Rainfall characteristics for southeastern Arizona

Abstract

Drop-size distributions were determined for thunderstorms in southeastern Arizona using a transducer whose output is a function of impact energy. Continuous observations were taken for 24 thunderstorms during 1981 and 1982. Median drop diameter and kinetic energy distributions were characterized at one minute intervals for each event. The kinetic energy distribution, calculated from the mass relationship was determined using a non-linear least squares regression. The resulting exponential relationship follows: KE = 7960 exp .1351•¹⁷⁵- 8030 where: KE = kinetic energy in foot tons(f)/acre in I = intensity in inches/hour The southeastern Arizona relationship yielded higher values than published kinetic energy relationships for Mississippi, Louisiana and Washington, D.C. Annual erosivity values (R) for 12 years of record at two sites on the Walnut Gulch Experimental Watershed yielded values about 15 percent higher than values calculated using the USLE kinetic energy term.