Large asymmetrical temperature trends at Mount Wilson, California

We compiled and analyzed a daily time series of temperatures and precipitat ion totals from Mount Wilson, California from 1918 to 1998. Our results sho w a large decline in maximum temperature, no change or an upward trend in m inimum temperature, and a substantial decline in the diurnal temperature ra nge (DTR). The interannual variations in monthly maximum temperature and DT R are significantly correlated with monthly precipitation levels, sea-surfa ce temperatures (SSTs) off the coast of Southern California, and the Southe rn Oscillation Index(SOI). El Nino periods and/or months with high SST anom alies tend to be wet with lower maximum temperatures and DTR while La Nifia periods and/or months of lower SSTs are hotter and drier with higher DTR v alues. It is noteworthy that the SOI and SSTs have significant trends towar d more El Nino-like conditions with higher SSTs off Southern California.