Estimation of areal rainfall using the radar echo area time integral

This work extends the Area Time Integral (ATI) method of Doneaud et al., developed for the lifetime rainfall from an individual storm, and the instantaneous areawide rainfall method of Atlas et al., to the measurement of the cumulative areawide rainfall for periods up to 12 h. The database is the radar and raingage network data for the three summers of the Florida Area Cumulus Experiment (FACE) II. For 12 h accumulations, V, over the area of 3.6 X 10⁴ km², we find correlations of 0.92 between radar deduced rainfall and ATI where the latter is computed at intervals from 5 min up to 1 hr. The slope of the regression line V/(ATI) is 3.4 mm h^-1. Using a gage network with density of ¹/11 km² over an area 1.5 X 10⁴ km² the correlation coefficient drops to 0.84, still sufficiently high to confirm the validity of the ATI approach. Also, with the gages the V/(ATI) slope decreases to 2.6 mm h^-1. -from Authors