Preprints
https://doi.org/10.5194/amt-2021-267
https://doi.org/10.5194/amt-2021-267

  05 Oct 2021

05 Oct 2021

Review status: this preprint is currently under review for the journal AMT.

Co-observation of strongly convective precipitation using VHF atmospheric radar and dual-polarized microwave radiometer during a typhoon passage

Shih-Chiao Tsai1, Yen-Hsyang Chu2, and Jenn-Shyong Chen3 Shih-Chiao Tsai et al.
  • 1Department of Environmental Information and Engineering, National Defense University, Taoyuan, Taiwan
  • 2Graduate Institute of Space Science and Engineering, National Central University, Taoyuan, Taiwan
  • 3Center for General Education, China Medical University, Taichung, Taiwan

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.

Shih-Chiao Tsai et al.

Status: open (until 10 Nov 2021)

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  • RC1: 'Comment on amt-2021-267', Anonymous Referee #1, 14 Oct 2021 reply

Shih-Chiao Tsai et al.

Shih-Chiao Tsai et al.

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Short summary
Automatically tracing the Doppler velocities of clear-air and precipitation echoes in the VHF Doppler spectra was developed. It was workable for ~98 % of the radar data used, when a typhoon was passing through the radar site. The information of water types yielded by a dual-polarized microwave radiometer showed that strong updraft and turbulent atmosphere could bring the liquid water to the height above the melting layer, producing plenty of ice crystals and graupels in the upper troposphere.