer-Dobson circulations.