Multidecadal variation of winter rainfall in northwestern Baja California

Abstract

Some climatic features regarding the precipitation over northwestern Baja California (Mexico) were examined relative to the interannual, decadal and multidecadal variability of some Pacific indexes. The analysis is based on annual values from 1900 to 2001 of the winter (November through April) rainfall data for Ensenada, Baja California, which is climatologically representative of northwestern Baja California. The Southern Oscillation Index (SOI) and Pacific Decadal Oscillation (PDO) were also examined. The results are derived from statistical and wavelet analysis of the rainfall data. The time-frequency evolution of the data shows close association with the interannual (2–7 years), decadal (10–20 years) and multidecadal (20–70 years) signals of the SOI and PDO. It is interesting to note that the multidecadal period of drought in northwestern Baja California (1941/1942 to 1976/1977) coincides with negative PDO values (characterized by cold sea surface waters off North America) and frequent La Niña events, whereas decadal rainy conditions (1977/1978 to 1998/1999) coincide with positive PDO values (characterized by warm sea surface waters off North America) and frequent and intense El Niño events. Finally, a future scenario, derived from the wavelet analysis, shows the possibility of a dry decadal period for northwestern Baja California from 1999 to 2015, approximately.