An apparent atmospheric teleconnection between snow cover and the North American monsoon

Snow cover has been shown to reduce lower-atmospheric temperatures thereby modifying atmospheric circulation patterns over time scales of days to months. Over the past three decades an inverse relationship between Eurasian winter snow cover extent and subsequent summer rainfall across India has been studied. Very little research has addressed the potential relationship between North American snow cover and the North American monsoon. The work presented here identifies an apparent inverse relationship between July and August snow cover across western North America and August precipitation across a portion of the southwestern U.S, that is susceptible to an annual monsoon circulation. Results suggest that during a summer season characterized by low snow cover across western North America, the typical subtropical ridge across the southern U.S. intensifies. The product appears to be an atmosphere that is conducive to advection of low-level moisture northward across areas of the southwestern U.S.