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The purpose of this investigation is twofold: (a) to estimate ATIs only for the growth portion of a convective stonn (while the rain volume is computed using the entire life history of the convective event); and (b) to nowcast the total rain volume of a convective system at the stage of its maximum development. For the aforementioned purpose, the A TIs were computed using the maximum echo area ~ 25 dBZ (A TIA), the maximum reflectivity (A TIR), and the maximum echo height (ARIH) as the end of the growth portion of the convective event. A simple linear regression analysis demonstrated that correlations between total rain volume (TVR) or the maximum rain volume (MVR) versus the A TIA were the strongest. In a log-log plot. the correlation coefficient and the standard error of estimates of total rain volume versus A TIA were 0.98 and 0.23 for the summer 1982 data, and 0.96 and 0.24 for the summer 1981 data, respectively. In percentage tenns, the corresponding range of variation of the rain volume for a given A TlA lies between 70% and -41 % (1982 data) and between 74% and -44% (1981 data). This is comparable to the uncertainties which typically occur in rain volume estimates obtained from radar data employing Z-R conversion followed by space and time integration. This demonstrates that the total rain volume of a stonn can be nowcasted at its maximum stage of development (max A TIA). The scatter in the rain volume and in the maximum volumetric rain rate estimates is somewhat smaller if a multiple linear regression instead of a simple linear regression is considered, but the improvement is of little significance. The tests with independent data confinned the consistency of the results for the region considered. Doneaud, A. A., J. R. Miller, Jr., and A. Makarau, 1986: A modified A TI technique for possible satellite applications. Preprints, 23rd Conference on Radar Meteorology and Conference on Cloud Physics, Snowmass, CO, September 22-26, 1986. American Meteorological Society, Boston, MA, Vol. 3, JP27-JP32. No abstract. Doneaud. A. A., S. Ionescu-Niscov, and J. R. Miller. Jr.. 1984: Convective rain rates and their evolution during stonns in a semiarid climate. Monthly Weather Review, 112:1602-1612. Rain rates and their evolution during summertime convective stonns were analyzed for the semiarid climate of the northern High Plains. Radar data from a total of 750 radar echo clusters from the 1980 and 1981 summer cloud seeding operations of the North Dakota Cloud Modification Project (NDCMP) were used. The analysis suggests that the average rain rate Ii. among stonns is, in a first approximation, independent of the total rain volume if the entire stonn duration is considered in the averaging process. This average rain rate depends primarily on the reflectivity threshold considered in calculating the area coverage integrated over the lifetime of the stonn, the area-time integral (ATI). For the 25 dBZ reflectivity threshold used in the A TI computations. Ii. was 4.0 mm h.J. with a standard deviation of 1.55 mm h-J being -20% higher for wet season conditions. The evolution of rain rates during stonns was analyzed by dividing each stonn lifetime into 10 min, I, 2, and 4 h, and growing and decaying periods. A lO-min time increment was used in computing the parameters for all time intervals. A stonn cluster reached its maximum growth after an average of 56% of its lifetime. The average rain rate for the growing period exceeded that for the decaying period by about 10%. As the time interval used in the computations approached the stonn lifetime, the scatter of the average rain rates was reduced, thus increasing the accuracy of rainfall estimates using the area-time integral. The value of Ii. remained independent of the total rain volume when the growing or decaying '\ I I .1 30