Influence of convection on stratospheric water vapor in the North American Monsoon region

Abstract. We quantify the connection between deep convection occurrence and summertime 100-hPa water vapor anomaly over the North America (NA) region and find substantial consistency of their interannual variations and that the water vapor mixing ratio over the NA region is up to ~1ppmv higher when deep convection occurs. We use a Lagrangian trajectory model to demonstrate that the structure and the location of the NA anticyclone, as well as the tropical upper tropospheric temperature, determine how much contribution the deep convection could make to moistening the lower stratosphere. 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. Our hypothesis explains both the summer seasonal cycle and interannual variability of the convective moistening efficiency in the NA region, and can provide valuable insight on modeling stratospheric water vapor.

Influence of convection on stratospheric water vapor in the North American Monsoon region Institutional Repository Document