Seasonality in the impact of ENSO and the North Atlantic high on Caribbeanrainfall

Caribbean rainfall is affected by climate variability of Pacific and Atlant ic origin, e.g. the El Nine-Southern Oscillation (ENSO) phenomenon, and var iability in the North Atlantic High sea level pressure (SLP) center, respec tively. During the lifetime of an ENSO cycle, the basin experiences dry and wet extremes. In the case of a warm event, the dry extreme precedes the ma ture ENSO phase, and can be explained in terms of a direct response to the atmospheric anomaly generated by the warm sea surface temperatures (SST) in the eastern equatorial Pacific. The wet extreme follows the mature phase, and is consistent with the lagged warming effect of ENSO on tropical North Atlantic SSTs. The wintertime state of the North Atlantic High is hypothesi zed to affect Caribbean rainfall through its effect on tropical SST. A stro ng North Atlantic High SLP center during the early months of the calendar y ear strengthens the trade winds, hence cooling SSTs in the tropical latitud es of the North Atlantic. The effect lingers on most noticeably until the s tart of the Caribbean rainy season, in May-June, when cool SSTs are associa ted with deficient rainfall in the basin. (C) 2000 Elsevier Science Ltd. Al l rights reserved.