Increased Occurrence of Stratiform Clouds in the Caribbean Dry Season Since 1971 From Surface Observations

Abstract This study examines low cloud trends over 1971–2020 by utilizing a unique, surface based cloud record generated by human observers at Caribbean island weather stations. In the dry season (December–April), when low clouds dominate cloud behavior in the Caribbean, Stratocumulus cloud frequency increases at the expense of Cumulus clouds. Low cloud cover varies positively with Stratocumulus clouds and exhibits a slight increasing trend. Rainfall frequency, observed at a subset of co‐located stations, varies positively with Stratocumulus frequency, corroborating their increasing trend. Trends in temperature and humidity show stronger warming aloft compared to the surface and drying at low levels. Stratocumulus are shown to respond positively to increases in the surface latent heat flux and to a stronger inversion in this study region. These results suggest that observed increases in Stratocumulus could be driven by increases in moisture fluxes into the more strongly capped boundary layer. Increased wintertime cloud cover and precipitation frequency may represent a de‐amplifying feedback to Caribbean warming and drying. Climate indices such as the North Atlantic Oscillation and ENSO do not show significant relationships with Stratocumulus variability, nor do variations in aerosol concentration.