This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from ...This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation(MJO)on the Tibetan Plateau Vortex(TPV).Wavelet and composite analysis are used.Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period.In addition,during the active period,the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7.After compositing phases 1 and 7 separately,all meteorological elements in phase 1 are apparently conducive to the generation of the TPV,whereas those in phase 7 are somewhat constrained.With its eastward propagation process,the MJO convection centre spreads eastward,and the vertical circulation within the tropical atmosphere changes.Due to the interaction between the mid-latitude and low-latitude atmosphere,changes occur in the baroclinic characteristics of the atmosphere,the available potential energy and eddy available potential energy of the atmosphere,and the circulation structures of the atmosphere over the Tibetan Plateau(TP) and surrounding areas.This results in significantly different water vapour transportation and latent heat distribution.Advantageous and disadvantageous conditions therefore alternate,leading to a significant difference among the numbers of plateau vortex in different phases.展开更多
In this paper,the relationship between a pair of low-frequency vortexes over the equatorial Indian Ocean and the South China Sea(SCS) summer monsoon onset is studied based on a multi-year(1980-2003) analysis.A pair of...In this paper,the relationship between a pair of low-frequency vortexes over the equatorial Indian Ocean and the South China Sea(SCS) summer monsoon onset is studied based on a multi-year(1980-2003) analysis.A pair of vortexes symmetric about the equator is an important feature prior to the SCS summer monsoon onset.A composite analysis shows that the life cycle of the pair of vortexes is closely associated with the SCS summer monsoon onset.The westerly between the twin cyclones is an important factor to the SCS summer monsoon onset process.展开更多
Spatiotemporal vector and phase properties of interference field of low-frequency signalling tone between three local vortices in a real shallow sea wave-guide have been studied.It has been demonstrated that in the fi...Spatiotemporal vector and phase properties of interference field of low-frequency signalling tone between three local vortices in a real shallow sea wave-guide have been studied.It has been demonstrated that in the field of constructive interference,components of particle velocity field and acoustic pressure are coherent.As a consequence the transfer of signal energy alog the axis of a shallow sea wave-guide is accomplished with plane wave.Physical objects are detected in the field of destructive interference,which,according to known deterministic signs,can be defined as local vortices of the intensity vector.A large-scale vorticity with acoustic intensity vector curl,components different from zero originates in the vicinity of local vortices.Regular particle displacements of local vortices have been detected against combined receiving device phase centre along the axis of a wave-guide.It has been demonstrated that the structure of vortices depends on signal/noise ratio.Local vortices and vorticity form vortex structure of vector acoustic field.Signalling tone with frequency of 88 ± 1 Hz from near-surface moving sound source was taken into consideration.Introduced results of full-scale experiment expand our concepts of real fundamental properties of shallow sea acoustic field and are to be considered in theoretical models.展开更多
为进一步探讨高原低涡与高原大气的基本状况及其联系,通过对1981-2015年低涡频次及OLR、500 h Pa经纬向风场的统计,分析其气候变化及低频振荡特征,并初步探讨了低涡频次与其他三者低频信号之间的联系。结果表明:4-8月是低涡的频发时段;...为进一步探讨高原低涡与高原大气的基本状况及其联系,通过对1981-2015年低涡频次及OLR、500 h Pa经纬向风场的统计,分析其气候变化及低频振荡特征,并初步探讨了低涡频次与其他三者低频信号之间的联系。结果表明:4-8月是低涡的频发时段;低涡频次呈逐年增加的趋势,存在显著的2 a、4 a变化周期和55 d、30 d低频振荡周期;在低涡频发期内,OLR平均值为212.2 W·m^(-2),存在显著的10~12 a变化周期和45 d、20 d低频振荡,滤波中心存在东进和西退的移动特征,在纬向上表现为向南移动,500 h Pa纬向风均值为3.56 m·s^(-1),其逐年及逐日变化均呈下降趋势,存在4 a、10 a的变化周期和75 d、45 d的低频振荡周期,30~60 d滤波信号中心以西退和北进为主要移动特征,60~90 d滤波信号中心向南移动特征明显,500 h Pa经向风以北风分量为主,其逐年及逐日变化均为减小趋势,存在4 a变化周期和10-20 d低频振荡;低涡频次与500 h Pa纬向风区域平均值在1996年发生突变;低涡频次与大气低频振荡存在密切联系,其与500 h Pa经向风呈负相关性,7-8月尤为显著,与OLR和500 h Pa纬向风在4月至7月中旬呈显著正相关,7月中旬至8月转为负相关,其中与OLR 30-60 d滤波信号呈高度负相关性;500 h Pa纬向风滤波信号中心的移动能较好的对应低涡频次空间分布的变化。展开更多
In the mid 20th century, great efforts were made to investigate the formation process of high-latitude cold vortex, which is regarded as a major weather system in the atmospheric circulation. In the late 1970s, Chines...In the mid 20th century, great efforts were made to investigate the formation process of high-latitude cold vortex, which is regarded as a major weather system in the atmospheric circulation. In the late 1970s, Chinese researchers noticed that the Northeast China cold vortex （NECV） is an active and frequently occurring weather system over Northeast Asia, which is generated under specific conditions of topography and land-sea thermal contrast on the local and regional scales. Thereby, the NECV study was broadened to include synoptic situations, mesoscale and dynamic features, the heavy rain process, etc. Since the 21st century, in the context of the global warming, more attention has been paid to studies of the mechanisms that cause the NECV variations during spring and early summer as well as the climatic impacts of the NECV system. Note that the NECV activity, frequent or not, not only affects local temperature and precipitation anomalies, but also regulates the amount of precipitation over northern China, the Huai River basin, and the middle and lower reaches of Yangtze River. The NECV influence can even reach the Guangdon~ Guangxi region. However, compared to the achievements for the blocking system study, theoretical studies with regard to the NECV system are still insufficient. Research activities regarding the mechanisms for the NECV formation, particularly theoretical studies using linear or weak nonlinear methods need to be strengthened in the future. Meanwhile, great efforts should be made to deepen our understanding of the relations of the NECV system to the oceanic thermal forcing, the low-frequency atmospheric variations over mid-high latitudes, and the global warming.展开更多
The onset of the Asian summer monsoon has been a focus in the monsoon study for many years. In this paper, we study the variability and predictability of the Asian summer monsoon onset and demonstrate that this onset ...The onset of the Asian summer monsoon has been a focus in the monsoon study for many years. In this paper, we study the variability and predictability of the Asian summer monsoon onset and demonstrate that this onset is associated with specific atmospheric circulation characteristics. The outbreak of the Asian summer mol）~soon is found to occur first over the southwestern part of the South China Sea （SCS） and the Malay Peninsula region, and the monsoon onset is closely related to intra-seasonal oscillations in the lower atmosphere. These intra-seasonal oscillations consist of two low-frequency vortex pairs, one located to the east of the Philippines and the other over the tropical eastern Indian Ocean. Prior to the Asian summer monsoon onset, a strong low-frequency westerly emerges over the equatorial Indian Ocean and the low-frequency vortex pair develops symmetrically along the equator. The formation and evolution of these low-frequency vortices are important and serve as a good indicator for the Asian summer monsoon onset. The relationship between the northward jumps of the westerly jet over East Asia and the Asian summer monsoon onset over SCS is investigated. It is shown that the northward jump of the westerly jet occurs twice during the transition from winter to summer and these jumps are closely related to the summer monsoon development. The first northward jump （from 25°-28°N to around 30°N） occurs on 8 May on average, about 7 days ahead of the summer monsoon onset over the SCS. It is found that the reverse of meridional temperature gradient in the upper-middle troposphere （500-200 hPa） and the enhancement and northward movement of the subtropical jet in the Southern Hemispheric subtropics are responsible for the first northward jump of the westerly jet.展开更多
Based on the winter 1984/ 1985 ECMWF grid point data subjected to the 30-60 day band-pass filtering and composite analysis,a study is undertaken of the LFO (low-frequency oscillation) structure in the eastern Asian we...Based on the winter 1984/ 1985 ECMWF grid point data subjected to the 30-60 day band-pass filtering and composite analysis,a study is undertaken of the LFO (low-frequency oscillation) structure in the eastern Asian westerly jet entrance and exit regions and the Asia-Pacific low-frequency vortex activity characteristics.Results show that zonal wind oscillations on both sides of the jet core are in anti-phase,in close relation to the E-W displacement of the core. Ranging in NW-SE direction is a low-frequency vortex train (LFVT) emanating from Ural via central Asia to East Asia.A low-frequency vortex of Ural origin,when reaching around 50,80,is split into two parts,one travelling eastward and the other southward,and finally they arc connected cyclonically or anticyclonically at low latitudes,form- ing a vigorous low frequency cyclone or anticyclone in the eastern part of China mainland,completing a full cycle of the LFVT.Further,observed in the central Pacific are a meridional LFVT and a cyclone/anticyclone couplet looping in a counterclockwise sense,giving rise to the LFVT phase shift over this region.展开更多
基金National Basic Research Program of China(2012CB417202)National Natural Science Foundation of China(41175045,91337215,Ul 133603)Special Fund for Meteorological Research in the Public Interest(GYHY201206042)
文摘This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation(MJO)on the Tibetan Plateau Vortex(TPV).Wavelet and composite analysis are used.Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period.In addition,during the active period,the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7.After compositing phases 1 and 7 separately,all meteorological elements in phase 1 are apparently conducive to the generation of the TPV,whereas those in phase 7 are somewhat constrained.With its eastward propagation process,the MJO convection centre spreads eastward,and the vertical circulation within the tropical atmosphere changes.Due to the interaction between the mid-latitude and low-latitude atmosphere,changes occur in the baroclinic characteristics of the atmosphere,the available potential energy and eddy available potential energy of the atmosphere,and the circulation structures of the atmosphere over the Tibetan Plateau(TP) and surrounding areas.This results in significantly different water vapour transportation and latent heat distribution.Advantageous and disadvantageous conditions therefore alternate,leading to a significant difference among the numbers of plateau vortex in different phases.
基金financed by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No. KZCX2-YW-Q11-03)the National Basic Research Program of China(Grant No.2010CB950401)
文摘In this paper,the relationship between a pair of low-frequency vortexes over the equatorial Indian Ocean and the South China Sea(SCS) summer monsoon onset is studied based on a multi-year(1980-2003) analysis.A pair of vortexes symmetric about the equator is an important feature prior to the SCS summer monsoon onset.A composite analysis shows that the life cycle of the pair of vortexes is closely associated with the SCS summer monsoon onset.The westerly between the twin cyclones is an important factor to the SCS summer monsoon onset process.
文摘Spatiotemporal vector and phase properties of interference field of low-frequency signalling tone between three local vortices in a real shallow sea wave-guide have been studied.It has been demonstrated that in the field of constructive interference,components of particle velocity field and acoustic pressure are coherent.As a consequence the transfer of signal energy alog the axis of a shallow sea wave-guide is accomplished with plane wave.Physical objects are detected in the field of destructive interference,which,according to known deterministic signs,can be defined as local vortices of the intensity vector.A large-scale vorticity with acoustic intensity vector curl,components different from zero originates in the vicinity of local vortices.Regular particle displacements of local vortices have been detected against combined receiving device phase centre along the axis of a wave-guide.It has been demonstrated that the structure of vortices depends on signal/noise ratio.Local vortices and vorticity form vortex structure of vector acoustic field.Signalling tone with frequency of 88 ± 1 Hz from near-surface moving sound source was taken into consideration.Introduced results of full-scale experiment expand our concepts of real fundamental properties of shallow sea acoustic field and are to be considered in theoretical models.
文摘为进一步探讨高原低涡与高原大气的基本状况及其联系,通过对1981-2015年低涡频次及OLR、500 h Pa经纬向风场的统计,分析其气候变化及低频振荡特征,并初步探讨了低涡频次与其他三者低频信号之间的联系。结果表明:4-8月是低涡的频发时段;低涡频次呈逐年增加的趋势,存在显著的2 a、4 a变化周期和55 d、30 d低频振荡周期;在低涡频发期内,OLR平均值为212.2 W·m^(-2),存在显著的10~12 a变化周期和45 d、20 d低频振荡,滤波中心存在东进和西退的移动特征,在纬向上表现为向南移动,500 h Pa纬向风均值为3.56 m·s^(-1),其逐年及逐日变化均呈下降趋势,存在4 a、10 a的变化周期和75 d、45 d的低频振荡周期,30~60 d滤波信号中心以西退和北进为主要移动特征,60~90 d滤波信号中心向南移动特征明显,500 h Pa经向风以北风分量为主,其逐年及逐日变化均为减小趋势,存在4 a变化周期和10-20 d低频振荡;低涡频次与500 h Pa纬向风区域平均值在1996年发生突变;低涡频次与大气低频振荡存在密切联系,其与500 h Pa经向风呈负相关性,7-8月尤为显著,与OLR和500 h Pa纬向风在4月至7月中旬呈显著正相关,7月中旬至8月转为负相关,其中与OLR 30-60 d滤波信号呈高度负相关性;500 h Pa纬向风滤波信号中心的移动能较好的对应低涡频次空间分布的变化。
基金Supported by the National Natural Science Foundation of China(41630424,41275096,41175083,41305059,and 41405094)China Meteorological Administration Special Public Welfare Research Fund(GYHY201106016 and GYHY201006020)
文摘In the mid 20th century, great efforts were made to investigate the formation process of high-latitude cold vortex, which is regarded as a major weather system in the atmospheric circulation. In the late 1970s, Chinese researchers noticed that the Northeast China cold vortex （NECV） is an active and frequently occurring weather system over Northeast Asia, which is generated under specific conditions of topography and land-sea thermal contrast on the local and regional scales. Thereby, the NECV study was broadened to include synoptic situations, mesoscale and dynamic features, the heavy rain process, etc. Since the 21st century, in the context of the global warming, more attention has been paid to studies of the mechanisms that cause the NECV variations during spring and early summer as well as the climatic impacts of the NECV system. Note that the NECV activity, frequent or not, not only affects local temperature and precipitation anomalies, but also regulates the amount of precipitation over northern China, the Huai River basin, and the middle and lower reaches of Yangtze River. The NECV influence can even reach the Guangdon~ Guangxi region. However, compared to the achievements for the blocking system study, theoretical studies with regard to the NECV system are still insufficient. Research activities regarding the mechanisms for the NECV formation, particularly theoretical studies using linear or weak nonlinear methods need to be strengthened in the future. Meanwhile, great efforts should be made to deepen our understanding of the relations of the NECV system to the oceanic thermal forcing, the low-frequency atmospheric variations over mid-high latitudes, and the global warming.
基金the National Natural Science Foundation of China （Grant No. 40233033） the Chinese Academy of Sciences （KZCX3-SW-226）.
文摘The onset of the Asian summer monsoon has been a focus in the monsoon study for many years. In this paper, we study the variability and predictability of the Asian summer monsoon onset and demonstrate that this onset is associated with specific atmospheric circulation characteristics. The outbreak of the Asian summer mol）~soon is found to occur first over the southwestern part of the South China Sea （SCS） and the Malay Peninsula region, and the monsoon onset is closely related to intra-seasonal oscillations in the lower atmosphere. These intra-seasonal oscillations consist of two low-frequency vortex pairs, one located to the east of the Philippines and the other over the tropical eastern Indian Ocean. Prior to the Asian summer monsoon onset, a strong low-frequency westerly emerges over the equatorial Indian Ocean and the low-frequency vortex pair develops symmetrically along the equator. The formation and evolution of these low-frequency vortices are important and serve as a good indicator for the Asian summer monsoon onset. The relationship between the northward jumps of the westerly jet over East Asia and the Asian summer monsoon onset over SCS is investigated. It is shown that the northward jump of the westerly jet occurs twice during the transition from winter to summer and these jumps are closely related to the summer monsoon development. The first northward jump （from 25°-28°N to around 30°N） occurs on 8 May on average, about 7 days ahead of the summer monsoon onset over the SCS. It is found that the reverse of meridional temperature gradient in the upper-middle troposphere （500-200 hPa） and the enhancement and northward movement of the subtropical jet in the Southern Hemispheric subtropics are responsible for the first northward jump of the westerly jet.
基金This study is supported by the National Natural Science Foundation of China
文摘Based on the winter 1984/ 1985 ECMWF grid point data subjected to the 30-60 day band-pass filtering and composite analysis,a study is undertaken of the LFO (low-frequency oscillation) structure in the eastern Asian westerly jet entrance and exit regions and the Asia-Pacific low-frequency vortex activity characteristics.Results show that zonal wind oscillations on both sides of the jet core are in anti-phase,in close relation to the E-W displacement of the core. Ranging in NW-SE direction is a low-frequency vortex train (LFVT) emanating from Ural via central Asia to East Asia.A low-frequency vortex of Ural origin,when reaching around 50,80,is split into two parts,one travelling eastward and the other southward,and finally they arc connected cyclonically or anticyclonically at low latitudes,form- ing a vigorous low frequency cyclone or anticyclone in the eastern part of China mainland,completing a full cycle of the LFVT.Further,observed in the central Pacific are a meridional LFVT and a cyclone/anticyclone couplet looping in a counterclockwise sense,giving rise to the LFVT phase shift over this region.
