Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The su...Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.展开更多
The impact of warming and wetting on the ecological environment of the Qinghai-Tibet Plateau(TP)under the background of climate change has been a concern of the global scientific community.In this paper,the optimized ...The impact of warming and wetting on the ecological environment of the Qinghai-Tibet Plateau(TP)under the background of climate change has been a concern of the global scientific community.In this paper,the optimized interpolation variational correction approach is adopted for the analysis of monthly high-resolution satellite precipitation products and observations from meteorological stations during the past 20 years.As a result,the corrected precipitation products can not only supplement the“blank area”of precipitation observation stations on the TP,but also improve the accuracy of the original satellite precipitation products.The precipitation over the TP shows different spatial changes in the vegetation growing season,known as the time from May to September.The precipitation in the vegetation growing season and leaf area index(LAI)in the following month show a similar change pattern,indicating a“one-month lag”response of LAI to precipitation on the TP.Further analysis illustrates the influence of water vapor transport driven by the Asian summer monsoon.Water vapor derived from trans-equatorial air flows across the Indian Ocean and Arabian Sea is strengthened,leading to the increase of precipitation in the central and northern TP,where the trend of warming and wetting and the increase of vegetation tend to be more obvious.By contrast,as a result of the weakening trend of water vapor transport in the middle and low levels in southern TP,the precipitation decreases,and the LAI shows a downtrend,which inhibits the warming and wetting ecological environment in this area.展开更多
A heavy rainstorm named Beijing "7.21"heavy rainstorm hit Beijing on 21 to 22 July 2012, which is recorded as the most severe rainstorm since 1951. The daily precipitation amount in many stations in Beijing ...A heavy rainstorm named Beijing "7.21"heavy rainstorm hit Beijing on 21 to 22 July 2012, which is recorded as the most severe rainstorm since 1951. The daily precipitation amount in many stations in Beijing has broken the history record. Based on the NCAR/NCEP reanalysis data and precipitation observation,the large-scale conditions which caused the "7.21"heavy rainstorm are investigated, with the emphasis on the relationship between it and an equatorial convergence zone, Asian summer monsoon as well as the tropical cyclone over the ocean from the Philippines to the South China Sea(SCS). The results indicated that a great deal of southerly warm and wet moisture carried by northward migrating Asian summer monsoon provided plenty of moisture supplying for the "7.21"heavy rainstorm. When the warm and wet moisture met with the strong cold temperature advection induced by cold troughs or vortexes, an obviously unstable stratification formed, thus leading to the occurrence of heavy precipitation. Without this kind of intense moisture transport, the rainstorm only relying on the role of the cold air from mid-and higher-latitudes could not reach the record-breaking intensity. Further research suggested that the northward movement of an Asian monsoonal warm and wet moisture transport conveyor(MWWTC) was closely related with the active phase of a 30-60 day intra-seasonal oscillation of the Asian summer monsoon. During this time, the monsoon surge triggered and maintained the northward movement of the MWWTC. In addition, compared with another heavy rainstorm named"63.8"heavy rainstorm, which occurred over the Huaihe River Basin in the mid-August 1963 and seriously affected North China, a similar MWWTC was also observed. It was just the intense interaction of the MWWTC with strong cold air from the north that caused this severe rainstorm.展开更多
Based on oceanic and atmospheric parameters retrieved by satellite remote sensing using a neural network method, air-sea heat fluxes over the western Pacific warm pool area were calculated with the advanced the advanc...Based on oceanic and atmospheric parameters retrieved by satellite remote sensing using a neural network method, air-sea heat fluxes over the western Pacific warm pool area were calculated with the advanced the advanced Coupled Ocean-Atmosphere Response Experiment 3.0 (COARE3.0) bulk algorithm method. Then, the average annual and interannual characteristics of these fluxes were analyzed. The rela- tionship between the fluxes and the South China Sea (SCS) summer monsoon onset is highlighted. The results indicate that these fluxes have clear temporal and spatial characteristics. The sensible heat flux is at its maximum in the Kuroshio area, while the latent heat flux is at its maximum in the North Equatorial Current and Kuroshio area. The distribution of average annual air-sea heat fluxes shows that both sensible and latent heat fluxes are maximized in winter and minimized in summer. The air-sea heat fluxes have obvious interannual variations. Correlation analysis indicates a close lag-correlation between air-sea heat fluxes in the western Pacific warm pool area and at the SCS summer monsoon onset. The lagcorrelation can therefore predict the SCS summer monsoon onset, providing a reference for the study of precipitation related to the monsoon.展开更多
The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.Th...The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM.The monsoon indexes for East Asian summer monsoon and land-sea thermal difference,which characterize the intensity of the EASM,show an obvious increase during the onset period of the EASM.Moreover,the land-sea thermal difference is more sensitive to warmer SST.Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China,South China Sea,and the Western Pacific Ocean to the east of the Philippines.While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China,precipitation increases notably in northern China,the South China Sea,the East China Sea,the Yellow Sea,and the Western Pacific to the east of the Philippines.North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent.The surface air temperature shows a warming trend.The warming in the entire troposphere between 30oN and 50oN increases the land-sea thermal contrast,which plays an important role in the enhancement of the EASM.Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension.展开更多
In the present paper, correlation between the South China Sea summer monsoon （SCSSM） onset and heat content in the upper layer of the warm pool in the western Pacific Ocean is examined using the Scripps Institution ...In the present paper, correlation between the South China Sea summer monsoon （SCSSM） onset and heat content in the upper layer of the warm pool in the western Pacific Ocean is examined using the Scripps Institution of Oceanography dataset for the period of 1955-1998 and an approach to prediction the SCSSM onset is proposed. Correlation showes that there exists interdecadal variability of the SCSSM onset demarcated by 1970 with the largest correlation coefficient in the area west of the center of the warm pool rather than near its centers, implying certain effect from other factors involved besides ENSO. As the correlation is poor for the period before 1970, the heat content anomaly of the warm pool after 1970 is used to indicate early or late onset of the SCSSM beforehand. An ideal representative area （1°×1°） for the warm pool heat content was determined with its center at 3°N/138°E. The nearest TAO （TAO-Tropical Atmosphere Ocean-array） mooring to the center is at 2°N/137°E, and chosen to calculate the heat content for prediction. It is suggested that the TAO mooring at 2°N/137°E could be used to predict the SCSSM onset with the heat content in the upper layer, if the correlation between the SCSSM onset and the heat content of the warm pool runs like that of after 1970. On the other hand, if the situation does like the one before 1970, the representative station is determined at 13°S/74°E with relatively poor correlation, meaning that the warm pool in the western Pacific Ocean plays more important role in the SCSSM onset than the Indian Ocean.展开更多
In this study, the East Asian summer climate changes under the 1.5 ℃ global warming （1.5 GW） target in 30 simulations derived from 15 coupled models within the Coupled Model Intercomparison Program phase 5 （CMIP5...In this study, the East Asian summer climate changes under the 1.5 ℃ global warming （1.5 GW） target in 30 simulations derived from 15 coupled models within the Coupled Model Intercomparison Program phase 5 （CMIP5） are examined. Compared with the current summer climate （1975-2005）, both surface air temperature and precipitation increase significantly over the East Asian continent during the 1.5 GW period （average period 2021-2051）. In northeastern China this is particularly pronounced with regional averaged precipitation increases of more than 7.2%, which is greater than that for the whole East Asian continent （approximately 4.2%）. Due to stronger enhancement of precipitation north of 40°N, the leading empirical orthogonal function （EOF） mode of summer precipitation over the East Asian continent changes from tripolar-like mode to dipole mode. As there is stronger surface warming over the East Asian continent than that over surrounding ocean, the land-sea thermal contrast is enhanced during the 1.5 GW period. As a result, the monsoon circulation in the lower troposphere is significantly strengthened, which causes the increased summer precipitation over the East Asian continent. In addition, larger interannual variabilities of East Asian summer monsoon circulation and associated precipitation are also suggested for the 1.5 GW period.展开更多
Based on the monthly mean OLR, geopotential height and wind data from the NCEP/NCAR reanalyzed data sets for 1982-1996, the atmospheric teleconnection associated with the warm pool of the tropical western Pacific and ...Based on the monthly mean OLR, geopotential height and wind data from the NCEP/NCAR reanalyzed data sets for 1982-1996, the atmospheric teleconnection associated with the warm pool of the tropical western Pacific and Asian monsoon region during E1 Nino and non-El Nino years are studied diagnostically in this paper. It is found that, the teleconnection pattern caused by the activity of the Asian summer monsoon (ASM) emanates from the Asian monsoon region to the tropical eastern Pacific via the Aleutians in summer of the El Nino years. In the non-El Nino years, however, the ASM-related teleconnection pattern stretches northward and westward from the Asian monsoon region, exerting its influences mainly on the circulation over middle and high latitude rather than that over the tropical eastern Pacific. Evidences also show that the anomalous convection over the tropical western Pacific warm pool leads to the East Asia/Pacific(EAP) teleconnection pattern during the non-El Nino years. It is interesting to note that the teleconnection in the 500 height field associated with the warm pool convection disappears in the El Nino years. The differences of the teleconnection pattern between the El Nino years and the non-El Nino years suggest that the activities of the ASM and the convection over the warm pool of the tropical western Pacific, the most energetic weather events in boreal summer, are intertwined and interactive with other global-scale circulation in different ways under different climate backgrounds.展开更多
The influence of the tropical Indo-Pacific Ocean heat content on the onset of the Bay of Bengal summer monsoon （BOBSM） onset was investigated using atmospheric data from the NCEP and ocean subsurface temperature dat...The influence of the tropical Indo-Pacific Ocean heat content on the onset of the Bay of Bengal summer monsoon （BOBSM） onset was investigated using atmospheric data from the NCEP and ocean subsurface temperature data from the Japan Metorology Agency （JMA）. Results showed that the onset time of the BOBSM is highly related to the tropical Pacific upper ocean heat content （HC）, especially in the key region of the western Pacific warm pool （WPWP）, during the preceding winter and spring. When the HC anomalies in the WPWP are positive （negative）, the onset of the BOBSM is usually early （late）. Accompanied by the variation of the convection activity over the WPWP, mainly induced by the underlying ocean temperature anomalies, the Walker circulation becomes stronger or weaker. This enhances or weakens the westerly over the tropical Indian Ocean flowing into the BOB in the boreal spring, which is essential to BOBSM onset. The possible mechanism of influence of cyclonic/anti-cyclonic circulation over the northwestern tropical Pacific on BOBSM onset is also discussed.展开更多
The East Asian summer climate is modulated by a low-pressure system over northern East Asia（NEAL） and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little ...The East Asian summer climate is modulated by a low-pressure system over northern East Asia（NEAL） and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little is known about NEAL, especially its change in the future under global warming scenarios. This study investigates the projected change in NEAL in the late twenty-first century, using the outputs of 20 models from Phase 5 of the Coupled Model Intercomparison Project — specifically, their historical climate simulations（HIST） and future climate projections under the Representative Concentration Pathway 4.5（RCP4.5） and 8.5（RCP8.5） scenarios. The results show that the models capture the NEAL well in HIST. The NEAL is weakened in the late twenty-first century under the two RCP scenarios, with a stronger weakening under RCP8.5 than under RCP4.5.The weakened NEAL increases the geopotential height zonal gradient in the west and causes a southerly anomaly, which may bring more moisture and rainfall to northern East Asia.展开更多
This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere co...This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature （SST） anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone （ANWPA）. Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i,e., when the Indian Summer Monsoon （ISM） reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying E1 Nifio. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research.展开更多
南海夏季风的爆发和推进影响着中国夏季雨带的进程。采用美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)和美国国家大气研究中心(National Center for Atmospheric Research,NCAR)再分析资料分析全球变暖...南海夏季风的爆发和推进影响着中国夏季雨带的进程。采用美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)和美国国家大气研究中心(National Center for Atmospheric Research,NCAR)再分析资料分析全球变暖前、后南海夏季风的演变特征。研究结果表明,全球变暖导致南海夏季风减弱,主要出现以下特征:(1)南海夏季风的平均建立时间提早,平均撤退时间推迟,历时长度更长,持续时间有上升趋势。(2)南海夏季风爆发后(6—9月),南海西北部对流层低层(700 hPa以下)由海陆热力差异导致的局地环流在全球变暖后有减弱趋势,进入中国华南和西南地区的西南夏季风有所减弱。(3)夏季风盛行期间,西南风携孟加拉湾水汽经过中南半岛进入中国南海的水汽呈减少趋势,且从南海输入华南的水汽减少,导致中国东部降水变化趋势存在空间差异。(4)南海夏季风指数表明,南海夏季风对南海中南部以及华南东部的影响加强,而对南海北部和西南地区的影响强度明显减弱。展开更多
Based on the Scripps/NODC Joint Environmental Data Analysis Center's data of heat content in upper ocean (1955--1998) and NCEP/NCAR reanalysis data,the relationship between the heat content anomalies in the warm p...Based on the Scripps/NODC Joint Environmental Data Analysis Center's data of heat content in upper ocean (1955--1998) and NCEP/NCAR reanalysis data,the relationship between the heat content anomalies in the warm pool area of the western Pacific (WP) and onset of South China Sea summer monsoon (SCSM) is examined.The results show that the warm pool area (WP) is the place where heat content in the tropical upper layer changes with maximum range and which is most obviously influential to South China Sea summer monsoon.Onset of SCSM is very closely related to the heat content anomaly during the previous period (previous winter and spring) of the WP so that the heat content of March to April in the WP area is a very good predictor for onset of SCSM.When the heat content of the WP area is positive,convection center will be located in the South China Sea-western Pacific with strong convection,a positive anomaly of monsoon circulation and Walker circulation will take place and the subtropical high will be weaker and farther east. Positive anomalous monsoon circulation and Walker circulation will be favorable for westerly and southwesterly flows-SCSM breaks off earlier than normal.Otherwise,SCSM comes later than usual.Large-scale anomalous change of monsoon circulation and Walker circulation seems one of the important mechanisms to influence SCSM.展开更多
We used outputs from climate models that participated in the fourth assessment (AR4) of the Intergovernmental Panel on Climate Change (IPCC) to evaluate the responses of the South Asian summer monsoon (SASM) and the E...We used outputs from climate models that participated in the fourth assessment (AR4) of the Intergovernmental Panel on Climate Change (IPCC) to evaluate the responses of the South Asian summer monsoon (SASM) and the East Asian summer monsoon (EASM) circulations to different warming over land and ocean under a medium warming scenario, SRES A1B. Our results suggest that, even though near-surface warming over the Tibetan Plateau (TP) is greater than that over the tropical Indian Ocean (TIO) and the northwestern Pacific (NWP), the upper-tropospheric land-sea thermal contrasts between the TP and the TIO (TP-TIO) and between the TP and the NWP (TP-NWP) will decrease. At interdecadal and longer time scales, the change in the SASM circulation is consistent with the TP-TIO upper-troposphere thermal contrast. Conversely, the change in the EASM circulation is consistent with the TP-NWP lower-troposphere thermal contrast. However, at the interannual time scale, both changes in the EASM and SASM are significantly correlated with the upper-troposphere thermal contrast. Further analyses suggest that increases in moisture and changes in cloud cover induced by global warming may cause amplified upper-tropospheric warming over the TP and the oceans resulting in inconsistent changes in the vertical temperature distribution over these regions. Because the warming over the TIO and NWP is greater than that over the TP, the TP-TIO meridional and TP-NWP zonal thermal contrasts will both decrease. However, at the lower layer, the difference in thermal capacity between land and sea result in a larger thermal effect in the near-surface region of the TP than those over the surrounding oceans. We showed that a range of factors that affect thermal conditions will likely cause changes in the Asian monsoon across a range of time scales under a warming scenario. These changes reflect differences in the influence of the greenhouse effect and natural variability.展开更多
During the boreal spring of 1966, a warm-core eddy is identified in the upper South China Sea (SCS) west of the Philippines through an analysis of the U.S. Navy′s Master Oceanographic Observation Data Set. This eddy ...During the boreal spring of 1966, a warm-core eddy is identified in the upper South China Sea (SCS) west of the Philippines through an analysis of the U.S. Navy′s Master Oceanographic Observation Data Set. This eddy occurred before the development of the northern summer monsoon and disappeared afterward. We propose that this eddy is a result of the radiative warming during spring and the downwelling due to the anticyclonic forcing at the surface. Our hypothesis suggests an air-sea feedback scenario that may explain the development and withdrawal of the summer monsoon over the SCS. The development phase of the warm-core eddy in this hypothesis is tested by using the Princeton Ocean model.展开更多
It is of practical significance to use the updated Coupled Model Intercomparison Project Phase 6(CMIP6)models to study the impact of changes in land‒sea thermodynamic contrast(TC)on the Asian summer monsoon under diff...It is of practical significance to use the updated Coupled Model Intercomparison Project Phase 6(CMIP6)models to study the impact of changes in land‒sea thermodynamic contrast(TC)on the Asian summer monsoon under different scenarios and to compare the similarities and differences of the impact mechanisms between different monsoon regions.In this study,we investigated future changes of the Asian summer monsoon under four Shared Socioeconomic Pathway(SSP)scenarios using 19 CMIP6 models.The intensity of the South Asian summer monsoon(SASM)is projected to decrease by 2.6%,6.3%,10.1%,and 11.1%,while the East Asian summer monsoon(EASM)intensity is projected to increase by 4.6%,7.9%,7.4%,and 9.8%until the end of the 21st century for SSP126,SSP245,SSP370,and SSP585 scenarios,respectively.Moreover,summer precipitation in Asia is projected to increase remarkably in 2015-2099 under all four scenarios.The inconsistent warming trends over the Tibetan Plateau(TP),Northwest Pacific,and tropical Indian Ocean would greatly impact the monsoon circulations.The upper-troposphere warming trend over the surrounding oceans is remarkably greater than that over the TP,while the near-surface warming trend over the surrounding oceans is smaller than that over the TP.The decrease of upper-troposphere TC between the TP and tropical Indian Ocean results in a weakening of the SASM circulation.The enhancement of the lower-troposphere TC between the TP and Northwest Pacific would strengthen the EASM circulation.Moisture budget analysis shows that the water-vapor would increase in the future,which would thermodynamically enhance summer precipitation through the anomalous vertical moisture transport associated with mean flow.The strengthening of the meridional circulation of the EASM would increase monsoon precipitation,while the weakening of zonal circulation of the SASM would dynamically reduce South Asian summer precipitation.展开更多
Based on the data of monthly precipitation and other monthly meteorological elements of 661 meteorological stations over China from 1961 to 2013, the temporal evolution characteristics of aridity in Hetao area of Nort...Based on the data of monthly precipitation and other monthly meteorological elements of 661 meteorological stations over China from 1961 to 2013, the temporal evolution characteristics of aridity in Hetao area of North China which is drying significantly were studied by using REOF, and the effects of summer monsoon and meteorological factors on the aridity index were discussed. The results showed that climatic aridity in Hetac area of North China tended to increase with time during 1961 -2013. The annual variation and overall trend of climatic aridity in Hetao area of North China was mainly influenced by /SASM1 before the 1990s, and the degree of the influence weakened with global warming. There were certain differ- ences between annual and decadal variations in the effects of the meteorological elements on climatic aridity. The impact of the thermal factors on aridity index was more significant than the dynamic factor after the 1990s, revealing that climate warming aggravated climatic aridity in Hetao area of North China.展开更多
基金National Key Basic Research and Development Planning Program of China(Program 973)(2013CB430202)Basic Research Program of Jiangsu Province,China(BK20130997)+1 种基金National Natural Science Fund of China(91337109)Project Funded by the Priority Academic program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.
基金the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0105)the S&T Development Fund of CAMS(2021KJ022,2021KJ013)。
文摘The impact of warming and wetting on the ecological environment of the Qinghai-Tibet Plateau(TP)under the background of climate change has been a concern of the global scientific community.In this paper,the optimized interpolation variational correction approach is adopted for the analysis of monthly high-resolution satellite precipitation products and observations from meteorological stations during the past 20 years.As a result,the corrected precipitation products can not only supplement the“blank area”of precipitation observation stations on the TP,but also improve the accuracy of the original satellite precipitation products.The precipitation over the TP shows different spatial changes in the vegetation growing season,known as the time from May to September.The precipitation in the vegetation growing season and leaf area index(LAI)in the following month show a similar change pattern,indicating a“one-month lag”response of LAI to precipitation on the TP.Further analysis illustrates the influence of water vapor transport driven by the Asian summer monsoon.Water vapor derived from trans-equatorial air flows across the Indian Ocean and Arabian Sea is strengthened,leading to the increase of precipitation in the central and northern TP,where the trend of warming and wetting and the increase of vegetation tend to be more obvious.By contrast,as a result of the weakening trend of water vapor transport in the middle and low levels in southern TP,the precipitation decreases,and the LAI shows a downtrend,which inhibits the warming and wetting ecological environment in this area.
基金National(Key)Basic Research,Development(973)Program of China(2013CB430202)National Natural Science Foundation of China(41130960)Special Project in Climate Change of China Meteorological Administration(CCSF201701)
文摘A heavy rainstorm named Beijing "7.21"heavy rainstorm hit Beijing on 21 to 22 July 2012, which is recorded as the most severe rainstorm since 1951. The daily precipitation amount in many stations in Beijing has broken the history record. Based on the NCAR/NCEP reanalysis data and precipitation observation,the large-scale conditions which caused the "7.21"heavy rainstorm are investigated, with the emphasis on the relationship between it and an equatorial convergence zone, Asian summer monsoon as well as the tropical cyclone over the ocean from the Philippines to the South China Sea(SCS). The results indicated that a great deal of southerly warm and wet moisture carried by northward migrating Asian summer monsoon provided plenty of moisture supplying for the "7.21"heavy rainstorm. When the warm and wet moisture met with the strong cold temperature advection induced by cold troughs or vortexes, an obviously unstable stratification formed, thus leading to the occurrence of heavy precipitation. Without this kind of intense moisture transport, the rainstorm only relying on the role of the cold air from mid-and higher-latitudes could not reach the record-breaking intensity. Further research suggested that the northward movement of an Asian monsoonal warm and wet moisture transport conveyor(MWWTC) was closely related with the active phase of a 30-60 day intra-seasonal oscillation of the Asian summer monsoon. During this time, the monsoon surge triggered and maintained the northward movement of the MWWTC. In addition, compared with another heavy rainstorm named"63.8"heavy rainstorm, which occurred over the Huaihe River Basin in the mid-August 1963 and seriously affected North China, a similar MWWTC was also observed. It was just the intense interaction of the MWWTC with strong cold air from the north that caused this severe rainstorm.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Science(KZCX2-YW-Q11-02)the National Basic Research Program of China (2012CB417402)
文摘Based on oceanic and atmospheric parameters retrieved by satellite remote sensing using a neural network method, air-sea heat fluxes over the western Pacific warm pool area were calculated with the advanced the advanced Coupled Ocean-Atmosphere Response Experiment 3.0 (COARE3.0) bulk algorithm method. Then, the average annual and interannual characteristics of these fluxes were analyzed. The rela- tionship between the fluxes and the South China Sea (SCS) summer monsoon onset is highlighted. The results indicate that these fluxes have clear temporal and spatial characteristics. The sensible heat flux is at its maximum in the Kuroshio area, while the latent heat flux is at its maximum in the North Equatorial Current and Kuroshio area. The distribution of average annual air-sea heat fluxes shows that both sensible and latent heat fluxes are maximized in winter and minimized in summer. The air-sea heat fluxes have obvious interannual variations. Correlation analysis indicates a close lag-correlation between air-sea heat fluxes in the western Pacific warm pool area and at the SCS summer monsoon onset. The lagcorrelation can therefore predict the SCS summer monsoon onset, providing a reference for the study of precipitation related to the monsoon.
基金National Program on Key Basic Research Project of China (973 Program) (2007CB411805 2010CB428505)National Natural Science Foundation of China (40830958)
文摘The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM.The monsoon indexes for East Asian summer monsoon and land-sea thermal difference,which characterize the intensity of the EASM,show an obvious increase during the onset period of the EASM.Moreover,the land-sea thermal difference is more sensitive to warmer SST.Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China,South China Sea,and the Western Pacific Ocean to the east of the Philippines.While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China,precipitation increases notably in northern China,the South China Sea,the East China Sea,the Yellow Sea,and the Western Pacific to the east of the Philippines.North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent.The surface air temperature shows a warming trend.The warming in the entire troposphere between 30oN and 50oN increases the land-sea thermal contrast,which plays an important role in the enhancement of the EASM.Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension.
基金Supported by the National Basic Research Program of China (973 Programm) (No.2007CB411802 and 2006CB403603)
文摘In the present paper, correlation between the South China Sea summer monsoon （SCSSM） onset and heat content in the upper layer of the warm pool in the western Pacific Ocean is examined using the Scripps Institution of Oceanography dataset for the period of 1955-1998 and an approach to prediction the SCSSM onset is proposed. Correlation showes that there exists interdecadal variability of the SCSSM onset demarcated by 1970 with the largest correlation coefficient in the area west of the center of the warm pool rather than near its centers, implying certain effect from other factors involved besides ENSO. As the correlation is poor for the period before 1970, the heat content anomaly of the warm pool after 1970 is used to indicate early or late onset of the SCSSM beforehand. An ideal representative area （1°×1°） for the warm pool heat content was determined with its center at 3°N/138°E. The nearest TAO （TAO-Tropical Atmosphere Ocean-array） mooring to the center is at 2°N/137°E, and chosen to calculate the heat content for prediction. It is suggested that the TAO mooring at 2°N/137°E could be used to predict the SCSSM onset with the heat content in the upper layer, if the correlation between the SCSSM onset and the heat content of the warm pool runs like that of after 1970. On the other hand, if the situation does like the one before 1970, the representative station is determined at 13°S/74°E with relatively poor correlation, meaning that the warm pool in the western Pacific Ocean plays more important role in the SCSSM onset than the Indian Ocean.
基金This research was supported by the National Key R＆D Program of China （2017YFA0603802）, the National Natural Science Foundation of China （41661144005 and 41320104007）, and the CAS-PKU Joint Research Program. We would like to thanks the IPCC for providing the CMIP5 datasets （http：//www.ipccdata.org/sim/gcm_monthly/AR5/Reference-Archive.html）.
文摘In this study, the East Asian summer climate changes under the 1.5 ℃ global warming （1.5 GW） target in 30 simulations derived from 15 coupled models within the Coupled Model Intercomparison Program phase 5 （CMIP5） are examined. Compared with the current summer climate （1975-2005）, both surface air temperature and precipitation increase significantly over the East Asian continent during the 1.5 GW period （average period 2021-2051）. In northeastern China this is particularly pronounced with regional averaged precipitation increases of more than 7.2%, which is greater than that for the whole East Asian continent （approximately 4.2%）. Due to stronger enhancement of precipitation north of 40°N, the leading empirical orthogonal function （EOF） mode of summer precipitation over the East Asian continent changes from tripolar-like mode to dipole mode. As there is stronger surface warming over the East Asian continent than that over surrounding ocean, the land-sea thermal contrast is enhanced during the 1.5 GW period. As a result, the monsoon circulation in the lower troposphere is significantly strengthened, which causes the increased summer precipitation over the East Asian continent. In addition, larger interannual variabilities of East Asian summer monsoon circulation and associated precipitation are also suggested for the 1.5 GW period.
文摘Based on the monthly mean OLR, geopotential height and wind data from the NCEP/NCAR reanalyzed data sets for 1982-1996, the atmospheric teleconnection associated with the warm pool of the tropical western Pacific and Asian monsoon region during E1 Nino and non-El Nino years are studied diagnostically in this paper. It is found that, the teleconnection pattern caused by the activity of the Asian summer monsoon (ASM) emanates from the Asian monsoon region to the tropical eastern Pacific via the Aleutians in summer of the El Nino years. In the non-El Nino years, however, the ASM-related teleconnection pattern stretches northward and westward from the Asian monsoon region, exerting its influences mainly on the circulation over middle and high latitude rather than that over the tropical eastern Pacific. Evidences also show that the anomalous convection over the tropical western Pacific warm pool leads to the East Asia/Pacific(EAP) teleconnection pattern during the non-El Nino years. It is interesting to note that the teleconnection in the 500 height field associated with the warm pool convection disappears in the El Nino years. The differences of the teleconnection pattern between the El Nino years and the non-El Nino years suggest that the activities of the ASM and the convection over the warm pool of the tropical western Pacific, the most energetic weather events in boreal summer, are intertwined and interactive with other global-scale circulation in different ways under different climate backgrounds.
基金supported by the National Basic Research Program (973 Program)(Grant No. 2012CB417403)the National Natural Science Foundation of China (Grant Nos. 40890151,and 41106016)
文摘The influence of the tropical Indo-Pacific Ocean heat content on the onset of the Bay of Bengal summer monsoon （BOBSM） onset was investigated using atmospheric data from the NCEP and ocean subsurface temperature data from the Japan Metorology Agency （JMA）. Results showed that the onset time of the BOBSM is highly related to the tropical Pacific upper ocean heat content （HC）, especially in the key region of the western Pacific warm pool （WPWP）, during the preceding winter and spring. When the HC anomalies in the WPWP are positive （negative）, the onset of the BOBSM is usually early （late）. Accompanied by the variation of the convection activity over the WPWP, mainly induced by the underlying ocean temperature anomalies, the Walker circulation becomes stronger or weaker. This enhances or weakens the westerly over the tropical Indian Ocean flowing into the BOB in the boreal spring, which is essential to BOBSM onset. The possible mechanism of influence of cyclonic/anti-cyclonic circulation over the northwestern tropical Pacific on BOBSM onset is also discussed.
基金supported by the National Natural Science Foundation of China[grant number 41375086],[grant number41305063]
文摘The East Asian summer climate is modulated by a low-pressure system over northern East Asia（NEAL） and a subtropical high over the western North Pacific. Many studies have focused on the subtropical high, but little is known about NEAL, especially its change in the future under global warming scenarios. This study investigates the projected change in NEAL in the late twenty-first century, using the outputs of 20 models from Phase 5 of the Coupled Model Intercomparison Project — specifically, their historical climate simulations（HIST） and future climate projections under the Representative Concentration Pathway 4.5（RCP4.5） and 8.5（RCP8.5） scenarios. The results show that the models capture the NEAL well in HIST. The NEAL is weakened in the late twenty-first century under the two RCP scenarios, with a stronger weakening under RCP8.5 than under RCP4.5.The weakened NEAL increases the geopotential height zonal gradient in the west and causes a southerly anomaly, which may bring more moisture and rainfall to northern East Asia.
基金Supported by the National Basic Research Program of China(973 Program)(Nos.2010CB428504,2012CB956002)the National Natural Science Foundation of China(Nos.40906005,41105059,41065005,GYHY201106017,GYHY201306027)the National Key Technology Research and Development Program(No.2009BAC51B01)
文摘This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature （SST） anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone （ANWPA）. Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i,e., when the Indian Summer Monsoon （ISM） reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying E1 Nifio. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research.
文摘南海夏季风的爆发和推进影响着中国夏季雨带的进程。采用美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)和美国国家大气研究中心(National Center for Atmospheric Research,NCAR)再分析资料分析全球变暖前、后南海夏季风的演变特征。研究结果表明,全球变暖导致南海夏季风减弱,主要出现以下特征:(1)南海夏季风的平均建立时间提早,平均撤退时间推迟,历时长度更长,持续时间有上升趋势。(2)南海夏季风爆发后(6—9月),南海西北部对流层低层(700 hPa以下)由海陆热力差异导致的局地环流在全球变暖后有减弱趋势,进入中国华南和西南地区的西南夏季风有所减弱。(3)夏季风盛行期间,西南风携孟加拉湾水汽经过中南半岛进入中国南海的水汽呈减少趋势,且从南海输入华南的水汽减少,导致中国东部降水变化趋势存在空间差异。(4)南海夏季风指数表明,南海夏季风对南海中南部以及华南东部的影响加强,而对南海北部和西南地区的影响强度明显减弱。
基金National Climbing Project A:"South China Sea Monsoon Experiments"CAS Innovation Project (No.ZKCX2-SW-210)Project of Natural Sciences Fund of Shandong Province"A study of relationship between warm pool thermal state anomalies and summer rainfall in Shandong"
文摘Based on the Scripps/NODC Joint Environmental Data Analysis Center's data of heat content in upper ocean (1955--1998) and NCEP/NCAR reanalysis data,the relationship between the heat content anomalies in the warm pool area of the western Pacific (WP) and onset of South China Sea summer monsoon (SCSM) is examined.The results show that the warm pool area (WP) is the place where heat content in the tropical upper layer changes with maximum range and which is most obviously influential to South China Sea summer monsoon.Onset of SCSM is very closely related to the heat content anomaly during the previous period (previous winter and spring) of the WP so that the heat content of March to April in the WP area is a very good predictor for onset of SCSM.When the heat content of the WP area is positive,convection center will be located in the South China Sea-western Pacific with strong convection,a positive anomaly of monsoon circulation and Walker circulation will take place and the subtropical high will be weaker and farther east. Positive anomalous monsoon circulation and Walker circulation will be favorable for westerly and southwesterly flows-SCSM breaks off earlier than normal.Otherwise,SCSM comes later than usual.Large-scale anomalous change of monsoon circulation and Walker circulation seems one of the important mechanisms to influence SCSM.
基金supported by the National Basic Research Program of China (2010CB428606)the National Key Science and Technology Program of China (2007BAC29B01)
文摘We used outputs from climate models that participated in the fourth assessment (AR4) of the Intergovernmental Panel on Climate Change (IPCC) to evaluate the responses of the South Asian summer monsoon (SASM) and the East Asian summer monsoon (EASM) circulations to different warming over land and ocean under a medium warming scenario, SRES A1B. Our results suggest that, even though near-surface warming over the Tibetan Plateau (TP) is greater than that over the tropical Indian Ocean (TIO) and the northwestern Pacific (NWP), the upper-tropospheric land-sea thermal contrasts between the TP and the TIO (TP-TIO) and between the TP and the NWP (TP-NWP) will decrease. At interdecadal and longer time scales, the change in the SASM circulation is consistent with the TP-TIO upper-troposphere thermal contrast. Conversely, the change in the EASM circulation is consistent with the TP-NWP lower-troposphere thermal contrast. However, at the interannual time scale, both changes in the EASM and SASM are significantly correlated with the upper-troposphere thermal contrast. Further analyses suggest that increases in moisture and changes in cloud cover induced by global warming may cause amplified upper-tropospheric warming over the TP and the oceans resulting in inconsistent changes in the vertical temperature distribution over these regions. Because the warming over the TIO and NWP is greater than that over the TP, the TP-TIO meridional and TP-NWP zonal thermal contrasts will both decrease. However, at the lower layer, the difference in thermal capacity between land and sea result in a larger thermal effect in the near-surface region of the TP than those over the surrounding oceans. We showed that a range of factors that affect thermal conditions will likely cause changes in the Asian monsoon across a range of time scales under a warming scenario. These changes reflect differences in the influence of the greenhouse effect and natural variability.
文摘During the boreal spring of 1966, a warm-core eddy is identified in the upper South China Sea (SCS) west of the Philippines through an analysis of the U.S. Navy′s Master Oceanographic Observation Data Set. This eddy occurred before the development of the northern summer monsoon and disappeared afterward. We propose that this eddy is a result of the radiative warming during spring and the downwelling due to the anticyclonic forcing at the surface. Our hypothesis suggests an air-sea feedback scenario that may explain the development and withdrawal of the summer monsoon over the SCS. The development phase of the warm-core eddy in this hypothesis is tested by using the Princeton Ocean model.
基金funded by the Second Tibetan Plateau Scientific Expedition and Research Program of China(2019QZKK0208)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20100304)+1 种基金the National Natural Science Foundation of China(41790471)the National Key Research and Development Program of China(2016YFA0602200,2019YFC1510400).
文摘It is of practical significance to use the updated Coupled Model Intercomparison Project Phase 6(CMIP6)models to study the impact of changes in land‒sea thermodynamic contrast(TC)on the Asian summer monsoon under different scenarios and to compare the similarities and differences of the impact mechanisms between different monsoon regions.In this study,we investigated future changes of the Asian summer monsoon under four Shared Socioeconomic Pathway(SSP)scenarios using 19 CMIP6 models.The intensity of the South Asian summer monsoon(SASM)is projected to decrease by 2.6%,6.3%,10.1%,and 11.1%,while the East Asian summer monsoon(EASM)intensity is projected to increase by 4.6%,7.9%,7.4%,and 9.8%until the end of the 21st century for SSP126,SSP245,SSP370,and SSP585 scenarios,respectively.Moreover,summer precipitation in Asia is projected to increase remarkably in 2015-2099 under all four scenarios.The inconsistent warming trends over the Tibetan Plateau(TP),Northwest Pacific,and tropical Indian Ocean would greatly impact the monsoon circulations.The upper-troposphere warming trend over the surrounding oceans is remarkably greater than that over the TP,while the near-surface warming trend over the surrounding oceans is smaller than that over the TP.The decrease of upper-troposphere TC between the TP and tropical Indian Ocean results in a weakening of the SASM circulation.The enhancement of the lower-troposphere TC between the TP and Northwest Pacific would strengthen the EASM circulation.Moisture budget analysis shows that the water-vapor would increase in the future,which would thermodynamically enhance summer precipitation through the anomalous vertical moisture transport associated with mean flow.The strengthening of the meridional circulation of the EASM would increase monsoon precipitation,while the weakening of zonal circulation of the SASM would dynamically reduce South Asian summer precipitation.
基金Supported by the State Key Development Program for Basic Research of China(2013CB430200)
文摘Based on the data of monthly precipitation and other monthly meteorological elements of 661 meteorological stations over China from 1961 to 2013, the temporal evolution characteristics of aridity in Hetao area of North China which is drying significantly were studied by using REOF, and the effects of summer monsoon and meteorological factors on the aridity index were discussed. The results showed that climatic aridity in Hetac area of North China tended to increase with time during 1961 -2013. The annual variation and overall trend of climatic aridity in Hetao area of North China was mainly influenced by /SASM1 before the 1990s, and the degree of the influence weakened with global warming. There were certain differ- ences between annual and decadal variations in the effects of the meteorological elements on climatic aridity. The impact of the thermal factors on aridity index was more significant than the dynamic factor after the 1990s, revealing that climate warming aggravated climatic aridity in Hetao area of North China.
