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  • Author or Editor: Jerry M. Straka x
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Valery Melnikov
and
Jerry M. Straka

Abstract

A novel method of retrieving the mean axis ratio (width/length) and standard deviation of orientation angles (σθ , which is called herein the intensity of fluttering) of ice cloud particles from polarimetric radar data is described. The method is based on measurements of differential reflectivity Z DR and the copolar correlation coefficient in cloud areas with Z DR > 4 dB. In three analyzed cases, the values of the retrieved axis ratio were in an interval from 0.15 to 0.4 and σθ found in an interval from 2° to 20°. The latter values indicate that the particles experienced light to moderate fluttering. Ambiguities in the retrievals because of uncertainties in the bulk ice density of the particles and possible presence of columnar crystals are considered. The retrieval method is applicable for centimeter-wavelength radars; the analyzed data were collected with the dual-polarization S-band Weather Surveillance Radar-1988 Doppler (WSR-88D).

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Jerry M. Straka
,
Erik N. Rasmussen
, and
Sherman E. Fredrickson

Abstract

A mobile weather observing system (mobile mesonet) was designed to augment existing meteorological networks in the study of severe local storms and other mesoscale weather phenomena in conjunction with the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX). Fifteen mobile mesonet units were built, each consisting of meteorological instruments mounted on standard automobiles. for high temporal and spatial resolution observations. While the most accurate measurements are possible from stationary mobile mesonet vehicles, accurate observations also are possible from moving vehicles. The mobile mesonet instruments measure pressure (600–1100 mb), temperature (−33° to 48°C), relative humidity (0%–100%), and wind direction and speed (0°–360° and 0–60 m s−1). Onboard each vehicle, a Global Positioning System (GPS) receiver and a flux-gate compass obtain universal time, vehicle location (latitude, longitude, altitude), and vehicle heading and speed. A standard laptop computer stores data, computes derived variables, and provides real-time data display. Instrument compatibility with the Oklahoma Mesonet allows for high-quality instrument calibration and maintenance.

The purpose of this paper is to provide a technical overview of the mobile mesonet system. The rationale for choice of instrumentation and justification for method of exposure are discussed. The performance of the mobile mesonet is demonstrated with two examples of data collected during VORTEX-1994 and comparisons with data from an Oklahoma Mesenet site.

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