A Modern Statistical Analysis and Documentation of Historical Temperature Records in California, Oregon and Washington, 1821–1964

Abstract

An analysis is made of historical temperature records in the western United States. An investigation of the power spectra of monthly mean and extreme temperature fluctuations in the frequency range between 0 and 6 cycles per year showed that significant periodicities were associated only with the annual and semi-annual temperature fluctuations. The amplitude of the annual oscillation varies between 2 and 12C and increases rapidly when proceeding from the coast inland; the amplitude of the semiannual oscillation, where significant, is of the order of 1C. There have been no secular temperature changes in nonurban environments over the past century; however, in big cities, the temperature has increased significantly. The mean duration of positive and negative temperature anomalies (from long term monthly means) varies between two and three months, and decreases from the coast inland. The extreme duration of these anomalies ranges from 10 to 20 months and does not depend on latitude or local environment. The probability functions for the mean duration and for the extremes of the maxima and minima agree with those expected from theory for a stationary random variable of known variance and spectral width. Nonseasonal temperature oscillation, along the Pacific coast are coherent over distances of the order of 1500 km; good coherence is also observed between coastal and inland stations. There is strong and in-phase relation between nonseasonal fluctuations of air and sea surface temperatures at all frequencies between 0 and 6 cycles per year.