Based on observations and reanalysis data,the characteristics of the evolution of climatological spring precipitation over Southern China(SPSC) and the associated climatological intraseasonal oscillation(CISO) and atm...Based on observations and reanalysis data,the characteristics of the evolution of climatological spring precipitation over Southern China(SPSC) and the associated climatological intraseasonal oscillation(CISO) and atmospheric circulation are studied.Results show that SPSC increases in an oscillatory way.Although the evolution of SPSC is similar in different regions,there are also differences.In different regions of Southern China,the onset dates of the rain season are from the 12 th to 24 th pentad and the peak dates are after the 20 th pentad.CISO is an important component of SPSC,which is not only statistically significant,but also accompanies a dynamically coherent structure.The peak wet/dry phase of each CISO cycle corresponds to a significant rainfall increasing/decreasing period and modulates the evolution of SPSC.The rainfall growth in the second half of March and mid-April is the result of the modulation.The wet/dry phase of CISO is accompanied by low-level convergent(upper-level divergent) and cyclonic(anti-cyclonic) circulation,which favors ascending motion to develop over Southern China.展开更多
[Objective] The research aimed to study the structure and propagation characteristics of climatological mean kinetic energy of disturbance of intraseasonal oscillation in Asian summer monsoon zone. [Method] When South...[Objective] The research aimed to study the structure and propagation characteristics of climatological mean kinetic energy of disturbance of intraseasonal oscillation in Asian summer monsoon zone. [Method] When South China Sea monsoon started to break out, the kinetic energy of intraseasonal oscillation disturbance in the monsoon zone was analyzed, especially the researches about the variation of South China Sea monsoon, the development of Indian monsoon and the advancement of East Asian monsoon. [Result] The developed process of Asian summer monsoon had the close relationship with the kinetic energy activity of 30-60 d low-frequency oscillation disturbance. The kinetic energy of disturbance explained the eruption, occurrence, development and termination of monsoon from the energy angle. It was found that the kinetic energy of disturbance in Arabian Sea zone, Bay of Bengal and South China Sea area was the strongest, especially in Arabian Sea zone. It illustrated that Arabian Sea zone (Somali jet) was the biggest energy source of Asian monsoon. The starting mark of monsoon eruption in the whole Asia was the abrupt eruption of South China Sea monsoon. The eruption of South China Sea monsoon in the middle dekad of May was the westward transmission result of kinetic energy of disturbance on the east sea surface of Philippines. The kinetic energy of disturbance in East Asian monsoon zone had the seasonal northward advancement in summer. The high kinetic energy center of disturbance in Indian monsoon zone changed from one to two. They were respectively in Arabian Sea and Bay of Bengal. [Conclusion] The research provided the theory basis for analyzing the atmospheric intraseasonal oscillation.展开更多
The impact of tropical intraseasonal oscillations on the precipitation of Guangdong in Junes and its physical mechanism are analyzed using 30-yr(1979 to 2008), 86-station observational daily precipitation of Guangdong...The impact of tropical intraseasonal oscillations on the precipitation of Guangdong in Junes and its physical mechanism are analyzed using 30-yr(1979 to 2008), 86-station observational daily precipitation of Guangdong and daily atmospheric data from NCEP-DOE Reanalysis. It is found that during the annually first rainy season(April to June),the modulating effect of the activity of intraseasonal oscillations propagating eastward along the equator(MJO) on the June precipitation in Guangdong is different from that in other months. The most indicative effect of MJO on positive(negative) anomalous precipitation over the whole or most of the province is phase 3(phase 6) of strong MJO events in Junes. A Northwest Pacific subtropical high intensifies and extends westward during phase 3. Water vapor transporting along the edge of the subtropical high from Western Pacific enhances significantly the water vapor flux over Guangdong, resulting in the enhancement of the precipitation. The condition is reverse during phase 6. The mechanism for which the subtropical high intensifies and extends westward during phase 3 is related to the atmospheric response to the asymmetric heating over the eastern Indian Ocean. Analyses of two cases of sustained strong rainfall of Guangdong in June 2010 showed that both of them are closely linked with a MJO state which is both strong and in phase 3, besides the effect from a westerly trough. It is argued further that the MJO activity is indicative of strong rainfall of Guangdong in June. The results in the present work are helpful in developing strategies for forecasting severe rainfall in Guangdong and extending, combined with the outputs of dynamic forecast models, the period of forecasting validity.展开更多
利用谐波分析、功率谱分析的方法,对全国730个站点自1951~2000年逐日降水资料进行气候平均分析,研究全国降水季节内振荡的分布特征。研究结果表明,中国大部分地区的降水主要以季节变化为主,而在长江中下游流域主要以季节内振荡为...利用谐波分析、功率谱分析的方法,对全国730个站点自1951~2000年逐日降水资料进行气候平均分析,研究全国降水季节内振荡的分布特征。研究结果表明,中国大部分地区的降水主要以季节变化为主,而在长江中下游流域主要以季节内振荡为主。气候平均下降水的准双周振荡和Madden and Julian Oscillation(简称MJO)的振幅都在4月份开始加强,在11月份开始减弱,而MJO全年表现都很显著,准双周振荡主要在夏季显著;MJO主要分布在36°N以南的长江巾下游地区,准舣周振荡主要分布在115°E以西的内陆。展开更多
利用2007年全球降水气候计划GPCP(the Global Precipitation Climatology Project)卫星红外窗口导出的全球降水指数GPI(the Global Precipitation Index)的日降水资料及频率-波数分析方法,分析2007年南海夏季风季节内振荡(Intraseasonal...利用2007年全球降水气候计划GPCP(the Global Precipitation Climatology Project)卫星红外窗口导出的全球降水指数GPI(the Global Precipitation Index)的日降水资料及频率-波数分析方法,分析2007年南海夏季风季节内振荡(Intraseasonal Oscillation,ISO)的传播特征,并使用美国国家环境预报中心(NCEP)/美国大气研究中心(NCAR)再分析的逐日资料,探讨影响其传播的主要因子。结果表明,南海夏季风ISO有明显的北传趋势,并且明显比南传分量占优。影响南海夏季风ISO北传的主要因子是平均纬向风垂直切变和平均经向风对异常水汽的输送。之所以异常经向风对平均水汽的输送及海-气相互作用的影响在南海地区不重要,而在印度季风区有一定的贡献,是因为平均水汽和纬向风分布在两个地区的差异。展开更多
The intraseasonal oscillation(ISO) of the South China Sea(SCS, 105-120°E, 5-20°N) convection and its influences on the genesis and track of the western North Pacific(WNP) tropical cyclones(TCs) were explored...The intraseasonal oscillation(ISO) of the South China Sea(SCS, 105-120°E, 5-20°N) convection and its influences on the genesis and track of the western North Pacific(WNP) tropical cyclones(TCs) were explored, based on the daily average of NCEP/NCAR reanalysis data, the OLR data and the western North Pacific tropical cyclone best-track data from 1979 to 2008. The mechanism of the influences of ISO on TC movement and the corresponding large-scale circulation were discussed by a trajectory model. It was found as follows.(1) During the SCS summer monsoon, the SCS convection exhibits the ISO features with active phases alternating with inactive phases. The monsoon circulation patterns are significantly different during these two phases. When the SCS convection is active(inactive), the SCS-WNP monsoon trough stretches eastward(retreats westward) due to the activity(inactivity) of SCS monsoon, and the WNP subtropical high retreats eastward(stretches westward), which enhances(suppresses) the monsoon circulation.(2) The amount of TC genesis in the active phase is much more than that in the inactive phase. A majority of TCs form west of 135 °E during the active phases but east of 135 °E in the inactive phases.(3) The TCs entering the area west of 135 °E and south of 25 °N would move straight into the SCS in the active phase, or recurve northward in the inactive phase.(4) Simulation results show that the steering flow associated with the active(inactive)phases is in favor of straight-moving(recurving) TCs. Meanwhile, the impacts of the locations of TC genesis on the characteristics of TC track cannot be ignored. TCs that occurred father westward are more likely to move straight into the SCS region.展开更多
In this paper,the synoptic-climatology of Meiyu in East Asia is discussed.It is proposed that the location of the rain band of Meiyu is stable from the viewpoint of climatology,even though the active(wet)and break(dry...In this paper,the synoptic-climatology of Meiyu in East Asia is discussed.It is proposed that the location of the rain band of Meiyu is stable from the viewpoint of climatology,even though the active(wet)and break(dry)Meiyu are influenced by synoptic systems.The duration and the onset and retreat dates of Meiyu exhibit tremendous interannual variabilities,and thus,they are almost unpredictable in seasonal climate prediction.The Meiyu has been used as a synoptic concept and applied to the operational forecast for many decades by meteorological agencies in East Asian countries.As a result,the prediction of the onset and retreat dates of Meiyu has become an important operational work for meteorological services.This has also misled the public’s and scientists’attention.The northward propagation of the East Asian summer monsoon(EASM)surge associated with the intraseasonal oscillation is closely related to the active and break Meiyu.The activities and propagation of the EASM surge modulate the active/break Meiyu that cause concentrative severe precipitation processes and floods or droughts;hence,the authors suggest changing the current forecasting methodology of Meiyu.It is more meaningful from the scientific as well as application viewpoints to establish the monitoring and forecasting of the EASM surge to replace the current operational forecast of Meiyu after the seasonal progress enters the climatological Meiyu period in a year.展开更多
基金National Program for Key Fundamental Research and Development(2012CB417205)International Cooperation Project for Ministry of Science and Technology(2009DFA23010)+2 种基金National Project for Science and Technology Support(2009BAC51B)Project of Science and Technology for Guangdong Province(Meteorological Sector)(200905)National Natural Science Foundation of China(41205069)
文摘Based on observations and reanalysis data,the characteristics of the evolution of climatological spring precipitation over Southern China(SPSC) and the associated climatological intraseasonal oscillation(CISO) and atmospheric circulation are studied.Results show that SPSC increases in an oscillatory way.Although the evolution of SPSC is similar in different regions,there are also differences.In different regions of Southern China,the onset dates of the rain season are from the 12 th to 24 th pentad and the peak dates are after the 20 th pentad.CISO is an important component of SPSC,which is not only statistically significant,but also accompanies a dynamically coherent structure.The peak wet/dry phase of each CISO cycle corresponds to a significant rainfall increasing/decreasing period and modulates the evolution of SPSC.The rainfall growth in the second half of March and mid-April is the result of the modulation.The wet/dry phase of CISO is accompanied by low-level convergent(upper-level divergent) and cyclonic(anti-cyclonic) circulation,which favors ascending motion to develop over Southern China.
基金Supported by National Natural Science Fund (40975019)
文摘[Objective] The research aimed to study the structure and propagation characteristics of climatological mean kinetic energy of disturbance of intraseasonal oscillation in Asian summer monsoon zone. [Method] When South China Sea monsoon started to break out, the kinetic energy of intraseasonal oscillation disturbance in the monsoon zone was analyzed, especially the researches about the variation of South China Sea monsoon, the development of Indian monsoon and the advancement of East Asian monsoon. [Result] The developed process of Asian summer monsoon had the close relationship with the kinetic energy activity of 30-60 d low-frequency oscillation disturbance. The kinetic energy of disturbance explained the eruption, occurrence, development and termination of monsoon from the energy angle. It was found that the kinetic energy of disturbance in Arabian Sea zone, Bay of Bengal and South China Sea area was the strongest, especially in Arabian Sea zone. It illustrated that Arabian Sea zone (Somali jet) was the biggest energy source of Asian monsoon. The starting mark of monsoon eruption in the whole Asia was the abrupt eruption of South China Sea monsoon. The eruption of South China Sea monsoon in the middle dekad of May was the westward transmission result of kinetic energy of disturbance on the east sea surface of Philippines. The kinetic energy of disturbance in East Asian monsoon zone had the seasonal northward advancement in summer. The high kinetic energy center of disturbance in Indian monsoon zone changed from one to two. They were respectively in Arabian Sea and Bay of Bengal. [Conclusion] The research provided the theory basis for analyzing the atmospheric intraseasonal oscillation.
基金Key National Science Research Program(2014CB953901)Science and Technology Planning Project fo Guangdong Province(2012A061400012)+1 种基金Natural Science Foundation of China(41575043,41205069)Project for China Meteorological Administration(GYHY201406009)
文摘The impact of tropical intraseasonal oscillations on the precipitation of Guangdong in Junes and its physical mechanism are analyzed using 30-yr(1979 to 2008), 86-station observational daily precipitation of Guangdong and daily atmospheric data from NCEP-DOE Reanalysis. It is found that during the annually first rainy season(April to June),the modulating effect of the activity of intraseasonal oscillations propagating eastward along the equator(MJO) on the June precipitation in Guangdong is different from that in other months. The most indicative effect of MJO on positive(negative) anomalous precipitation over the whole or most of the province is phase 3(phase 6) of strong MJO events in Junes. A Northwest Pacific subtropical high intensifies and extends westward during phase 3. Water vapor transporting along the edge of the subtropical high from Western Pacific enhances significantly the water vapor flux over Guangdong, resulting in the enhancement of the precipitation. The condition is reverse during phase 6. The mechanism for which the subtropical high intensifies and extends westward during phase 3 is related to the atmospheric response to the asymmetric heating over the eastern Indian Ocean. Analyses of two cases of sustained strong rainfall of Guangdong in June 2010 showed that both of them are closely linked with a MJO state which is both strong and in phase 3, besides the effect from a westerly trough. It is argued further that the MJO activity is indicative of strong rainfall of Guangdong in June. The results in the present work are helpful in developing strategies for forecasting severe rainfall in Guangdong and extending, combined with the outputs of dynamic forecast models, the period of forecasting validity.
文摘利用谐波分析、功率谱分析的方法,对全国730个站点自1951~2000年逐日降水资料进行气候平均分析,研究全国降水季节内振荡的分布特征。研究结果表明,中国大部分地区的降水主要以季节变化为主,而在长江中下游流域主要以季节内振荡为主。气候平均下降水的准双周振荡和Madden and Julian Oscillation(简称MJO)的振幅都在4月份开始加强,在11月份开始减弱,而MJO全年表现都很显著,准双周振荡主要在夏季显著;MJO主要分布在36°N以南的长江巾下游地区,准舣周振荡主要分布在115°E以西的内陆。
文摘利用2007年全球降水气候计划GPCP(the Global Precipitation Climatology Project)卫星红外窗口导出的全球降水指数GPI(the Global Precipitation Index)的日降水资料及频率-波数分析方法,分析2007年南海夏季风季节内振荡(Intraseasonal Oscillation,ISO)的传播特征,并使用美国国家环境预报中心(NCEP)/美国大气研究中心(NCAR)再分析的逐日资料,探讨影响其传播的主要因子。结果表明,南海夏季风ISO有明显的北传趋势,并且明显比南传分量占优。影响南海夏季风ISO北传的主要因子是平均纬向风垂直切变和平均经向风对异常水汽的输送。之所以异常经向风对平均水汽的输送及海-气相互作用的影响在南海地区不重要,而在印度季风区有一定的贡献,是因为平均水汽和纬向风分布在两个地区的差异。
基金National Basic Research Program of China(2015CB953904)National Natural Science Foundation of China(41575081)+1 种基金Startup Foundation for Introducing Talent of NUIST(2015r035)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The intraseasonal oscillation(ISO) of the South China Sea(SCS, 105-120°E, 5-20°N) convection and its influences on the genesis and track of the western North Pacific(WNP) tropical cyclones(TCs) were explored, based on the daily average of NCEP/NCAR reanalysis data, the OLR data and the western North Pacific tropical cyclone best-track data from 1979 to 2008. The mechanism of the influences of ISO on TC movement and the corresponding large-scale circulation were discussed by a trajectory model. It was found as follows.(1) During the SCS summer monsoon, the SCS convection exhibits the ISO features with active phases alternating with inactive phases. The monsoon circulation patterns are significantly different during these two phases. When the SCS convection is active(inactive), the SCS-WNP monsoon trough stretches eastward(retreats westward) due to the activity(inactivity) of SCS monsoon, and the WNP subtropical high retreats eastward(stretches westward), which enhances(suppresses) the monsoon circulation.(2) The amount of TC genesis in the active phase is much more than that in the inactive phase. A majority of TCs form west of 135 °E during the active phases but east of 135 °E in the inactive phases.(3) The TCs entering the area west of 135 °E and south of 25 °N would move straight into the SCS in the active phase, or recurve northward in the inactive phase.(4) Simulation results show that the steering flow associated with the active(inactive)phases is in favor of straight-moving(recurving) TCs. Meanwhile, the impacts of the locations of TC genesis on the characteristics of TC track cannot be ignored. TCs that occurred father westward are more likely to move straight into the SCS region.
基金supported by the National Basic Research Program of China(2012CB417205)Open Fund of State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences(2012LASW-A02)Basic Research Fund of Chinese Academy of Meteorological Sciences(2010Z001)
文摘In this paper,the synoptic-climatology of Meiyu in East Asia is discussed.It is proposed that the location of the rain band of Meiyu is stable from the viewpoint of climatology,even though the active(wet)and break(dry)Meiyu are influenced by synoptic systems.The duration and the onset and retreat dates of Meiyu exhibit tremendous interannual variabilities,and thus,they are almost unpredictable in seasonal climate prediction.The Meiyu has been used as a synoptic concept and applied to the operational forecast for many decades by meteorological agencies in East Asian countries.As a result,the prediction of the onset and retreat dates of Meiyu has become an important operational work for meteorological services.This has also misled the public’s and scientists’attention.The northward propagation of the East Asian summer monsoon(EASM)surge associated with the intraseasonal oscillation is closely related to the active and break Meiyu.The activities and propagation of the EASM surge modulate the active/break Meiyu that cause concentrative severe precipitation processes and floods or droughts;hence,the authors suggest changing the current forecasting methodology of Meiyu.It is more meaningful from the scientific as well as application viewpoints to establish the monitoring and forecasting of the EASM surge to replace the current operational forecast of Meiyu after the seasonal progress enters the climatological Meiyu period in a year.
基金jointly supported by the National Natural Science Foundation of China [grant numbers 41475057,41775052,and41505049]the Special Fund for Public Welfare Industry [grant number GYHY20140619]+1 种基金the Basic Scientific Research and Operation Foundation of CAMS [grant numbers 2018Z006 and2017R001]the Jiangsu Collaborative Innovation Center for Climate Change