Aircraft measurement of the probability distribution of precipitation rate and liquid water content in the hurricane: measurement and model criteria for prescription of a variable moisture climate
Robert A. Black, NOAA/AOML, Miami, FL; and J. Hallett
Aircraft measurement of precipitation in the hurricane leads to insights into its origins, to interpretation of observed radar echo, to estimates of surface precipitation rates not measurable by other techniques and to design criteria for aircraft and surface instruments subject to such a harsh environment. Analysis of such data as obtained by optical array sensors provide greater insight into these events when analyzed as a probability distribution function for data sets selected on a regional, hurricane location, or hurricane evolution basis. Liquid water content, precipitation rate and radar reflectivity are inferred from cross-sections of particle images. Each sequence, from seconds to seasons is presented in a probability format to display changing functional relationships for the selected intervals. The probability of intercepting a given quantity during a flight provides guidance in required instrument sensitivity together with the frequency of precipitation and LWC events for given rainfall totals.
Data are analyzed from 8 seasons of aircraft measurements taken during mostly radial penetrations of the eyewall in 11 hurricanes ranging in intensity from Saffir-Simpson category 1 to 4. Radial legs that extended approximately twice the eyewall diameter in length were combined to provide the Probability Distribution Function (PDF) of liquid water content, radar reflectivity and precipitation rate. We compare the measured PDF of radar reflectivity with model derived PDF from a fully-developed simulated hurricane . This comparison shows that there are serious differences that must be reconciled in newer revisions of the numerical models, perhaps created by the failure of the current precipitation parameterizations to work properly at the finer spatial resolutions the models are beginning to utilize.
Extended Abstract (768K)
Session 7B, Tropical cyclones
Tuesday, 13 January 2009, 3:30 PM-5:30 PM, Room 129B
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