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# Changes in Typhoon Regional Heavy Precipitation Events over China from 1960 to 2018

• In earlier studies, objective techniques have been used to determine the contribution of tropical cyclones to precipitation (TCP) in a region, where the Tropical cyclone Precipitation Event (TPE) and the Regional Heavy Precipitation Events (RHPEs) are defined and investigated. In this study, TPE and RHPEs are combined to determine the Typhoon Regional Heavy Precipitation Events (TRHPEs), which is employed to evaluate the contribution of tropical cyclones to regional extreme precipitation events. Based on the Objective Identification Technique for Regional Extreme Events (OITREE) and the Objective Synoptic Analysis Technique (OSAT) to define TPE, temporal and spatial overlap indices are developed to identify the combined events as TRHPE. With daily precipitation data and TC best-track data over the western North Pacific from 1960 to 2018, 86 TRHPEs have been identified. TRHPEs contribute as much as 20% of the RHPEs, but 100% of events with extreme individual precipitation intensities. The major TRHPEs continued for approximately a week after tropical cyclone landfall, indicating a role of post landfall precipitation. The frequency and extreme intensity of TRHPEs display increasing trends, consistent with an observed positive trend in the mean intensity of TPEs as measured by the number of daily station precipitation observations exceeding 100 mm and 250 mm. More frequent landfalling Southeast and South China TCs induced more serious impacts in coastal areas in the Southeast and the South during 1990−2018 than 1960−89. The roles of cyclone translation speed and “shifts” in cyclone tracks are examined as possible explanations for the temporal trends.
摘要: 随着区域性强降水事件（RHPE）的频繁发生，热带气旋降水（TPE）在其中的贡献不可忽视。在早期的研究中，区域性极端事件的客观识别技术已被用于确定热带气旋对某一地区降水的贡献。在本研究中，通过将两类降水事件相结合来确定台风区域强降水事件（TRHPE），以评估热带气旋对区域极端降水事件的贡献。我们基于区域性极端事件的客观识别技术（OITREE，Ren et al.，2012）和TC降水天气图客观识别技术（OSAT，Ren et al.，2007）建立了用以识别台风区域性强降水事件的客观识别方法。研究结果表明：在1960–2018年，共有86个台风区域性强降水事件，占所有区域性强降水事件的20%。热带气旋登陆后，台风区域强降水事件持续约一周，表明登陆后台风对降水的作用。值得注意的是，台风停编后，大部分强降水仍在继续，即登陆后热带气旋的残余环流对区域性强降雨事件有重要贡献。从时空分布特征来看，台风区域强降水事件的频率和极端强度有不断增加的趋势，这与热带气旋降水平均强度的趋势相一致；在空间上呈现出从东南向西北方向强度频次均递减的趋势；与1960–1989年相比，1990–2018年期间，TC更频繁地登陆中国东南、华南并在东南部和南部的沿海地区产生了更严重的影响。除此之外，台风路径的偏移和台风移速或成为上述分布特征的可能解释。
• Figure 1.  Distribution of the 2112 stations applied in this study

Figure 2.  Flowchart for the objective identification of typhoon regional heavy precipitation events (TRHPEs)

Figure 3.  The distribution of 191 potential typhoon regional heavy precipitation events (TRHPEs). The abscissa is average RHPE station overlap rate ${R}_{1}$ while the ordinate is average TPE station overlap rate ${R}_{2}$.

Figure 4.  TRHPE frequency (blue line, right hand ordinate) for different extreme intensity values. The extreme intensity values displayed on the abscissa are the highest daily rainfall at a single station during the event. The columns (left hand ordinate) show the ratio of the number of TRHPEs to RHPEs (orange column) and to TPEs (grey column).

Figure 5.  Annual variations of (a) TRHPE frequency, (b) RHPE frequency, (c)TPE frequency, (d) ratio of TRHPEs to RHPEs, and (e) ratio of TRHPEs to TPEs (the dotted line represents the linear trend).

Figure 6.  Seasonal variations of TRHPEs over China during 1960−2018: (a) frequency; (b) maximum extreme intensity (mm).

Figure 7.  Spatial distribution of TRHPE frequency and accumulated intensity (${I}_{2}$, units: mm) over China. Frequency/accumulated intensity: (a/b) during 1960−2018, (c/d) the difference between 1990−2018 and 1960−1989 (later period minus earlier period).

Figure 8.  Temporal variations of Mean Intensity Indices (MIIs) for tropical cyclone precipitation events (TPE) of grade (a) ≥100 mm, (b) ≥250 mm for the period 1960−2018.

Figure 9.  The TC tracks causing TRHPEs during (a) 1960−89 and (b) 1990−2018.

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## Manuscript History

Manuscript revised: 21 May 2021
Manuscript accepted: 10 June 2021
###### 通讯作者: 陈斌, bchen63@163.com
• 1.

沈阳化工大学材料科学与工程学院 沈阳 110142

## Changes in Typhoon Regional Heavy Precipitation Events over China from 1960 to 2018

###### Corresponding author: Fumin REN, fmren@163.com;
• 1. College of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China
• 2. State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China
• 3. Honorary, School of Earth Science, University of Melbourne, and Research and Development Division, Bureau of Meteorology, Melbourne, VIC 3010, Australia
• 4. Haikou Meteorological Observatory, Haikou Meteorological Bureau, Haikou 570100, China

Abstract: In earlier studies, objective techniques have been used to determine the contribution of tropical cyclones to precipitation (TCP) in a region, where the Tropical cyclone Precipitation Event (TPE) and the Regional Heavy Precipitation Events (RHPEs) are defined and investigated. In this study, TPE and RHPEs are combined to determine the Typhoon Regional Heavy Precipitation Events (TRHPEs), which is employed to evaluate the contribution of tropical cyclones to regional extreme precipitation events. Based on the Objective Identification Technique for Regional Extreme Events (OITREE) and the Objective Synoptic Analysis Technique (OSAT) to define TPE, temporal and spatial overlap indices are developed to identify the combined events as TRHPE. With daily precipitation data and TC best-track data over the western North Pacific from 1960 to 2018, 86 TRHPEs have been identified. TRHPEs contribute as much as 20% of the RHPEs, but 100% of events with extreme individual precipitation intensities. The major TRHPEs continued for approximately a week after tropical cyclone landfall, indicating a role of post landfall precipitation. The frequency and extreme intensity of TRHPEs display increasing trends, consistent with an observed positive trend in the mean intensity of TPEs as measured by the number of daily station precipitation observations exceeding 100 mm and 250 mm. More frequent landfalling Southeast and South China TCs induced more serious impacts in coastal areas in the Southeast and the South during 1990−2018 than 1960−89. The roles of cyclone translation speed and “shifts” in cyclone tracks are examined as possible explanations for the temporal trends.

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