Testing the Clausius-Clapeyron constraint on the aerosol-induced changes in mean and extreme precipitation

The impacts of aerosol and greenhouse gas forcing of the 20th century on the climatological mean and extremes of precipitation are compared in an atmospheric GCM with improved parameterizations of aerosol direct and indirect effects. In spite of different forcing patterns, the thermodynamic effects of aerosol cooling and greenhouse gas warming on the zonally averaged precipitation have similar latitudinal patterns but opposite signs, plausibly due to the effects of temperature on atmospheric water vapor content and moisture flux. The fractional thermodynamic change, for both the moisture convergence in mid-and high latitudes and precipitation extremes at all latitudes, scales linearly with the abundance of atmospheric moisture at a rate of similar to 5%/K, somewhat less than the expectation from the Clausius-Clapeyron relation. Citation: Chen, G., Y. Ming, N. D. Singer, and J. Lu (2011), Testing the Clausius-Clapeyron constraint on the aerosol-induced changes in mean and extreme precipitation, Geophys. Res. Lett., 38, L04807, doi:10.1029/2010GL046435.