Impacts of low land use on a Tropical Montane Cloud Forest under a changing coastal climate

Tropical Montane Cloud Forests (TMCF) are a primary source of fresh water in tropical locations and are highly sensitive to climate changes. Climatic analysis for El Yunque Rain Forest, a TMCF, located in North Eastern of the Island of Puerto Rico 40km south-east of the coastal city of San Juan, reflects changes in the regional meteorology reflected by increasing surface air temperatures in certain regions within this forest. This TMCF is the main water resource of San Juan, one of the largest cities in the Caribbean, and it is surrounded by increasing urban sprawl in the lower elevations; these changes in the low lands have affected atmospheric and surface variables such as sensible heat flux, surface albedo and surface roughness, and the overall energy budget within the forest. It is also hypothesized that increases in sea surface temperatures are also influencing the climate of the forest. The focus of the present research is to quantify the impacts of changes in land use close to coastal TMCFs, characterized by the case of El Yunque in the north-eastern coast of Puerto Rico during the dry season.; A climatological and numerical analysis is presented to characterize these land use processes under a changing coastal climate. The research makes use of a high resolution visible imagery from the NASA ATLAS sensor to characterize the current land use conditions of the area. Surface parameters such as albedo and land classes were introduced into a Mesoscale Model RAMS (Regional Atmospheric Modeling System). The atmospheric model was calibrated favorably against a high density network of surface temperature sensors located in and around the TMCF. The coupled and decoupled effects of land use changes and global warming (GW represented by SSTs) are investigated in detail by organizing an ensemble of simulation runs that include reconstructed past land-use, present land use, reconstructed average past atmospheric variables and present climate conditions. Results indicate significant impacts due to GW effects with increasing SSTs, which are highly reflected on a TMCF environment, generating variations in its sensitive variables such as cloud base, cloud cover, air temperature and precipitation.; Contrary, Land use changes generate local affects, which are less pronounced than GW, generating variations in physical variables close to the land. The variables that most influence the TMCF fresh water productivity are the GW effects.