In September 2017, Hurricane Maria severely defoliated Puerto Rico's landscape, coinciding with a series of persistent hydrological consequences involving the atmospheric, terrestrial, and marine components of the water cycle. During the defoliated period, the atmosphere's thermodynamic structure more strongly explained daily cloud activity (R2PRE = 0.02; R2POST = 0.40) and precipitation (R2PRE = 0.19; R2POST = 0.33) than before landfall, indicating that post‐Maria land‐atmosphere interactions were comparatively muted, with similar precipitation patterns also found following Hurricanes Hugo (1989) and Georges (1998). Meanwhile, modeled post‐Maria runoff exceeded statistical expectations given the magnitude of contemporaneous precipitation. Enhanced runoff also coincided with greater sediment loads in nearshore waters, increasing sediment content greater than twofold. This study offers a holistic narrative of hydrospheric disturbance and recovery, whereby the instantaneous, large‐scale removal of vegetation is accompanied by hydrologic changes “upstream” in the atmosphere and “downstream” in rivers and estuaries.
Mesoscale convective complexes (MCCs) are meteorological events that result in severe storms, hail, flood, and tornadoes, but they are difficult to forecast. In South America (SA), MCCs are usually larger and last longer than those in the USA. Southern Brazil (SB) is one of their preferred regions of occurrence. This study’s objective was to contribute to the identification of the main physical characteristics and atmospheric environment that favors the occurrence of MCCs in SB and determine how these events are unique relative to other subtropical SA (OSSA) regions. Results indicate that SB MCCs last longer (+3 h) and their average maximum extent is at least 50000 km2 larger than OSSA MCCs. The atmospheric environment of SB MCCs meets the criteria already indicated in previous studies, with the northerly low-level jet (LLJ), which brings humidity from the Amazon Basin to the SB MCCs genesis area, coupling with the upper-level jet (ULJ). Moreover, SB MCCs have the South Atlantic as their second source of moisture, which is advected by anticyclonic circulation in the southwestern South Atlantic. This indicates that SB MCCs have unique characteristics compared to OSSA MCCs, including 2 main atmospheric circulation systems responsible for moisture advection to the SB genesis region. For comparison, OSSA MCCs are more dependent on the South Atlantic Convergence Zone (SACZ) and the advection of moisture by the LLJ from the Amazon Basin to north-central Argentina and west-central and southeast Brazil.
The insular Caribbean experiences numerous climate and environmental hazards, including but not limited to hurricanes, floods, earthquakes, and drought. While some hazards are well explored in scientific literature, drought is considered one of the neglected hazards because of the lack of studies focusing on its causes and effects. This study identifies the spatial distribution of seasonal drought in insular Caribbean from 1950 to 2017, and its relationship with eastern Pacific (EP) and central Pacific (CP) ENSO, North Atlantic Oscillation (NAO), and Atlantic Meridional Mode (AMM). It brings a new perspective over the region by dividing the Caribbean into Greater Antilles and Bahamas (GA), and the Lesser Antilles (LA) to compare the role of those three teleconnection patterns on drought events over larger versus smaller islands. We used an existing high‐resolution drought atlas (4 km) based on monthly estimates of the self‐calibrating Palmer Drought Severity Index (scPDSI). Results indicate that there is a drying trend in all seasonal‐average scPDSI for both the GA and the LA, but more intense and frequent drought events occur in the LA. The LA is also the region with more widespread drought events, registering 12 years when the mid‐summer dry spell (MSD; July–August) had drought ≥80% of the area, while the GA registered only 2 years of MSD drought that extensive. The peak season AMM had the strongest positive correlation with GA and LA drought during April–November, while NAO was slightly stronger correlated with GA than with LA from July–November. For ENSO, CP El Niño years related stronger with drought in the LA from December–July, while the relationship between the two types of ENSO and the GA was not statistically significant. This effort aims to improve drought forecasts to help the region to better prepare for the prediction of seasonal droughts.
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