Solar-Irradiance Variations and Regional Precipitations in the Western United States

By Charles A. Perry, U.S. Geological Survey, Lawrence, KS, 66049, U.S.A.

Abstract

Changes in total solar irradiance can be linked to changes in regional precipitation. A possible mechanism responsible for this linkage begins with the absorption of varying amounts of solar energy by the tropical oceans which creates ocean temperature anomalies. These anomalies are then transported by major ocean currents to locations where the stored energy is released into the atmosphere, altering atmospheric pressure and moisture patterns that can ultimately affect regional precipitation.

Correlation coefficients between annual differences in empirically modeled solar-irradiance variations and annual state-divisional precipitation in the United States for the period 1950-88 were computed with lag times of 0 to 7 years. The most significant correlations occur in the Pacific Northwest with a lag time of 4 years, which is approximately equal to the travel time of water within the Pacific Gyre from the western tropical Pacific Ocean to the Gulf of Alaska. Precipitation in the Desert Southwest correlates significantly with solar irradiance lagged 3 and 5 years, which suggests a link with ocean-water temperature anomalies transported by the Equatorial Countercurrent as well as the North Pacific Gyre. With the correlations obtained, droughts coincide with periods of negative irradiance differences (dry high-pressure development), and wet periods coincidewith periods of positive differences (moist low-pressure development).

Additional information on Solar Irradiance and Streamflow can be found at: http://ks.water.usgs.gov/waterdata/climate/.

Perry, C.A., 1994, Solar-Irradiance Variations and Regional Precipitations in the Western United States: International Journal of Climatology, v. 14, November 1994, p. 969-983.

To request a paper copy of this journal article, email: cperry@.usgs.gov