Interannual and intra-annual variability of rainfall in Haiti (1905–2005)
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The interannual variability of annual and monthly rainfall in Haiti is examined from a database of 78 rain gauges in 1905–2005. The spatial coherence of annual rainfall is rather low, which is partly due to Haiti’s rugged landscape, complex shoreline, and surrounding warm waters (mean sea surface temperatures >27 °C from May to December). The interannual variation of monthly rainfall is mostly shaped by the intensity of the low-level winds across the Caribbean Sea, leading to a drier- (or wetter-) than-average rainy season associated with easterly (or westerly) anomalies, increasing (or decreasing) winds. The varying speed of low-level easterlies across the Caribbean basin may reflect at least four different processes during the year: (1) an anomalous trough/ridge over the western edge of the Azores high from December to February, peaking in January; (2) a zonal pressure gradient between Eastern Pacific and the tropical Northern Atlantic from May/June to September, with a peak in August (i.e. lower-than-average rainfall in Haiti is associated with positive sea level pressure anomalies over the tropical North Atlantic and negative sea level pressure anomalies over the Eastern Pacific); (3) a local ocean–atmosphere coupling between the speed of the Caribbean Low Level Jet and the meridional sea surface temperature (SST) gradient across the Caribbean basin (i.e. colder-than-average SST in the southern Caribbean sea is associated with increased easterlies and below-average rainfall in Haiti). This coupling is triggered when the warmest Caribbean waters move northward toward the Gulf of Mexico; (4) in October/November, a drier- (or wetter-) than-usual rainy season is related to an almost closed anticyclonic (or cyclonic) anomaly located ENE of Haiti on the SW edge of the Azores high. This suggests a main control of the interannual variations of rainfall by intensity, track and/or recurrence of tropical depressions traveling northeast of Haiti. During this period, the teleconnection of Haitian rainfall with synchronous Atlantic and Eastern Pacific SST is at a minimum.
KeywordsHaiti Caribbean basin Rainfall variability Precipitation regime Ocean–atmosphere coupling
This research was partly funded by the Agencia Española de Cooperación Internacional para el Desarrollo (AECID) and in close collaboration with the Haitian Comité inter-ministériel de l’Aménagement du Territoire (CIAT). We warmly thank the Centre National de l’Information Géo‐Spatiale (CNIGS), the Chemonics company, and the Coordination Nationale pour la Sécurité Alimentaire (CNSA) for having provided the rainfall data. Data from the twentieth century reanalyses and from the ERSST dataset have been freely downloaded from http://www.esrl.noaa.gov/psd/data/20thC_Rean/. Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE) program, and Office of Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office. Lastly, We warmly thank Mea Halperin (IRI, Columbia University) for her proofreading and corrections to our text.
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