Wavelet analysis of precipitation variability in northern California, U.S.A.

Precipitation temporal variability on 96 years is studied by the application of the wavelet transform to five precipitation series at locations in northern California, U.S.A. The wavelet transform spectra are computed for annual total precipitation and wetseas on precipitation of each record. Comparing two results based on annual and wet season data, all components appear seasonally dependent. Meanwhile, monotonic trends estimated by wavelet transform indicate wetting in the northern California precipitation data. According to the wavelet analysis, the spatial pattern of the precipitation field may have been changed since 1945, and the dominant period is about 16 years. In addition, the recent increasing precipitation trend in northern California can be interpreted as the coupled effect of the extremely long-period component and multi-decadal period components.