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US. GIoball CI °Harm^ esear,::[° IPirogirarn Global Climate Change Impacts in the United States Projected Changes in the Water Cycle W MI rilr1r'ii rr ( .:rwr rflfid ric Hnto,ri nr % focet), 14ntfinrlkAP ffiit f""r nrlIf'dio,inrz MP nnir The water cycle exhibits many changes as the Earth warms. Wet and dry areas respond differently. NIC)AA /Nc::r.X: In addition, changes in atmospheric circulation will tend to move storm tracks northward with the result that dry areas will become drier and wet areas wetter. Hence, the and Southwest is projected to experience longer and more severe droughts from the combination of increased evaporation and reductions in precipitation.' 42 Changes in Snowfall Contributions to Wintertime Precipitation 1949 to 2005 Less snow',,,'', .. More snow Trends in winter snow -to -total precipitation ratio from 1949 to 2005. Red circles indicate less snow, while blue squares indicate more snow. Large circles and squares indicate the most significant trend S.'4' Areas south of 37 °N latitude were excluded from the analysis because most of that area receives little snowfall. White areas above that line have inadequate data for this analysis. The additional atmospheric moisture contributes to more overall precipita- tion in some areas, especially in much of the Northeast, Midwest, and Alas- ka. Over the past 50 years, precipita- tion and streamflow have increased in much of the Northeast and Midwest, with a reduction in drought duration and severity. Much of the South- east and West has had reductions in precipitation and increases in drought severity and duration, especially in the Southwest. In most areas of the country, the frac- tion of precipitation falling as rain versus snow has increased during the last 50 years. Despite this general shift from snow to rain, snowfalls