Diagnostics of observed dry trends in Caribbean precipitation

Abstract

AbstractDuring the last decades, the variability of the Caribbean precipitation has been characterized by dry trends over land. Aiming to gain insights into their drivers from an observational perspective, in this study such trends are diagnosed in relation to their concomitant low‐tropospheric circulation by applying linear regressions and Canonical Correlation Analysis to different datasets, but particularly using GPCP and ERA5 for the 1979–2019 period. During this period, two multidecadal modes of natural variability exhibited one‐signed trends: the Atlantic Multidecadal Oscillation (AMO) exhibited a positive trend, and the Pacific Decadal Oscillation (PDO) exhibited a negative trend. However, as shown by the results, the influence of these large‐scale trends cannot be directly associated with the dry precipitation trends: their influence would explain a pattern of anomalous low‐tropospheric westerlies that typically tends to cause episodes of above‐average rainfall. Also, the observed dry trends cannot be associated with two circulation features that cause dry episodes in the region: an intrusion of the North Atlantic subtropical high, and an intensified Caribbean Low‐Level Jet. On the other hand, the results suggest that the dry trends might have been intensified by the land–sea contrast trend that has characterized the effects of global warming on the low‐tropospheric pressure fields during the last decades; land–sea contrast would increase the vertical stability over land, suppressing convection. From these results, the influence of the AMO and the PDO is speculated to have been instrumental in preventing even drier trends. These insights suggest that dry trends in the region might be expected to worsen in the coming decades since the AMO and the PDO are expected to change their phase, and the land–sea contrast trend is expected to continue with a positive trend.