Maps of SOI Relations to Western U.S. Winter Climate


June-November Southern Oscillation Index (SOI) vs.
October-March Precipitation and Temperature

Areas in reddish colors are wetter (for precipitation) and warmer (for temperature) in years with Summer/Autumn negative Southern Oscillation Index ("El Nino").

Areas in bluish colors are drier (for precipitation) and colder (for temperature) in years with Summer/Autumn negative Southern Oscillation Index ("El Nino").

84 climate divisions in the 11 westernmost continental U.S. states. Degree of coloration represents the statistical significance of the relationships. Climate divisions with dots do not have statistically significant relations, but the colors of the dots nonetheless represent the tendency.


Maps of SOI Relations to Western North America Winter Climate

June-November Southern Oscillation Index (SOI) vs.
October-March Precipitation and Temperature

The following analyses are based on a coarsely gridded monthly precipitation data set prepared by the Climatic Research Unit at the University of East Anglia, United Kingdom. They extend the analysis to Canada and Alaska to the north, and to Mexico to the south. Data from 1935/36 through 1988/89.

Coloration again represents the sense of the relationship. Reddish areas experience wetter winters during El Nino years and drier winters during La Nina years. Bluish areas experience drier winters during El Nino winters and wetter winters during La Nina years. Green areas do not pass statistical significance tests, but tend the same way as bluish areas. Brown areas do not pass statistical significance tests, but tend the same way as reddish areas.

Map 5: Correlation coefficient times 100. Significance colored.
Map 6: Student's t-value times 10. Significance colored.


Western Regional Climate Center, Dr. Kelly Redmond, krwrcc@dri.edu