Influence of condensate evaporation on water vapor and its stable isotopes in a GCM

The direct effect of condensate evaporation on atmospheric water vapor and its isotopic composition is assessed in a climate model. The model contains two parallel hydrologic cycles, an active one which influences the model physics and dynamics and a passive one which does not. Two model simulations are performed, one in which passive cloud and precipitation can evaporate and one in which they cannot. The active hydrologic cycles, and thus the simulated circulations and temperatures, are identical in both simulations. Eliminating passive condensate evaporation reduces the specific humidity in the passive cycle by around 5%; this reduction varies from a few percent to 25% of the control value, depending on location. Zonal mean water vapor in the lower and middle troposphere is enriched in HDO relative to the control case, and is depleted in the upper troposphere. Citation: Wright, J. S., A. H. Sobel, and G. A. Schmidt (2009), Influence of condensate evaporation on water vapor and its stable isotopes in a GCM, Geophys. Res. Lett., 36, L12804, doi:10.1029/2009GL038091.