Seasonal climatology and dynamical mechanisms of rainfall in the Caribbean

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.

Climatic trends and regional climate models intercomparison over the CORDEX‐CAM (Central America, Caribbean, and Mexico) domain

“…Moreover, the AMO and ENSO appear to have a significant role on the variability and trends (of temperature and precipitation) in regions affected by the MSD region; wet periods are significantly correlated with the +AMO and La Niña events, while warm periods are associated with the +AMO and El Niño events, consistent with other studies in different parts of the domain (Seager et al ., ; Mendez and Magaña, ; Hidalgo et al ., ). Temperature and precipitation variability and trends in the Caribbean and Central America are also influenced by the sea surface temperature contrasts between the North Atlantic and the eastern Pacific through different dynamic combinations of the NASH, AMO, and ENSO, which in turn modulate the seasonal intensity of the CLLJ, moisture extent in the region, and the frequency of tropical cyclones (e.g., Enfield and Alfaro, ; Amador et al ., ; Alfaro, ; Martinez et al ., ).…”

“…() and Hidalgo et al . (), precipitation and temperature trends in Central America are also modulated by ENSO events and by temperature gradients between the North Pacific and the tropical Pacific Oceans (Amador et al ., ; Maldonado and Alfaro, ), through dynamical changes in the extension and position of the North Atlantic subtropical high (NASH; e.g., Li et al ., ; Martinez et al ., ) and the zonal wind intensity of the Caribbean low‐level jet (CLLJ) which modify the extent of the regional moisture (Enfield and Alfaro, ; Fuentes‐Franco et al ., ; Martinez et al ., ).…”

“…This is due in part to a southwards (northwards) location of the subtropical westerly jet stream (e.g., Ropelewski and Halpert, 1986;Cavazos and Hastenrath, 1990;Seager et al, 2009), especially during the +PDO (−PDO) regime (e.g., Gershunov and Barnett, 1998;Pavia et al, 2006). According to Hidalgo et al (2017) and Hidalgo et al (2019), precipitation and temperature trends in Central America are also modulated by ENSO events and by temperature gradients between the North Pacific and the tropical Pacific Oceans (Amador et al, 2010;Maldonado and Alfaro, 2011), through dynamical changes in the extension and position of the North Atlantic subtropical high (NASH; e.g., Li et al, 2011;Martinez et al, 2019) and the zonal wind intensity of the Caribbean low-level jet (CLLJ) which modify the extent of the regional moisture (Enfield and Alfaro, 1999;Fuentes-Franco et al, 2015;Martinez et al, 2019).…”

Sub-monthly evolution of the Caribbean Low-Level Jet and its relationship with regional precipitation and atmospheric circulation

“…4 and 6). Interestingly, the two anomalies exhibit a different temporal evolution: the former is geographically stationary and has peak negative values at lag 0, concurrently with the temporal evolution of the CLLJ and of the divergence area upstream of the jet core (e.g., Whyte et al 2008;Martinez et al 2019). By contrast, the latter anomaly gradually increases expanding eastward pentads.…”

“…4 displays the vertically-integrated stationary moisture transport and its convergence; note that the contribution of the transient component (in time) of these fluxes is generally of minor importance (Martinez et al 2019). Moisture transport from the oceans and its convergence is crucial to generating precipitation in the Caribbean region (e.g., Wang 2007;Durán-Quesada et al 2010;Hidalgo et al 2015;Martinez et al 2019). Moisture convergence anomalies show a remarkable similarity in pattern and magnitude to the precipitation ones, attesting for the secondary contribution of evaporation in the formation of the precipitation anomalies described above.…”