Using Regional Climate Models and Lagrangian Back Trajectories to Estimate the Source Areas of Water Vapor.

Where did the water vapor that rained here, come from? This is the basic question behind studies into water vapor source regions and precipitation recycling. Estimates of precipitation recycling using highly simplified bulk formulations have existed for some time. Over the last decade, attempts to estimate water vapor source regions more generally using back trajectories have appeared. Some fairly strong and often broken assumptions are required by these back trajectory methods. In this study I use the output from a regional climate model simulation to calculate back trajectories and estimate water vapor source regions. This is done multiple times, each time further relaxing the assumptions involved. The impact this has on the water vapor source regions, precipitation recycling and the limitations of the method are explored.