Previous studies have found amplified warming over Europe-West Asia and Northeast Asia in summer since the mid- 1990s relative to elsewhere on the Eurasian continent, but the cause of the amplification in these two re...Previous studies have found amplified warming over Europe-West Asia and Northeast Asia in summer since the mid- 1990s relative to elsewhere on the Eurasian continent, but the cause of the amplification in these two regions remains unclear. In this study, we compared the individual contributions of influential factors for amplified warming over these two regions through a quantitative diagnostic analysis based on CFRAM (climate feedback-response analysis method). The changes in surface air temperature are decomposed into the partial changes due to radiative processes (including CO2 concentration, incident solar radiation at the top of the atmosphere, surface albedo, water vapor content, ozone concentration, and clouds) and non-radiative processes (including surface sensible heat flux, surface latent heat flux, and dynamical processes). Our results suggest that the enhanced warming over these two regions is primarily attributable to changes in the radiative processes, which contributed 0.62 and 0.98 K to the region-averaged warming over Europe-West Asia (1.00 K) and Northeast Asia (1.02 K), respectively. Among the radiative processes, the main drivers were clouds, CO2 concentration, and water vapor content. The cloud term alone contributed to the mean amplitude of warming by 0.40 and 0.85 K in Europe-West Asia and Northeast Asia, respectively. In comparison, the non-radiative processes made a much weaker contribution due to the combined impact of surface sensible heat flux, surface latent heat flux, and dynamical processes, accounting for only 0.38 K for the warming in Europe-West Asia and 0.05 K for the warming in Northeast Asia. The resemblance between the influential factors for the amplified warming in these two separate regions implies a common dynamical origin. Thus, this validates the possibility that they originate from the Silk Road pattern.展开更多
By analyzing the features of cold and warm summer of the northeast China during 1961-2002,the results showed the time from 1960s to late 1970s was the phase of cold summer took place,and the time from 1980s to early 1...By analyzing the features of cold and warm summer of the northeast China during 1961-2002,the results showed the time from 1960s to late 1970s was the phase of cold summer took place,and the time from 1980s to early 1990s was the phase of cold and warm summer alternately took place.After the middle and late period of 1990s,it was the concentrated occurrence period of warm summer.The cool and warm summer had the continuity and cluster occurrence characteristics.The frequency of the cool summer was more than the warm summer,and the abnormal degree of warm summer was stronger than the cool summer,and the influence scope was wide.The cool summer had 4 frequent occurrence centers,and the warm summer had 2 frequent occurrence centers,located at the mountain zone and the hills zone.Not only the cool summer was easy to appear,but also the warm summer was easy to happen in the west and the east of Heilongjiang province.Comparatively speaking,the cool summer was easier to appear in the Changbai Mountain 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
Two independent SST atlases are compared for the western tropical North pacific by means of their monthly mean charts. Good agreement is found in three cases involving the 80 F isotherm in the ship-injection temperatu...Two independent SST atlases are compared for the western tropical North pacific by means of their monthly mean charts. Good agreement is found in three cases involving the 80 F isotherm in the ship-injection temperature atlas and the 25 C isotherm in the BT atlas. From winter to summer the area between the equator and the particular isotherms doubles in size while the SST variation inside the areas is small. Also the average northward speed of the isotherms is the same: about 15 cm/sec. Mixed layer depth charts in the BT atlas strengthen an earlier prediction that in the spring and summer of every year excess absorbed solar radiation is advected out of the tropics toward the sub-polar regions, pushed by a downward slope to the north in sea level set up by thermal expansion in the deep and long surface layer trough described earlier. This is the main result of the paper.展开更多
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
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
基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0606403 and 2015CB453202)the National Natural Science Foundation of China(Grant Nos.41790473 and 41421004)
文摘Previous studies have found amplified warming over Europe-West Asia and Northeast Asia in summer since the mid- 1990s relative to elsewhere on the Eurasian continent, but the cause of the amplification in these two regions remains unclear. In this study, we compared the individual contributions of influential factors for amplified warming over these two regions through a quantitative diagnostic analysis based on CFRAM (climate feedback-response analysis method). The changes in surface air temperature are decomposed into the partial changes due to radiative processes (including CO2 concentration, incident solar radiation at the top of the atmosphere, surface albedo, water vapor content, ozone concentration, and clouds) and non-radiative processes (including surface sensible heat flux, surface latent heat flux, and dynamical processes). Our results suggest that the enhanced warming over these two regions is primarily attributable to changes in the radiative processes, which contributed 0.62 and 0.98 K to the region-averaged warming over Europe-West Asia (1.00 K) and Northeast Asia (1.02 K), respectively. Among the radiative processes, the main drivers were clouds, CO2 concentration, and water vapor content. The cloud term alone contributed to the mean amplitude of warming by 0.40 and 0.85 K in Europe-West Asia and Northeast Asia, respectively. In comparison, the non-radiative processes made a much weaker contribution due to the combined impact of surface sensible heat flux, surface latent heat flux, and dynamical processes, accounting for only 0.38 K for the warming in Europe-West Asia and 0.05 K for the warming in Northeast Asia. The resemblance between the influential factors for the amplified warming in these two separate regions implies a common dynamical origin. Thus, this validates the possibility that they originate from the Silk Road pattern.
文摘By analyzing the features of cold and warm summer of the northeast China during 1961-2002,the results showed the time from 1960s to late 1970s was the phase of cold summer took place,and the time from 1980s to early 1990s was the phase of cold and warm summer alternately took place.After the middle and late period of 1990s,it was the concentrated occurrence period of warm summer.The cool and warm summer had the continuity and cluster occurrence characteristics.The frequency of the cool summer was more than the warm summer,and the abnormal degree of warm summer was stronger than the cool summer,and the influence scope was wide.The cool summer had 4 frequent occurrence centers,and the warm summer had 2 frequent occurrence centers,located at the mountain zone and the hills zone.Not only the cool summer was easy to appear,but also the warm summer was easy to happen in the west and the east of Heilongjiang province.Comparatively speaking,the cool summer was easier to appear in the Changbai Mountain 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.
文摘Two independent SST atlases are compared for the western tropical North pacific by means of their monthly mean charts. Good agreement is found in three cases involving the 80 F isotherm in the ship-injection temperature atlas and the 25 C isotherm in the BT atlas. From winter to summer the area between the equator and the particular isotherms doubles in size while the SST variation inside the areas is small. Also the average northward speed of the isotherms is the same: about 15 cm/sec. Mixed layer depth charts in the BT atlas strengthen an earlier prediction that in the spring and summer of every year excess absorbed solar radiation is advected out of the tropics toward the sub-polar regions, pushed by a downward slope to the north in sea level set up by thermal expansion in the deep and long surface layer trough described earlier. This is the main result of the paper.
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.
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。
