Comparative Statistical Study of Hourly Precipitation Determined by Radar-Based Stage IV and Ground-Based Methods in the North Central United States

摘要

For long-range modeling of dispersion and wet deposition of particulate matter and water-soluble pollutants using the CALPUFF model, detailed hourly precipitation data are required. In sparsely-populated areas such as the north central United States, ground-based (TD3240) precipitation measurement stations may be too widely-spaced to offer a complete and accurate spatial representation of hourly precipitation within a large modeling domain. For this reason, a radar-based method of precipitation measurement (Stage Ⅳ) is proposed for use in the CALPUFF model, in which hourly precipitation rates to within 0.01 inch are estimated for over a million grid cells, each about 4 km on a side, which covers the entire continental United States and portions of Canada, Mexico, and the Atlantic and Pacific Oceans. This method would enable hourly precipitation to be determined to a much finer spatial resolution than ground-based precipitation measurements, but the validity needs to be tested by comparison to ground-based precipitation measurements. This paper presents a statistical comparison between hourly precipitation measurements for the years 2006 through 2008 at 25 ground-based (TD3240) stations in the north central United States and Stage Ⅳ (radar-based) precipitation measurements at the nearest grid cell to each TD3240 station. The parameters studied include Mean Bias between the two methods, number of hours of measurable precipitation by each method, correlation coefficient, and total quarterly and annual precipitation by each method. It was also found that the statistical agreement between the two methods depends strongly on whether the ground-based hourly precipitation is measured to within 0.1 inch/hour or to within 0.01 inch/hour.