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

ESTIMATION OF THE TROPOPAUSE HEIGHTUSING THE VERTICAL ECHO PEAK AND ASPECT SENSITIVITYCHARACTERISTICS OF A VHF RADARBok-Haeng Heo 1 , Kyung-Eak Kim 2 , Bernard Campistron 3 and Vladislav Klaus 41 Observation Division, Korea Meteorological Administration, Korea2 Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Korea3 Laboratoire d’Aerologie(CNRS), Observatoire Midi-Pyrenees, Université Paul Sabatier, France4 Meteo-France, Laboratoire d’Aerologie (CNRS), France1. IntroductionEnhancement of the vertical echo power of VHF radars often occurs at or above thetropopause height (Gage and Green, 1978; Röttger and Liu, 1978; Green and Gage, 1980;Balsley and Gage, 1981; Gage et al., 1981). The characteristic of vertical echo peaks has beenused to estimate the tropopause. The methods used for the tropopause estimation are specularreflection method (Gage and Green, 1978; Röttger and Liu, 1978; Gage and Green, 1979), Zachsmethod (Westwater et al., 1983), maximum echo power method (Vaughan et al., 1995) andmaximum echo power gradient method (Vaughan et al., 1995).The previous methods require to set up a limit of estimated height interval and are not veryefficient in estimating the tropopause height when there were more than two peaks due to cloudlayer, precipitation layer, or inversion layer in the profile of vertical echo power (Green andGage, 1980).In the present study a new improved method for estimating the tropopause height using VHFradar data was suggested. The method was evaluated by comparing between the tropopauseheights determined from rawinsonde data and radar data.2. Data and instrumentationThe data used in the present study were from two sources: VHF radar observation andrawinsonde data. The VHF radar observation was performed at La Ferté Vidame VHF radarobservatory (0.88°E, 48.62°N) during the period from 0000 UTC 6 to 2400 UTC 9 February1998. The main characteristics of this profiler radar were a 52-MHz transmitted frequency, witha 18-kW peak pulse power, an a 1,000-m pulse length. The profiler used five beam positions -one vertical and four oblique - with a one-way half-power aperture of 6.5°. The oblique beams,with an off-zenith angle of 11.5°, were disposed every 90° in azimuth.The rawinsonde observations were performed two times a day(0000 and 1200 UTC) atTrappes upper-air observatory (2.02°E, 48.77°N).346