Abstract
The decadal variability of precipitation over San Ramón, Costa Rica (SR-CR) and its relationship with the ONI, CLLJ, AMO indexes, and the frequency of tropical cyclones is investigated. Correlation tests are applied between the different indices with eight decades of precipitation in San Ramon. De-cadal precipitation shows that the driest were 1960-69 and 1980-89, and the wettest were 1970-79 and 1990-99. Every twenty years there is a climate change from wet to dry or dry to wet. During El Niño (ONI) events, the Pacific increases sea surface temperature (SST) and precipitation decreases in SR-CR and during La Niña, SST decreases and tends to rain more in SR-CR. Low values of the CLLJ tend to increase the incidence of precipitation in the area. Cyclonic activity has an appreciable influence on rainfall in SR-CR, the first two decades there were one and two cyclones. However, the rest of the decades showed more cyclones per decade, as is the case with 2010-19 with 8 cyclones. The relation-ship between the AMO index and precipitation in San Ramon has a 3-month lag.