Covariabilities of spring soil moisture and summertime United States precipitation in a climate simulation



This paper explores the space-time connections between springtime soil moisture and summer precipitation over the continental United States by applying a singular value decomposition (SVD) method to a 50-year climate simulation. The first two SVD modes were analyzed. The two leading SVD modes account for 43% of the squared covariance between spring soil moisture and summer precipitation. Their corresponding components explain 14% of the soil moisture variance and 19% of the precipitation variance, respectively, which is larger than that contributed by tropical Pacific sea-surface temperatures (SSTs). The temporal correlations between the two expansion coefficients of each SVD mode are 0.83 and 0.88, respectively, indicating a significant association between spring soil moisture variation and summer precipitation variability. Both positive and negative cross-correlations exist over different regions of the United States in the two modes. Linear regression relates surface relative humidity and surface air temperature to the soil moisture SVD time series. The patterns revealed by the SVD analysis show where the local soil moisture-precipitation coupling contributes to the model's simulation of precipitation. Copyright © 2006 Royal Meteorological Society