Laserfiche WebLink
<br />002555 <br /> <br />CONTRACTOR: Meteorology Research, Inc., Altadena, California <br />CONTRACT NO. 14-06-0-7536 <br />PRINCIPAL INVESTIGATOR: Theodore B. Smith <br />PERIOD: July 1,1974, to June 30,1975 <br />FUNDING: $50,532 <br /> <br />This study evaluated a combination of precipitation-measuring tech- <br />niques. The potential for improving the accuracy and reliability of <br />data was investigated by comparing radar, aircraft, and surface <br />rain gage measurements which could be applied to projects such as <br />HIPLEX. <br /> <br />Findings showed that: <br /> <br />(1) The precision in size distribution measurements of a single <br />l-km sample is relatively low. <br /> <br />(2) The precision of l-km sample measurements decreases slightly <br />with increase in measured rainfall amounts. <br /> <br />(3) For a given size distribution, the reliability in the esti- <br />mates of LWC, R, and Z decreases in the order given. <br /> <br />(4) The RR40 device yields the most reliable measurements of <br />drop size distribution, followed respectively by the PMS and foil <br />(automode) devices for size ranges where measurements can be made <br />by all three instruments. <br /> <br />(5) Compared to the PMS device, the RR40 device yields higher <br />estimates of LWC and R, but lower estimates of Z for particle size <br />ranges where measurements can be made by both instruments. <br /> <br />(6) Negligible biases exist in the estimate of Rand Z between <br />the PMS and foil devices. <br /> <br />(7) The PMS device measures raindrop size distributions more <br />accurately than the other devices. This conclusion is based upon <br />the close correspondence found in the estimates of Rand Z with <br />the respective measurements of the surface gages and the WSR-57 <br />radar. Indirectly, the superior radar estimates of surface <br />rainfall which were based on the R vs. Z relationships derived <br />from the PMS measurements further indicate that the measurements <br />are more accurate. In cont rast, 1 arge di screpanci es in the <br />surface rainfall radar estimates were found based on the R vs. Z <br />relationships derived from measurements by the RR40 device. <br /> <br />Based upon the limited number of storm cases analyzed in this study, <br />it is indicated that: <br /> <br />111-8 <br />