24 Oct 2022
24 Oct 2022
Status: this preprint is currently under review for the journal HESS.

Assessing KDP-based QPE for the record-breaking rainfall over Zhengzhou city on 20 July 2021

Haoran Li1,2, Dmitri Moisseev2, Yali Luo1, Liping Liu1, Zheng Ruan1, Liman Cui3, and Xinghua Bao1 Haoran Li et al.
  • 1State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing, China
  • 2Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, University of Helsinki, Finland
  • 3Henan Meteorological Observatory, Zhengzhou, China

Abstract. Although radar-based quantitative precipitation estimation (QPE) has been widely investigated from various perspectives, very few studies have been devoted into extreme rainfall QPE. In this study, the performance of KDP-based QPE during the record-breaking Zhengzhou rainfall event occurred on 20 July 2021 was assessed. Firstly, OTT disdrometer observations were used as input to T-matrix simulation and different assumptions were made to construct R(KDP) estimators. Then, KDP estimates from three algorithms were compared for obtaining best KDP estimates, and gauge observations were used to evaluate R(KDP) estimates. Our results in general agree with previous known-truth tests, and provide more practical insights from the perspective of QPE applications. For rainfall rates below 100 mm h-1, R(KDP) agrees rather well with gauge observations, and the selection of KDP estimation method or controlling factor has minimal impact on QPE performance provided that the used controlling factor is not too extreme. For higher rain rates, significant underestimation was found for R(KDP), and a smaller window length results in higher KDP thus less underestimation of rain rates. We show that the “best KDP estimate”-based QPE cannot reproduce the gauge measurement of 201.9 mm h-1 with commonly used assumptions for R(KDP), and potential responsible factors were discussed. We further show that the gauge with the 201.9 mm h-1 report was located at the vicinity of local rainfall hot spots during 16:00 ∼ 17:00 LST, while the 3-h rainfall accumulation center was located at the southwest of Zhengzhou city.

Haoran Li et al.

Status: open (until 19 Dec 2022)

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  • RC1: 'Comment on hess-2022-361', Anonymous Referee #1, 02 Dec 2022 reply

Haoran Li et al.

Haoran Li et al.


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Short summary
This extreme rainfall event occurred at Zhengzhou on 20 July 2021 is widely concerned, as it caused tremendous losses of both lives and properties. However, the evolution of areal rainfall is still not clear. In this study, Kdp observations were used for quantitatively estimating areal rainfall accumulation. Different estimation methods as well as QPE results were compared. We found that the selection of kdp estimation method has minimal impact on hourly rainfall accumulation.