IINFLUENCE OF CONVECTION ON STRATOSPHERIC WATER VAPOR IN NORTH AMERICAN MONSOON

Abstract

We quantify the connection between deep convection occurrence and the summertime 100-hPa water vapor anomaly over the North America (NA) region and find substantial consistency of their interannual variations. We also find that the water vapor mixing ratio over the NA region is up to ~1 ppmv higher when deep convection occurs. We use a Lagrangian trajectory model to demonstrate that the structure and the location of the NA monsoon anticyclone, as well as the tropical upper tropospheric temperature, mediate the moistening impact of convection. The deep convection mainly occurs over the Central Plains region, and most of the convectively moistened air is then transported to the center of the NA anticyclone and the anticyclonic structure helps maintain high water vapor content there. This explains both the summer seasonal cycle and interannual variability of the of the convective moistening efficiency in the NA region, and can provide valuable insights on modeling stratospheric water vapor.