Rainfall Variation Within a 4 km x 4 km Area in Western Puerto Rico

Algorithms have been developed to estimate near-real-time rainfall from radar and satellites. These data can be ingested into hydrologic models to estimate flash flooding. A major limitation of the methodology, however, is the relatively poor resolution of the remotely sensed rainfall. Large variations in rainfall can occur within the remotely sensed pixel area, which may be important hydrologically. For example, rain gauge data for a storm on October 22, 2006 measured within a 4 km x 4 km area located in a tropical coastal drainage basin in Western Puerto Rico, revealed large spatial variation. The rain gauge network consisted of sixteen gauges distributed throughout the area. The rainfall average and standard deviation for the storm were 40.6 mm and 25.5 mm, respectively. Maximum and minimum recorded gauge rainfalls were 68.1 mm and 5.9 mm, respectively, and the maximum rainfall gradient within the study area was 65 mm per km. The objective of this paper is to present results of rainfall distribution for selected storms within a 4 km x 4 km study area located near Mayagüez, PR, and to discuss the implications of the results on calibration/validation of quantitative precipitation estimation (QPE). In the future, the rain gauge network will be augmented and will be used to evaluate rainfall estimates from NOAA's Hydro-Estimator and SCaMPR QPE algorithms, NEXRAD, and the UPRM CASA distributed collaborative adaptive sensing radar network.