A Multiscale Analysis of a Nocturnal Extreme Rainfall Event of 14 July 2017 in Northeast China

2021 ◽  
Vol 149 (1) ◽  
pp. 173-187
Author(s):  
Gaili Wang ◽  
Da-Lin Zhang ◽  
Jisong Sun
Keyword(s):  
Northeast China ◽  
Global Analysis ◽  
Convective Available Potential Energy ◽  
Inversion Layer ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Convergence Zone ◽  
Extreme Rainfall Event ◽  
Hourly Rainfall ◽  
Convective Cells

AbstractA multiscale observational analysis of a nocturnal extreme rainfall event that occurred at Changtu in Northeast China on 14 July 2017 is performed using global analysis, automated surface observations, Doppler radar, rawinsonde, and disdrometer data. Results show that the large-scale environment was characterized by high convective available potential energy and precipitable water, moderate convective inhibition, and a southwesterly low-level jet (LLJ) capped by an inversion layer. The first and subsequent convective cells developed along a quasi-stationary surface convergence zone in a convection-void region of a previously dissipated meso-α-scale convective line. Continuous convective initiation through backbuilding at the western end and the subsequent merging of eastward-moving convective cells led to the formation of a near-zonally oriented meso-β-scale rainband, with reflectivity exceeding 45 dBZ (i.e., convective core intensity). This quasi-stationary rainband was maintained along the convergence zone by the LLJ of warm moist air, aided by local topographical lifting and convectively generated outflows. A maximum hourly rainfall amount of 96 mm occurred during 0200–0300 Beijing standard time as individual convective cores with a melting layer of >55 dBZ reflectivity moved across Changtu with little intermittency. The extreme-rain-producing stage was characterized with near-saturated vertical columns, and rapid number concentration increases of all raindrop sizes. It is concluded that the formation of the meso-β-scale rainband with continuous convective backbuilding, and the subsequent echo-training of convective cores with growing intensity and width as well as significant fallouts of frozen particles accounted for the generation of this extreme rainfall event. This extreme event was enhanced by local topography and the formation of a mesovortex of 20–30 km in diameter.

scholarly journals On the Extreme Rainfall Event of 7 May 2017 over the Coastal City of Guangzhou. Part I: Impacts of Urbanization and Orography

2020 ◽  
Vol 148 (3) ◽  
pp. 955-979 ◽  
Author(s):  
Jinfang Yin ◽  
Da-Lin Zhang ◽  
Yali Luo ◽  
Ruoyun Ma
Keyword(s):  
Doppler Radar ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Convective Initiation ◽  
Subsequent Formation ◽  
Coastal City ◽  
Hourly Rainfall ◽  
Extreme Rain ◽  
Convective Cells

Abstract In this study, a nocturnal extreme rainfall event induced by the urban heat island (UHI) effects of the coastal city of Guangzhou in South China on 7 May 2017 is examined using observational analyses and 18-h cloud-permitting simulations with the finest grid size of 1.33 km and the bottom boundary conditions nudged. Results show that the model reproduces convective initiation on Guangzhou’s downstream side (i.e., Huashan), where a shallow thermal mesolow is located, the subsequent back-building of convective cells as a larger-scale warm-moist southerly flow interacts with convectively generated cold outflows, and their eastward drifting and reorganization into a localized extreme-rain-producing storm near Jiulong under the influences of local orography. In particular, the model produces the maximum hourly, 3- and 12-hourly rainfall amounts of 146, 315, and 551 mm, respectively, at nearly the right location compared to their corresponding observed extreme amounts of 184, 382, and 542 mm. In addition, the model reproduces an intense meso-γ-scale vortex associated with the extreme-rain-producing Jiulong storm, as also captured by Doppler radar, with organized updrafts along cold outflow boundaries over a semicircle. A comparison of sensitivity and control simulations indicates that despite the occurrence of heavier rainfall amounts without the UHI effects than those without orography, the UHI effects appear to account directly for the convective initiation and heavy rainfall near Huashan, and indirectly for the subsequent formation of the Jiulong storm, while orography plays an important role in blocking cold outflows and enhancing cool pool strength for the sustained back-building of convective cells over the semicircle, thereby magnifying rainfall production near Jiulong.

scholarly journals Analysis of human vulnerability to the extreme rainfall event on 21–22 July 2012 in Beijing, China

2013 ◽  
Vol 13 (11) ◽  
pp. 2911-2926 ◽  
Author(s):  
J. Liu ◽  
S.-Y. Wang
Keyword(s):  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Linear Regression Models ◽  
Extreme Rainfall Events ◽  
Human Vulnerability ◽  
Hourly Rainfall ◽  
Temporal And Spatial Characteristics ◽  
Different Characteristics ◽  
The Impact

Abstract. The aim of this study is to characterize the extreme rainfall event on 21–22 July 2012 in Beijing, and its impact on human vulnerability. Based on the available meteorological and rainfall data from Beijing meteorological stations and Surface Weather Observation Stations, the study draws hourly rainfall maps to simulate the rainfall amount and spatial distribution. Using these maps, this paper provides a quantitative analysis of the impact of the temporal and spatial characteristics of rainfall on the vulnerability of three population groups, according to age, gender and total number of victims. The results of three linear regression models indicate the different effects of extreme rainfall parameters on victims with different characteristics. The analysis of victim data in this extreme rainfall event represents the distribution and characteristics of victims in the eight affected districts, and concludes that the "vulnerable group" are males and adults in this extreme rainfall event. This paper is an initial effort to analyze the impact of an extreme rainfall event on the vulnerability of populations with different characteristics quantitatively, which can be used by stakeholders to prioritize the extreme rainfall event impact issues, and develop contingency plans to address and prevent the human and structural damages caused by the extreme rainfall events.

scholarly journals Characteristics of rainfall triggering of debris flows in the Chenyulan watershed, Taiwan

2013 ◽  
Vol 13 (4) ◽  
pp. 1015-1023 ◽  
Author(s):  
J. C. Chen ◽  
C. D. Jan ◽  
W. S. Huang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Field Investigation ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Rainfall Index ◽  
Hourly Rainfall ◽  
Central Taiwan ◽  
Debris Flow Initiation

Abstract. This paper reports the variation in rainfall characteristics associated with debris flows in the Chenyulan watershed, central Taiwan, between 1963 and 2009. The maximum hourly rainfall Im, the maximum 24 h rainfall Rd, and the rainfall index RI (defined as the product RdIm) were analysed for each rainfall event that triggered a debris flow within the watershed. The corresponding number of debris flows initiated by each rainfall event (N) was also investigated via image analysis and/or field investigation. The relationship between N and RI was analysed. Higher RI of a rainfall event would trigger a larger number of debris flows. This paper also discusses the effects of the Chi-Chi earthquake (CCE) on this relationship and on debris flow initiation. The results showed that the critical RI for debris flow initiation had significant variations and was significantly lower in the years immediately following the CCE of 1999, but appeared to revert to the pre-earthquake condition about five years later. Under the same extreme rainfall event of RI = 365 cm2 h−1, the value of N in the CCE-affected period could be six times larger than that in the non-CCE-affected periods.

scholarly journals Extreme rainfall impacts on soil CO2 efflux in an urban forest ecosystem in Beijing, China

2016 ◽  
Vol 96 (4) ◽  
pp. 504-514 ◽  
Author(s):  
Wenjing Chen ◽  
Xin Jia ◽  
Chunyi Li ◽  
Haiqun Yu ◽  
Jing Xie ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Forest Ecosystem ◽  
Urban Forest ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Co2 Efflux ◽  
Abrupt Decrease ◽  
Environmental Controls ◽  
Beijing China

Extreme rainfall events are infrequent disturbances that affect urban environments and soil respiration (Rs). Using data measured in an urban forest ecosystem in Beijing, China, we examined the link between gross primary production (GPP) and soil respiration on a diurnal scale during an extreme rainfall event (i.e., the “21 July 2012 event”), and we examined diel and seasonal environmental controls on Rs. Over the seasonal cycle, Rs increased exponentially with soil temperature (Ts). In addition, Rs was hyperbolically related to soil volumetric water content (VWC), increasing with VWC below a threshold of 0.17 m3 m−3, and then decreasing with further increases in VWC. Following the extreme rainfall event (177 mm), Rs showed an abrupt decrease and then maintained a low value of ∼0.3 μmol m−2 s−1 for about 8 h as soil VWC reached the field capacity (0.34 m3 m−3). Rs became decoupled from Ts and increased very slowly, while GPP showed a greater increase. A bivariate Q10-hyperbolical model, which incorporates both Ts and VWC effects, better fits Rs than the Q10 model in summer but not for whole year.

Simulation of an extreme rainfall event over Mumbai using a regional climate model: a case study

2021 ◽  
Vol 134 (1) ◽  
Author(s):  
Manas Pant ◽  
Soumik Ghosh ◽  
Shruti Verma ◽  
Palash Sinha ◽  
R. K. Mall ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event

On the Localized Extreme Rainfall over the Great Bay Area in South China with Complex Topography and Strong UHI Effects

2021 ◽  
Author(s):  
Xiaoyan Sun ◽  
Yali Luo ◽  
Xiaoyu Gao ◽  
Mengwen Wu ◽  
Mingxin Li ◽  
...  
Keyword(s):  
South China ◽  
Global Analysis ◽  
Urban Canopy ◽  
Extreme Rainfall ◽  
Urban Agglomeration ◽  
Convective Initiation ◽  
Sea Breezes ◽  
Bay Area ◽  
Great Bay ◽  
Hourly Rainfall

AbstractIn this study, high-resolution surface and radar observations are used to analyze 24 localized extreme hourly rainfall (EXHR, > 60mm/h) events with strong urban heat island (UHI) effects over the Great Bay Area (GBA) in South China during 2011-2016 warm seasons. Quasi-idealized, convection-permitting ensemble simulations driven by diurnally varying lateral boundary conditions, which are extracted from the composite global analysis of 3-5 June 2013, are then conducted with a multi-layer urban canopy model to unravel the influences of the UHI and various surface properties nearby on the EXHR generation in a complex geographical environment with sea-land contrast, topography, and vegetation variation. Results show that EXHR is mostly distributed over the urban agglomeration and within about 40 km on its downwind side, and produced during the afternoon-to-evening hours by short-lived meso-γ to β-scale storms. On the EXHR days, the GBA is featured by a weak-gradient environment with abundant moisture, and a weak southwesterly flow prevailing in the boundary layer (BL). The UHI effects lead to the development of a deep mixed layer with “warm bubbles” over the urban agglomeration, in which the lower-BL convergence and BL-top divergence is developed, assisting in convective initiation. Such urban BL processes and associated convective development with moisture supply by the synoptic low-level southwesterly flow are enhanced by orographically increased horizontal winds and sea breezes under the influence of the herringbone coastline, thereby increasing the inhomogeneity and intensity of rainfall production over the “Π-shaped” urban clusters. Vegetation variations are not found to be an important factor in determining the EXHR production over the region.

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