Seasonal climatology and dynamical mechanisms of rainfall in the Caribbean

Carlos Martinez,Yochanan Kushnir,Lisa Goddard,Mingfang Ting

doi:10.1007/s00382-019-04616-4

Carlos Martinez, Yochanan Kushnir + Show 2 more

Open Access

https://doi.org/10.1007/s00382-019-04616-4

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Abstract

The Caribbean is a complex region that heavily relies on its rainfall cycle for its economic and societal needs. This makes the Caribbean especially susceptible to hydro-meteorological disasters (i.e. droughts and floods). Previous studies have investigated the seasonal cycle of rainfall in the Caribbean with monthly or longer resolutions that often mask the seasonal transitions and regional differences of rainfall. This has resulted in inconsistent findings on the seasonal cycle. In addition, the mechanisms that shape the climatological rainfall cycle in the region are not fully understood. To address these problems, this study conducts: (i) a principal component analysis of the annual cycle of precipitation across 38 Caribbean stations using daily observed precipitation data; and, (ii) a moisture budget analysis for the Caribbean, using the ERA-Interim Reanalysis. This study finds that the seasonal cycle of rainfall in the Caribbean hinges on three main facilitators of moisture convergence: the Eastern Pacific ITCZ, the Atlantic ITCZ, and the western flank of the North Atlantic Subtropical High (NASH). The Atlantic Warm Pool and Caribbean Low-Level Jet modify the extent of moisture provided by these main facilitators. The expansion and contraction of the western flank of NASH generate the bimodal pattern of the precipitation annual cycle in the northwestern Caribbean, central Caribbean, and with the Eastern Pacific ITCZ the western Caribbean. This study identifies the Atlantic ITCZ as the major source of precipitation for the central and southern Lesser Antilles, which is responsible for their unimodal rainfall pattern. Convergence by sub-monthly transients contributes little to Caribbean rainfall.

Highlights

The Caribbean is identified as a highly-vulnerable region to climate variability and change (Taylor et al 2012)
From the mid to upper portion of the Lesser Antilles, the U.S Virgin Islands, and some in Puerto Rico have positive correlations with PC2, while stations in Florida, Cuba, and the Bahamas have negative correlations. This implies that the Early-Rainy Season (ERS) peaking in June has a stronger signature in the NW Caribbean than in the SE Caribbean while the opposite is seen during the climatological Late-Rainy Season (LRS)
Given the negative correlations seen in PC2 in the NW Caribbean, and a later peak of the LRS seen in PC3, the negative correlations in PC3 in the NW Caribbean suggest this region has a stronger signature of the MSD and an earlier

Summary

Introduction

The Caribbean is identified as a highly-vulnerable region to climate variability and change (Taylor et al 2012). The region’s vulnerability to climate is a result of a variety of factors including: limited human/natural resources; topography; densely populated coastal, low-lying urban areas; and, high-risk industries, such as tourism and agriculture (Taylor et al 2012; Simpson et al 2010; Lewsey et al 2004; FAO 2016; OCHA 2015). Numerous modeling studies have found systematic biases in the simulation of Caribbean rainfall (Ryu and Hayhoe 2013; Eichhorn and Bader 2017). These biases are attributed to an insufficient understanding of how small and large-scale atmospheric and oceanic processes interact to shape the seasonal rainfall pattern in the Caribbean. Better understanding and prediction of rainfall and its variability in space and time in the Caribbean is critical

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