Building the Weather to Climate Bridge: The Caribbean Rain-Belt

Abstract:

An annual bimodal rainfall cycle with peaks during the late spring and late summer is observed throughout the Intra-American Sea. A rainfall minimum occurs after the late spring early rainfall season (ERS) and is known as the “mid-summer drought” (MSD). Despite the interest in the well-studied MSD, there is a lack of research describing the onset and variability of the ERS. Rainfall during the ERS is important for Caribbean farmers as it moistens the soil after the dry season and can provide a catalyst for significant agricultural success.

 Contrary to the acceptance of long term regional anecdotal evidence, heavy rainfall during the ERS is not simply the result of mid-latitude fronts. Instead, heavy rainfall during the ERS arises through a series of storms or “weather events” that result from the simultaneous occurrence of two primary ingredients over the region: upper tropospheric uplift dynamics and lower tropospheric tropical moisture advection steered by the “Panama Low”. A seasonal rainfall pattern emerges during the late spring in the western Caribbean, known as the Caribbean rain-belt, from the accumulated rainfall of each weather event during the ERS.

 During some years the Caribbean rain-belt is weak or absent, however, it remains a climatological rainfall feature that is shaped by the consistency of late spring weather events. Sub-daily rainfall time series’ from the COCONet rain gauge network are used to construct the pattern of daily weather events that are then used to decompose the climatological Caribbean rain-belt. In addition, sub-daily rainfall observations are used to calculate the percent of seasonal rainfall that originates from the Caribbean rain-belt.

 Farmers depend on the succession of ERS weather events that shape the Caribbean rain-belt, but deadly flooding and landslides have also been recorded along the its path