Spring returns with every thing growing.As the f irst high-level forum held after the Two Sessions,the China Development Forum(hereinaf ter refer red to as the Forum)brought together Chinese and foreign political and ...Spring returns with every thing growing.As the f irst high-level forum held after the Two Sessions,the China Development Forum(hereinaf ter refer red to as the Forum)brought together Chinese and foreign political and business people and became a weathervane for observing China’s economy.展开更多
On October 24,the opening ceremony of the MercedesBenz China Fashion Week was held in Beijing’s China Central Place.The Chinese Textile Industry Association,the China Fashion Association,the Beijing Textile Industry ...On October 24,the opening ceremony of the MercedesBenz China Fashion Week was held in Beijing’s China Central Place.The Chinese Textile Industry Association,the China Fashion Association,the Beijing Textile Industry Association and other relevant leaders attended the ceremony,and the Italian National Fashion Association honorary Chairman,European Design Center honorary president Mr.展开更多
In our previous study, a statistical linkage between the spring Arctic sea ice concentration （SIC） and the succeeding Chinese summer rainfall during the period 1968-2005 was identified. This linkage is demonstrated ...In our previous study, a statistical linkage between the spring Arctic sea ice concentration （SIC） and the succeeding Chinese summer rainfall during the period 1968-2005 was identified. This linkage is demonstrated by the leading singular value decomposition （SVD） that accounts for 19% of the co-variance. Both spring SIC and Chinese summer rainfall exhibit a coherent interannual variability and two apparent interdecadal variations that occurred in the late 1970s and the early 1990s. The combined impacts of both spring Arctic SIC and Eurasian snow cover on the summer Eurasian wave train may explain their statistical linkage. In this study, we show that evolution of atmospheric circulation anomalies from spring to summer, to a great extent, may explain the spatial distribution of spring and summer Arctic SIC anomalies, and is dynamically consistent with Chinese summer rainfall anomalies in recent decades. The association between spring Arctic SIC and Chinese summer rainfall on interannual time scales is more important relative to interdecadal time scales. The summer Arctic dipole anomaly may serve as the bridge linking the spring Arctic SIC and Chinese summer rainfall, and their coherent interdecadal variations may reflect the feedback of spring SIC variability on the atmosphere. The summer Arctic dipole anomaly shows a closer relationship with the Chinese summer rainfall relative to the Arctic Oscillation.展开更多
This study documents a weakening of the relationship between the spring Arctic Oscillation （AO） and the following summer tropical cyclone （TC） formation frequency over the eastern part （150°-180°E） of ...This study documents a weakening of the relationship between the spring Arctic Oscillation （AO） and the following summer tropical cyclone （TC） formation frequency over the eastern part （150°-180°E） of the western North Pacific （WNP）. The relationship is strong and statistically significant during 1968-1986, but becomes weak during 1989-2007. The spring AO- related SST, atmospheric dynamic, and thermodynamic conditions are compared between the two epochs to understand the possible reasons for the change in the relationship. Results indicate that the spring AO leads to an E1 Nifio-like SST anomaly, lower-level anomalous cyclonic circulation, upper-level anomalous anticyclonic circulation, enhanced ascending motion, and a positive midlevel relative humidity anomaly in the tropical western-central Pacific during 1968-1986, whereas the AOrelated anomalies in the above quantities are weak during 1989-2007. Hence, the large-scale dynamic and thermodynamic anomalies are more favorable for TC formation over the eastern WNP during 1968-1986 than during 1989-2007.展开更多
The present study reveals the fact that the relationship between the spring(April–May)North Atlantic Oscillation(NAO)and the following summer(June–September)tropical cyclone(TC)genesis frequency over the western Nor...The present study reveals the fact that the relationship between the spring(April–May)North Atlantic Oscillation(NAO)and the following summer(June–September)tropical cyclone(TC)genesis frequency over the western North Pacific(WNP)during the period of 1950–2018 was not stationary.It is shown that the relationship between the two has experienced a pronounced interdecadal shift,being weak and insignificant before yet strong and statistically significant after the early 1980 s.Next we compare the spring NAO associated dynamic and thermodynamic conditions,sea surface temperature(SST)anomalies,and atmospheric circulation processes between the two subperiods of 1954–1976 and 1996–2018,so as to illucidate the possible mechanism for this interdecadal variation in the NAO-TC connection.During the latter epoch,when the spring NAO was positive,enhanced low-level vorticity,reduced vertical zonal wind shear,intensified vertical velocity and increased middle-level relative humidity were present over the WNP in the summer,which is conducive to the genesis of WNP TCs.When the spring NAO is negative,the dynamic and thermodynamic factors are disadvantageous for the summertime TC formation and development over the WNP.The results of further analysis indicate that the persistence of North Atlantic tri-pole SST anomalies from spring to the subsequent summer induced by the spring NAO plays a fundamental role in the linkage between the spring NAO and summer atmospheric circulation.During the period of 1996–2018,a remarkable eastward propagating wave-train occurred across the northern Eurasian continent,forced by the anomalous SST tri-pole in the North Atlantic.The East Asian jet flow became greatly intensified,and the deep convection in the tropics was further enhanced via the changes of the local Hadley circulation,corresponding to a positive spring NAO.During the former epoch,the spring NAO-induced tri-pole SST anomalies in the North Atlantic were non-existent,and the related atmospheric circulation anomalies were extremely weak,thereby leading to the linkage between spring NAO and WNP TC genesis frequency in the following summer being insignificant.展开更多
Intensive grazing in spring-summer has been responsible for environmental degradation of the Gurbantunggut Desert in recent years. The coverage of plants and biological crusts, sand surface stability and physicochemic...Intensive grazing in spring-summer has been responsible for environmental degradation of the Gurbantunggut Desert in recent years. The coverage of plants and biological crusts, sand surface stability and physicochemical characteristics of soil on the dune surface were conducted in 2002 （winter grazing） and 2005 （spring-summer grazing）. The results showed that over 80% of the total area of the dune surface was covered by well-developed biological crusts and plants in 2002, when the interdune and middle to lower part of dune slopes were stabilized and only the crest had 10-40 m wide mobile belt. Affected by spring-summer grazing in 2005, over 80% of the total cover of biological crust was destructed and the plant coverage only reached 1/5 of that in 2002, especially the ephemeral plant cover had a great change. The value of sand transport potential in 2005 only reached 1/3 of that in 2002, but the total surface activity in 2005 was 1.6 times stronger than that in 2002. Meanwhile the mobile area began to expand from the dune top to the whole dune surface following spring-summer grazing. Compared with 2002, medium sand content of the dune surface soil increased by 13.9%, while that of fine and very fine sands decreased by 7.4% and 8.0% respectively in 2005 and the soil organic matter in 2005 was only about 1/2 of that in 2002. It is obvious that the presence of snow cover and frozen soil in winter could avoid the surface structure destruction in winter, while spring-summer grazing made excessive damage to biologic crusts and ephemeral plants. Spring is the main windy season in Gurbantunggut Desert and therefore intensive activity of dune surface occurred following spring-summer grazing, which led to a great loss of fine sand and organic matter. It can be seen that grazing season have a significant influence on the sustainable development of the desert ecosystem in Northwest China.展开更多
The present study evaluates the precipitation variability over the South China Sea（SCS） and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition（April–May–June,AMJ） simulate...The present study evaluates the precipitation variability over the South China Sea（SCS） and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition（April–May–June,AMJ） simulated by 23 Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project Phase 5 coupled models.Most of the models have the capacity to capture the AMJ precipitation variability in the SCS.The precipitation and SST anomaly（SSTA） distribution in the SCS,tropical Pacific Ocean（TPO）,and tropical Indian Ocean（TIO） domains is evaluated based on the pattern correlation coefficients between model simulations and observations.The analysis leads to several points of note.First,the performance of the SCS precipitation anomaly pattern in AMJ is model dependent.Second,the SSTA pattern in the TPO and TIO is important for capturing the AMJ SCS precipitation variability.Third,a realistic simulation of the western equatorial Pacific（WEP） and local SST impacts is necessary for reproducing the AMJ SCS precipitation variability in some models.Fourth,the overly strong WEP SST impacts may disrupt the relationship between the SCS precipitation and the TPO–TIO SST.Further work remains to be conducted to unravel the specific reasons for the discrepancies between models and observations in various aspects.展开更多
In view of that existing opening technologies of front cover for rocket launch canister have disadvantages such as causing damage on the ground equipment,not being reused and easily broken.A novel reusable non-separat...In view of that existing opening technologies of front cover for rocket launch canister have disadvantages such as causing damage on the ground equipment,not being reused and easily broken.A novel reusable non-separation spring-driven opening scheme is proposed to achieve rapid and reliable opening of the front cover.The mathematical model of the opening process of the front cover is established by the rigid body dynamics theory.To establish a response surface model to optimize the opening scheme,three main influencing factors of the opening process are obtained through the designed experiments,including the pre-compression,the stiffness of the thrust spring,and the thrust spring force arm length.In addition,the prescribed kinematic law was taken as constraint,and the smaller thrust spring preliminary pressure and angular velocity was taken as optimization expectations.The results show that the opening scheme meets the design requirements on opening process well.It also shows that the optimized scheme can reduce the kinetic energy of the front cover,and the impact on the canister effectively,achieving a reliable and rapid opening of the front cover.展开更多
The inverse relationship between the warm phase of the El Nino Southern Oscillation(ENSO)and the Indian Summer Monsoon Rainfall(ISMR)is well established.Yet,some El Nino events that occur in the early months of the ye...The inverse relationship between the warm phase of the El Nino Southern Oscillation(ENSO)and the Indian Summer Monsoon Rainfall(ISMR)is well established.Yet,some El Nino events that occur in the early months of the year(boreal spring)transform into a neutral phase before the start of summer,whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season.This study investigates the distinct influences of an exhausted spring El Nino(springtime)and emerging summer El Nino(summertime)on the regional variability of ISMR.The two ENSO categories were formulated based on the time of occurrence of positive SST anomalies over the Nino-3.4 region in the Pacific.The ISMR’s dynamical and thermodynamical responses to such events were investigated using standard metrics such as the Walker and Hadley circulations,vertically integrated moisture flux convergence(VIMFC),wind shear,and upper atmospheric circulation.The monsoon circulation features are remarkably different in response to the exhausted spring El Nino and emerging summer El Nino phases,which distinctly dictate regional rainfall variability.The dynamic and thermodynamic responses reveal that exhausted spring El Nino events favor excess monsoon rainfall over eastern peninsular India and deficit rainfall over the core monsoon regions of central India.In contrast,emerging summer El Nino events negatively impact the seasonal rainfall over the country,except for a few regions along the west coast and northeast India.展开更多
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 ...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.展开更多
This study documents the decadal changes of the spring meridional circulation （SMC） over 110°E- 165°E and the relationship between the SMC and summer （June-July-August-September） typhoon activity over th...This study documents the decadal changes of the spring meridional circulation （SMC） over 110°E- 165°E and the relationship between the SMC and summer （June-July-August-September） typhoon activity over the Western North Pacific （WNP） during 1948-2010. The authors found that the SMC was changed after 1969. Before its change, the SMC had no clear relation with the summer typhoon number over the WNP （TNWNP）, but after the change, it has become positively correlated with the TNWNP, with a correlation coefficient of 0.57 be- tween them （above the 99% confidence level）. It was ob- served that after the SMC was changed, the positive tropical sea surface temperature anomaly associated with the SMC was shifted from the Equatorial Eastern Pacific （El Nifio） to the equatorial middle Pacific （El Nifio Mo- doki）; at the same time, the Pacific decadal oscillation （PDO） pattern over the North Pacific, which is associated with the SMC, was enhanced. The SMC and the TNWNP are both modulated by the E1 Nifio Modoki after 1969, so the relationship between them becomes significant.展开更多
The distribution of winter-spring snow cover over the Tibetan Plateau （TP） and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley （MLYRV） during 2003-2013 have been ...The distribution of winter-spring snow cover over the Tibetan Plateau （TP） and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley （MLYRV） during 2003-2013 have been investigated with the moderate-resolution imaging spectrometer （MODIS） Terra data （MOD10A2） and precipitation observations. Results show that snow cover percentage （SCP） remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency （SCF） over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003-2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. Hie multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning,development and cessation of the rain belt in eastern China.展开更多
文摘Spring returns with every thing growing.As the f irst high-level forum held after the Two Sessions,the China Development Forum(hereinaf ter refer red to as the Forum)brought together Chinese and foreign political and business people and became a weathervane for observing China’s economy.
文摘On October 24,the opening ceremony of the MercedesBenz China Fashion Week was held in Beijing’s China Central Place.The Chinese Textile Industry Association,the China Fashion Association,the Beijing Textile Industry Association and other relevant leaders attended the ceremony,and the Italian National Fashion Association honorary Chairman,European Design Center honorary president Mr.
基金supported by the National Key Basic Research and Development Project of China(Grant Nos2004CB418300 and 2007CB411505)Chinese COPES project(GYHY200706005)the Na-tional Natural Science Foundation of China(Grant No40875052)
文摘In our previous study, a statistical linkage between the spring Arctic sea ice concentration （SIC） and the succeeding Chinese summer rainfall during the period 1968-2005 was identified. This linkage is demonstrated by the leading singular value decomposition （SVD） that accounts for 19% of the co-variance. Both spring SIC and Chinese summer rainfall exhibit a coherent interannual variability and two apparent interdecadal variations that occurred in the late 1970s and the early 1990s. The combined impacts of both spring Arctic SIC and Eurasian snow cover on the summer Eurasian wave train may explain their statistical linkage. In this study, we show that evolution of atmospheric circulation anomalies from spring to summer, to a great extent, may explain the spatial distribution of spring and summer Arctic SIC anomalies, and is dynamically consistent with Chinese summer rainfall anomalies in recent decades. The association between spring Arctic SIC and Chinese summer rainfall on interannual time scales is more important relative to interdecadal time scales. The summer Arctic dipole anomaly may serve as the bridge linking the spring Arctic SIC and Chinese summer rainfall, and their coherent interdecadal variations may reflect the feedback of spring SIC variability on the atmosphere. The summer Arctic dipole anomaly shows a closer relationship with the Chinese summer rainfall relative to the Arctic Oscillation.
基金supported by the National Natural Science Foundation of China(Grant Nos.41461164005,41275001 and 41230527)
文摘This study documents a weakening of the relationship between the spring Arctic Oscillation （AO） and the following summer tropical cyclone （TC） formation frequency over the eastern part （150°-180°E） of the western North Pacific （WNP）. The relationship is strong and statistically significant during 1968-1986, but becomes weak during 1989-2007. The spring AO- related SST, atmospheric dynamic, and thermodynamic conditions are compared between the two epochs to understand the possible reasons for the change in the relationship. Results indicate that the spring AO leads to an E1 Nifio-like SST anomaly, lower-level anomalous cyclonic circulation, upper-level anomalous anticyclonic circulation, enhanced ascending motion, and a positive midlevel relative humidity anomaly in the tropical western-central Pacific during 1968-1986, whereas the AOrelated anomalies in the above quantities are weak during 1989-2007. Hence, the large-scale dynamic and thermodynamic anomalies are more favorable for TC formation over the eastern WNP during 1968-1986 than during 1989-2007.
基金The National Natural Science Foundation of China under contract No.41505050the Open Fund of the Key Laboratory of Ocean Circulation and Waves,Chinese Academy of Sciences under contract No.KLOCW1902。
文摘The present study reveals the fact that the relationship between the spring(April–May)North Atlantic Oscillation(NAO)and the following summer(June–September)tropical cyclone(TC)genesis frequency over the western North Pacific(WNP)during the period of 1950–2018 was not stationary.It is shown that the relationship between the two has experienced a pronounced interdecadal shift,being weak and insignificant before yet strong and statistically significant after the early 1980 s.Next we compare the spring NAO associated dynamic and thermodynamic conditions,sea surface temperature(SST)anomalies,and atmospheric circulation processes between the two subperiods of 1954–1976 and 1996–2018,so as to illucidate the possible mechanism for this interdecadal variation in the NAO-TC connection.During the latter epoch,when the spring NAO was positive,enhanced low-level vorticity,reduced vertical zonal wind shear,intensified vertical velocity and increased middle-level relative humidity were present over the WNP in the summer,which is conducive to the genesis of WNP TCs.When the spring NAO is negative,the dynamic and thermodynamic factors are disadvantageous for the summertime TC formation and development over the WNP.The results of further analysis indicate that the persistence of North Atlantic tri-pole SST anomalies from spring to the subsequent summer induced by the spring NAO plays a fundamental role in the linkage between the spring NAO and summer atmospheric circulation.During the period of 1996–2018,a remarkable eastward propagating wave-train occurred across the northern Eurasian continent,forced by the anomalous SST tri-pole in the North Atlantic.The East Asian jet flow became greatly intensified,and the deep convection in the tropics was further enhanced via the changes of the local Hadley circulation,corresponding to a positive spring NAO.During the former epoch,the spring NAO-induced tri-pole SST anomalies in the North Atlantic were non-existent,and the related atmospheric circulation anomalies were extremely weak,thereby leading to the linkage between spring NAO and WNP TC genesis frequency in the following summer being insignificant.
基金National Basic Research Program of China,No.2009CB421303National Natural Science Foundation of China,No.40771032National Science Supporting Program,No.2007BAC17B03
文摘Intensive grazing in spring-summer has been responsible for environmental degradation of the Gurbantunggut Desert in recent years. The coverage of plants and biological crusts, sand surface stability and physicochemical characteristics of soil on the dune surface were conducted in 2002 （winter grazing） and 2005 （spring-summer grazing）. The results showed that over 80% of the total area of the dune surface was covered by well-developed biological crusts and plants in 2002, when the interdune and middle to lower part of dune slopes were stabilized and only the crest had 10-40 m wide mobile belt. Affected by spring-summer grazing in 2005, over 80% of the total cover of biological crust was destructed and the plant coverage only reached 1/5 of that in 2002, especially the ephemeral plant cover had a great change. The value of sand transport potential in 2005 only reached 1/3 of that in 2002, but the total surface activity in 2005 was 1.6 times stronger than that in 2002. Meanwhile the mobile area began to expand from the dune top to the whole dune surface following spring-summer grazing. Compared with 2002, medium sand content of the dune surface soil increased by 13.9%, while that of fine and very fine sands decreased by 7.4% and 8.0% respectively in 2005 and the soil organic matter in 2005 was only about 1/2 of that in 2002. It is obvious that the presence of snow cover and frozen soil in winter could avoid the surface structure destruction in winter, while spring-summer grazing made excessive damage to biologic crusts and ephemeral plants. Spring is the main windy season in Gurbantunggut Desert and therefore intensive activity of dune surface occurred following spring-summer grazing, which led to a great loss of fine sand and organic matter. It can be seen that grazing season have a significant influence on the sustainable development of the desert ecosystem in Northwest China.
基金supported by the National Key Basic Research Program of China(Grant No.2014CB953902)the support of the Hong Kong Research Grants Council(Grant No.CUHK403612)+4 种基金the National Natural Science Foundation of China(Grants Nos.41275081 and 41475081)a Chinese University of Hong Kong direct grant(Grant No.4052057)the support of a Chinese Academy of Sciences project(Grant No.XDA11010402)the National Natural Science Foundation of China(Grant Nos.41305065 and 41305068)the support of the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology of Chinese Academy of Sciences(Grant No.LTO1203)
文摘The present study evaluates the precipitation variability over the South China Sea（SCS） and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition（April–May–June,AMJ） simulated by 23 Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project Phase 5 coupled models.Most of the models have the capacity to capture the AMJ precipitation variability in the SCS.The precipitation and SST anomaly（SSTA） distribution in the SCS,tropical Pacific Ocean（TPO）,and tropical Indian Ocean（TIO） domains is evaluated based on the pattern correlation coefficients between model simulations and observations.The analysis leads to several points of note.First,the performance of the SCS precipitation anomaly pattern in AMJ is model dependent.Second,the SSTA pattern in the TPO and TIO is important for capturing the AMJ SCS precipitation variability.Third,a realistic simulation of the western equatorial Pacific（WEP） and local SST impacts is necessary for reproducing the AMJ SCS precipitation variability in some models.Fourth,the overly strong WEP SST impacts may disrupt the relationship between the SCS precipitation and the TPO–TIO SST.Further work remains to be conducted to unravel the specific reasons for the discrepancies between models and observations in various aspects.
文摘In view of that existing opening technologies of front cover for rocket launch canister have disadvantages such as causing damage on the ground equipment,not being reused and easily broken.A novel reusable non-separation spring-driven opening scheme is proposed to achieve rapid and reliable opening of the front cover.The mathematical model of the opening process of the front cover is established by the rigid body dynamics theory.To establish a response surface model to optimize the opening scheme,three main influencing factors of the opening process are obtained through the designed experiments,including the pre-compression,the stiffness of the thrust spring,and the thrust spring force arm length.In addition,the prescribed kinematic law was taken as constraint,and the smaller thrust spring preliminary pressure and angular velocity was taken as optimization expectations.The results show that the opening scheme meets the design requirements on opening process well.It also shows that the optimized scheme can reduce the kinetic energy of the front cover,and the impact on the canister effectively,achieving a reliable and rapid opening of the front cover.
基金funding support from the National Monsoon Mission program of the Ministry of Earth Sciences(MoES),New Delhi。
文摘The inverse relationship between the warm phase of the El Nino Southern Oscillation(ENSO)and the Indian Summer Monsoon Rainfall(ISMR)is well established.Yet,some El Nino events that occur in the early months of the year(boreal spring)transform into a neutral phase before the start of summer,whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season.This study investigates the distinct influences of an exhausted spring El Nino(springtime)and emerging summer El Nino(summertime)on the regional variability of ISMR.The two ENSO categories were formulated based on the time of occurrence of positive SST anomalies over the Nino-3.4 region in the Pacific.The ISMR’s dynamical and thermodynamical responses to such events were investigated using standard metrics such as the Walker and Hadley circulations,vertically integrated moisture flux convergence(VIMFC),wind shear,and upper atmospheric circulation.The monsoon circulation features are remarkably different in response to the exhausted spring El Nino and emerging summer El Nino phases,which distinctly dictate regional rainfall variability.The dynamic and thermodynamic responses reveal that exhausted spring El Nino events favor excess monsoon rainfall over eastern peninsular India and deficit rainfall over the core monsoon regions of central India.In contrast,emerging summer El Nino events negatively impact the seasonal rainfall over the country,except for a few regions along the west coast and northeast India.
基金National Planning Project for the Research and Development of Key National FundamentalResearch (2004CB418303)Innovative Project for Training Post Graduates in Jiangsu Province (E30000008098-2)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant No.41130103)
文摘This study documents the decadal changes of the spring meridional circulation （SMC） over 110°E- 165°E and the relationship between the SMC and summer （June-July-August-September） typhoon activity over the Western North Pacific （WNP） during 1948-2010. The authors found that the SMC was changed after 1969. Before its change, the SMC had no clear relation with the summer typhoon number over the WNP （TNWNP）, but after the change, it has become positively correlated with the TNWNP, with a correlation coefficient of 0.57 be- tween them （above the 99% confidence level）. It was ob- served that after the SMC was changed, the positive tropical sea surface temperature anomaly associated with the SMC was shifted from the Equatorial Eastern Pacific （El Nifio） to the equatorial middle Pacific （El Nifio Mo- doki）; at the same time, the Pacific decadal oscillation （PDO） pattern over the North Pacific, which is associated with the SMC, was enhanced. The SMC and the TNWNP are both modulated by the E1 Nifio Modoki after 1969, so the relationship between them becomes significant.
基金supported by the National Natural Science Foundation of China(Grant No.41130960)the Project of the China Meteorological Administration(Grant Nos.CCSF201515 and CMAGJ2013M51)
文摘The distribution of winter-spring snow cover over the Tibetan Plateau （TP） and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley （MLYRV） during 2003-2013 have been investigated with the moderate-resolution imaging spectrometer （MODIS） Terra data （MOD10A2） and precipitation observations. Results show that snow cover percentage （SCP） remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency （SCF） over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003-2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. Hie multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning,development and cessation of the rain belt in eastern China.
