Changes Seen in Land-Atmosphere Interaction after a Large Hurricane

The planetary boundary layer (PBL) is directly affected by land changes in moisture, temperature, and carbon. One way to change the land and thus the land-atmosphere (L-A) interaction is by the passing of a large hurricane, which defoliates the canopy and adds leaf litter to the land surface. Here we present changes to the PBL after the recent hurricane measured by a ceilometer placed in the Luquillo Experimental Forest (LEF) in Puerto Rico. The LEF is about 20 km from the ocean in the windward trade wind direction, and contains a cloud forest atop 1 km mountains. The LEF lost around 50% of its greenness with Hurricane Maria, as seen from satellite vegetation indices. Instruments on the ground and satellites showed the canopy loss and litter addition increased soil, canopy, and litter moisture; increased the soil and air temperature; and lowered the humidity. These land surface factors were measured on the path to recovery concurrently with measurements of the base of the PBL by the ceilometer as well as measurements of the PBL depth by satellites passing on nearby tracks. The pre-hurricane PBL looks like a typical land PBL. Immediately after the hurricane the PBL looks more oceanic: less frequent and perhaps thinner. The cloud pattern also appears modified. As the months pass, the disrupted L-A interaction continues with a PBL and cloud pattern that has lower seasonality than usual. The L-A interaction after a hurricane is complex; this study documents the changes in the PBL as corresponding with the land recovery.