Proceedings with Extended Abstracts (single PDF file) - Radio ...

VORTICAL MOTIONS OBSERVED WITH THE NEW MCGILL VHFRADAR AND ASSOCIATED DYNAMICAL CHARACTERISTICSEdwin F. Campos 1 and Wayne Hocking 21. Dept. of Atmospheric & Oceanic Sciences, McGill University, Montreal, Quebec, Canada2. Dept. of Physics, University of Western Ontario, London, Ontario, Canada1. Sensor descriptionThe McGill VHF WindTtracker (Wind and Turbulence tracker) radar is a Windprofilerlocated near the city of Montreal, at 45 o 24’33”N, 73 o 56’12”W, at an elevation of 30 m abovesea level. This radar has been operational since the summer of 2002. It operates at afrequency of 52.0 MHz and samples at ranges between 1.5 km and 20.5 km with a resolutionof typically 500 m, using better resolution at lower heights and poorer resolution at upperaltitudes. Maximum useful altitudes achieved are typically 14 to 17 km. (A boundary layermode will be added in due course.) The signal processing of this radar is basically the sameas that described in Hocking [1997]. The details are given in Table 1.Table 1. General characteristics of the McGill VHF Wind Profiler.Variable:Description:Frequency [wavelength] 52.0 MHz [5.77 m]Antenna area [cross shaped]2 000 m 2 [100 m long]Peak transmitted power40 kW2-way beam half-width1.6 oOff-vertical angle10.9 oPulse Repetition frequencyNormally operates at 3kHz to 10kHzTime resolution at one heightData recorded at 60 - 100 HzHeight resolution[gradually decreasing with height, from 1.5 km]500 m[from 0.5 km to 1 km]Location [Montreal, Canada]45.409 o Latitude North,73.937 o Longitude West2. Winds Validation2.1 Weather S-band radar.The McGill S-band weather radar is located just 2 km from the McGill VHF wind profiler, atan elevation of about 80 m above sea level. It derives operationally (when there isprecipitation) vertical profiles of winds using the Velocity-Azimuth-Display method (VAD,e.g., Doviak and Zrnic 1993, section 9.3.3). To construct each wind profile, the followingconditions are used (see Fig. 1): The VAD method uses 13 elevation angles (Ø between 0.5 oand 14.6 o ) and 360 azimuth angles. For a given elevation and azimuth, the radial direction issampled every 10 km until a range r s is reached. This r s is obtained when the height hreaches 8.5 km or when the horizontal distance d reaches 50 km, whichever occurs first.Thus, the analyzed volumes correspond to h < 8.5 km and d < 50 km. For a particular height,the sampling region is an approximately cylindrical volume of depth equal to the rangeresolution with a circular surface of radius d. In the following comparisons, we use onlythose observations that have useful weather-radar echoes in at least 50% of this cylindricalvolume. Measurements were generated every 5 minutes.415