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

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But in case of period until 1800 UTC 6 of Fig. 2a, the method erroneously estimatedtropopause heights between approximately 9.5 and 20 km. To improve this disadvantage, themethod combined maximum echo power gradient method was introduced. The maximum echopower method <strong>with</strong>out limit of estimated height applied in case that the power ratio of vertical tooblique echo power was less than 6 dB.The tropopause heights estimated by the method combined maximum echo power gradientmethod are shown in Fig. 2b. The combined method also correctly estimated the tropopauseheight not only when there were more than two strong inversion layers due to a tropopause butalso when there were more than two strong inversion layers due to a tropopause folding.5. ConclusionsIn the present study, an improved method for estimating the tropopause height using VHFradar data was suggested and evaluated by applying to time series of a VHF radar data.The proposed method employed aspect sensitivity characteristics to distinguish the reflectionecho layer due to the tropopause from other peak echo layers, and estimated the tropopauseheight <strong>with</strong>out limit of estimated height interval.The tropopause heights estimated by the method when temperature lapse rate abovetropopause height was more than 6 °Ckm-1 and the tropopause sharpness was classified intointermediate or definite type. The improved method estimated reliably the tropopause heightwhen there were more than two peaks due to cloud layer, precipitation layer, or inversion layer inthe pro<strong>file</strong> of vertical echo power. Therefore, the method is very useful to estimating tropopauseheight when tropopause breaks and slopes during the stratospheric and tropopause exchange.ReferencesBalsley, B. B., and K. S. Gage, On the vertical incidence VHF backscattered power pro<strong>file</strong> fromthe stratosphere, Geophys. Res. Lett., 8, 1173-1175, 1981.Gage, K. S., B. B. Balsley, and J. L. Green, A Fresnel scattering model for the specular echoesobserved by VHF radar, <strong>Radio</strong> Sci., 16, 1447-1453, 1981.Gage, K. S., and J. L. Green, Evidence for specular reflection from monostatic VHF radarobservations of the stratosphere, <strong>Radio</strong> Sci., 13, 991-1001, 1978.Gage, K. S., and J. L. Green, Tropopause detection by partial specular reflection using VHFradar, Science, 203, 1238-1240. 1979.Green, J. L., and K. S. Gage, Observations of stable layers in the troposphere and stratosphereusing VHF radar, <strong>Radio</strong> Sci., 15, 395-406, 1980.Röttger, J., and C. H. Liu, Partial reflection and scattering of VHF radar signals from the clearatmosphere, Geophys. Res. Lett., 5, 357-360, 1978.Vaughan, G., A. Howells, and J. D. Price, Use of MST radars to probe the mesoscale structure ofthe tropopause, Tellus, 47A, 759-765, 1995.Westwater, E. R., M. T. Decker, A. Zachs, and K. S. Gage, Ground-based remote sensing oftemperature pro<strong>file</strong>s by a combination of microwave radiometry and radar, J. ClimateAppl. Meteor., 22, 126-133, 1983349

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