Trends in spring snowpack over a half-century of climate warming in California, USA

Linear trends in 1 April snow water equivalent (SWE) in California, USA, are determined from a dense network of observations over the period 1950-2002. These trends are compared to concurrent time series of precipitation and temperature and Pacific Ocean climate indices. We find increased winter temperatures have accompanied both decreasing and increasing SWE trends, resulting in a weak overall negative trend in spring SWE. The spatial distribution of SWE trend is dependent on both latitude and elevation. Increases in both precipitation and temperature have led to increases in SWE at high elevations in southern Sierra Nevada and decreases at lower elevations. Increased temperature and decreased precipitation are associated with SWE loss in northern California. Trends in SWE can partially be attributed to shifts in Pacific Ocean climate indices.