Land cover and land use (LCLU) changes have been shown to have great local climate impacts in coastal tropical regions, but the interaction of these changes with global-scale climate change (GC) have seldom been examined. Using the Regional Atmospheric Modeling System (RAMS) as the main research tool, this work is an attempt to breach this gap. To achieve this goal an ensemble of climate simulations were performed centered in the northeastern region of Puerto Rico, combining two LCLU and two GC scenarios. Reconstructed agricultural maps combined with reconstructed sea surface temperatures (SST) form the Past (1951-1956) climate scenario, while the Present (2000-2004) scenario was supported with high-resolution remote sensing data. The climate reconstruction approach is validated with observational data from surface weather stations for both time frames. Results indicate that LCLU changes produced the largest air temperature differences over heavily urbanized regions and that these changes occur near the surface.
The influence of the global climate change signal is to induce a positive inland gradient for maximum temperature, possibly due to increased trade winds in the present climatology. In terms of minimum temperatures, the global climate change signal induces temperature increases along the coastal plains and inland lowlands. The stronger trade winds with an easterly-southeasterly direction in the global signal also cause a shift in the location of a convergence zone previously on the Central Mountains ridge, now, without the additional orographic cloud formation mechanism, clouds have higher bases and the total liquid water content has decreased in the atmospheric column above the higher elevations. This combination of factors translates into a dramatic decrease in surface accumulated precipitation in the highlands of the region of interest due to global climate change. To further investigate these climate impacts the thermal response number (TRN) was studied. The TRN is a surface property defined as the ratio of the surface net radiation, which integrates the effects of the non-radiative fluxes over short periods of time, and the rate of change in surface temperature. Significant changes in TRN were observed in the San Juan Metropolitan Area for the two periods analyzed, reflecting a reduction in TRN for the present time frame consistent with an increasing thermal mass and intense urbanization.
Visit Coordinator: Jeff Luvall (NASA/UAH)