By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the E...By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought / flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For example, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.展开更多
In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study i...In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study is made of the high's influence on Asian summer monsoon circulation and dryness / wetness of eastern China based on case contrast andcontrol experiments. Rusults show that as an excitation source, the blocking high produces a SE-NW stationarywavetrain with its upper-air atnicyclonic divergent circulation oust over a lower-level trough zone) precisely over themiddle to lower reaches of the Changjiang River, enhancing East Asian westerly jet, a situation that contributes toPerturbation growth, causing an additional secondary meridional circulation at the jet entrance, which intensifies theupdraft in the monsoon area. As such, the high's presence and its excited steady wavetrain represent the large-scalekey factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in the easternpart of the land.展开更多
The features of water vapor transport, such as temporal evolution, vertical structure and spatial pattern, over North China during the prolonged drought in the summer of 1980 have been analyzed through computation of ...The features of water vapor transport, such as temporal evolution, vertical structure and spatial pattern, over North China during the prolonged drought in the summer of 1980 have been analyzed through computation of water vapor flux based on the once daily ECMWF grid-point data at 12GMT. The results indicate that it is unlikely that the characteristics of the atmospheric mass divergence, ascending motion and stratification stability in North China were completely opposite to those in the Yangtze River Valley, where the heavy flood occurred in the summer of 1980. It is major differences that the strong ascending motion and significant water vapor convergence overlap fairly well each other in the vertical levels in the Yangtze River Valley, while the maximum ascending motion is accompanied by water vapor divergence or weak water vapor convergence in North China. This vertical structure in North China results in insufficient water vapor supply and, therefore, little condensation and precipitation in the middle and upper atmosphere were produced. Additionally, a mode of monthly-scale low frequency oscillation can be found in water vapor flux, which is in correspondence to the fluctuation period of rainfall.展开更多
By applying rotated complex empirical orthogonal function (RCEOF) analysis on 1880-1999 summer rainfall at 28 selected stations over the east part of China, the spatio-temporal variations of China summer rainfall are ...By applying rotated complex empirical orthogonal function (RCEOF) analysis on 1880-1999 summer rainfall at 28 selected stations over the east part of China, the spatio-temporal variations of China summer rainfall are investigated. Six divisions are identified, showing strong temporal variability, the middle and lower reaches of the Yangtze River, the Huaihe River, Southeast China, North China, Southwest China, and Northeast China. The locations of all divisions except Southwest China are in a good agreement with those of the rainband which moves northward from Southeast China to Northeast China from June-August. The phase relationship revealed by the RCEOF analysis suggests that rainfall anomalies in the middle and lower reaches of the Yangtze River, Southeast China, and Northeast China are all characterized by a stationary wave, while a traveling wave is more pronounced in the Huaihe River division, North China, and Southwest China. The fourth RCEOF mode indicates that rainfall anomalies can propagate from south of Northeast China across lower reaches of the Huanghe River and the Huaihe River to the lower reaches of the Yangtze River. A 20-25-year oscillation is found at the middle and lower reaches of the Yangtze River, the Huaihe River valley, North China, and Northeast China. The middle and lower reaches of the Yangtze River and Northeast China also show an approximately-60-year oscillation. Northeast China and the Huaihe River division are dominated by a 36-year and a 70-80-year oscillation, respectively. An 11-year oscillation is also evident in North China, with a periodicity similar to sunspot activity. The interdecadal variability in the middle and lower reaches of the Yangtze River, the Huaihe River valley, and North China shows a significant positive correlation with the solar activity.展开更多
Vast convective activities over tropical zones are analyzed for both wet and dry summers in North China. An ITCZ synthesis index is designed using OLR data. The index can demonstrate quite clearly and objectively the ...Vast convective activities over tropical zones are analyzed for both wet and dry summers in North China. An ITCZ synthesis index is designed using OLR data. The index can demonstrate quite clearly and objectively the seasonal features of deep convection in Asia monsoon areas. The differences of ITCZ activities in Indian as well as East Asian monsoon regions in winter-spring period are significant and so is the time-lagged correlation, which would be able to provide a new way to the long-lead prediction of summer rain in North China. The propagation characters of low frequency fluctuation are also different between wet and dry years. The intensity of low frequency fluctuation is stronger and the area is larger in wet years than that in dry years in both hemispheres, The fluctuation moves from south to north successively in wet years, which may lead to the leap of the subtropical high northwards, while it remains quasi-stationary in the Southern Hemisphere or the equatorial zone in dry years.展开更多
Proposed are a set of new regional flood/drought indices and a scheme of grading their severity whereby 1951-2000 summer wet/dry events are investigated for North China (NC) in terms of 160 station monthly precipitati...Proposed are a set of new regional flood/drought indices and a scheme of grading their severity whereby 1951-2000 summer wet/dry events are investigated for North China (NC) in terms of 160 station monthly precipitation data from NCC (China National Center of Climate).Results suggest that 7 heavy droughts during 1951-2000 are 1965,1968,1972,1980,1983,1997 and 1999,while 6 heavy floods are 1954,1956,1959,1964,1973 and 1996. Based on 1951-2000 summer flood/drought severity graded by the new scheme,atmospheric circulation characteristics associated with the disasters over the NC are addressed in terms of monthly NCEP (National Centers for Environmental Prediction) reanalysis of geopotential heights,winds,surface temperature and PW (precipitable water).Evidences suggest that prominent anomalies benefiting to the heavy droughts occur over the Northern Hemisphere.The variations over middle-high latitudes especially the negative ones on Ural Mountain to western Siberia deepen the normal trough there and are indicative of stronger than normal cold air activity. At middle latitudes,remarkable positive anomalies present on the south to Baikal lead to the fact that the normal ridge shifts eastward over NC concomitant with anomaly sinking motion in the whole troposphere,which is helpful for the maintenance of the continent high.And the opposed ones over Korea and Japan force the trough moving eastward running against northwestward shifting of the western Pacific subtropical high.In addition,the anomaly west-east pressure gradient at middle latitudes profits northerly flow there.The southerly monsoon flow at low levels is weaker than normal with weak East Asian summer monsoon,and the related water vapor transportation is also weak with deficit PW over NC.Besides,sea surface temperature (SST) rises in the equatorial eastern and central Pacific and associated convective region moves to the east accordingly companied with weak Walker circulation in the droughts.And the opposed situations will occur during the floods.展开更多
[Objective] The aim was to study the relation among summer rainfall in south Shandong and high pressure in South Asia and atmospheric circulation.[Method] Taking the precipitation in south Shandong along the Yellow Ri...[Objective] The aim was to study the relation among summer rainfall in south Shandong and high pressure in South Asia and atmospheric circulation.[Method] Taking the precipitation in south Shandong along the Yellow River and Huaihe River,using the NCEP/NCAR data and summer rainfall data in south Shandong in summer from 1961 to 2005,the characteristics of high pressure in South Asia and atmospheric circulation in drought year and flood year in summer in south Shandong Province were expounded.The mechanism of 100 hPa pressure in South Asian influencing precipitation in south Shandong Province was discussed.The interaction of different equipment,different altitude and different system of atmosphere circulation in low and high layer was expounded.[Results] The first mode of EOF decomposition of precipitation in summer in south Shandong Province explained above 63% variances and reflected universal form of precipitation.The difference of central position of the central position of height field of high pressure in South Asia in drought and flood year was small.But the wind field center was inconsistent.As the area of SAH was smaller and its eastern ridge line stretched to the Western Pacific between the middle of south Shandong and Changjiang Estuary,flood summer occurred when there was an unusual cyclone lied in the east of 90° E and south of Lake Baikal.The area of SAH was larger and its eastern ridge line stretching to the Western Pacific over Changjiang Estuary,drought summer occurred,when there was an unusual anticyclone lied in the east of 90° E and south of Lake Baikal.SAH and summer rainfall also had close relationship with Tele-connection Patterns over the Eurasia continent and EAP Tele-connection.When the height anomaly was in '+-+' form in the north of the Caspian Sea,around Lake Baikal and Kamchatka,and when the height anomaly in East Asia-West Pacific area was in '-+' form from low altitude to high altitude,there was much precipitation in summer;and conversely,it was drought in summer in south Shandong.[Conclusion] It provided the oretical basis for summer rainfall in south Shandong.展开更多
Based on the drought/flood grades of 90 meterological stations over eastern China and summer average sea-level pressure （SLP） during 1850-2008 and BPCCA statistical methods, the coupling relationship between the dro...Based on the drought/flood grades of 90 meterological stations over eastern China and summer average sea-level pressure （SLP） during 1850-2008 and BPCCA statistical methods, the coupling relationship between the drought/flood grades and the East Asian summer SLP is analyzed. The East Asian summer monsoon index which is closely related with interdecadal variation of drought/flood distribution over eastern China is defined by using the key areas of SLP. The impact of the interdecadal variation of the East Asian summer monsoon on the distribution of drought/flood over eastern China in the last 159 years is researched. The results show that there are four typical drought and flood spatial distribution patterns in eastern China, i.e. the distribution of drought/flood in southern China is contrary to the other regions, the distribution of drought/flood along the Huanghe River–Huaihe River Valley is contrary to the Yangtze River Valley and regions south of it, the distribution of drought/flood along the Yangtze River Valley and Huaihe River Valley is contrary to the other regions, the distribution of drought/flood in eastern China is contrary to the western. The main distribution pattern of SLP in summer is that the strength of SLP is opposite in Asian continent and West Pacific. It has close relationship between the interdecadal variation of drought/flood distribution patterns over eastern China and the interdecadal variation of the East Asian summer monsoon which was defined in this paper, but the correlation is not stable and it has a significant difference in changes of interdecadal phase. When the East Asian summer monsoon was stronger （weaker）, regions north of the Yangtze River Valley was more susceptible to drought （flood）, the Yangtze River Valley and regions south of it were more susceptible to flood （drought） before the 1920s; when the East Asian summer monsoon was stronger （weaker）, the regions north of the Yangtze River Valley was prone to flood （drought）, the Yangtze River Valley and regions south of it were prone to drought （flood） after the 1920s. It is indicated that by using the data of the longer period could get much richer results than by using the data of the last 50–60 years. The differences in the interdecadal phase between the East Asian summer monsoon and the drought/flood distributions in eastern China may be associated with the nonlinear feedback, which is the East Asian summer monsoon for the extrinsic forcing of solar activity.展开更多
Previous study comes to the conclusion： based on the anomalies of the South Asian high （SAH）, 100-hPa geopotential height, and 100-hPa circulation over tropical and subtropical regions, we can predict precipitation...Previous study comes to the conclusion： based on the anomalies of the South Asian high （SAH）, 100-hPa geopotential height, and 100-hPa circulation over tropical and subtropical regions, we can predict precipitation anomaly in the Yangtze River Valley and North China. To test its validity, a series of experiments have been designed and operated, which include controlled experiment, sensitivity experiment （which has added anomalies into 100-hPa geopotential height and wind field）, and four-composite experiments. Experiments based on the composed initial field such as EPR-CF, EPR-CD, EPR-HF, and EPR-HD, can reproduce the floods or droughts in the Yangtze River Valley and North China. It suggests that anomalies of the SAH, 100- hPa geopotential height, and circulation over tropical and subtropical regions may probably imply summer precipitation anomalies in the two regions. Sensitivity experiment results show that anomalies of the SAH, 100-hPa geopotential height, and southwest flow in the previous period is a signal of droughts or floods for the following summer in the Yangtze River Valley and North China. And it is also one of the factors that have impact on summer precipitation anomaly in the two regions. Positive anomaly of 100-hPa geopotential height and the anomalous intensifying of the SAH and southwest flow will induce floods in the Yangtze River Valley and droughts in North China; while negative anomaly of 100-hPa geopotential height and anomalous weakening of the SAH and southwest flow will induce droughts in the Yangtze River Valley and floods in North China.展开更多
Attributions of floods/cooler along the Yangtze River Valley anddroughts/warmer in North China for the last 25 years have been reviewed in this paper. Both naturalclimate variability and human activities are considere...Attributions of floods/cooler along the Yangtze River Valley anddroughts/warmer in North China for the last 25 years have been reviewed in this paper. Both naturalclimate variability and human activities are considered. Some stronger evidences contributed to thenatural climate variability, such as decadal and interdecadal variabilities of East Asian summermonsoon, the periodicities and transitions of rainfall and temperature changes in China, abruptclimate change, NAO, AO, AAO, ENSO, and snow cover. The signals produced by the human activitiessuch as greenhouse gases and 'brown clouds' likely play the role for the patterns. But the physicalfeedbacks and mechanisms still keep ambiguous and vague. More researches should be carried out infuture to solve this issue.展开更多
基金This study is one of the research projects sponsored by the Monsoon Research Foundation of State Meteorological Administration.
文摘By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought / flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For example, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.
文摘In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study is made of the high's influence on Asian summer monsoon circulation and dryness / wetness of eastern China based on case contrast andcontrol experiments. Rusults show that as an excitation source, the blocking high produces a SE-NW stationarywavetrain with its upper-air atnicyclonic divergent circulation oust over a lower-level trough zone) precisely over themiddle to lower reaches of the Changjiang River, enhancing East Asian westerly jet, a situation that contributes toPerturbation growth, causing an additional secondary meridional circulation at the jet entrance, which intensifies theupdraft in the monsoon area. As such, the high's presence and its excited steady wavetrain represent the large-scalekey factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in the easternpart of the land.
基金This research is sponsored by the National Natural Science Foundation of China.
文摘The features of water vapor transport, such as temporal evolution, vertical structure and spatial pattern, over North China during the prolonged drought in the summer of 1980 have been analyzed through computation of water vapor flux based on the once daily ECMWF grid-point data at 12GMT. The results indicate that it is unlikely that the characteristics of the atmospheric mass divergence, ascending motion and stratification stability in North China were completely opposite to those in the Yangtze River Valley, where the heavy flood occurred in the summer of 1980. It is major differences that the strong ascending motion and significant water vapor convergence overlap fairly well each other in the vertical levels in the Yangtze River Valley, while the maximum ascending motion is accompanied by water vapor divergence or weak water vapor convergence in North China. This vertical structure in North China results in insufficient water vapor supply and, therefore, little condensation and precipitation in the middle and upper atmosphere were produced. Additionally, a mode of monthly-scale low frequency oscillation can be found in water vapor flux, which is in correspondence to the fluctuation period of rainfall.
基金The authors wish to thank Professor Wang Shaowu from the Department of AtmosphericSciences of Peking University, who generously provided the China Summer Rainfall Station Data used in this study. This research was supported by the National Key Program
文摘By applying rotated complex empirical orthogonal function (RCEOF) analysis on 1880-1999 summer rainfall at 28 selected stations over the east part of China, the spatio-temporal variations of China summer rainfall are investigated. Six divisions are identified, showing strong temporal variability, the middle and lower reaches of the Yangtze River, the Huaihe River, Southeast China, North China, Southwest China, and Northeast China. The locations of all divisions except Southwest China are in a good agreement with those of the rainband which moves northward from Southeast China to Northeast China from June-August. The phase relationship revealed by the RCEOF analysis suggests that rainfall anomalies in the middle and lower reaches of the Yangtze River, Southeast China, and Northeast China are all characterized by a stationary wave, while a traveling wave is more pronounced in the Huaihe River division, North China, and Southwest China. The fourth RCEOF mode indicates that rainfall anomalies can propagate from south of Northeast China across lower reaches of the Huanghe River and the Huaihe River to the lower reaches of the Yangtze River. A 20-25-year oscillation is found at the middle and lower reaches of the Yangtze River, the Huaihe River valley, North China, and Northeast China. The middle and lower reaches of the Yangtze River and Northeast China also show an approximately-60-year oscillation. Northeast China and the Huaihe River division are dominated by a 36-year and a 70-80-year oscillation, respectively. An 11-year oscillation is also evident in North China, with a periodicity similar to sunspot activity. The interdecadal variability in the middle and lower reaches of the Yangtze River, the Huaihe River valley, and North China shows a significant positive correlation with the solar activity.
文摘Vast convective activities over tropical zones are analyzed for both wet and dry summers in North China. An ITCZ synthesis index is designed using OLR data. The index can demonstrate quite clearly and objectively the seasonal features of deep convection in Asia monsoon areas. The differences of ITCZ activities in Indian as well as East Asian monsoon regions in winter-spring period are significant and so is the time-lagged correlation, which would be able to provide a new way to the long-lead prediction of summer rain in North China. The propagation characters of low frequency fluctuation are also different between wet and dry years. The intensity of low frequency fluctuation is stronger and the area is larger in wet years than that in dry years in both hemispheres, The fluctuation moves from south to north successively in wet years, which may lead to the leap of the subtropical high northwards, while it remains quasi-stationary in the Southern Hemisphere or the equatorial zone in dry years.
基金"National Key Program for Developing Basic Sciences-Research on the Formation Mechanism and Prediction Theory of Severe Climate Disasters in China"G1998040901-3
文摘Proposed are a set of new regional flood/drought indices and a scheme of grading their severity whereby 1951-2000 summer wet/dry events are investigated for North China (NC) in terms of 160 station monthly precipitation data from NCC (China National Center of Climate).Results suggest that 7 heavy droughts during 1951-2000 are 1965,1968,1972,1980,1983,1997 and 1999,while 6 heavy floods are 1954,1956,1959,1964,1973 and 1996. Based on 1951-2000 summer flood/drought severity graded by the new scheme,atmospheric circulation characteristics associated with the disasters over the NC are addressed in terms of monthly NCEP (National Centers for Environmental Prediction) reanalysis of geopotential heights,winds,surface temperature and PW (precipitable water).Evidences suggest that prominent anomalies benefiting to the heavy droughts occur over the Northern Hemisphere.The variations over middle-high latitudes especially the negative ones on Ural Mountain to western Siberia deepen the normal trough there and are indicative of stronger than normal cold air activity. At middle latitudes,remarkable positive anomalies present on the south to Baikal lead to the fact that the normal ridge shifts eastward over NC concomitant with anomaly sinking motion in the whole troposphere,which is helpful for the maintenance of the continent high.And the opposed ones over Korea and Japan force the trough moving eastward running against northwestward shifting of the western Pacific subtropical high.In addition,the anomaly west-east pressure gradient at middle latitudes profits northerly flow there.The southerly monsoon flow at low levels is weaker than normal with weak East Asian summer monsoon,and the related water vapor transportation is also weak with deficit PW over NC.Besides,sea surface temperature (SST) rises in the equatorial eastern and central Pacific and associated convective region moves to the east accordingly companied with weak Walker circulation in the droughts.And the opposed situations will occur during the floods.
文摘[Objective] The aim was to study the relation among summer rainfall in south Shandong and high pressure in South Asia and atmospheric circulation.[Method] Taking the precipitation in south Shandong along the Yellow River and Huaihe River,using the NCEP/NCAR data and summer rainfall data in south Shandong in summer from 1961 to 2005,the characteristics of high pressure in South Asia and atmospheric circulation in drought year and flood year in summer in south Shandong Province were expounded.The mechanism of 100 hPa pressure in South Asian influencing precipitation in south Shandong Province was discussed.The interaction of different equipment,different altitude and different system of atmosphere circulation in low and high layer was expounded.[Results] The first mode of EOF decomposition of precipitation in summer in south Shandong Province explained above 63% variances and reflected universal form of precipitation.The difference of central position of the central position of height field of high pressure in South Asia in drought and flood year was small.But the wind field center was inconsistent.As the area of SAH was smaller and its eastern ridge line stretched to the Western Pacific between the middle of south Shandong and Changjiang Estuary,flood summer occurred when there was an unusual cyclone lied in the east of 90° E and south of Lake Baikal.The area of SAH was larger and its eastern ridge line stretching to the Western Pacific over Changjiang Estuary,drought summer occurred,when there was an unusual anticyclone lied in the east of 90° E and south of Lake Baikal.SAH and summer rainfall also had close relationship with Tele-connection Patterns over the Eurasia continent and EAP Tele-connection.When the height anomaly was in '+-+' form in the north of the Caspian Sea,around Lake Baikal and Kamchatka,and when the height anomaly in East Asia-West Pacific area was in '-+' form from low altitude to high altitude,there was much precipitation in summer;and conversely,it was drought in summer in south Shandong.[Conclusion] It provided the oretical basis for summer rainfall in south Shandong.
基金National Natural Science Foundation of China No.40890053 Special Scientific Fund for Non-profit Public Industry （Meteorology） No.GYHY200906016 No.GYHY201006038
文摘Based on the drought/flood grades of 90 meterological stations over eastern China and summer average sea-level pressure （SLP） during 1850-2008 and BPCCA statistical methods, the coupling relationship between the drought/flood grades and the East Asian summer SLP is analyzed. The East Asian summer monsoon index which is closely related with interdecadal variation of drought/flood distribution over eastern China is defined by using the key areas of SLP. The impact of the interdecadal variation of the East Asian summer monsoon on the distribution of drought/flood over eastern China in the last 159 years is researched. The results show that there are four typical drought and flood spatial distribution patterns in eastern China, i.e. the distribution of drought/flood in southern China is contrary to the other regions, the distribution of drought/flood along the Huanghe River–Huaihe River Valley is contrary to the Yangtze River Valley and regions south of it, the distribution of drought/flood along the Yangtze River Valley and Huaihe River Valley is contrary to the other regions, the distribution of drought/flood in eastern China is contrary to the western. The main distribution pattern of SLP in summer is that the strength of SLP is opposite in Asian continent and West Pacific. It has close relationship between the interdecadal variation of drought/flood distribution patterns over eastern China and the interdecadal variation of the East Asian summer monsoon which was defined in this paper, but the correlation is not stable and it has a significant difference in changes of interdecadal phase. When the East Asian summer monsoon was stronger （weaker）, regions north of the Yangtze River Valley was more susceptible to drought （flood）, the Yangtze River Valley and regions south of it were more susceptible to flood （drought） before the 1920s; when the East Asian summer monsoon was stronger （weaker）, the regions north of the Yangtze River Valley was prone to flood （drought）, the Yangtze River Valley and regions south of it were prone to drought （flood） after the 1920s. It is indicated that by using the data of the longer period could get much richer results than by using the data of the last 50–60 years. The differences in the interdecadal phase between the East Asian summer monsoon and the drought/flood distributions in eastern China may be associated with the nonlinear feedback, which is the East Asian summer monsoon for the extrinsic forcing of solar activity.
基金Supported by the National Key Developing Programme for Basic Science Project under No.1998040900 amd the Key Project of National Natural Science Foundation of China under No.40175021.
文摘Previous study comes to the conclusion： based on the anomalies of the South Asian high （SAH）, 100-hPa geopotential height, and 100-hPa circulation over tropical and subtropical regions, we can predict precipitation anomaly in the Yangtze River Valley and North China. To test its validity, a series of experiments have been designed and operated, which include controlled experiment, sensitivity experiment （which has added anomalies into 100-hPa geopotential height and wind field）, and four-composite experiments. Experiments based on the composed initial field such as EPR-CF, EPR-CD, EPR-HF, and EPR-HD, can reproduce the floods or droughts in the Yangtze River Valley and North China. It suggests that anomalies of the SAH, 100- hPa geopotential height, and circulation over tropical and subtropical regions may probably imply summer precipitation anomalies in the two regions. Sensitivity experiment results show that anomalies of the SAH, 100-hPa geopotential height, and southwest flow in the previous period is a signal of droughts or floods for the following summer in the Yangtze River Valley and North China. And it is also one of the factors that have impact on summer precipitation anomaly in the two regions. Positive anomaly of 100-hPa geopotential height and the anomalous intensifying of the SAH and southwest flow will induce floods in the Yangtze River Valley and droughts in North China; while negative anomaly of 100-hPa geopotential height and anomalous weakening of the SAH and southwest flow will induce droughts in the Yangtze River Valley and floods in North China.
基金This review was supported by China-IPCC Climate Special Projects and LCS Projects.
文摘Attributions of floods/cooler along the Yangtze River Valley anddroughts/warmer in North China for the last 25 years have been reviewed in this paper. Both naturalclimate variability and human activities are considered. Some stronger evidences contributed to thenatural climate variability, such as decadal and interdecadal variabilities of East Asian summermonsoon, the periodicities and transitions of rainfall and temperature changes in China, abruptclimate change, NAO, AO, AAO, ENSO, and snow cover. The signals produced by the human activitiessuch as greenhouse gases and 'brown clouds' likely play the role for the patterns. But the physicalfeedbacks and mechanisms still keep ambiguous and vague. More researches should be carried out infuture to solve this issue.
