Abstract
The Chung-Li very-high-frequency (VHF at 52 MHz) atmospheric radar and a dual-polarized microwave radiometer were operated collaboratively to investigate strongly convective precipitation while the typhoon Trami just passed through the Taiwan in Aug, 2013. First, respective Doppler velocities of clear-air and precipitation echoes were identified automatically by the VHF radar as clearly as possible. Two approaches were designed for this purpose: contour-based and peak-finding processes. The two approaches initially determined some major spectral centers or peaks, which were usually redundant, and then proper sifting and clustering were performed for the redundant spectral centers or peaks to yield several mean locations of Doppler velocities for profiling. The outcomes of the two approaches were consistent in general. With the estimated Doppler velocities, a tracing process was developed for Doppler profiling, in which Doppler velocity shear was one of the significant criteria in the tracing process. The radar echoes collected by the VHF radar during rainy and strongly convective atmosphere have been investigated to validate the two approaches and the tracing process. About 98 % of the tracings could identify the Doppler profiles of clear air and precipitation, even the atmosphere was disturbed severely. The radar spectral parameters, Doppler profiles, and the information from a dual-polarized microwave radiometer as well as the simulation of weather model, were examined jointly. It signified that strong updraft and turbulent atmosphere could bring the liquid water to the height above the melting layer, and then the Bergeron effect and coalescence process on formation of ice crystal and graupel above the height of the melting layer occurred accordingly.
Highlights
25 Atmospheric radars operated at very-high-frequency (VHF) and ultra-high-frequency (UHF) bands are powerful instruments in remote sensing of the atmosphere from troposphere to ionosphere
The radar echoes collected by the VHF radar during rainy and strongly convective atmosphere have been investigated to validate the two approaches and the tracing process
About 98% of the tracings could identify the Doppler profiles of clear air and precipitation, even the atmosphere was disturbed severely
Summary
25 Atmospheric radars operated at very-high-frequency (VHF) and ultra-high-frequency (UHF) bands are powerful instruments in remote sensing of the atmosphere from troposphere to ionosphere. We intend to propose a new tracing process of Doppler profiling of clear air and precipitation echoes, and obtain the required Doppler parameters for further study. To this end, two approaches of identifying the spectral peaks of clear air and precipitation were developed, that is, contour-based and peak-finding approaches. A collaborative observation of the VHF radar and a dual-polarization microwave radiometer for convective precipitations were carried out to show a potential application of these approaches and tracing process. Co-observations of precipitation with VHF radar and dual-polarized microwave radiometer are shown, where the spectral parameters, estimated from the proposed approaches, and the hydrometeor parameters, observed by the radiometer, are jointly discussed.
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