In this study,the unprecedented extreme rainfall event during 19-20 July 2021,which caused devastating flooding in Zhengzhou City and its nearby areas,is examined based on observational data analysis and WRF model 40-...In this study,the unprecedented extreme rainfall event during 19-20 July 2021,which caused devastating flooding in Zhengzhou City and its nearby areas,is examined based on observational data analysis and WRF model 40-h simulations on 1-km horizontal resolution.The results show that the model successfully reproduces(i)major synopticscale weather systems(i.e.,the western Pacific subtropical high,the Tibetan high,two typhoons,and the Huang-Huai cyclone),(ii)convective initiation along the east to north edge of the Songshan Mountain,where orographic lifting is obvious,and(iii)subsequent formation of the convective storm producing the extreme rainfall in Zhengzhou.In particular,the model generates the maximum rainfall rate of 233 mm h^(-1)and 40-h accumulated rainfall of 704 mm,corresponding well to the observed extreme values of 201.9 mm h^(-1)and 818 mm,at nearly observed timing and location.Importantly,the model reproduces an intense quasi-stationary,well-organized meso-γ-scale convective system,surrounded by an arc-shaped convergence zone,allowing the development of convective updrafts in a three-quarter circle around the convective system,in a way similar to“multidirectional pumping,”attracting all associated precipitation overlaid and concentrated into the same trailing region to generate the extreme hourly rainfall over Zhengzhou.Our study emphasizes the significant contribution of the unique dynamic structure of the well-organized meso-γ-scale convective system to the record-high hourly rainfall.A possible dynamic mechanism for short-time extreme rainfall production is proposed.That is,the arc-shaped convergence zone of the mesoscale convective system,acting like multidirectional lifting pumps,transports precipitation from different directions into the same region,and thus produces the extreme rainfall.The results gained herein may shed new light on better understanding and forecasting of short-time extreme rainfall.展开更多
The cause–effect relationship between meso-γ-scale rotation and extreme short-term precipitation events remains elusive in mesoscale meteorological research.We aimed to elucidate this relationship by analyzing a rai...The cause–effect relationship between meso-γ-scale rotation and extreme short-term precipitation events remains elusive in mesoscale meteorological research.We aimed to elucidate this relationship by analyzing a rainstorm over the Pearl River Delta during the nocturnal hours of 15 May 2017 based on 6-min radar observations and 1-min rain gauge data.This rainstorm had a maximum hourly rainfall of 100.1 mm,with 26 stations recording hourly rainfall>60 mm h^(−1) in 5 h.Extreme heavy precipitation was produced in association with a convergence zone along the southern side of a synoptic low-level shear line,where southwesterly warm,humid airflows with precipitable water of>60 mm,little convection inhibition(<10 J kg^(−1)),and a low lifting condensation level(about 300 m)dominated.A meso-γ-scale vortex was quantitatively identified during the hour with the largest number of gauges observing extreme hourly rainfall.The vortex had a mean diameter of 6.1 km and a peak intensity of 3.1×10^(−3) s^(−1) during its lifetime of 54 min.The vortex initialized and remained inside the region of extreme rain rates(radar-retrieved rain rates>100 mm h^(−1)),reached its peak intensity after the peak of the collocated 6-min rainfall accumulation,and then weakened rapidly after the extreme rainfall region moved away.The radar-retrieved liquid water path was about five to seven times the ice water path and the specific differential phase(Kdp)below 0°C increased sharply downward during the lifetime of the vortex,suggesting the presence of active warm rain microphysical processes.These results indicate that the release of the latent heat of condensation induced by extreme rainfall could have contributed to the formation of the vortex in an environment with a weak 0–1-km vertical wind shear(about 4–5 m s^(−1))through enhanced lowlevel convergence,although the strengthening of low-level updrafts by rotational dynamic effects and short-term rainfall cannot be ruled out.展开更多
为了更好地认识山西暴雨的形成机制,利用红外辐射亮温、多普勒雷达和气柱水汽总量等资料,对2013年7月3—4日发生在山西境内的强对流暴雨进行多尺度特征分析。结果表明:(1)700、850 h Pa暖切变线是暴雨发生的α中尺度触发系统,自动站极...为了更好地认识山西暴雨的形成机制,利用红外辐射亮温、多普勒雷达和气柱水汽总量等资料,对2013年7月3—4日发生在山西境内的强对流暴雨进行多尺度特征分析。结果表明:(1)700、850 h Pa暖切变线是暴雨发生的α中尺度触发系统,自动站极大风速风场切变线和气旋性涡旋是强对流暴雨发生的β中尺度触发系统,γ中尺度气旋是大暴雨产生的直接影响系统。(2)在700 h Pa与850 h Pa切变线之间,对流云团在自动站极大风速风场切变线、中尺度涡旋附近的合并与发展,是导致暴雨中心多次雨峰的主要原因。(3)-53℃的冷云盖超前40 d Bz以上的雷达组合反射率、-53℃的冷云盖几何中心与雷达组合反射率≥45 d Bz的区域相重叠,分别是阳城辽河第1次和第2次雨峰云的垂直结构特征。展开更多
基金Supported by the National Key Research and Development Program of China(2017YFC1501806,2018YFC1507404)National Natural Science Foundation of China(42075083)。
文摘In this study,the unprecedented extreme rainfall event during 19-20 July 2021,which caused devastating flooding in Zhengzhou City and its nearby areas,is examined based on observational data analysis and WRF model 40-h simulations on 1-km horizontal resolution.The results show that the model successfully reproduces(i)major synopticscale weather systems(i.e.,the western Pacific subtropical high,the Tibetan high,two typhoons,and the Huang-Huai cyclone),(ii)convective initiation along the east to north edge of the Songshan Mountain,where orographic lifting is obvious,and(iii)subsequent formation of the convective storm producing the extreme rainfall in Zhengzhou.In particular,the model generates the maximum rainfall rate of 233 mm h^(-1)and 40-h accumulated rainfall of 704 mm,corresponding well to the observed extreme values of 201.9 mm h^(-1)and 818 mm,at nearly observed timing and location.Importantly,the model reproduces an intense quasi-stationary,well-organized meso-γ-scale convective system,surrounded by an arc-shaped convergence zone,allowing the development of convective updrafts in a three-quarter circle around the convective system,in a way similar to“multidirectional pumping,”attracting all associated precipitation overlaid and concentrated into the same trailing region to generate the extreme hourly rainfall over Zhengzhou.Our study emphasizes the significant contribution of the unique dynamic structure of the well-organized meso-γ-scale convective system to the record-high hourly rainfall.A possible dynamic mechanism for short-time extreme rainfall production is proposed.That is,the arc-shaped convergence zone of the mesoscale convective system,acting like multidirectional lifting pumps,transports precipitation from different directions into the same region,and thus produces the extreme rainfall.The results gained herein may shed new light on better understanding and forecasting of short-time extreme rainfall.
基金Supported by the National Natural Science Foundation of China(42030610)National Key Research and Development Program of China for Intergovernmental Cooperation(2019YFE0110100).
文摘The cause–effect relationship between meso-γ-scale rotation and extreme short-term precipitation events remains elusive in mesoscale meteorological research.We aimed to elucidate this relationship by analyzing a rainstorm over the Pearl River Delta during the nocturnal hours of 15 May 2017 based on 6-min radar observations and 1-min rain gauge data.This rainstorm had a maximum hourly rainfall of 100.1 mm,with 26 stations recording hourly rainfall>60 mm h^(−1) in 5 h.Extreme heavy precipitation was produced in association with a convergence zone along the southern side of a synoptic low-level shear line,where southwesterly warm,humid airflows with precipitable water of>60 mm,little convection inhibition(<10 J kg^(−1)),and a low lifting condensation level(about 300 m)dominated.A meso-γ-scale vortex was quantitatively identified during the hour with the largest number of gauges observing extreme hourly rainfall.The vortex had a mean diameter of 6.1 km and a peak intensity of 3.1×10^(−3) s^(−1) during its lifetime of 54 min.The vortex initialized and remained inside the region of extreme rain rates(radar-retrieved rain rates>100 mm h^(−1)),reached its peak intensity after the peak of the collocated 6-min rainfall accumulation,and then weakened rapidly after the extreme rainfall region moved away.The radar-retrieved liquid water path was about five to seven times the ice water path and the specific differential phase(Kdp)below 0°C increased sharply downward during the lifetime of the vortex,suggesting the presence of active warm rain microphysical processes.These results indicate that the release of the latent heat of condensation induced by extreme rainfall could have contributed to the formation of the vortex in an environment with a weak 0–1-km vertical wind shear(about 4–5 m s^(−1))through enhanced lowlevel convergence,although the strengthening of low-level updrafts by rotational dynamic effects and short-term rainfall cannot be ruled out.
文摘为了更好地认识山西暴雨的形成机制,利用红外辐射亮温、多普勒雷达和气柱水汽总量等资料,对2013年7月3—4日发生在山西境内的强对流暴雨进行多尺度特征分析。结果表明:(1)700、850 h Pa暖切变线是暴雨发生的α中尺度触发系统,自动站极大风速风场切变线和气旋性涡旋是强对流暴雨发生的β中尺度触发系统,γ中尺度气旋是大暴雨产生的直接影响系统。(2)在700 h Pa与850 h Pa切变线之间,对流云团在自动站极大风速风场切变线、中尺度涡旋附近的合并与发展,是导致暴雨中心多次雨峰的主要原因。(3)-53℃的冷云盖超前40 d Bz以上的雷达组合反射率、-53℃的冷云盖几何中心与雷达组合反射率≥45 d Bz的区域相重叠,分别是阳城辽河第1次和第2次雨峰云的垂直结构特征。
