Influence of SST on humidity and temperature in the outflow of tropical deep convection: Observational basis for evaluating model simulations

Multiple years of measurements of tropical upper-tropospheric temperature and humidity by MOZAIC (Measurements of Ozone and Water Vapor by Airbus In-Service Aircraft) project were analyzed in the vicinity of deep convective outflow to study the variation of upper-tropospheric humidity (UTH) and the influence of SST on the outflow air properties. The UTH distribution depends on where a convective system is sampled by the MOZAIC aircraft: deep inside the system, relative humidity with respect to ice (RHi) is unimodal at ~ 114%; near the outskirt of the system, bimodal distribution of RHi starts to emerge. Both temperature and specific humidity of the outflow air increase with SST and they compete with each other to determine the change of relative humidity (RH). We also investigated the variations of temperature and humidity outside of deep convective regions using 3D air back trajectories to estimate the time since last convection. This gives a Lagrangian perspective of how upper-tropospheric air properties vary in relation to deep convection and SST. The MOZAIC measurements and analysis conducted in this study represent a unique observational basis against which model simulations of upper-tropospheric temperature and humidity and their connection to deep convection can be evaluated. We are pursuing this route.