Implications of all-sky heating rates for water, clouds, and upward transport in the Tropical Tropopause Layer

Recent work has shown that including clouds as observed by the CLOUDSAT and CALIOP satellite instruments has a significant effect on radiative heating rates in the Tropical Tropopause Layer (TTL) and the tropical Upper Troposphere (TUT). In particular, when clouds are included (all-sky), positive heating rates are found as low as 13 km in boreal winter, about 2 km lower than the level derived from clear-sky calculations. If these heating rates can be used to directly diagnose vertical motion through potential temperature surfaces, air from the main convective outflow level near 13 km in the tropics can directly reach the stratosphere. This has implications for the chemical composition of air entering the stratosphere, the relative humidity in the TUT and the TTL, and in situ cloud formation in the TTL. Comparisons of water vapor simulations with a trajectory-based microphysical model show that the heating rates have an impact on water vapor comparable to the inclusion of processes such as convective injection, sub grid scale gravity waves, or heterogeneous microphysics. Focusing on boreal winter, this paper examines the implications of all-sky heating rates for the locations of convection that affect air in the middle TTL, and the water vapor and cloud distributions. Schematic of the TTL based on all-sky heating rates.