THE RELATIONSHIP BETWEEN THE ATMOSPHERIC HEATING SOURCE/SINK ANOMALIES OF ASIAN MONSOON AND FLOOD/DROUGHT IN THE YANGTZE RIVER BASIN IN THE MEIYU PERIOD

NCEP/NCAR reanalysis data and a 30-year precipitation dataset of observed daily rainfall from 109 gauge stations are utilized in this paper. Using the REOF we analyzed the spatial distribution of precipitation in the 109 stations in the Yangtze River Basin in Meiyu periods from 1978 to 2007. The result showed that the spatial distribution of precipitation in the Yangtze River Basin can be divided into the south and north part. As a result, relationships between an atmospheric heating source (hereafter called ) over the Asian region and the precipitation on the south and north side of Yangtze River in Meiyu periods were separately studied in this paper. The results are shown as follows. The flood/drought to the north of Yangtze River (NYR) was mainly related to the over the East Asia summer monsoon region: when the over the Philippines through Western Pacific and the south China was weakened (strengthened), it would probably result in the flood (drought) in NYR; and the precipitation on the south side of Yangtze River (SYR) was related to the over the east Asia and Indian summer monsoon region: when the over the areas from south China to the northern East China Sea and Yellow Sea and south-eastern Japan was strengthened (weakened), and the over the areas from the Bay of Bengal to south-eastern Tibetan Plateau was weakened (strengthened), it will lead to flood (drought) in SYR.     

Contrasts of Atmospheric Circulation and Associated Tropical Convection between Huaihe River Valley and Yangtze River Valley Mei-yu Flooding

The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu(i.e.,the East Asian rainy season in June) and the related tropical convection were investigated.During the both flooding cases,although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere,the phase of the Rossby wave train is different over Eurasian continent.During flooding in the Huaihe River valley,only one single blocking anticyclone is located over Baikal Lake.In contrast,during flooding in the Yangtze River valley,there are two blocking anticyclones.One is over the Ural Mountains and the other is over Northeast Asia.In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific(SAWP) in both flooding cases,but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding.Furthermore,abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula.However,the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific.Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation;and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation.While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south,along with abundant rainfall.     

RELATIONSHIPS BETWEEN SPRING KUROSHIO SSTA AND SUMMER RAINFALL IN CHINA

Based on the data of SST and NCEP/NCAR reanalysis data, the relationship is analyzed of spring SSTA in the Kuroshio region with summer precipitation in China, summer 500 hPa field and water vapor transport, using the methods of Morlet wave, correlation and composite analysis. The results show that annual and interdecadal change of spring SST in the Kuroshio region is distinct. Spring SST displays a significantly increasing trend and there exist different periodic oscillations in the Kuroshio region, with the 23-year periodic oscillation being the most obvious. Troughs and ridges in the mid- and higher- latitudes turn deeper in high Kuroshio SSTA years. At the same time, the western Pacific subtropical high strengthens and stretches westwards. As a result, the warm / wet air from the west of the subtropical high locates in the mid- and lower- reaches of the Yangtze River and south China and summer rainfall in the above regions increases accordingly. Composite anomalous water vapor flux fields indicate that the vapor transport from the South China Sea and western Pacific and the vapor from the north converge over the mid- and lower- reaches of the Yangtze River and south China, which results in the increase of the summer rainfall in the mid- and lower- reaches of the Yangtze River and south China. On the contrary, the summer rainfall in the mid- and lower- reaches of the Yangtze River and south China decreases correspondingly in low Kuroshio SSTA years.     

Relationship between winter snow cover days in Northeast China and rainfall near the Yangtze River basin in the following summer

Based on observed snow and precipitation data and NCEP/NCAR reanalysis data,the relationship between the number of winter snow cover days in Northeast China and the following summer’s rainfall in the northern part of southern China is analyzed and the possible underlying mechanisms are discussed.The results indicate that a negative relationship is significant throughout the study period,especially more obvious after the 1980s.The pre-winter circulation patterns in years with more snow cover days and less summer rainfall in the south bank of the Yangtze River are almost the same.In years with more snow cover days,lower temperatures at the lower level over Northeast China are found in winter and spring.The winter monsoon is weaker and retreats later in these years than in those with fewer snow cover days.In spring of years with more snow cover days,anomalous cyclonic circulation is observed over Northeast China,and anomalous northerly wind is found in eastern China.In summer of these years,anomalous northeasterly wind at the lower level is found from the area south of the Yangtze River to the East China Sea and Yellow Sea;and with less southwesterly water vapor transport,the rainfall in the area south of the Yangtze River is less than normal,and the opposite patterns are true in years with fewer snow cover days.In recent years,the stable relationship between winter snow cover in Northeast China and summer rainfall in the Yangtze River basin can be used for summer rainfall prediction.The results are of great importance to short-term climate prediction for summer rainfall.     

A study on response of precipitation in china to monsoon intraseasonal oscillation北大核心CSCD

Temporal and spatial evolution characteristics of the 30-60 day oscillation (intraseasonal oscillation, ISO) of summer rainfall in China and the effects of East Asian monsoon on the rainfall ISO are analyzed in this paper. Results show that the annual and decadal variations of the oscillation exist between 1960 and 2008, and the intensity is weakest in the late 1970s and early 1980s. In the typical strong years of the rainfall ISO obtained from empirical orthogonal functions (EOF mode 1), an anticyclone is in northwestern Pacific and a cyclone is in the east of China. In the typical weak years, the wind ISO is much weaker. The low-frequency zonal wind and water vapor transport from the low latitudes to mid-latitudes in the typical strong years, and the oscillation strength of diabatic heating is much stronger than that in the weak years of the rainfall ISO. The anomaly characteristics of the rainfall ISO show anti-phases between the Yangtze River basin and south of China. As for the typical strong years of the rainfall ISO in the Yangtze River basin (EOF mode 2), the main oscillation center of water vapor is in the east of China (20-30°N, 110-130°E). In the peak (break) phase of the rainfall oscillation, a low-frequency cyclone (anticyclone) is in the Yangtze River basin and an anticyclone (cyclone) is near Taiwan Island. In addition, the peak rainfall corresponds to the heat source in the Yangtze River basin and the heat sink in the Qinghai-Tibet Plateau. As for the typical strong years of the rainfall ISO in the south of China, the main oscillation center of water vapor is south of 20°N. In the peak (break) phase of the rainfall ISO, a low-frequency cyclone (anticyclone) is in the south of China and an anticyclone (cyclone) is in the Philippines. The peak rainfall corresponds to the heat source in the south of China and the South China Sea, and the heat sink in the west of Indochina.     

A STUDY ON RESPONSE OF PRECIPITATION IN CHINA TO MONSOON INTRASEASONAL OSCILLATION

Temporal and spatial evolution characteristics of the 30-60 day oscillation (intraseasonal oscillation, ISO) of summer rainfall in China and the effects of East Asian monsoon on the rainfall ISO are analyzed in this paper. Results show that the annual and decadal variations of the oscillation exist between 1960 and 2008, and the intensity is weakest in the late 1970s and early 1980s. In the typical strong years of the rainfall ISO obtained from empirical orthogonal functions (EOF mode 1), an anticyclone is in northwestern Pacific and a cyclone is in the east of China. In the typical weak years, the wind ISO is much weaker. The low-frequency zonal wind and water vapor transport from the low latitudes to mid-latitudes in the typical strong years, and the oscillation strength of diabatic heating is much stronger than that in the weak years of the rainfall ISO. The anomaly characteristics of the rainfall ISO show anti-phases between the Yangtze River basin and south of China. As for the typical strong years of the rainfall ISO in the Yangtze River basin (EOF mode 2), the main oscillation center of water vapor is in the east of China (20-30°N, 110-130°E). In the peak (break) phase of the rainfall oscillation, a low-frequency cyclone (anticyclone) is in the Yangtze River basin and an anticyclone (cyclone) is near Taiwan Island. In addition, the peak rainfall corresponds to the heat source in the Yangtze River basin and the heat sink in the Qinghai-Tibet Plateau. As for the typical strong years of the rainfall ISO in the south of China, the main oscillation center of water vapor is south of 20°N. In the peak (break) phase of the rainfall ISO, a low-frequency cyclone (anticyclone) is in the south of China and an anticyclone (cyclone) is in the Philippines. The peak rainfall corresponds to the heat source in the south of China and the South China Sea, and the heat sink in the west of Indochina.     

Interdecadal Change of the Relationship Between the Tropical Indian Ocean Dipole Mode and the Summer Climate Anomaly in China

The interdecadal change of the relationship between the tropical Indian Ocean dipole(IOD) mode and the summer climate anomaly in China is investigated by using monthly precipitation and temperature records at 210 stations in China and the NCEP/NCAR reanalysis data for 1957-2005.The results indicate that along with the interdecadal shift in the large-scale general circulation around the late 1970s,the relationship between the IOD mode and the summer climate anomaly in some regions of China has significantly changed.Before the late 1970s,a developing IOD event is associated with an enhanced East Asian summer monsoon,which tends to decrease summer precipitation and increase summer temperature in South China;while after the late 1970s,it is associated with a weakened East Asian summer monsoon,which tends to increase(decrease) precipitation and decrease(increase) temperature in the south(north) of the Yangtze River.During the next summer,following a positive IOD event,precipitation is increased in most of China before the late 1970s,while it is decreased(increased) south(north) of the Yangtze River after the late 1970s.There is no significant correlation between the IOD and surface air temperature anomaly in most of China in the next summer before the late 1970s;however,the IOD tends to increase the next summer temperature south of the Yellow River after the late 1970s.     

The Impact of Atmospheric Heat Sources over the Eastern Tibetan Plateau and the Tropical Western Pacific on the Summer Rainfall over the Yangtze-River Basin

The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter （namely, mode station variance percentage） based on 1951-2000 summer rainfall data from 160 stations in China. Compared with mode variance friction, the mode station variance percentage not only reveals more localized characteristics of the variability of the summer rainfall, but also helps to distinguish the regions with a high degree of dominant EOF modes representing the analyzed observational variable. The atmospheric circulation diagnostic studies with the NCEP/NCAR reanalysis daily data from 1966 to 2000 show that in summer, abundant （scarce） rainfall in the belt-area from the upper-middle reaches of the Yangtze River northeastward to the Huaihe River basin is linked to strong （weak） heat sources over the eastern Tibetan Plateau, while the abundant （scarce） rainfall in the area to the south of the middle-lower reaches of the Yangtze River is closely linked to the weak （strong） heat sources over the tropical western Pacific.     

冬季热带太平洋海温异常模态和次年夏季我国降水异常季节内变化的关系

In present study,EOF analysis and extended singular value decomposition (ESVD) analysis are performed to explore the relationship between the winter tropical sea surface temperature anomalies (SSTAs) in the Pacific and the following summer rainfall anomalies in China.The two leading modes of winter tropical SSTAs in the Pacific are the SSTAs pattern characterized by "positive anomalies in the East and negative anomalies in the West" like the typical eastern Pacific El Nio and negative anomalies in the West and the central Pacific warming pattern characterized by "positive anomalies in the central region but negative anomalies in the East and West".The intraseasonal variations of the rainfall anomalies during the following summer in China that are associated with the eastern Pacific warming mode are characterized by positive anomalies south of the Yangtze River and negative anomalies in the Yangtze-Huai River Valley in June,and negative anomalies in South China and positive anomalies in the Yangtze River Valley and North China in July and August.In contrast,after the central Pacific warming mode,the corresponding intraseasonal variations of China’s summer rainfall are characterized by a nearly consistent pattern during the three summer months,which is positive in the South China coast and North China and negative in the Yangtze River Valley except for the positive anomalies in the Yangtze-Huai River Valley in July.These results may provide a reference for the seasonal prediction of the summer drought and flood distributions in China.     

Projection of Future Precipitation Extremes Change (2001-2050) in the Yangtze River Basin

 Daily maximum rainfall (R1D) was higher in the Jialing River basin, the Taihu Lake area and the mid-lower main stream section of the Yangtze River basin in the 1990s, and there was a good relationship between ECHAM5/MPI-OM model simulation and the observed data about extreme precipitation (R1D). Under the IPCC SRES A2, A1B, and B1 scenarios, R1Ds are all projected to be in increasing trends in the upper Yangtze River basin during 2001-2050, and R1D shows a more significant increasing tendency under the A2 scenario when compared with the A1B scenario before 2020. With respect to the middle and lower Yangtze River basin, an increasing tendency is projected before 2025, and since then the increasing tendency will become insignificant. There might be more floods to the south of the Yangtze River and more droughts to the north in the next decades.     

Changes in the Diurnal Cycles of Precipitation over Eastern China in the Past 40 Years

This study analyzed the interdecadal changes in the diurnal variability of summer(June-August) precipitation over eastern China during the period 1966-2005 using hourly station rain gauge data.The results revealed that rainfall diurnal variations experienced significant interdecadal changes.Over the area to the south of the Yangtze River,as well as the area between the Yangtze and Yellow Rivers,the percentages of morning rainfall(0000-1200 LST) to total rainfall in terms of amount,frequency and intensity,all exhibited increasing interdecadal trends.On the contrary,over North China,decreasing trends were found.As a result,diurnal rainfall peaks also presented pronounced interdecadal variations.Over the area between the Yangtze and Yellow Rivers,there were 16 out of 46 stations with afternoon(1200-0000 LST) frequency peaks in the first 20 years of the 40-year period of study,while only eight remained in the latter 20 years.In North China,seven stations experienced the opposite changes,which accounted for about 21% of the total number of stations.The possible causes for the interdecadal changes in diurnal features were discussed.As the rainfall in the active monsoon period presents morning diurnal peaks,with afternoon peaks in the break period,the decrease(increase) of rainfall in the active monsoon period over North China(the area south of the Yangtze River and the area between the Yangtze and Yellow Rivers) may contribute to interdecadal changes in diurnal rainfall variability.     

ANALYSIS OF THE CHARACTERISTICS OF SUSTAINED TORRENTIAL RAINS IN JUNES DURING 1958-2000

Day-to-day precipitation data of Junes during the 43 years of 1958-2000 from stations to the south of Yangtze River are used to divide regions and run statistical analysis of sustained torrential rainfall processes. A preliminary analysis is then made based on it and the results show that June is the month in which torrential rains in the southern half of China take place frequently and sustained torrential rains occur at the same time in South China and the area to the south of Yangtze River. In addition, the analysis gives the basic features of sustained torrential rains of June in China and their interannual variability patterns, with the suggestion that the amount of these events increases significantly after the 1990s. Lastly, the sustained torrential rains occurring in Junes of 1994, 1998 and 2005 in the southern half of China are taken as examples in the research on the basic patterns and formation mechanisms of the evolution of double rain-bands during the rain season in South China and the area to the south of Yangtze River. The analysis shows that the large scale environment field in which sustained torrential rains occur is related to the stable sustaining of the South Asia High and upper level jet streams.     

Numerical Simulation of Regional Climate Change under IPCC A2 Scenario in China

Regional climate change in China under the IPCC A2 Scenario, was simulated for continuous 10-yr period by the MM5V3, using the output of an IPCC A2 run from CISRO Mark 3 climate system model as lateral and surface boundary conditions. The regional climate change of surface air temperature, precipitation, and circulation were analyzed. The results showed that （1） the distribution of mean circulation, surface air temperature, and precipitation was reproduced by the MM5V3. The regional climate model was capable to improve the regional climate simulation driven by GCM. （2） The climate change simulation under the IPCC A2 Scenario indicated that the surface air temperature in China would increase in the future, with a stronger trend in winter and the increasing magnitude from the south to the north. The precipitation distribution would appear a distinct change as well. Annual mean precipitation would remarkably increase in Northeast China, Yangtze and Huaihe River Valley, and the south area of the valley. Meanwhile, rainfall would show a decreasing trend in partial areas of North China, and many regions of Southwest and Northwest China.     

Main Energy Paths and Energy Cascade Processes of the Two Types of Persistent Heavy Rainfall Events over the Yangtze River–Huaihe River Basin

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.     

THE EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX AND ITS RELATION WITH THE CLIMATE ANOMALIES IN CHINA

A new East Asian subtropical summer monsoon circulation index is defined, where the barotropic and baroclinic components of circulation are included. Results show that this index can well indicate the interannual variability of summer precipitation and temperature anomalies in China. A strong monsoon is characterized by more rainfall in the Yellow River basin and northern China, less rainfall in the Yangtze River basin, and more rainfall in south and southeast China, in association with higher temperature in most areas of China. Furthermore, comparison is made between the index proposed in this paper and other monsoon indexes in representing climate anomalies in China.     

DECADAL VARIABILITY OF SUBSURFACE OCEAN TEMPERATURE ANOMALY IN TROPICAL PACIFIC AND ITS IMPACT ON CLIMATE OF CHINA

In this study,we investigate the decadal variability of subsurface ocean temperature anomaly(SOTA)in the tropical Pacific and associated anomalous atmospheric circulation over Asia-North Pacific-North America by analyzing 50 years of atmosphere-ocean data from the National Center for Environmental Prediction(NCEP)reanalysis project and Simple Ocean Data Assimilation(SODA).Relationship between the ENSO-Like variability and climate of China is also revealed.The results show that the decadal variability of tropical Pacific SOTA has two dominant ENSO-like modes:the primary mode is an ENSO-Like mature phase pattern,and the second mode is associated with the ENSO-like transition(developing or decaying)phase.These two modes consist of a cycle of ENSO-Like variability,which exhibits a quasi-40a fluctuation,superimposed with an oscillation of a 13a period.The ENSO-Like variability in the tropical Pacific influences the atmosphere system at the mid-and higher-latitudes and subtropical regions,resulting in decadal variability of south wind over North China,the East Asian monsoon and climate of China.During the mature phase of El Ni o-Like variability,the anomalous north wind prevails over the north part of China and the East Asian monsoon weakens,with little rain in North China but much rain in the middle-and lower-reaches of the Yangtze River.With El Ni o-Like decaying(La Ni a-Like developing),anomalous northerly wind also prevails over North China,then the East Asian monsoon weakens with drought occurring in North China.The situation during the La Ni a-Like variability is the opposite.The pattern of anomalous climate of China is primarily dominated by the first ENSO-like variability,while the second mode can modulate the contribution of the first one,depending on whether its phase agrees with that of the first mode.The climate shift in China around 1978 and successive occurrence of drought for more than 20 years in North China are primarily induced by the first two ENSO-like variabilities.The latest La Ni a-Like phase starts from 1998 and will presumably end around 2018.It is expected that more rainfall would be in North China and less rainfall would appear in the middle-and lower-reaches of the Yangtze River valley during this period.     

NUMERICAL SIMULATIONS OF EXTREME PRECIPITATION IN EASTERN CHINA UNDER A1B SCENARIO

The regional climate model （RegCM3）, developed by the Abdus Salam International Centre for Theoretical Physics and nested in one-way mode within the latest version of Community Climate System Model from the National Center for Atmospheric Research, is used to conduct a set of experiments to examine its capability of climate simulation for the past 50 years and to explore possible changes in extreme precipitation （EP） in the next 100 years under the A1B scenario. Compared with the observation from the Climate Research Unit at the University of East Anglia and CPC Merged Analysis of Precipitation, RegCM3 reasonably reproduces the spatiotemporal distributions of precipitation and EP in eastern China. Based on the present-day analysis, this study examines the changes in monsoonal precipitation over eastern China in mid- and late-21st century relative to the reference period of 1970-1999. It is found that the precipitation will increase over the middle and lower reaches of the Yangtze River and areas to its north, and decrease over coastal areas to its south, especially in late-21st century. The various indices reflecting extreme events showed that the EP will enhance 10%-15% over the middle and lower reaches of the Yangtze River and areas to its north, and weaken over the areas to its south. The summer monsoon will strengthen and shift northwards under SERS A1B, bringing more water vapor and energy from the Indian Ocean and South China Sea for precipitation and eventually more precipitation over northern China.     

近千年中国东部夏季雨带位置的变化

Based on the variations of geographical locations, the summer rain belts over eastern China were classified in this study into eight types: Inner Mongolia, North China, the Yellow River, the Huaihe River, the Yangtze River, the northern and southern parts of Jiangnan ( to the south of the lower Yangtze River valley), and South China. The file of 8-type rain belts was compiled from 1470 to 2005, and in order to extend the file of rain belts, it was further merged into a file of 4-type rain belts and also completed during the last millennium from 1000 to 1999. At last, the two files show that summer rain belts frequently occur in the Yangtze River valley in warm climate periods, but in the Yellow River or the Huaihe River valley in cold periods.     

Analysis of Simulated Heavy Rain over the Yangtze River Valley During 11-30 June 1998 Using RIEMS

RIEMS‘ ability to simulate extreme monsoon rainfall is examined using the 18-month (April 1997 September 1998) integrated results. Model-simulated heavy precipitation over the Yangtze River valley during 11-30 June 1998 is compared with the observation, and the relationships between this heavy rainfall process and the large-scale circulations, such as the westerly jet, low-level jet, and water vapor transport,are analyzed to further understand the mechanisms for simulating heavy monsoon rainfall. The analysis results show that (1) RIEMS can reproduce the pattern of heavy precipitation over the Yangtze River valley during 11-30 June 1998, but it is shifted northwestwards. (2) The simulated West Pacific Subtropical High (WPSH) that controls the East Asia Monsoon evolution is stronger than the observation and is extended westwards, which possibly leads to the north westward shift of the heavy rain belt. (3) The Westerly jet at 200 hPa and the Low-level jet at 850 hPa, both of which are related to the heavy monsoon rainfall,are reasonably reproduced by RIEMS during 11-30 June 1998~ although the intensities of the simulated Westerly/Low-level jets are strong and the location of the Westerly jet leans to the southeast,which may be the causes of RIEMS producing too much heavy rainfall in the north of the Yangtze River valley.     

A Simulation Study of a Heavy Rainfall Process over the Yangtze River Valley Using the Two-Way Nesting Approach

In this study,the major features of a heavy rainfall event in the Yangtze River region on 3-7 June 2011 and its event-related large-scale circulation and predictability were studied.Both observational analysis and model simulation were used,the latter being based on the Weather Research and Forecasting(WRF) model forced by NCEP Global Forecast System(GFS) datasets.It was found that,during 3-5 June,the western Pacific subtropical high apparently extended to the west and was much stronger,and the Indian summer monsoon trough was slightly weaker than in normal years.The east-west oriented shear line over the middle and lower reaches of the Yangtze River was favorable for the transportation and convergence of water vapor,and the precipitation band was located slightly to the south of the shear line.During 6-7 June,the western Pacific subtropical high retreated eastward,while the trough over the Okhotsk Sea deepened.The low vortex in Northeast China intensified,bringing much more cold air to the middle and lower reaches of the Yangtze River,and the shear line over this area moved slightly southward.The convection band moved southward and became weaker,so the rainfall during 6-7 June weakened and was located slightly to the south of the previous precipitation band.Many of the observed features,including background circulation and the distribution and amount of precipitation,were reproduced reasonably by the WRF,suggesting a feasibility of this model for forecasting extreme weather events in the Yangtze River region.