Laserfiche WebLink
<br />.' <br /> <br />over the area. In order to investigate this possible effect, <br />the rainfall patterns on the target area and immediately <br />east of the target area in eastern Colorado, western <br />Nebraska and Kansas were studied, using the Corps of <br />Engineers isopercential theory. This theory is based on <br />the observed fact that in basins .rliich have pronounced oro- <br />graphic effects, the rainfall depths of various stations for <br />a particular storm tend to be unifoF.,l percentago of a normal <br />for the storm type regardless of the magnitude of the rain- <br />fall, the altitude of the station, or the position of the <br />station vrith relation to "rain shadows". Isopercential <br />patterns consisting of lines connecting points of equal <br />percentage are drawn for type storms which occurred during <br />the seeding period and compared with the patterns of storms <br />of the same type occurring prior to the seeding period. <br />Within type groups of past storm statistical methods of <br />comparison are used. One method, concerning the target <br />area only, consisted of computing the standard deviations <br />of the precipitation recorded at stations on the target area <br />from the mean depth of precipitation on the area as a porcont <br />of the rlean depth and also in ablsolute values for similar <br />type storms which occurred durinG and prior to the seeding <br />period. Probability curves were then plotted for each case <br />and the frequency of occurrence of the standard deviations <br />which occurred during the seeding period were computed. <br /> <br />This method was also used for determining any change in <br />rainfall distribution resulting from cloud seeding for the <br />period of Harch, April, and Hay, 1951, as COlnpared with the <br />same period for each year from 1911 through 1950. <br /> <br />~ <br /> <br />14 <br /> <br />"- <br />i: <br />~ <br /> <br />4 <br />