Persistent heavy rainfall events （PHR events） comprise one category of weather- and climate- related extreme events. Based on daily rainfall data measured in China during the period of 1951-2004, several quantitativ...Persistent heavy rainfall events （PHR events） comprise one category of weather- and climate- related extreme events. Based on daily rainfall data measured in China during the period of 1951-2004, several quantitative criteria were developed to define PHR events by means of their precipitation intensity, temporal duration, spatial extent and persistence. Then a semi-objective classification based on these criteria was applied to summer daily rainfall data to identify all PHR events. A total of 197 events were observed during the study period. All events were further classified into 5 categories according to their comprehensive intensity; into 3 types according to their circulation regime; and into 8 groups according to the geographic locations of their rainbands. Based on these different classifications, finally, the behaviors of 130 PHR events identified as the most severe, severe and moderate categories since the year of 1951, including characteristics of the spatial and temporal distributions of their frequencies, intensities, and rainbands, were investigated in order to present a comprehensive description of the PHR events. The results will be helpful to the future study of revealing and understanding the processes that govern the production of the PHR events and to the improvement of the forecasts of the PHR events.展开更多
Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （N...Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events （PHREs） in the Huaihe River valley （HRV） and the distribution pattern of convective activity in the tropical western Pacific warm pool （WPWP） is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high （WPSH） show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent ＂north weak south strong＂ distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley （YRV） are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak （strong） manner across the whole WPWP, persistent heavy （light） rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the ＂north weak south strong＂ pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the ＂north weak south strong＂ distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.展开更多
This paper presents a concise summary of recent studies on the long-term variations of haze in NorthChina and on the environmental and dynamic conditions for severe persistent haze events. Resultsindicate that haze da...This paper presents a concise summary of recent studies on the long-term variations of haze in NorthChina and on the environmental and dynamic conditions for severe persistent haze events. Resultsindicate that haze days have an obviously rising trend over the past 50 years in North China. Theoccurrence frequency of persistent haze events has a similar rising trend due to the continuous riseof winter temperatures, decrease of surface wind speeds, and aggravation of atmospheric stability. InNorth China, when severe persistent haze events occur, anomalous southwesterly winds prevail in thelower troposphere, providing sufficient moisture for the formation of haze. Moreover, North China ismainly controlled by a deep downdraft in the mid-lower troposphere, which contributes to reducing thethickness of the planetary boundary layer, obviously reducing the atmospheric capacity for pollutants.This atmospheric circulation and sinking motion provide favorable conditions for the formation andmaintenance of haze in North China.展开更多
Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangt...Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangtze River; and type B, whose precipitation is mainly located to the north of the river. The present study investigated these two PHRE types using a newly derived set of energy equations to show the scale interaction and main energy paths contributing to the persistence of the precipitation. The main results were as follows. The available potential energy （APE） and kinetic energy （KE） associated with both PHRE types generally increased upward in the troposphere, with the energy of the type-A PHREs stronger than that of the type-B PHREs （except for in the middle troposphere）. There were two main common and universal energy paths of the two PHRE types： （1） the baroclinic energy conversion from APE to KE was the dominant energy source for the evolution of large-scale background circulations; and （2） the downscaled energy cascade processes of KE and APE were vital for sustaining the eddy flow, which directly caused the PHREs. The significant differences between the two PHRE types mainly appeared in the lower troposphere, where the baroclinic energy conversion associated with the eddy flow in type-A PHREs was from KE to APE, which reduced the intensity of the precipitation-related eddy flow; whereas, the conversion in type-B PHREs was from APE to KE, which enhanced the eddy flow.展开更多
Based on the National Oceanic and Atmospheric Administration （NOAA） daily satellite dataset of global outgoing longwave radiation （OLR） for the period of 1974-2004 and the NCEP-NCAR reanalysis for 1971- 2004, the ...Based on the National Oceanic and Atmospheric Administration （NOAA） daily satellite dataset of global outgoing longwave radiation （OLR） for the period of 1974-2004 and the NCEP-NCAR reanalysis for 1971- 2004, the linkage between persistent heavy rainfall （PHR） events in the vicinity of the Yangtze River valley and global OLR leading up to those events （with 1- to 3O-day lag） was investigated. The results reveal that there is a significant connection between the initiation of PHR events over the study area and anomalous convective activity over the tropical Indian Ocean, maritime continent, and tropical western Pacific Ocean. During the 30-day period prior to the onset of PHR events, the major significantly anomalous convective centers have an apparent dipole structure, always with enhanced convection in the west and suppressed convection in the east. This dipole structure continuously shifts eastward with time during the 30-day lead period. The influence of the anomalous convective activity over the tropical oceans on the initiation of PHR events over the study area is achieved via an interaction between tropical and extratropical latitudes. More specifically, anomalous convective activity weakens the Walker circulation cell over the tropical Indian Ocean first. This is followed by a weakening of the Indian summer monsoon background state and the excitation and dispersion of Rossby wave activity over Eurasia. Finally, a major modulation of the large scale background circulation occurs. As a result, the condition of a phase-lock among major large scale circulation features favoring PHR events is established over the study area.展开更多
In this study, regional persistent haze events（RPHEs） in the Beijing–Tianjin–Hebei（BTH） region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–201...In this study, regional persistent haze events（RPHEs） in the Beijing–Tianjin–Hebei（BTH） region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–2013. The formation mechanisms of the severe RPHEs were investigated with focus on the atmospheric circulation and dynamic mechanisms. Results indicated that：（1） 49 RPHEs occurred during the past 34 years.（2） The severe RPHEs could be categorized into two types according to the large-scale circulation, i.e. the zonal westerly airflow（ZWA） type and the high-pressure ridge（HPR） type. When the ZWA-type RPHEs occurred, the BTH region was controlled by near zonal westerly airflow in the mid–upper troposphere.Southwesterly winds prevailed in the lower troposphere, and near-surface wind speeds were only 1–2 ms^-1. Warm and humid air originating from the northwestern Pacific was transported into the region, where the relative humidity was 70% to 80%, creating favorable moisture conditions. When the HPR-type RPHEs appeared, northwesterly airflow in the mid–upper troposphere controlled the region. Westerly winds prevailed in the lower troposphere and the moisture conditions were relatively weak.（3） Descending motion in the mid-lower troposphere caused by the above two circulation types provided a crucial dynamic mechanism for the formation of the two types of RPHEs. The descending motion contributed to a reduction in the height of the planetary boundary layer（PBL）, which generated an inversion in the lower troposphere. This inversion trapped the abundant pollution and moisture in the lower PBL, leading to high concentrations of pollutants.展开更多
A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events...A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events (EPLTE) in China.During the persistence of such anomalous circulations,the split flow over the inner Asian continent and the influent flow over the southeast-ern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence,a strong,cold advection over south-eastern China.The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.展开更多
The distinct precursory signals of countrywide extensive and persistent extreme cold events (CECs) were investigated and contrasted with those of countrywide cold wave events (CCWs). It is shown that most CECs were ac...The distinct precursory signals of countrywide extensive and persistent extreme cold events (CECs) were investigated and contrasted with those of countrywide cold wave events (CCWs). It is shown that most CECs were accompanied by a CCW in the initial stages. From the comparison between the CECs and the CCWs that were independent of any CEC, it is found that a south- west-northeast-oriented tilted ridge at 500 hPa was present around the Europe-Barents Sea regions approximately 10 days prior to the start of the CEC. Consistent with this feature, a high sea level pressure and strong cold air accumulation occurred over a broad extent of northern Eurasia one week prior to the start of the CEC. The tilted ridge and the strong cold air accumulation were the precursory signals that were absent for the CCW, and they provide important clues for the early prediction of whether a CCW event might evolve into a CEC.展开更多
Persistent heavy rainfall events(PHREs)over the Yangtze–Huaihe River Valley(YHRV)during 1981–2020 are classified into three types(type-A,type-B and type-C)according to pattern correlation.The characteristics of the ...Persistent heavy rainfall events(PHREs)over the Yangtze–Huaihe River Valley(YHRV)during 1981–2020 are classified into three types(type-A,type-B and type-C)according to pattern correlation.The characteristics of the synoptic systems for the PHREs and their possible development mechanisms are investigated.The anomalous cyclonic disturbance over the southern part of the YHRV during type-A events is primarily maintained and intensified by the propagation of Rossby wave energy originating from the northeast Atlantic in the mid–upper troposphere and the northward propagation of Rossby wave packets from the western Pacific in the mid–lower troposphere.The zonal propagation of Rossby wave packets and the northward propagation of Rossby wave packets during type-B events are more coherent than those for type-A events,which induces eastward propagation of stronger anomaly centers of geopotential height from the northeast Atlantic Ocean to the YHRV and a meridional anomaly in geopotential height over the Asian continent.Type-C events have“two ridges and one trough”in the high latitudes of the Eurasian continent,but the anomalous intensity of the western Pacific subtropical high(WPSH)and the trough of the YHRV region are weaker than those for type-A and type-B events.The composite synoptic circulation of four PHREs in 2020 is basically consistent with that of the corresponding PHRE type.The location of the South Asian high(SAH)in three of the PHREs in 2020 moves eastward as in the composite of the three types,but the position of the WPSH of the four PHREs is clearly westward and northward.Two water vapor conveyor belts and two cold air conveyor belts are tracked during the four PHREs in 2020,but the water vapor path from the western Pacific is not seen,which may be caused by the westward extension of the WPSH.展开更多
Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic...Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic circulations and maintenance mechanisms between different PHRE types.There are two main types of PHREs:one is characterized by a rain belt west of 106°E over the SCB(WSB-PHREs),and the other features a rain belt east of 106°E over the SCB(ESB-PHREs).In total,there are 18 ESB-PHREs and 10 WSB-PHREs during the study period.Overall,the rain belts of WSB-PHREs are along the terrain distribution east of the Tibetan Plateau,while the precipitation intensity of ESB-PHREs is stronger.For the two types of PHREs,the shortwave trough over the SCB and the western Pacific subtropical high act as their favorable background environments,particularly for ESB-PHREs.The water vapor of WSB-PHREs is mainly transported from the South China Sea,whereas for ESB-PHREs the South China Sea and Bay of Bengal are their main moisture sources.The composite vorticity budgets of southwest vortices during their mature stage indicate that the convergence effect is a dominant factor for maintaining the two types of PHREs,and the strong vertical vorticity advection is also favorable,but the relative contribution of vertical advection is larger for WSB-PHREs.展开更多
Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year(1961-2005) and 86-station observational precipitation data of Guangdong,and the causes of drought events are disc...Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year(1961-2005) and 86-station observational precipitation data of Guangdong,and the causes of drought events are discussed from different angles(e.g.,atmospheric circulation,sea surface temperature) on the basis of global coverage datasets of sea surface temperature and atmospheric elements.It is found that the occurrence frequency of persistent drought events in Guangdong province is once every 26 months on average,and autumn-winter or winter-spring persistent drought events take up the majority.The persistent drought events possess large scale spatial characteristics.While the 1960s is the most frequent and strongest decade of drought events in the latter half of the 20th century,the occurrence is more frequent and the intensity is stronger in the first five years of the 21st century(2001-2005).This reflects the response of regional extreme climatic events in Guangdong to global climatic change.The atmospheric circulation,sea surface temperature,etc,appear to have different abnormal characteristics when drought events happen in different seasons.The results of this paper provide some good reference information for the drought forecast,especially for the dynamic interpretation of climatic model products.展开更多
By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during ...By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during persistent and intense rains in the Yangtze-Huaihe Rivers basin are studied. The results show that the position variation of WPSH is closely associated with the diabatic heating. There are strong apparent heating sources and moisture sinks in both the basin (to the north of WPSH) and the north of Bay of Bengal (to the west of WPSH) during persistent and intense rain events. In the basin, Q 1z begins to increase 3 days ahead of intense rainfall, maximizes 2 days later and then reduces gradually, but it changes little after precipitation ends, thus preventing the WPSH from moving northward. In the north of Bay of Bengal, 2 days ahead of strong rainfall over the basin, Q 1z starts to increase and peaks 1 day after the rain occurs, leading to the westward extension of WPSH. Afterwards, Q 1z begins declining and the WPSH makes its eastward retreat accordingly. Based on the complete vertical vorticity equation, in mid-troposphere, the vertical variation of heating in the basin is favorable to the increase of cyclonic vorticity north of WPSH, which counteracts the northward movement of WPSH and favors the persistence of rainbands over the basin. The vertical variation of heating in the north of Bay of Bengal is in favor of the increase of anti-cyclonic vorticity to the west of WPSH, which induces the westward extension of WPSH.展开更多
We investigate the characteristics and mechanisms of persistent wet–cold events(PWCEs)with different types of coldair paths.Results show that the cumulative single-station frequency of the PWCEs in the western part o...We investigate the characteristics and mechanisms of persistent wet–cold events(PWCEs)with different types of coldair paths.Results show that the cumulative single-station frequency of the PWCEs in the western part of South China is higher than that in the eastern part.The pattern of single-station frequency of the PWCEs are“Yangtze River(YR)uniform”and“east–west inverse”.The YR uniform pattern is the dominant mode,so we focus on this pattern.The cold-air paths for PWCEs of the YR uniform pattern are divided into three types—namely,the west,northwest and north types—among which the west type accounts for the largest proportion.The differences in atmospheric circulation of the PWCEs under the three types of paths are obvious.The thermal inversion layer in the lower troposphere is favorable for precipitation during the PWCEs.The positive water vapor budget for the three types of PWCEs mainly appears at the southern boundary.展开更多
This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased...This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased occurrence probabilities of PECEs over Northeast China are observed in phases 3 and 5 of the MJO,when MJOrelated convection is located over the eastern Indian Ocean and the western Pacific,respectively.Using the temperature tendency equation,it is found that the physical processes resulting in the cooling effects required for the occurrence of PECEs are distinct in the two phases of the MJO when MJO-related convection is consistently located over the warm pool area.The PECEs in phase 3 of the MJO mainly occur as a result of adiabatic cooling associated with ascending motion of the low-pressure anomaly over Northeast Asia.The cooling effect associated with phase 5 is stronger and longer than that in phase 3.The PECEs associated with phase 5 of the MJO are linked with the northwesterly cold advection of a cyclonic anomaly,which is part of the subtropical Rossby wave train induced by MJO-related convection in the tropical western Pacific.展开更多
Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regula...Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regularity of continuous heavy precipitation over Southern China(SC)from April to June in 1979-2020 was systematically analyzed.The interaction between specific humidity and circulation field at the background-scale,the intra-seasonal-scale and the synoptic-scale,and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed.The results are as follows.Persistent heavy rainfall events(PHREs)over the SC during the April-June rainy season occur frequently from mid-May to mid-and late-June,exhibiting significant intra-seasonal oscillation(10-30-day)features.Vertically integrated moisture flux convergence(VIMFC)can well represent the variation of the PHREs.A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor(greater than 30 days),intraseasonal circulation disturbance(10-30-day)and background circulation(greater than 30 days),and water vapor convergences are the main factor.The SC is under the control of a warm and humid background and a strong intraseasonal cyclonic circulation,with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs.Meanwhile,the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days,eventually leading to the occurrence,development and persistence of heavy precipitation.展开更多
Introduction: The incidence of acute pain after craniotomy differs remarkably in previous studies, and the prevalence of persistent pain is not precisely known. We conducted 6-month follow-up surveys on the incidence ...Introduction: The incidence of acute pain after craniotomy differs remarkably in previous studies, and the prevalence of persistent pain is not precisely known. We conducted 6-month follow-up surveys on the incidence and intensity of acute and persistent pain after elective craniotomy. Methods: We carried out a prospective cohort study via a series of structured questionnaires to record acute pain intensity preoperatively and postoperatively, and the incidence of persistent pain 3 and 6 months after a craniotomy in a tertiary care center. Patients scheduled for elective craniotomy were interviewed the day before surgery, postoperatively before discharge from the hospital, and 3 and 6 months after surgery. Pain was assessed on a numeric rating scale (0 - 10) at rest and movement, as well as expectations of pain before surgery, efficacy of pain therapy, and satisfaction with pain treatment. The incidence of adverse events, sleep time and interruptions caused by pain, different pain types, and drugs used for pain treatment were also recorded. Results: A total of 152 patients were enrolled in the study and completed the preoperative questionnaire;123 (81%) completed postoperative questionnaire and 108 (72%) completed the 3- and 6-month follow-ups. The average pain score at the time of the postoperative questionnaire was moderate, 4 at rest and 5 upon movement. The percentage of patients experiencing mild pain at rest and upon movement was 52% and 49%, and moderate pain was 15% and 16%, respectively. Severe postoperative pain was detected in 5% and 8% of patients at rest and upon movement, respectively. Three months after surgery, 6% of patients reported mild pain at rest, 3% moderate pain at rest, and 1% severe pain at rest. Persistent mild and moderate pain at rest after 6 months was reported by 3% and 1% of patients, respectively. The most common adverse events were postoperative nausea and vomiting (11%) and abdominal discomfort (8%). During postoperative pain treatment in the intensive care unit or post-anesthesia care unit, 92% of patients received acetaminophen, 88% fentanyl, and 24% oxycodone. During neurosurgical ward care, ibuprofen was used in 61% of patients. Satisfaction with analgesia was high throughout the study period with a median satisfaction score of 9 postoperatively and 10 at 3 and 6 months on the 0 - 10 scale. Conclusion: The findings indicate that most patients experience moderate or mild pain after craniotomy, but patient satisfaction with pain treatment is high. Persistent pain after 3 and 6 months is rare and mild in nature.展开更多
In February 2022,a persistent low-temperature rain and snow event(LRSE)occurred in the central Pan-Pearl River Delta(CPPRD)region of southern China,causing severe damage and economic losses.During the LRSE,both the te...In February 2022,a persistent low-temperature rain and snow event(LRSE)occurred in the central Pan-Pearl River Delta(CPPRD)region of southern China,causing severe damage and economic losses.During the LRSE,both the temperature and precipitation fields exhibited quasi-biweekly oscillation(QBWO)signals over the CPPRD region.Circulation analysis revealed that the eastward propagation of Rossby waves at mid–high latitudes enhanced the Baikal blocking high and the Mongolian high,facilitating the continuous southward migration of cold air.The strengthening India–Burma trough(i.e.,the southern branch trough)brought abundant warm and humid airflow,converging with cold air from the north in the CPPRD region.Moreover,deep convective activity originating in the northern Indian Ocean became exceptionally active,propagating to southern China and providing dynamic lifting conditions for precipitation in the study region.The combined effects of tropical and extratropical weather systems resulted in the LRSE occurrence.Partial lateral forcing(PLF)experiments were performed to quantify the contributions of the QBWO signals from different boundaries of the region.The extratropical QBWO signal from the northern boundary led to a temperature decrease of 1.61℃,with 77.83%of the whole region experiencing cooling greater than 1℃,whereas the tropical QBWO signal from the southwestern boundary caused an increase in precipitation of 13.1 mm day^(−1),with more than 40%of the entire region experiencing a precipitation increase of over 5 mm day^(−1).This study provides quantitative evidence that the QBWO was a key factor contributing to the occurrence of the LRSE,which can be used as a precursor signal for extended-range forecasts of future LRSEs.展开更多
华南前汛期降水量大,且常出现持续3天以上、甚至长达10天以上的持续性强降水事件(Persistent Heavy Rainfall Event,PHRE),给该地区带来严重的洪涝灾害,提升前汛期降水的延伸期(提前10~30天或2~6候)预报水平至关重要。重点论述华南降水...华南前汛期降水量大,且常出现持续3天以上、甚至长达10天以上的持续性强降水事件(Persistent Heavy Rainfall Event,PHRE),给该地区带来严重的洪涝灾害,提升前汛期降水的延伸期(提前10~30天或2~6候)预报水平至关重要。重点论述华南降水延伸期预报可预报性的来源,以及当前数值模式、动力-统计释用和机器学习在延伸期预报领域的应用情况,以期了解华南前汛期降水延伸期预报的主要进展。展开更多
基金This work was supported by the National Natural Science Foundation of China under Grant No. 40575015.
文摘Persistent heavy rainfall events （PHR events） comprise one category of weather- and climate- related extreme events. Based on daily rainfall data measured in China during the period of 1951-2004, several quantitative criteria were developed to define PHR events by means of their precipitation intensity, temporal duration, spatial extent and persistence. Then a semi-objective classification based on these criteria was applied to summer daily rainfall data to identify all PHR events. A total of 197 events were observed during the study period. All events were further classified into 5 categories according to their comprehensive intensity; into 3 types according to their circulation regime; and into 8 groups according to the geographic locations of their rainbands. Based on these different classifications, finally, the behaviors of 130 PHR events identified as the most severe, severe and moderate categories since the year of 1951, including characteristics of the spatial and temporal distributions of their frequencies, intensities, and rainbands, were investigated in order to present a comprehensive description of the PHR events. The results will be helpful to the future study of revealing and understanding the processes that govern the production of the PHR events and to the improvement of the forecasts of the PHR events.
基金This study was supported by the ＂National Key Programme for Developing Basic Science＂ projects under Grant No. 2004CB418303the National Natural Science Foundation of China under Grant No. 40705022.
文摘Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events （PHREs） in the Huaihe River valley （HRV） and the distribution pattern of convective activity in the tropical western Pacific warm pool （WPWP） is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high （WPSH） show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent ＂north weak south strong＂ distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley （YRV） are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak （strong） manner across the whole WPWP, persistent heavy （light） rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the ＂north weak south strong＂ pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the ＂north weak south strong＂ distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.
文摘This paper presents a concise summary of recent studies on the long-term variations of haze in NorthChina and on the environmental and dynamic conditions for severe persistent haze events. Resultsindicate that haze days have an obviously rising trend over the past 50 years in North China. Theoccurrence frequency of persistent haze events has a similar rising trend due to the continuous riseof winter temperatures, decrease of surface wind speeds, and aggravation of atmospheric stability. InNorth China, when severe persistent haze events occur, anomalous southwesterly winds prevail in thelower troposphere, providing sufficient moisture for the formation of haze. Moreover, North China ismainly controlled by a deep downdraft in the mid-lower troposphere, which contributes to reducing thethickness of the planetary boundary layer, obviously reducing the atmospheric capacity for pollutants.This atmospheric circulation and sinking motion provide favorable conditions for the formation andmaintenance of haze in North China.
基金supported by the National Key Basic Research and Development Project of China(Grant No.2012CB417201)the National Natural Science Foundation of China(Grant Nos.41375053 and 41505038)
文摘Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangtze River; and type B, whose precipitation is mainly located to the north of the river. The present study investigated these two PHRE types using a newly derived set of energy equations to show the scale interaction and main energy paths contributing to the persistence of the precipitation. The main results were as follows. The available potential energy （APE） and kinetic energy （KE） associated with both PHRE types generally increased upward in the troposphere, with the energy of the type-A PHREs stronger than that of the type-B PHREs （except for in the middle troposphere）. There were two main common and universal energy paths of the two PHRE types： （1） the baroclinic energy conversion from APE to KE was the dominant energy source for the evolution of large-scale background circulations; and （2） the downscaled energy cascade processes of KE and APE were vital for sustaining the eddy flow, which directly caused the PHREs. The significant differences between the two PHRE types mainly appeared in the lower troposphere, where the baroclinic energy conversion associated with the eddy flow in type-A PHREs was from KE to APE, which reduced the intensity of the precipitation-related eddy flow; whereas, the conversion in type-B PHREs was from APE to KE, which enhanced the eddy flow.
基金supported by the National Natural Science Foundation of China under Grant No.40575015
文摘Based on the National Oceanic and Atmospheric Administration （NOAA） daily satellite dataset of global outgoing longwave radiation （OLR） for the period of 1974-2004 and the NCEP-NCAR reanalysis for 1971- 2004, the linkage between persistent heavy rainfall （PHR） events in the vicinity of the Yangtze River valley and global OLR leading up to those events （with 1- to 3O-day lag） was investigated. The results reveal that there is a significant connection between the initiation of PHR events over the study area and anomalous convective activity over the tropical Indian Ocean, maritime continent, and tropical western Pacific Ocean. During the 30-day period prior to the onset of PHR events, the major significantly anomalous convective centers have an apparent dipole structure, always with enhanced convection in the west and suppressed convection in the east. This dipole structure continuously shifts eastward with time during the 30-day lead period. The influence of the anomalous convective activity over the tropical oceans on the initiation of PHR events over the study area is achieved via an interaction between tropical and extratropical latitudes. More specifically, anomalous convective activity weakens the Walker circulation cell over the tropical Indian Ocean first. This is followed by a weakening of the Indian summer monsoon background state and the excitation and dispersion of Rossby wave activity over Eurasia. Finally, a major modulation of the large scale background circulation occurs. As a result, the condition of a phase-lock among major large scale circulation features favoring PHR events is established over the study area.
基金jointly sponsored by the National Basic Research Program of China(973 Program)(Grant No.2013CB430202)the National Natural Science Foundation of China(Grant No.41401056)+1 种基金the China Meteorological Administration Special Public Welfare Research Fund(Grant No.GYHY201406001)the Research Innovation Program for College Graduates of Jiangsu Province(Grant No.KYLX15 0858)
文摘In this study, regional persistent haze events（RPHEs） in the Beijing–Tianjin–Hebei（BTH） region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–2013. The formation mechanisms of the severe RPHEs were investigated with focus on the atmospheric circulation and dynamic mechanisms. Results indicated that：（1） 49 RPHEs occurred during the past 34 years.（2） The severe RPHEs could be categorized into two types according to the large-scale circulation, i.e. the zonal westerly airflow（ZWA） type and the high-pressure ridge（HPR） type. When the ZWA-type RPHEs occurred, the BTH region was controlled by near zonal westerly airflow in the mid–upper troposphere.Southwesterly winds prevailed in the lower troposphere, and near-surface wind speeds were only 1–2 ms^-1. Warm and humid air originating from the northwestern Pacific was transported into the region, where the relative humidity was 70% to 80%, creating favorable moisture conditions. When the HPR-type RPHEs appeared, northwesterly airflow in the mid–upper troposphere controlled the region. Westerly winds prevailed in the lower troposphere and the moisture conditions were relatively weak.（3） Descending motion in the mid-lower troposphere caused by the above two circulation types provided a crucial dynamic mechanism for the formation of the two types of RPHEs. The descending motion contributed to a reduction in the height of the planetary boundary layer（PBL）, which generated an inversion in the lower troposphere. This inversion trapped the abundant pollution and moisture in the lower PBL, leading to high concentrations of pollutants.
基金supported by the National Key Technologies R&D Program of China (Grant No.2009BAC51B02)
文摘A pair of northeast-southwest-tilted mid-tropospheric ridges and troughs on the continental scale was observed to be the key circulation feature common among wintertime extensive and persistent low tempera-ture events (EPLTE) in China.During the persistence of such anomalous circulations,the split flow over the inner Asian continent and the influent flow over the southeast-ern coast of China correspond well to the expanded and amplified Siberian high with tightened sea level pressure gradients and hence,a strong,cold advection over south-eastern China.The western Pacific subtropical high tends to expand northward during the early stages of most EPLTEs.
基金supported by the National Key Technologies R&D Program of China (Grant No. 2009BAC51B02)
文摘The distinct precursory signals of countrywide extensive and persistent extreme cold events (CECs) were investigated and contrasted with those of countrywide cold wave events (CCWs). It is shown that most CECs were accompanied by a CCW in the initial stages. From the comparison between the CECs and the CCWs that were independent of any CEC, it is found that a south- west-northeast-oriented tilted ridge at 500 hPa was present around the Europe-Barents Sea regions approximately 10 days prior to the start of the CEC. Consistent with this feature, a high sea level pressure and strong cold air accumulation occurred over a broad extent of northern Eurasia one week prior to the start of the CEC. The tilted ridge and the strong cold air accumulation were the precursory signals that were absent for the CCW, and they provide important clues for the early prediction of whether a CCW event might evolve into a CEC.
基金This research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA23090101)National Natural Science Foundation of China(Grant No.41975056).
文摘Persistent heavy rainfall events(PHREs)over the Yangtze–Huaihe River Valley(YHRV)during 1981–2020 are classified into three types(type-A,type-B and type-C)according to pattern correlation.The characteristics of the synoptic systems for the PHREs and their possible development mechanisms are investigated.The anomalous cyclonic disturbance over the southern part of the YHRV during type-A events is primarily maintained and intensified by the propagation of Rossby wave energy originating from the northeast Atlantic in the mid–upper troposphere and the northward propagation of Rossby wave packets from the western Pacific in the mid–lower troposphere.The zonal propagation of Rossby wave packets and the northward propagation of Rossby wave packets during type-B events are more coherent than those for type-A events,which induces eastward propagation of stronger anomaly centers of geopotential height from the northeast Atlantic Ocean to the YHRV and a meridional anomaly in geopotential height over the Asian continent.Type-C events have“two ridges and one trough”in the high latitudes of the Eurasian continent,but the anomalous intensity of the western Pacific subtropical high(WPSH)and the trough of the YHRV region are weaker than those for type-A and type-B events.The composite synoptic circulation of four PHREs in 2020 is basically consistent with that of the corresponding PHRE type.The location of the South Asian high(SAH)in three of the PHREs in 2020 moves eastward as in the composite of the three types,but the position of the WPSH of the four PHREs is clearly westward and northward.Two water vapor conveyor belts and two cold air conveyor belts are tracked during the four PHREs in 2020,but the water vapor path from the western Pacific is not seen,which may be caused by the westward extension of the WPSH.
基金supported by the National Key R&D Program of China[grant number 2018YFC0809400]the National Natural Science Foundation of China[grant number 41975057].
文摘Based on hourly precipitation from national surface stations,persistent heavy rainfall events(PHREs)over the Sichuan Basin(SCB)are explored during the warm season(May to September)from 2000 to 2015 to compare synoptic circulations and maintenance mechanisms between different PHRE types.There are two main types of PHREs:one is characterized by a rain belt west of 106°E over the SCB(WSB-PHREs),and the other features a rain belt east of 106°E over the SCB(ESB-PHREs).In total,there are 18 ESB-PHREs and 10 WSB-PHREs during the study period.Overall,the rain belts of WSB-PHREs are along the terrain distribution east of the Tibetan Plateau,while the precipitation intensity of ESB-PHREs is stronger.For the two types of PHREs,the shortwave trough over the SCB and the western Pacific subtropical high act as their favorable background environments,particularly for ESB-PHREs.The water vapor of WSB-PHREs is mainly transported from the South China Sea,whereas for ESB-PHREs the South China Sea and Bay of Bengal are their main moisture sources.The composite vorticity budgets of southwest vortices during their mature stage indicate that the convergence effect is a dominant factor for maintaining the two types of PHREs,and the strong vertical vorticity advection is also favorable,but the relative contribution of vertical advection is larger for WSB-PHREs.
基金Project of Science Planning of Guangdong Province (2005B32601007)Natural Science Foundation of China (41075073,40675055)
文摘Variation characteristics of persistent drought events in Guangdong province are analyzed using 45-year(1961-2005) and 86-station observational precipitation data of Guangdong,and the causes of drought events are discussed from different angles(e.g.,atmospheric circulation,sea surface temperature) on the basis of global coverage datasets of sea surface temperature and atmospheric elements.It is found that the occurrence frequency of persistent drought events in Guangdong province is once every 26 months on average,and autumn-winter or winter-spring persistent drought events take up the majority.The persistent drought events possess large scale spatial characteristics.While the 1960s is the most frequent and strongest decade of drought events in the latter half of the 20th century,the occurrence is more frequent and the intensity is stronger in the first five years of the 21st century(2001-2005).This reflects the response of regional extreme climatic events in Guangdong to global climatic change.The atmospheric circulation,sea surface temperature,etc,appear to have different abnormal characteristics when drought events happen in different seasons.The results of this paper provide some good reference information for the drought forecast,especially for the dynamic interpretation of climatic model products.
基金Chinese National Key Technology R&D Program (2009BAC51B01)National Basic Research Program "973" of China (2012CB417403)+1 种基金Meteorological Science Foundation of Jiangsu Province (KM201207)‘333’Project of Jiangsu Province and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during persistent and intense rains in the Yangtze-Huaihe Rivers basin are studied. The results show that the position variation of WPSH is closely associated with the diabatic heating. There are strong apparent heating sources and moisture sinks in both the basin (to the north of WPSH) and the north of Bay of Bengal (to the west of WPSH) during persistent and intense rain events. In the basin, Q 1z begins to increase 3 days ahead of intense rainfall, maximizes 2 days later and then reduces gradually, but it changes little after precipitation ends, thus preventing the WPSH from moving northward. In the north of Bay of Bengal, 2 days ahead of strong rainfall over the basin, Q 1z starts to increase and peaks 1 day after the rain occurs, leading to the westward extension of WPSH. Afterwards, Q 1z begins declining and the WPSH makes its eastward retreat accordingly. Based on the complete vertical vorticity equation, in mid-troposphere, the vertical variation of heating in the basin is favorable to the increase of cyclonic vorticity north of WPSH, which counteracts the northward movement of WPSH and favors the persistence of rainbands over the basin. The vertical variation of heating in the north of Bay of Bengal is in favor of the increase of anti-cyclonic vorticity to the west of WPSH, which induces the westward extension of WPSH.
基金supported by the National Key Research and Development Program of China (Grant No. 2018YFC1505602)the National Natural Science Foundation of China (Grant No. 41705055)+2 种基金the Graduate Innovation Project of Jiangsu Province (Grant No. CXZZ11_0485)the Creative Teams of Jiangsu Qinglan Projectthe Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘We investigate the characteristics and mechanisms of persistent wet–cold events(PWCEs)with different types of coldair paths.Results show that the cumulative single-station frequency of the PWCEs in the western part of South China is higher than that in the eastern part.The pattern of single-station frequency of the PWCEs are“Yangtze River(YR)uniform”and“east–west inverse”.The YR uniform pattern is the dominant mode,so we focus on this pattern.The cold-air paths for PWCEs of the YR uniform pattern are divided into three types—namely,the west,northwest and north types—among which the west type accounts for the largest proportion.The differences in atmospheric circulation of the PWCEs under the three types of paths are obvious.The thermal inversion layer in the lower troposphere is favorable for precipitation during the PWCEs.The positive water vapor budget for the three types of PWCEs mainly appears at the southern boundary.
基金supported by the National Natural Science Foundation of China[grant number 42088101]the National Postdoctoral Program for Innovative Talent of China[grant number BX2021133]the China Postdoctoral Science Foundation of No.70 General Fund[grant number 2021M701753]。
文摘This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased occurrence probabilities of PECEs over Northeast China are observed in phases 3 and 5 of the MJO,when MJOrelated convection is located over the eastern Indian Ocean and the western Pacific,respectively.Using the temperature tendency equation,it is found that the physical processes resulting in the cooling effects required for the occurrence of PECEs are distinct in the two phases of the MJO when MJO-related convection is consistently located over the warm pool area.The PECEs in phase 3 of the MJO mainly occur as a result of adiabatic cooling associated with ascending motion of the low-pressure anomaly over Northeast Asia.The cooling effect associated with phase 5 is stronger and longer than that in phase 3.The PECEs associated with phase 5 of the MJO are linked with the northwesterly cold advection of a cyclonic anomaly,which is part of the subtropical Rossby wave train induced by MJO-related convection in the tropical western Pacific.
基金National Natural Science Foundation of China(42088101)。
文摘Based on daily precipitation data supplied by the Chinese meteorological administration,hourly reanalysis datasets provided by the ECMWF and daily outgoing long wave radiation supplied by the NOAA,the evolution regularity of continuous heavy precipitation over Southern China(SC)from April to June in 1979-2020 was systematically analyzed.The interaction between specific humidity and circulation field at the background-scale,the intra-seasonal-scale and the synoptic-scale,and its influence on persistent heavy precipitation over the SC during the April-June rainy season were quantitatively diagnosed and analyzed.The results are as follows.Persistent heavy rainfall events(PHREs)over the SC during the April-June rainy season occur frequently from mid-May to mid-and late-June,exhibiting significant intra-seasonal oscillation(10-30-day)features.Vertically integrated moisture flux convergence(VIMFC)can well represent the variation of the PHREs.A multiscale quantitative diagnosis of the VIMFC shows that the pre-summer PHREs over the SC are mainly affected by the background water vapor(greater than 30 days),intraseasonal circulation disturbance(10-30-day)and background circulation(greater than 30 days),and water vapor convergences are the main factor.The SC is under the control of a warm and humid background and a strong intraseasonal cyclonic circulation,with strong convergence and ascending movements and abundant water vapor conditions during the period of the PHREs.Meanwhile,the westward inter-seasonal oscillation of tropical atmosphere keeps the precipitation system over the SC for several consecutive days,eventually leading to the occurrence,development and persistence of heavy precipitation.
文摘Introduction: The incidence of acute pain after craniotomy differs remarkably in previous studies, and the prevalence of persistent pain is not precisely known. We conducted 6-month follow-up surveys on the incidence and intensity of acute and persistent pain after elective craniotomy. Methods: We carried out a prospective cohort study via a series of structured questionnaires to record acute pain intensity preoperatively and postoperatively, and the incidence of persistent pain 3 and 6 months after a craniotomy in a tertiary care center. Patients scheduled for elective craniotomy were interviewed the day before surgery, postoperatively before discharge from the hospital, and 3 and 6 months after surgery. Pain was assessed on a numeric rating scale (0 - 10) at rest and movement, as well as expectations of pain before surgery, efficacy of pain therapy, and satisfaction with pain treatment. The incidence of adverse events, sleep time and interruptions caused by pain, different pain types, and drugs used for pain treatment were also recorded. Results: A total of 152 patients were enrolled in the study and completed the preoperative questionnaire;123 (81%) completed postoperative questionnaire and 108 (72%) completed the 3- and 6-month follow-ups. The average pain score at the time of the postoperative questionnaire was moderate, 4 at rest and 5 upon movement. The percentage of patients experiencing mild pain at rest and upon movement was 52% and 49%, and moderate pain was 15% and 16%, respectively. Severe postoperative pain was detected in 5% and 8% of patients at rest and upon movement, respectively. Three months after surgery, 6% of patients reported mild pain at rest, 3% moderate pain at rest, and 1% severe pain at rest. Persistent mild and moderate pain at rest after 6 months was reported by 3% and 1% of patients, respectively. The most common adverse events were postoperative nausea and vomiting (11%) and abdominal discomfort (8%). During postoperative pain treatment in the intensive care unit or post-anesthesia care unit, 92% of patients received acetaminophen, 88% fentanyl, and 24% oxycodone. During neurosurgical ward care, ibuprofen was used in 61% of patients. Satisfaction with analgesia was high throughout the study period with a median satisfaction score of 9 postoperatively and 10 at 3 and 6 months on the 0 - 10 scale. Conclusion: The findings indicate that most patients experience moderate or mild pain after craniotomy, but patient satisfaction with pain treatment is high. Persistent pain after 3 and 6 months is rare and mild in nature.
基金Supported by the National Key Research and Development Program of China (2018YFC1505602)National Natural Science Foundation of China (41705055)+2 种基金Graduate Innovation Project of Jiangsu Province (CXZZ11_0485)Innovation Teams of Jiangsu Qinglan ProjectPriority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘In February 2022,a persistent low-temperature rain and snow event(LRSE)occurred in the central Pan-Pearl River Delta(CPPRD)region of southern China,causing severe damage and economic losses.During the LRSE,both the temperature and precipitation fields exhibited quasi-biweekly oscillation(QBWO)signals over the CPPRD region.Circulation analysis revealed that the eastward propagation of Rossby waves at mid–high latitudes enhanced the Baikal blocking high and the Mongolian high,facilitating the continuous southward migration of cold air.The strengthening India–Burma trough(i.e.,the southern branch trough)brought abundant warm and humid airflow,converging with cold air from the north in the CPPRD region.Moreover,deep convective activity originating in the northern Indian Ocean became exceptionally active,propagating to southern China and providing dynamic lifting conditions for precipitation in the study region.The combined effects of tropical and extratropical weather systems resulted in the LRSE occurrence.Partial lateral forcing(PLF)experiments were performed to quantify the contributions of the QBWO signals from different boundaries of the region.The extratropical QBWO signal from the northern boundary led to a temperature decrease of 1.61℃,with 77.83%of the whole region experiencing cooling greater than 1℃,whereas the tropical QBWO signal from the southwestern boundary caused an increase in precipitation of 13.1 mm day^(−1),with more than 40%of the entire region experiencing a precipitation increase of over 5 mm day^(−1).This study provides quantitative evidence that the QBWO was a key factor contributing to the occurrence of the LRSE,which can be used as a precursor signal for extended-range forecasts of future LRSEs.
文摘华南前汛期降水量大,且常出现持续3天以上、甚至长达10天以上的持续性强降水事件(Persistent Heavy Rainfall Event,PHRE),给该地区带来严重的洪涝灾害,提升前汛期降水的延伸期(提前10~30天或2~6候)预报水平至关重要。重点论述华南降水延伸期预报可预报性的来源,以及当前数值模式、动力-统计释用和机器学习在延伸期预报领域的应用情况,以期了解华南前汛期降水延伸期预报的主要进展。
