Observational relationship of sea surface temperatures and precedent soil moisture with summer precipitation in the US Great Plains

摘要

In this study, the relationship between precedent soil moisture anomalies and summer precipitation in the U.S. Great Plains was examined using Variable Infiltration Capacity (VIC)-simulated soil moisture and the Standardized Precipitation Index (SPI). The influence of Nino sea surface temperatures (SSTs) on summer precipitation was also investigated to compare their relative contributions to those from local moisture recycling. Results indicate that spring (May 1st) soil moisture is significantly correlated with summer SPI only during periods when Nino SSTs are not strongly correlated with summer SPI (e.g. 1920s-1930s). During periods when Nino SSTs are strongly correlated with summer SPI (e.g. 1940s-1980s), spring soil moisture is not a good predictor of summer precipitation in the U.S. Great Plains. The periods of strong correlation between Nino SSTs and summer precipitation are associated with strong SST persistence. Results also indicate that the impact of soil moisture anomalies and SST on summer precipitation varies greatly in space and time. Positive soil moisture-precipitation correlations are generally associated with high soil moisture persistence and negative soil moisture-precipitation correlations are linked to low soil moisture persistence. In addition, high SST persistence tends to favour (inhibit) negative (positive) soil moisture-precipitation correlations. This study suggests that both local soil moisture and remote SST anomalies influence summer precipitation in the U.S. Great Plains. The soil moisture anomalies are of greatest importance during years when Nino SST persistence is low.