Examining spring soil moisture-summer precipitation interactions over the U.S. Great Plains: Results from the coupled land-atmosphere model CAM3-CLM3

The influence of spring soil moisture anomalies on summer precipitation variations in the U.S. Great Plains was investigated using the stand-alone version of Community Atmosphere Model version 3 (CAM3). A series of experiments were conducted to examine how spring soil moisture anomalies influence summer precipitation. Results demonstrate that there are significant differences in precipitation response depending on the sign, timing and duration of the spring soil moisture anomalies. Dry soil moisture anomalies tend to affect subsequent precipitation for longer than wet soil moisture anomalies when initialized on May 1st. However, when initialized on April 1, wet soil moisture anomalies influence summer precipitation for longer than dry anomalies initialized on the same date. Dry soils can have a statistically significant influence on summer precipitation for ~2-3 months, but our results also suggest that the length of soil moisture memory depends on when soil moisture anomalies occur. These differences illustrate the importance of timing. The precipitation response to wet soil moisture anomalies is quicker and greater in magnitude than the response to dry soil moisture anomalies. Soil moisture anomalies that are sustained for an entire month produced a larger precipitation response than those applied on the first day of the month. Further study is needed to determine whether these findings are model specific.