Contributions of Soil Moisture Interactions to Future Precipitation Changes in the GLACE-CMIP5 Experiment

Abstract:

The contributions of the projected changes in soil moisture to the overall future changes in various aspects of precipitation over land areas at the end of the 21st century are quantified using the simulations from the GLACE-CMIP5 experiment. This is done by directly comparing the overall projected future changes in climate, which are partly related to changes in soil moisture, to the changes in climate that are not affected by any changes in soil moisture. As the five different climate models contributing to the experiment show quite different geographical distributions of the future changes in soil moisture as well as different magnitudes, we do not consider ensemble mean values based on the corresponding simulations with these models but rather analyze the simulations from the different models separately. We focus on the soil moisture-precipitation coupling/feedback, distinguishing between different aspects of precipitation, i.e., the intensity and frequency of daily precipitation events, the intensity of heavy daily precipitation events as well as the frequency and length of dry spells and wet spells.

The simulations show marked future changes in soil moisture content, with a general tendency of increases in the tropics and decreases in the subtropics as well as in the southern parts of Europe and North America. The changes in soil moisture content are found to give major contributions to the overall changes in the latent heat flux and in different aspects of precipitation. The impact of soil moisture changes is notably stronger for the frequency of daily precipitation events than for their intensity. Hence, the changes in soil moisture give stronger contributions to the overall changes in the characteristics of wet and dry spells rather than to the changes in the intensity of heavy daily precipitation events.