Evaluation of Pilot Estimated Updrafts Using Aircraft Integrated Meteorological Measurement System (AIMMS) Measurements
Keywords:Updrafts, Airborne Measurements, Hygroscopic Seeding
AbstractHygroscopic seeding operations usually acquire cloud base updraft (positive vertical wind) velocities from pilot estimates. Though useful, pilot estimates are subjective and hence potentially inconsistent from case to case and from one project to the next. The Aircraft-Integrated Meteorological Measurements System (AIMMS) provides an objective measurement of updrafts. The objective is to use AIMMS measurement to evaluate pilot estimates of updrafts encountered while flying under developing cumulus clouds. The analysis compares the pilot estimated maximum updraft to statistical distribution parameters of 1 Hz AIMMS measurements. Specifically, the five minute distribution mean and 95th percentile values are compared to the range of maximum sustained updrafts that the pilot estimates. Six cases with mean updrafts in the range of 0.6 to 1.4 m s-1 (120 to 275 ft min-1) were obtained during the Polarimetric Cloud Analysis and Seeding Test 2012 (POLCAST-2012) field project. Three cases show pilot estimates agreeing with the mean updraft AIMMS velocities; however, the pilot estimates are high for the remaining three cases. For five cases, the pilot estimates are below the 95th percentile range of AIMMS 1.0 Hz measurements. The POLCAST-2012 cases demonstrate the difficulty for pilots to discern the difference between a 1.0 m s-1 (200 ft min-1) and a 2.0 m s-1 (400 ft min-1) updraft.
Technical Notes and Correspondence
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