Based on a 30-year Atmospheric Model Intercomparison Project(AMIP) simulation using IAP AGCM4.0, the relationship between the East Asian subtropical westerly jet(EASWJ) and summer precipitation over East Asia has been...Based on a 30-year Atmospheric Model Intercomparison Project(AMIP) simulation using IAP AGCM4.0, the relationship between the East Asian subtropical westerly jet(EASWJ) and summer precipitation over East Asia has been investigated, and compared with observation. It was found the meridional displacement of the EASWJ has a closer relationship with the precipitation over East Asia both from model simulation and observation, with an anomalous southward shift of EASWJ being conducive to rainfall over the Yangtze-Huaihe River Valley(YHRV), and an anomalous northward shift resulting in less rainfall over the YHRV. However, the simulated precipitation anomalies were found to be weaker than observed from the composite analysis, and this would be related to the weakly reproduced mid-upper-level convergence in the mid-high latitudes and ascending motion in the lower latitudes.展开更多
The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the...The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the lower atmosphere over central China to be smaller than the fluxes over southern and northern China by generating more clouds. The existence of a larger quantity of clouds over central China reflects a greater amount of solar radiation back into space. The vertical gradients of upward shortwave radiative fluxes in the atmosphere below 8 km are greater than those above 8 km. The latitudinal-altitude distributions of downward longwave radiative fluxes show a slantwise decreasing trend from low latitudes to high latitudes that gradually weaken in the downward direction. The upward longwave radiative fluxes also weaken in the upward direction but with larger gradients. The maximum heating rates by solar radiation and cooling rates by longwave infrared radiation are located over 28 40°N at 7 8 km mean sea level (MSL), and they are larger than the rates in the northern and southern regions. The heating and cooling rates match well both vertically and geographically.展开更多
Gravity wave activity and dissipation in the height range from the low stratosphere to the low thermosphere(25–115 km)covering latitudes between 50°S and 50°N are statistically studied by using 9-year(Janua...Gravity wave activity and dissipation in the height range from the low stratosphere to the low thermosphere(25–115 km)covering latitudes between 50°S and 50°N are statistically studied by using 9-year(January 22,2002–December 31,2010)SABER/TIMED temperature data.We propose a method to extract realistic gravity wave fluctuations from the temperature profiles and treat square temperature fluctuations as GW activity.Overall,the gravity wave activity generally increases with height.Near the equator(0°–10°),the gravity wave activity shows a quasi-biennial variation in the stratosphere(below 40 km)while from 20°to 30°,it exhibits an annual variation below 40 km;in low latitudes(0°–30°)between the upper stratosphere and the low thermosphere(40–115 km),the gravity wave activity shows a semi-annual variation.In middle latitudes(40°–50°),the gravity wave activity has a clear annual variation below 85 km.In addition,we observe a four-monthly variation with peaks occurring usually in April,August,December in the northern hemisphere and in February,June,October in the southern hemisphere,respectively,above 85 km in middle latitudes,which has been seldom reported in gravity wave activity.In order to study the dissipation of gravity wave propagation,we calculate the gravity wave dissipation ratio,which is defined as the ratio of the gravity wave growth scale height to the atmosphere density scale height.The height variation of the dissipation ratio indicates that strong gravity wave dissipation mainly concentrates in the three height regions:the stratosphere(30–60 km),the mesopause(around 85 km)and the low thermosphere(above 100 km).Besides,gravity wave energy enhancement can be also observed in the background atmosphere.展开更多
NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric ci...NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric circulation anomalies on the troposphere.Stratospheric temperature and water-vapor anomalies provided good leading indicators of this weather event.The period from December 1st 2007 to February 28th 2008 was divided into 18 pentads.During the 6th pentad,temperature decreased significantly at 10 hPa in the near-polar stratospheric region,and the decreasing trend strengthened and extended downward and southward to middle and lower latitudes.During the 14th-18th pentads,the temperature decrease reached its maximum and extended to 30°N.This coincided with the widespread freezing rain and snow event.By the end of January 2008,the temperature decrease ended in the near-polar stratospheric region,but continued in the mid-latitude area of the troposphere as the freezing rain and snow weather persisted.Similar to the temperature variations,positive anomalies of relative humidity in the stratospheric near-polar region also strengthened and extended downward and southward,coinciding with the freezing rain and snow event.Along with the significant relationship between the freezing rain and snow disaster and stratospheric circulation anomalies,the stratospheric polar vortex changed its shape in late December,intensifying and spreading downward from the top of the stratosphere and southward to the Asian continent,resulting in a deepening of the East Asian Trough and a strengthening of meridional circulation.Before the occurrence of the freezing rain and snow event,temperature and vapor increases in the stratosphere transferred downward to the troposphere,along with a stratospheric flow in the near-polar region southward to lower latitudes.展开更多
Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island,South China) is recognized as Chaneya hainanensis sp.nov.This new species is characterized by persistent corolla of five obovate pet...Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island,South China) is recognized as Chaneya hainanensis sp.nov.This new species is characterized by persistent corolla of five obovate petals with three subparallel primary venation linked by arching secondary veins,circular central disk bearing two orbicular ovaries or fruit bodies.This discovery confirms the presence of the extinct fruit genus Chaneya in low-latitude tropical area,providing significant fossil evidence for investigating the origin,migration,and phytogeography of this genus and discussing the Tertiary floristic exchanges among North America,eastern Asia,and Europe.Considering the distribution of this genus and its extant relatives and the climate changes during the Cenozoic,we hypothesize that Chaneya was a widespread tropical or subtropical taxon,but,with climate cooling,became extinct in northern latitudes and evolved into Picrasma (Simaroubaceae) and Rutaceae mainly in modern tropics and subtropics.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05110202)the National Natural Science Foundation of China (Grant Nos. 41175073 and U1133603)
文摘Based on a 30-year Atmospheric Model Intercomparison Project(AMIP) simulation using IAP AGCM4.0, the relationship between the East Asian subtropical westerly jet(EASWJ) and summer precipitation over East Asia has been investigated, and compared with observation. It was found the meridional displacement of the EASWJ has a closer relationship with the precipitation over East Asia both from model simulation and observation, with an anomalous southward shift of EASWJ being conducive to rainfall over the Yangtze-Huaihe River Valley(YHRV), and an anomalous northward shift resulting in less rainfall over the YHRV. However, the simulated precipitation anomalies were found to be weaker than observed from the composite analysis, and this would be related to the weakly reproduced mid-upper-level convergence in the mid-high latitudes and ascending motion in the lower latitudes.
基金supported by the National Natural Science Foundation of China(Grant Nos.40875084and40705012)the National Key Technologies R&D Program of China(Grant No.2008BAC40B00)
文摘The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the lower atmosphere over central China to be smaller than the fluxes over southern and northern China by generating more clouds. The existence of a larger quantity of clouds over central China reflects a greater amount of solar radiation back into space. The vertical gradients of upward shortwave radiative fluxes in the atmosphere below 8 km are greater than those above 8 km. The latitudinal-altitude distributions of downward longwave radiative fluxes show a slantwise decreasing trend from low latitudes to high latitudes that gradually weaken in the downward direction. The upward longwave radiative fluxes also weaken in the upward direction but with larger gradients. The maximum heating rates by solar radiation and cooling rates by longwave infrared radiation are located over 28 40°N at 7 8 km mean sea level (MSL), and they are larger than the rates in the northern and southern regions. The heating and cooling rates match well both vertically and geographically.
基金supported by the National Basic Research Program of China(Grant No.2012CB825605)the National Natural Science Foundation of China(Grants Nos.41174126+6 种基金4082501341221003 and 40974082)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20100141110020)the Ocean Public Welfare Scientific Research Project of the State Oceanic Administration of the People’s Republic of China(Grant No.201005017)a China Meteorological Administration(Grant No.GYHY201106011)the Open Programs of State Key Laboratory of Space Weatherthe Fundamental Research Funds for the Central Universities
文摘Gravity wave activity and dissipation in the height range from the low stratosphere to the low thermosphere(25–115 km)covering latitudes between 50°S and 50°N are statistically studied by using 9-year(January 22,2002–December 31,2010)SABER/TIMED temperature data.We propose a method to extract realistic gravity wave fluctuations from the temperature profiles and treat square temperature fluctuations as GW activity.Overall,the gravity wave activity generally increases with height.Near the equator(0°–10°),the gravity wave activity shows a quasi-biennial variation in the stratosphere(below 40 km)while from 20°to 30°,it exhibits an annual variation below 40 km;in low latitudes(0°–30°)between the upper stratosphere and the low thermosphere(40–115 km),the gravity wave activity shows a semi-annual variation.In middle latitudes(40°–50°),the gravity wave activity has a clear annual variation below 85 km.In addition,we observe a four-monthly variation with peaks occurring usually in April,August,December in the northern hemisphere and in February,June,October in the southern hemisphere,respectively,above 85 km in middle latitudes,which has been seldom reported in gravity wave activity.In order to study the dissipation of gravity wave propagation,we calculate the gravity wave dissipation ratio,which is defined as the ratio of the gravity wave growth scale height to the atmosphere density scale height.The height variation of the dissipation ratio indicates that strong gravity wave dissipation mainly concentrates in the three height regions:the stratosphere(30–60 km),the mesopause(around 85 km)and the low thermosphere(above 100 km).Besides,gravity wave energy enhancement can be also observed in the background atmosphere.
基金supported by National Natural Science Foundation of China(Grant Nos.41005021,40830955)Scientific Research Foundation of CUIT(Grant No.CSRF20102)Special Fund for Public Welfare Industry(meteorology)(Grant No.GYHY(QX)2007-6-37)
文摘NCEP/NCAR reanalysis data were used to characterize stratospheric temperature and water-vapor anomalies before and after the freezing rain and snow disaster of South China in 2008,and the influence of stratospheric circulation anomalies on the troposphere.Stratospheric temperature and water-vapor anomalies provided good leading indicators of this weather event.The period from December 1st 2007 to February 28th 2008 was divided into 18 pentads.During the 6th pentad,temperature decreased significantly at 10 hPa in the near-polar stratospheric region,and the decreasing trend strengthened and extended downward and southward to middle and lower latitudes.During the 14th-18th pentads,the temperature decrease reached its maximum and extended to 30°N.This coincided with the widespread freezing rain and snow event.By the end of January 2008,the temperature decrease ended in the near-polar stratospheric region,but continued in the mid-latitude area of the troposphere as the freezing rain and snow weather persisted.Similar to the temperature variations,positive anomalies of relative humidity in the stratospheric near-polar region also strengthened and extended downward and southward,coinciding with the freezing rain and snow event.Along with the significant relationship between the freezing rain and snow disaster and stratospheric circulation anomalies,the stratospheric polar vortex changed its shape in late December,intensifying and spreading downward from the top of the stratosphere and southward to the Asian continent,resulting in a deepening of the East Asian Trough and a strengthening of meridional circulation.Before the occurrence of the freezing rain and snow event,temperature and vapor increases in the stratosphere transferred downward to the troposphere,along with a stratospheric flow in the near-polar region southward to lower latitudes.
基金supported by National Natural Science Foundation of China (Grant Nos. 40972011,31070200)National Basic Research Program of China (973 Program) (Grant No. 2012CB822003)+2 种基金the joint Project of National Natural Science Foundation of China and Russian Foundation for Basic Research (Grant Nos. 41111120083,11-04-91175)Guangdong Natural Science Foundation (Grant No. 10151027501000020)Key Project of the Sun Yat-sen University for inviting foreign teachers and Scientific Research Fund, Hongda Zhang, Sun Yat-sen University
文摘Fossil reproductive structure from the Eocene of the Changchang Basin (Hainan Island,South China) is recognized as Chaneya hainanensis sp.nov.This new species is characterized by persistent corolla of five obovate petals with three subparallel primary venation linked by arching secondary veins,circular central disk bearing two orbicular ovaries or fruit bodies.This discovery confirms the presence of the extinct fruit genus Chaneya in low-latitude tropical area,providing significant fossil evidence for investigating the origin,migration,and phytogeography of this genus and discussing the Tertiary floristic exchanges among North America,eastern Asia,and Europe.Considering the distribution of this genus and its extant relatives and the climate changes during the Cenozoic,we hypothesize that Chaneya was a widespread tropical or subtropical taxon,but,with climate cooling,became extinct in northern latitudes and evolved into Picrasma (Simaroubaceae) and Rutaceae mainly in modern tropics and subtropics.
