Utility of radar-based rainfall estimates in augmenting decision making in the Southeast

Business and management decisions that are rainfall-dependent may be especially difficult considering the localized nature of rain and lack of high resolution data. ASOS stations, as well as some mesonets, provide high quality ground-truth rainfall measurements. However, the spatial density of such networks is often insufficient to monitor rainfall at a micro-scale.

The National Centers for Environmental Prediction (NCEP) have created national mosaics of radar- and satellite-based precipitation estimates calibrated with surface gauge observations around the country. These gridded products are provided at hourly, 6-hourly, and 24-hourly accumulation timescales on a 4.765 km grid using Multi-sensor Precipitation Estimates algorithms used by the National Weather Service (NWS) River Forecast Centers. Root mean square error of daily MPE is ~0.3 inches over the eastern United States.

The North Carolina Department of Transportation (NCDOT) is required to prepare a weekly erosion control checklist for each of their construction sites. Operating requirements state that NCDOT must inspect stormwater control devices within 24 hours after a rainfall event of >= 0.5 inches occurs. One conventional approach would be to deploy rain gages at each construction site. This approach would be too costly because of the number of sites to monitor and amount of manpower required to routinely check and maintain gages. In 2006, the State Climate Office of NC developed a customized website for NCDOT engineers to monitor rainfall using MPE data. The website enables engineers to spatially view rainfall estimates over a defined period of time or retrieve estimates at a given terrestrial point. Users can also configure e-mail and/or text message alerts for rainfall monitoring. To date, 634 NCDOT engineers use the system. An estimated 113,000 people-hours are saved annually as a result of less travel and maintenance.

Drought has affected the Southeast U.S. in recent years. To monitor drought conditions, one must analyze local and regional rainfall data, streamflow data, groundwater data, and seasonal demands of water resources. Using normal precipitation based on PRISM, MPE can be compared to historical averages in order to quantify difference from normal and percent of normal precipitation for drought monitoring. This is currently being used nationally as input for the US Drought Monitoring and locally in North Carolina for weekly assessments of both drought and flood vulnerabilities.

We present the applications of MPE-based estimates along with the benefits, value and limitations.

The State Climate Office of North Carolina is the primary source for NC weather and climate information and is involved in all aspects of climate research, education, and extension services. The State Climate Office is a public-service center, part of the UNC system, housed at North Carolina State University and was one of the first officially recognized state climate offices by the American Association of State Climatologists.