Changes in the tropical hydrologic cycle in a warming environment: influence on organized deep convection

In this study, changes in the interaction between organized deep convection and the tropical environment at radiative-convective equilibrium, and under conditions of surface warming, are examined using three-dimensional cloud system resolving simulations on a large horizontal domain. Three separate simulations are driven with fixed sea surface temperatures of 298 K, 300 K, and 302 K, and all exhibit deep convection that organizes into coherent regions of large-scale ascent separated by areas with relatively clear air and troposphere-deep ascent. Aspects of our simulations correspond to previously observed features of the tropical climate system, including the transition to strong precipitation above a critical value of total column water vapor and an increase in convective intensity with SST amidst weakening of the large-scale overturning circulation. Results of our experiments indicate a positive feedback between deep convective intensity and surface warming, but also one that operates as a nonmonotonic function of SST, and with complex interaction between deep convection and the environmental relative humidity and static stability profile.