Soil moisture is important in many water-related applications, such as climate modeling and drought prediction. Due to the existence of land memory, the antecedent soil moisture conditions may play a significant role in modifying the local and remote climate. It is suggested that antecedent winter and spring soil moisture anomalies are strongly correlated with summer precipitation through the interaction between land surface and atmosphere. Previous studies have shown that this relationship is spatially variable from region to region. So far, the study of the role of antecedent soil moisture condition on summer precipitation variability has focused on North American Monsoon in the southwestern United States. However, the relationship between preceding soil moisture conditions and summer precipitation in the northern Great Plains has not been extensively studied.

In this study, the Variable Infiltration Capacity (VIC) model simulated soil moisture data from 1915 to 2004 were used to examine the impact of fall and spring soil moisture anomalies on summer precipitation. Palmer's Z-index (Palmer, 1965) was used to characterize summer precipitation conditions in the northern Great Plains since previous studies have shown that this index is appropriate for monitoring drought conditions in this region. Preliminary results show that there is a significant correlation between fall/spring soil moisture and summer precipitation over the northern Great Plains. However, this correlation varies over time and space. The correlation is significant only during periods 1922-1937, 1946-1951, and 1971-1978. Further investigation of the relationship reveals that there is a much stronger correlation between summer precipitation and soil moisture during the years that have large soil moisture anomalies. For instance, there are 11 wet (>1 std dev) and 12 dry (<-1 std dev) springs during the period 1915 to 2004. All wet / dry springs followed by wetter / drier than normal summers. The correlation between the 23 springs and associated summer precipitation is 0.83. It is concluded that antecedent soil moisture conditions play a significant role in modifying summer precipitation and examining the soil moisture conditions is very useful for predicting summer drought conditions in the northern Great Plains.