Topographic - thermal circulations and associated GPS-measured moisture variability at Mayaguez, Puerto Rico
Wednesday, 17 December 2014
To investigate topographic-thermal circulations and the associated moisture variability over western Puerto Rico, field data were collected from 15 - 31 March 2011 as part of an undergraduate educational field experience. Surface meteorological instruments and ground based GPS receivers measured the circulation and precipitable water with high spatial and temporal resolution, and the Weather Research Forecast (WRF) model was used to simulate the mesoscale flow at 1 km resolution. A westerly on-shore flow of ~4 m/s over Mayaguez Bay was observed on many days, due to an interaction between thermally driven (3°C /10 km) sea-breeze circulation and an island wake comprised of twin gyres. The thermally driven sea-breeze occurred only when easterly synoptic winds favorably oriented the gyres with respect to the coast. Moisture associated with onshore flow was characterized by GPS measured precipitable water (PW). There is diurnal cycling of PW > 3 cm over the west coast during periods of onshore flow. The WRF model tends to overestimate PW on the west side of the island, suggesting evapotranspiration as the process needing further attention. Fluctuations of PW can affect local rainfall forecasts in times of convective instability.