Convective Influence of Lower Stratospheric Water Vapor in the Boreal Summer Monsoon Regions

Processes maintaining the localized maxima in lower stratospheric water vapor over the boreal summer monsoon regions are investigated using trajectory and cloud models that resolve the detailed cloud microphysical processes, with observation-based convection and radiation schemes, driven by reliable temperature fields with wave-driven variability, and constrained by NASA satellite observations. We examine the impact of convective influence along parcel trajectories on cloud formation and dehydration by tracing the trajectories through time-dependent fields of convective cloud top heights estimated from 3-hrly geostationary satellite imagery and TRMM rainfall measurements. The atmospheric column is saturated up to the cloud top altitude at every convective encounter. Convection moistens preferentially along the southern flank of the North American monsoon anticyclone and over equatorial Africa, with a tropical mean moistening of 0.4 ppmv at the 100 hPa level. Convective source and transport pathways of water vapor over the Asian monsoon region are examined.