Using high-resolution observations,mesoscale simulations,and idealized experiments,this study investigates the mechanisms governing an episode of orographic convection initiation(CI)during the North China Heavy Rainfa...Using high-resolution observations,mesoscale simulations,and idealized experiments,this study investigates the mechanisms governing an episode of orographic convection initiation(CI)during the North China Heavy Rainfall Experiment.On 4 August 2024,repeated CI occurred over the eastern slopes of the Taihang Mountains in the late afternoon,subsequently enhancing an upstream downhill convective storm.Wind profiler radar data and dense automatic weather stations reveal that CI was supported by strengthening southeasterly upslope winds.These winds primarily resulted from the migration of the mountain-plain solenoid and the mountainward-propagating outflow from a convective cold pool over the plain,with sensitivity experiments showing the latter contributed roughly 22%of the wind strength.The upslope flows gradually transported unstable air from the plain to the slope,fostering CI.Mesoscale simulations further highlight the key role of orographic waves near the mountain ridge,which generated strong downslope winds.The near-surface convergence between downslope and upslope flows,combined with wave-induced divergence aloft,produced deep ascent over the slope.Removing mountain ridges weakened wave strength and reduced downslope wind speeds by~8 m s^(-1).Without orographic heating in the idealized simulation(i.e.,no mountain-plain solenoid),only strong wave descent occurred below 2km,inhibiting CI.These findings underscore the critical interplay among plain convection,orographic waves,and the mountain-plain solenoid,offering new insight into the processes controlling orographic CI in North China.展开更多
Extreme rainfall events(EREs)frequently hit the middle and lower reaches of the Yellow River basin(YRB)during boreal summer.Recent observations have indicated that EREs exhibit teleconnection patterns across long spat...Extreme rainfall events(EREs)frequently hit the middle and lower reaches of the Yellow River basin(YRB)during boreal summer.Recent observations have indicated that EREs exhibit teleconnection patterns across long spatial distances.This study investigated ERE teleconnections in the YRB using the Event Synchronization(ES)method in combination with Complex Network(CN)theory.EREs in the YRB are significantly synchronized with other regions from regional to global scales.Additionally,high-resolution CMIP6 models in general show better skill in capturing these characteristics compared to low-resolution models.A further examination shows that the spatial synchronization patterns exhibit pronounced timescale dependence.Significant ERE synchronizations between the YRB and Europe were uncovered,where the YRB lags Eastern Europe by 3-5 days and Western Europe by 5-7 days,with Rossby wave propagation playing a key role.Wave trains from Europe propagate downstream along the Eurasian jet,inducing anomalous circulations over the YRB that enhance vertical upward motion and moisture transport,ultimately triggering EREs.Two distinct wave trains are observed:one is associated with Eastern Europe-YRB synchronization,occurring in the midlatitude region;the other is linked to Western Europe-YRB synchronization,positioned at higher latitudes.Notably,17.5%of Eastern Europe-YRB synchronization cases and 17.0%of Western Europe-YRB cases overlap.Quantitative analysis indicates that the synchronized events between Eastern(Western)Europe and the YRB account for roughly 28%(30%)of EREs in the YRB.These findings are critical for better understanding ERE mechanisms,offering guidance for forecasting and early warning capabilities for EREs in the YRB.展开更多
Persistent severe rainfall(PSR)events,defined as regional-scale rainfall processes with daily precipitation no less than 50 mm for at least three consecutive days,frequently occur over South China(SC)and the middle-to...Persistent severe rainfall(PSR)events,defined as regional-scale rainfall processes with daily precipitation no less than 50 mm for at least three consecutive days,frequently occur over South China(SC)and the middle-to-lower Yangtze River Basin(MLYRB),with distinct dynamic mechanisms and moisture conditions in the two regions.Based on daily precipitation observations from China’s national meteorological stations and ERA5 reanalysis during 2012-21,this study investigates the spatiotemporal distribution of PSR events in SC and MLYRB and their associated three-dimensional circulation dynamics.The analysis integrates diagnostics of 200 hPa wave activity flux,perturbation streamfunction,500 hPa geopotential height,850 hPa wind fields,and integrated water vapor transport.Results show that PSR events in SC mainly occur during May-June,with rainfall centers over coastal and central Guangdong and Guangxi.In contrast,MLYRB events peak during June-July,with a banded rainfall pattern along the middle-to-lower Yangtze River.Dynamical diagnostics indicate that,in SC,sustained northwest-southeast propagation of 200 hPa disturbances,the southward shift of the 500 hPa trough,and steady subtropical high maintenance provide continuous dynamical support.Concurrently,strong and persistent 850 hPa southwesterlies and long-lasting moisture transport form favorable moisture conditions.In contrast,MLYRB events are marked by rapid phase transitions of 200 hPa streamfunction anomalies and northward-westward expansion of the 500 hPa subtropical high,triggering intense rainfall development.Simultaneously,abrupt enhancement of 850 hPa southwesterlies and rapid formation of a southwest moisture corridor ensure abundant and timely moisture supply,facilitating PSR onset.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2024YFC3013003)the National Natural Science Foundation of China(Grant Nos.424B2033 and 42475002)+3 种基金projects supported by the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant Nos.SML2024SP035,SML2024SP012,311024001)the Guangdong Project of Basic and Applied Basic Research(Grant Nos.2024A1515510005 and2025A1515011974)the Key Innovation Team of the China Meteorological Administration(Grant No.CMA2023ZD08)the State Key Laboratory of Severe Weather Meteorological Science and Technology(Grant No.2025QZA10)。
文摘Using high-resolution observations,mesoscale simulations,and idealized experiments,this study investigates the mechanisms governing an episode of orographic convection initiation(CI)during the North China Heavy Rainfall Experiment.On 4 August 2024,repeated CI occurred over the eastern slopes of the Taihang Mountains in the late afternoon,subsequently enhancing an upstream downhill convective storm.Wind profiler radar data and dense automatic weather stations reveal that CI was supported by strengthening southeasterly upslope winds.These winds primarily resulted from the migration of the mountain-plain solenoid and the mountainward-propagating outflow from a convective cold pool over the plain,with sensitivity experiments showing the latter contributed roughly 22%of the wind strength.The upslope flows gradually transported unstable air from the plain to the slope,fostering CI.Mesoscale simulations further highlight the key role of orographic waves near the mountain ridge,which generated strong downslope winds.The near-surface convergence between downslope and upslope flows,combined with wave-induced divergence aloft,produced deep ascent over the slope.Removing mountain ridges weakened wave strength and reduced downslope wind speeds by~8 m s^(-1).Without orographic heating in the idealized simulation(i.e.,no mountain-plain solenoid),only strong wave descent occurred below 2km,inhibiting CI.These findings underscore the critical interplay among plain convection,orographic waves,and the mountain-plain solenoid,offering new insight into the processes controlling orographic CI in North China.
基金the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2023B1515020084)the National Natural Science Foundation of China (Grant Nos.42175068, 42475057, and 42261144687)
文摘Extreme rainfall events(EREs)frequently hit the middle and lower reaches of the Yellow River basin(YRB)during boreal summer.Recent observations have indicated that EREs exhibit teleconnection patterns across long spatial distances.This study investigated ERE teleconnections in the YRB using the Event Synchronization(ES)method in combination with Complex Network(CN)theory.EREs in the YRB are significantly synchronized with other regions from regional to global scales.Additionally,high-resolution CMIP6 models in general show better skill in capturing these characteristics compared to low-resolution models.A further examination shows that the spatial synchronization patterns exhibit pronounced timescale dependence.Significant ERE synchronizations between the YRB and Europe were uncovered,where the YRB lags Eastern Europe by 3-5 days and Western Europe by 5-7 days,with Rossby wave propagation playing a key role.Wave trains from Europe propagate downstream along the Eurasian jet,inducing anomalous circulations over the YRB that enhance vertical upward motion and moisture transport,ultimately triggering EREs.Two distinct wave trains are observed:one is associated with Eastern Europe-YRB synchronization,occurring in the midlatitude region;the other is linked to Western Europe-YRB synchronization,positioned at higher latitudes.Notably,17.5%of Eastern Europe-YRB synchronization cases and 17.0%of Western Europe-YRB cases overlap.Quantitative analysis indicates that the synchronized events between Eastern(Western)Europe and the YRB account for roughly 28%(30%)of EREs in the YRB.These findings are critical for better understanding ERE mechanisms,offering guidance for forecasting and early warning capabilities for EREs in the YRB.
基金funded by the Science and Technology Development Fund of Macao Special Administrative Region(Grant No.0009/2024/RIB1)the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030004).
文摘Persistent severe rainfall(PSR)events,defined as regional-scale rainfall processes with daily precipitation no less than 50 mm for at least three consecutive days,frequently occur over South China(SC)and the middle-to-lower Yangtze River Basin(MLYRB),with distinct dynamic mechanisms and moisture conditions in the two regions.Based on daily precipitation observations from China’s national meteorological stations and ERA5 reanalysis during 2012-21,this study investigates the spatiotemporal distribution of PSR events in SC and MLYRB and their associated three-dimensional circulation dynamics.The analysis integrates diagnostics of 200 hPa wave activity flux,perturbation streamfunction,500 hPa geopotential height,850 hPa wind fields,and integrated water vapor transport.Results show that PSR events in SC mainly occur during May-June,with rainfall centers over coastal and central Guangdong and Guangxi.In contrast,MLYRB events peak during June-July,with a banded rainfall pattern along the middle-to-lower Yangtze River.Dynamical diagnostics indicate that,in SC,sustained northwest-southeast propagation of 200 hPa disturbances,the southward shift of the 500 hPa trough,and steady subtropical high maintenance provide continuous dynamical support.Concurrently,strong and persistent 850 hPa southwesterlies and long-lasting moisture transport form favorable moisture conditions.In contrast,MLYRB events are marked by rapid phase transitions of 200 hPa streamfunction anomalies and northward-westward expansion of the 500 hPa subtropical high,triggering intense rainfall development.Simultaneously,abrupt enhancement of 850 hPa southwesterlies and rapid formation of a southwest moisture corridor ensure abundant and timely moisture supply,facilitating PSR onset.
