EVIDENCE FOR A RELATIONSHIP BETWEEN SPRING SNOW COVER IN NORTH-AMERICA AND SUMMER RAINFALL IN NEW-MEXICO

Two possible mechanisms for interannual modulation of precipitation an omalies in the Southwest U.S. are examined. The association between El Nino/Southern Oscillation (ENSO) fluctuations and New Mexico precipit ation anomalies is found to vary with season: positive Pacific Ocean s urface temperature anomalies are associated with positive winter-sprin g precipitation anomalies in New Mexico but negative summer anomalies. We propose that the spring snow extent across the west-central U.S. a cts to enhance or suppress the subsequent summer monsoon circulation a ffecting the American Southwest, such that excessive snow leads to def icient summer rain, and deficient snow leads to abundant rain. This me chanism is consistent with the observed seasonal variation in the ENSO - precipitation relationship.