利用1948-2010年NCEP/NCAR全球大气逐日平均的再分析资料分析了青藏高原夏季风和南海夏季风大气低频振荡的可能关系。结果表明,夏半年高原地区和南海地区季风均存在明显的30~50天的振荡周期,并且两者在这个振荡周期上存在明显的位相关系...利用1948-2010年NCEP/NCAR全球大气逐日平均的再分析资料分析了青藏高原夏季风和南海夏季风大气低频振荡的可能关系。结果表明,夏半年高原地区和南海地区季风均存在明显的30~50天的振荡周期,并且两者在这个振荡周期上存在明显的位相关系,即南海夏季风的低频振荡比青藏高原夏季风提前约3/4个位相,对500 h Pa和850 h Pa低频风场的研究也得出同样的结果。两者存在明显位相关系的原因之一可能是3月下旬开始南海向青藏高原地区的低频输送。展开更多
The distribution characteristics of cloud-top and tropopause height in the tropics and subtropics in boreal summer are analyzed based on CALIPSO data for the period 2008-2012.The maximum values of cloud-top vertical c...The distribution characteristics of cloud-top and tropopause height in the tropics and subtropics in boreal summer are analyzed based on CALIPSO data for the period 2008-2012.The maximum values of cloud-top vertical cumulative frequency above the tropopause （CTAT） are concentrated in three tropical regions：the Asian summer monsoon region,Central America,and western Africa.The contributions to the area-weighted CTAT frequency in the three regions from the Northern Hemisphere are 49.0%,13.5%,and 12.4%,respectively.Moreover,the contribution of troposphere-to-stratosphere transport （TST） in the Asian monsoon region to global TST can be far greater than 50%,according to analysis of the continuous equation,velocity potential,and divergent wind from ERA-Interim data.Furthermore,the Asian summer monsoon circulation system controls the distribution of the cloud top.On the south side of the Tibetan Plateau,the maximum frequency of the cloud top,more than 10% per 500 m vertically,is most likely to appear in the core of the high-level easterlyjet near the tropopause height （16.5 km）.Over the Tibetan Plateau,the maximum frequency of the cloud top,greater than 3% per 500 m vertically,is suppressed below 11 km,far away from the thermodynamic tropopause height but close to the dynamic tropopause height of 2 PVU （potential vorticity units）.展开更多
In this paper, Geostationary Meteorological Satellite (GMS) infrared black-body temperature (Tbb) data from June to August 1998 are used to automatically track the activity of Mesoscale Convective System (MCS) over th...In this paper, Geostationary Meteorological Satellite (GMS) infrared black-body temperature (Tbb) data from June to August 1998 are used to automatically track the activity of Mesoscale Convective System (MCS) over the Tibetan Plateau in China. Consequently, the features of MCS, such as area, intensity, life cycle, activity region and shape, are obtained. High Resolution Limited Area Analysis and Forecasting System (HLAFS) values provided by China National Meteorological Center are used to study the relationships between the MCS trajectories and their environmental physical field values, based on the distribution and trajectories of MCSs over the Tibetan Plateau. Favorable environmental physical field charts of influencing MCS movement out of the Tibetan Plateau in different UTC (Universal Time Coordinate) are developed by using spatial data mining techniques at levels of 400hPa and 500hPa, respectively.展开更多
There are numerous lakes on the Tibetan Plateau(TP),but the role of lake temperature in precipitation over the TP remains unclear.Here the Weather Research and Forecasting(WRF) model was used to detect the impact of l...There are numerous lakes on the Tibetan Plateau(TP),but the role of lake temperature in precipitation over the TP remains unclear.Here the Weather Research and Forecasting(WRF) model was used to detect the impact of lakes on summer rainfall.Three test cases were used to evaluate the effect of lakes surface temperature(LSTs) on precipitation variability.The three cases used different methods to determine initial LSTs,including using sea surface temperature data(SST),the WRF inland water module(avg_tsfc),and a lake model.Results show that when precipitation was stimulated over the TP,LSTs cannot be initialized using SST,which led to large discrepancies of precipitation.Compared with the simulations,the simulated precipitation were improved obviously with LSTs using avg_tsfc,indicating that LSTs have an considerable influence on determining precipitation over the TP.Due to a lack of observational data,the lake scheme does not improve on rainfall simulation,but does effectively simulate precipitation pattern over lakes,such as rainfall over the lakes was dominated by convection during the nighttime.Though the simulated precipitation using SST to initialize LSTs caused largediscrepancies,it suggested that precipitation increase especially convective precipitation with increase in LSTs,which confirmed that the moisture from lakes cannot be neglected over the TP.Generally,it was necessary to monitor the LSTs for accurate weather and climate prediction over the TP.展开更多
Based on the observation data and the reanalysis datasets, the variability and the circulation features influencing precipitation in the Tibetan Plateau (TP) are investigated. Taking into account the effects of topogr...Based on the observation data and the reanalysis datasets, the variability and the circulation features influencing precipitation in the Tibetan Plateau (TP) are investigated. Taking into account the effects of topography, surface winds are deconstructed into flow-around and flow-over components relative to the TP. Climatologically, the flow-around component mainly represents cyclonic circulation in the TP during the summer. The transition zone of total precipitation in the summer parallels the convergence belt between the southerlies and the northerlies of the flow-over component. The leading mode of rainfall anomalies in the TP has a meridional dipole structure, and the first principal component (PC1) mainly depicts the variation of rainfall in the southern TP. The wet southern TP experiences strengthened flow-over, which in turn mechanistically favors intensified ascent forced by the flow-over component. In addition, variations in the Indian summer monsoon (ISM) have an important role in influencing the flow over the southern TP, and the ISM ultimately impacts the precipitation over southern TP.展开更多
We present validation studies of MLS V2.2 and V3.3 water vapor(WV) and ozone profiles over the Tibetan Plateau(Naqu and Lhasa) and its adjacent region(Tengchong) respectively by using the balloon-borne Cryogenic Frost...We present validation studies of MLS V2.2 and V3.3 water vapor(WV) and ozone profiles over the Tibetan Plateau(Naqu and Lhasa) and its adjacent region(Tengchong) respectively by using the balloon-borne Cryogenic Frost point Hygrometer and Electrochemical Concentration Cell ozonesonde. Coincident in situ measurements were selected to compare the MLS V2.2 and V3.3 WV and ozone profiles for understanding the applicability of the two version MLS products over the region. MLS V2.2 and V3.3 WV profiles respectively show their differences within ?2.2±15.7%(n=74) and 0.3±14.9%(n=75) in the stratosphere at and above 82.5 h Pa. Accordingly, at 100 h Pa, the altitude approaching the tropopuase height, differences are within 9.8± 46.0%(n=18) and 23.0±45.8%(n=17), and they are within 21.5±90.6%(n=104) and 6.0±83.4%(n=99) in upper troposphere. The differences of MLS ozone are within ?11.7±16.3%(n=135, V2.2) and 15.6±24.2%(n=305, V3.3) at and above 82.5 h Pa. At 100 h Pa, they are within ?3.5±54.4%(n=27) and ?8.7±41.6%(n=38), and within 18.0±79.1%(n=47) and 34.2±76.6%(n=160) in the upper troposphere. The relative difference of MLS WV and ozone profile has significant oscillation and scatter at upper troposphere and lower stratosphere partly due to the stronger gradients of WV and ozone concentrations here as well the linear interpolation of sonde data for the intercomparison. At and below 70 h Pa, the relative differences of MLS ozone are significantly larger over Lhasa during the Tibetan Plateau "ozone valley" season, which is also the Asian Summer Monsoon period. The MLS ozone differences over the three sites are similar in their vertical distributions during that period. A simple linear correlation analysis between MLS and sonde profiles indicates that the sensitivity of MLS profile products is related to concentrations at each pressure level. The MLS V3.3 product sensitivity is slightly improved for WV at and above 82.5 h Pa, whereas it is not obvious for ozone. The possible factors contributing to the differences of the MLS profile products of WV and ozone are discussed.展开更多
Based on numerical simulation, this study explored the characteristics and interactions of surface sensible heating and atmospheric latent heating over the main part of the Tibetan Plateau, i.e., terrain at elevations...Based on numerical simulation, this study explored the characteristics and interactions of surface sensible heating and atmospheric latent heating over the main part of the Tibetan Plateau, i.e., terrain at elevations >2 km in summer. The impacts of these two types of heating on local vertical motion and monsoonal meridional circulation were compared. Theoretical analysis and numerical experimentation demonstrated that by changing the configuration of the upper-tropospheric air temperature and circulation, the two types of heating could generate both minimum absolute vorticity and abnormal potential vorticity forcing near the tropopause, enhance the meridional circulation of the Asian summer monsoon, and produce an eastward-propagating Rossby wave train within the mid-latitude westerly flow. Consequently, the manifestations of these features were shown to influence the circulation of the Northern Hemisphere.展开更多
文摘利用1948-2010年NCEP/NCAR全球大气逐日平均的再分析资料分析了青藏高原夏季风和南海夏季风大气低频振荡的可能关系。结果表明,夏半年高原地区和南海地区季风均存在明显的30~50天的振荡周期,并且两者在这个振荡周期上存在明显的位相关系,即南海夏季风的低频振荡比青藏高原夏季风提前约3/4个位相,对500 h Pa和850 h Pa低频风场的研究也得出同样的结果。两者存在明显位相关系的原因之一可能是3月下旬开始南海向青藏高原地区的低频输送。
基金supported by National Key Research and Development Program of China[grant number 2017YFC1501802]the National Natural Science Foundation of China[grant number 41375047],[grant number 91537213],and[grant number 41675039]
文摘The distribution characteristics of cloud-top and tropopause height in the tropics and subtropics in boreal summer are analyzed based on CALIPSO data for the period 2008-2012.The maximum values of cloud-top vertical cumulative frequency above the tropopause （CTAT） are concentrated in three tropical regions：the Asian summer monsoon region,Central America,and western Africa.The contributions to the area-weighted CTAT frequency in the three regions from the Northern Hemisphere are 49.0%,13.5%,and 12.4%,respectively.Moreover,the contribution of troposphere-to-stratosphere transport （TST） in the Asian monsoon region to global TST can be far greater than 50%,according to analysis of the continuous equation,velocity potential,and divergent wind from ERA-Interim data.Furthermore,the Asian summer monsoon circulation system controls the distribution of the cloud top.On the south side of the Tibetan Plateau,the maximum frequency of the cloud top,more than 10% per 500 m vertically,is most likely to appear in the core of the high-level easterlyjet near the tropopause height （16.5 km）.Over the Tibetan Plateau,the maximum frequency of the cloud top,greater than 3% per 500 m vertically,is suppressed below 11 km,far away from the thermodynamic tropopause height but close to the dynamic tropopause height of 2 PVU （potential vorticity units）.
基金Under the auspices of the National Natural Science Foundation of China (No. 40371080), Key Project of ChineseMinistry of Education (No. 104083), Foundation of Wuhan University State Key Laboratory of Information Engineering in Survey-ing, Mapping and Remote Sensing (No. WKL(03) 0103), the Scientific Research Foundation for the Returned Overseas ChineseScholars, Ministry of Education
文摘In this paper, Geostationary Meteorological Satellite (GMS) infrared black-body temperature (Tbb) data from June to August 1998 are used to automatically track the activity of Mesoscale Convective System (MCS) over the Tibetan Plateau in China. Consequently, the features of MCS, such as area, intensity, life cycle, activity region and shape, are obtained. High Resolution Limited Area Analysis and Forecasting System (HLAFS) values provided by China National Meteorological Center are used to study the relationships between the MCS trajectories and their environmental physical field values, based on the distribution and trajectories of MCSs over the Tibetan Plateau. Favorable environmental physical field charts of influencing MCS movement out of the Tibetan Plateau in different UTC (Universal Time Coordinate) are developed by using spatial data mining techniques at levels of 400hPa and 500hPa, respectively.
基金The National Natural Science Foundation of China(Grant Nos.41401226 and 41190080)the China Postdoctoral Science Foundation(Grant No.2015M570865) joint support this work
文摘There are numerous lakes on the Tibetan Plateau(TP),but the role of lake temperature in precipitation over the TP remains unclear.Here the Weather Research and Forecasting(WRF) model was used to detect the impact of lakes on summer rainfall.Three test cases were used to evaluate the effect of lakes surface temperature(LSTs) on precipitation variability.The three cases used different methods to determine initial LSTs,including using sea surface temperature data(SST),the WRF inland water module(avg_tsfc),and a lake model.Results show that when precipitation was stimulated over the TP,LSTs cannot be initialized using SST,which led to large discrepancies of precipitation.Compared with the simulations,the simulated precipitation were improved obviously with LSTs using avg_tsfc,indicating that LSTs have an considerable influence on determining precipitation over the TP.Due to a lack of observational data,the lake scheme does not improve on rainfall simulation,but does effectively simulate precipitation pattern over lakes,such as rainfall over the lakes was dominated by convection during the nighttime.Though the simulated precipitation using SST to initialize LSTs caused largediscrepancies,it suggested that precipitation increase especially convective precipitation with increase in LSTs,which confirmed that the moisture from lakes cannot be neglected over the TP.Generally,it was necessary to monitor the LSTs for accurate weather and climate prediction over the TP.
基金supported by the National Basic Research Program of China (973 program, Grant No.2010CB950400)the National Natural Science Foundation of China (Grant No. 41030961)
文摘Based on the observation data and the reanalysis datasets, the variability and the circulation features influencing precipitation in the Tibetan Plateau (TP) are investigated. Taking into account the effects of topography, surface winds are deconstructed into flow-around and flow-over components relative to the TP. Climatologically, the flow-around component mainly represents cyclonic circulation in the TP during the summer. The transition zone of total precipitation in the summer parallels the convergence belt between the southerlies and the northerlies of the flow-over component. The leading mode of rainfall anomalies in the TP has a meridional dipole structure, and the first principal component (PC1) mainly depicts the variation of rainfall in the southern TP. The wet southern TP experiences strengthened flow-over, which in turn mechanistically favors intensified ascent forced by the flow-over component. In addition, variations in the Indian summer monsoon (ISM) have an important role in influencing the flow over the southern TP, and the ISM ultimately impacts the precipitation over southern TP.
基金supported by the National Natural Science Foundation of China(Grant No.40875014)the Special Fund for Meteorological Research in the Public Interest(Grant No.GYHY201106023)+1 种基金the Scientific and Technological Innovation Team Project of Chinese Academy of Meteorological Sciences(Grant No.2011Z003)supported by the Tengchong Meteorological Bureau in Yunnan,Naqu Meteorological Bureau,and Lhasa Meteorological Bureau in Tibet
文摘We present validation studies of MLS V2.2 and V3.3 water vapor(WV) and ozone profiles over the Tibetan Plateau(Naqu and Lhasa) and its adjacent region(Tengchong) respectively by using the balloon-borne Cryogenic Frost point Hygrometer and Electrochemical Concentration Cell ozonesonde. Coincident in situ measurements were selected to compare the MLS V2.2 and V3.3 WV and ozone profiles for understanding the applicability of the two version MLS products over the region. MLS V2.2 and V3.3 WV profiles respectively show their differences within ?2.2±15.7%(n=74) and 0.3±14.9%(n=75) in the stratosphere at and above 82.5 h Pa. Accordingly, at 100 h Pa, the altitude approaching the tropopuase height, differences are within 9.8± 46.0%(n=18) and 23.0±45.8%(n=17), and they are within 21.5±90.6%(n=104) and 6.0±83.4%(n=99) in upper troposphere. The differences of MLS ozone are within ?11.7±16.3%(n=135, V2.2) and 15.6±24.2%(n=305, V3.3) at and above 82.5 h Pa. At 100 h Pa, they are within ?3.5±54.4%(n=27) and ?8.7±41.6%(n=38), and within 18.0±79.1%(n=47) and 34.2±76.6%(n=160) in the upper troposphere. The relative difference of MLS WV and ozone profile has significant oscillation and scatter at upper troposphere and lower stratosphere partly due to the stronger gradients of WV and ozone concentrations here as well the linear interpolation of sonde data for the intercomparison. At and below 70 h Pa, the relative differences of MLS ozone are significantly larger over Lhasa during the Tibetan Plateau "ozone valley" season, which is also the Asian Summer Monsoon period. The MLS ozone differences over the three sites are similar in their vertical distributions during that period. A simple linear correlation analysis between MLS and sonde profiles indicates that the sensitivity of MLS profile products is related to concentrations at each pressure level. The MLS V3.3 product sensitivity is slightly improved for WV at and above 82.5 h Pa, whereas it is not obvious for ozone. The possible factors contributing to the differences of the MLS profile products of WV and ozone are discussed.
基金supported by the Nsyionsl Natural Science Foundation of China (Grant Nos. 41275088, 91437219 & 41328006)the Special Fund for Public Welfare Industry (Meteorology) administered by the Chinese Ministry of Finance and the Ministry of Science and Technology (Grant No. GYHY201406001)
文摘Based on numerical simulation, this study explored the characteristics and interactions of surface sensible heating and atmospheric latent heating over the main part of the Tibetan Plateau, i.e., terrain at elevations >2 km in summer. The impacts of these two types of heating on local vertical motion and monsoonal meridional circulation were compared. Theoretical analysis and numerical experimentation demonstrated that by changing the configuration of the upper-tropospheric air temperature and circulation, the two types of heating could generate both minimum absolute vorticity and abnormal potential vorticity forcing near the tropopause, enhance the meridional circulation of the Asian summer monsoon, and produce an eastward-propagating Rossby wave train within the mid-latitude westerly flow. Consequently, the manifestations of these features were shown to influence the circulation of the Northern Hemisphere.
