ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Characteristics of Raindrop Size Distribution of the Residual Vortex of Typhoon Haikui and its impact on the S/X-band QPE Algorithms
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Abstract:
Multiple DSG5 raindrop distrometers are utilized to analyze the raindrop size distribution of the residual vortex of Typhoon Haikui (2311) in the Pearl River Delta and evaluate the performance of different QPE algorithms in the S/X bands. The results indicate that the impact of the residual vortex of Haikui on rainfall in the Pearl River Delta can be divided into two main stages. The first stage is primarily influenced by the convergence of the southwest monsoon and easterly airflow on the eastern side of the vortex itself, with a deep moisture convergence layer. The microphysical processes of rainfall are relatively uniform with relatively small mass-weighted mean diameter (Dm) and higher normalized intercept parameter (lgNw), i.e., smaller particle sizes and higher number concentrations of raindrops. The second stage is characterized by intense rainfall caused by the convergence of southerly winds in the boundary layer on the outskirts of the residual vortex, with shallower moisture convergence layer. The rainfall particles are more dispersed, with more rainfall events featuring large Dm and low lgNw rain drops. Overall, medium-sized raindrops make a?major contribution to the total rainfall amount, but as rainfall intensity increases, the contribution of extremely large raindrops to rain rate at the second stage is significantly higher than that at the first stage. The dual-polarization parameters derived from raindrop size distribution of this process shows that, under the same rain rate (R), horizontal reflectivity factor (Zh), specific differential phase (KDP), and differential reflectivity (ZDR) at the first stage are smaller than those at the second stage. The deviation of QPE algorithms in the S/X bands calculated based on distrometers data shows that, R(Zh) has relatively large biases in both the S-band and X-band, while the bias of R(Zh, ZDR) is relatively small in the S-band but increases significantly with increasing rain rate in the X-band and R(KDP) has better performance in the X-band . R(KDP, ZDR) performs the best in both the S/X band and is minimally affected by changes in raindrop size distribution, with little difference between the two stages.
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