Quasi Quintennial Scale ENSO

The atmospheric manifestation of El Niños and La Niñas in the PNW is well documented. El Niños are correlated with warmer winter temperatures, reduced precipitation (Redmond and Koch 1991), and reduced snowpack and streamflow (Cayan and Webb 1992) in the region. The reverse tends to be true for La Niña years. Heavy-rain-bearing storms tend to be a feature of La Niña years. The large flood of February 1996 is a case in point. January, February, and March 1996 were marked by La Niña conditions. An earlier major flood in 1964 also occurred when El Niño conditions were changing over to La Niña conditions.

Recent forest fire history at the Andrews LTER site is probably, at least in part, a response to climate variability. El Niño years tend to lead to drier and warmer winter conditions in the PNW. The strong El Niño year of 1987 was accompanied by numerous large forest fires in the PNW in 1987 and 1988. The El Niño years of the early 1990s were also accompanied by large fires in 1992 and 1994.

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