A springtime tropopause fold event, found to be related to a cold trough intrusion from the north, was detected in the northeastern Tibetan Plateau (TP) based on various observations. A nested high-resolution mesosc...A springtime tropopause fold event, found to be related to a cold trough intrusion from the north, was detected in the northeastern Tibetan Plateau (TP) based on various observations. A nested high-resolution mesoscale model was employed to investigate the effect of orography on the stratosphere-troposphere exchange. The model was found to be able to capture plausible tropopause fold properties. The propagation of the tropopause fold changed significantly when the terrain height in the model was altered. However, decreasing the terrain height had no significant effect on the morphology of folds. When a fold passed over an elevated surface, a leeside jet stream and a layer of humid air in the middle troposphere tended to develop. This strong leeside descent of air masses and high mid-level potential instability (PI) could give rise to deep upward motions in the leeside and inject tropospheric air into the lower stratosphere. Besides, when the flow encounters an elevated surface, forced lifting together with mid-level PI can trigger deep convective motions on the windward slope. The troposphere to stratosphere transport was found to be persistent and almost stationary over the windward slope of the TP during the evolution of the fold.展开更多
A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric excha...A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric exchange event that occurred over East Asia in March 2001.The result revealed that the ozone flux across the tropopause in this event was an order of magnitude higher than the global and hemispheric average. Compared to the traditional method using a linear relationship between ozone mixing ratio and potential vorticity near the tropopause, the cross-tropopause ozone flux evaluated with ozonesonde data was somewhat higher, although the orders of the two values were the same.展开更多
Recent advances in studies of the middle and upper atmosphere and their coupling with the lower atmosphere in China are briefly reviewed. This review emphasizes four aspects: (1) Development of instrumentation for mid...Recent advances in studies of the middle and upper atmosphere and their coupling with the lower atmosphere in China are briefly reviewed. This review emphasizes four aspects: (1) Development of instrumentation for middle and upper atmosphere observation; (2) Analyses and observation of middle and upper atmosphere; (3) Theoretical and modeling studies of planetary wave and gravity wave activities in the middle atmosphere and their relation to lower atmospheric processes; (4) Study on the coupling between the stratosphere and the troposphere.展开更多
The European Centre for Medium-Range Weather orology and measurements from the Microwave Limb Forecasts Re-Analysis Interim (ERA-Interim) meteSounder, High Resolution Dynamics Limb Sounder, and Ozone Monitoring Inst...The European Centre for Medium-Range Weather orology and measurements from the Microwave Limb Forecasts Re-Analysis Interim (ERA-Interim) meteSounder, High Resolution Dynamics Limb Sounder, and Ozone Monitoring Instrument onboard the Earth Observing System Aura satellite were applied to analyze the dynamical and chemical features of a cutoff low (COL) event over northeast China in early July 2007. The results showed the polar stratospheric origin of an upper-level warm-core cyclone at 100 300 hPa, associated with a funnel-shaped tropopause intruding into the mid-troposphere just above the COL center. The impacts of the stratospheric intrusion on both column ozone and ozone profiles were investigated using satellite measurements. When the intensity of the COL peaked on 10 July 2007, the total column ozone (TCO) increase reached a maximum (40-70 DU). This could be dynamically attributed to both the descent of the tropopause (~75%) and the downward transport of stratospheric ozone across the tropopause (~25%). Analysis of the tropospheric ozone profiles provided evidence for irreversible transport/mixing of ozone-rich stratospheric air across the tropopause near the upper-level front region ahead of the COL center. This ozone intrusion underwent downstream transport by the upper tropospheric winds, leading to further increase in TCO by 12 16 DU over broad regions extending from east China toward the northern Japan Sea via South Korea. Meteorological analysis also showed the precedence of the stratospheric intrusion ahead of the development of cyclones in the middle and lower troposphere.展开更多
In this paper advances on study of middle and upper atmosphere and their cou pling with lower atmosphere in China in recent two years are briefly reviewed.This review emphasized three aspects, ie. (1) analysis and obs...In this paper advances on study of middle and upper atmosphere and their cou pling with lower atmosphere in China in recent two years are briefly reviewed.This review emphasized three aspects, ie. (1) analysis and observation of mid and upper atmosphere over China; (2) theoretical and modelling study of grav ity wave activities in middle atmosphere and their relation to lower atmospheric processes; (3) coupling between the stratosphere and troposphere.展开更多
The 10-year climatological features related to midlatitude double tropopause events (DTs) are examined using ERA- Interim data from 2003 to 2012. The analysis is based on tropopauses defined by lapse rate. Results s...The 10-year climatological features related to midlatitude double tropopause events (DTs) are examined using ERA- Interim data from 2003 to 2012. The analysis is based on tropopauses defined by lapse rate. Results show that DTs are permanent or semi-permanent in the midlatitudes, and high DT frequency bands move poleward in winter and equatorward in summer, which is consistent with the seasonal movement of the subtropical jet. Based on our statistics, the second tropopause is found at about 100 hPa in the subtropics and at slightly lower altitudes in sub-polar regions. The thickness between the first and second tropopause is smaller in the subtropics and increases with latitude. Next, the origin of air sandwiched between the first and second tropopause of DTs is studied with a revised version of the UK Universities Global Atmospheric Modelling Programme Offline Trajectory Code (Version 3) diabatic trajectory model. The results show that, in the lower or middle troposphere, air is transported into the DTs from lower latitudes, mainly in the tropics. The dominant source regions are mainly areas of deep convection and steep orography, e.g., the western Pacific and Himalayan Mountains, and they show strong seasonality following the seasonal shift of these strong upwelling regions.展开更多
The Tibetan Plateau(TP)has unique atmospheric dynamics and thermal structures that originate from its giant terrain and complex climate.High vertical-resolution thermal radiosondes were launched near the central(Lhasa...The Tibetan Plateau(TP)has unique atmospheric dynamics and thermal structures that originate from its giant terrain and complex climate.High vertical-resolution thermal radiosondes were launched near the central(Lhasa,91°06′E,29°36′N,3670 m above sea level(ASL))and marginal(Da Qaidam,95°21′E,37°51′N,3180 m ASL)areas of the TP during the summers of 2018 and 2020,respectively.Atmospheric turbulence parameters were calculated,and the characteristics of the atmospheric turbulent vertical structure at sunset in these two areas were analyzed and compared.Affected by TP thermal forcing and stably controlled by the summer monsoon anticyclone,the atmospheric refractive index structure constant(C_(n)^(2))tended to increase and then decrease with increasing height,reaching a maximum at the tropopause(~18 km ASL)at the Lhasa site.Although C_(n)^(2) at the Da Qaidam site also tended to increase at the tropopause,the position of the strong turbulent band(STB)(5–7 km ASL)was below the tropopause height corresponding to the potential temperature lapse rate minimum.The vertical distribution of C_(n)^(2) at the two sites,particularly regarding the position of the STB,was highly correlated with the atmospheric stability(Ri)and the thermal mixing scale(L_(T)).The significant correlations among the three parameters(STB,Ri,and L_(T))indicated that the strong fluctuations in temperature caused by thermal mixing were the dominant factor causing the Ri to be less than its critical value of 0.25.Moreover,the suppression strength involving the upward transport of the heat sources was the main reason for the different turbulent vertical structures and STB positions at the two sites.The zonal mean thermodynamic and dynamical fields derived from the reanalysis data also showed a height difference in the heat sources transported to the troposphere at the two sites.In the marginal TP,the material and energy in the lower troposphere were transported by the turbulent atmosphere upward along the slope of the mountain and converged at the central TP(28°N–35°N)with strong thermal forcing up to the tropopause.In the STB of the Lhasa site,the turbulent dissipation rate and eddy diffusion coefficient increased sharply,indicating that the turbulent atmosphere in this central site was highly diffused,and the small-scale turbulence transported the material and energy upward.展开更多
基金provided by the National Natural Sciences Foundation of China (40730949)the National Basic Research Program of China (2010CB428604)the International Cooperation Project (40710059003)
文摘A springtime tropopause fold event, found to be related to a cold trough intrusion from the north, was detected in the northeastern Tibetan Plateau (TP) based on various observations. A nested high-resolution mesoscale model was employed to investigate the effect of orography on the stratosphere-troposphere exchange. The model was found to be able to capture plausible tropopause fold properties. The propagation of the tropopause fold changed significantly when the terrain height in the model was altered. However, decreasing the terrain height had no significant effect on the morphology of folds. When a fold passed over an elevated surface, a leeside jet stream and a layer of humid air in the middle troposphere tended to develop. This strong leeside descent of air masses and high mid-level potential instability (PI) could give rise to deep upward motions in the leeside and inject tropospheric air into the lower stratosphere. Besides, when the flow encounters an elevated surface, forced lifting together with mid-level PI can trigger deep convective motions on the windward slope. The troposphere to stratosphere transport was found to be persistent and almost stationary over the windward slope of the TP during the evolution of the fold.
文摘A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric exchange event that occurred over East Asia in March 2001.The result revealed that the ozone flux across the tropopause in this event was an order of magnitude higher than the global and hemispheric average. Compared to the traditional method using a linear relationship between ozone mixing ratio and potential vorticity near the tropopause, the cross-tropopause ozone flux evaluated with ozonesonde data was somewhat higher, although the orders of the two values were the same.
基金supported by the National Natural Science Foundation of China under Grant Nos.40333034,40075007,and 40175002the.Chinese Academy of Sciences under Grant No.KZCX-SW-217.
文摘Recent advances in studies of the middle and upper atmosphere and their coupling with the lower atmosphere in China are briefly reviewed. This review emphasizes four aspects: (1) Development of instrumentation for middle and upper atmosphere observation; (2) Analyses and observation of middle and upper atmosphere; (3) Theoretical and modeling studies of planetary wave and gravity wave activities in the middle atmosphere and their relation to lower atmospheric processes; (4) Study on the coupling between the stratosphere and the troposphere.
基金funded by the National Basic Research Program of China (Grant No.2010CB428604)National Science Foundation of China(Grant No. 41105025)+1 种基金the Dragon 3 Programme (ID:10577)Research at Harvard-Smithsonian was funded by NASA and the Smithsonian Institution
文摘The European Centre for Medium-Range Weather orology and measurements from the Microwave Limb Forecasts Re-Analysis Interim (ERA-Interim) meteSounder, High Resolution Dynamics Limb Sounder, and Ozone Monitoring Instrument onboard the Earth Observing System Aura satellite were applied to analyze the dynamical and chemical features of a cutoff low (COL) event over northeast China in early July 2007. The results showed the polar stratospheric origin of an upper-level warm-core cyclone at 100 300 hPa, associated with a funnel-shaped tropopause intruding into the mid-troposphere just above the COL center. The impacts of the stratospheric intrusion on both column ozone and ozone profiles were investigated using satellite measurements. When the intensity of the COL peaked on 10 July 2007, the total column ozone (TCO) increase reached a maximum (40-70 DU). This could be dynamically attributed to both the descent of the tropopause (~75%) and the downward transport of stratospheric ozone across the tropopause (~25%). Analysis of the tropospheric ozone profiles provided evidence for irreversible transport/mixing of ozone-rich stratospheric air across the tropopause near the upper-level front region ahead of the COL center. This ozone intrusion underwent downstream transport by the upper tropospheric winds, leading to further increase in TCO by 12 16 DU over broad regions extending from east China toward the northern Japan Sea via South Korea. Meteorological analysis also showed the precedence of the stratospheric intrusion ahead of the development of cyclones in the middle and lower troposphere.
基金Supported by the National Natural Science Foundation of China(No. 40175002, 40075007) and The Chinese Academy of Sciences.
文摘In this paper advances on study of middle and upper atmosphere and their cou pling with lower atmosphere in China in recent two years are briefly reviewed.This review emphasized three aspects, ie. (1) analysis and observation of mid and upper atmosphere over China; (2) theoretical and modelling study of grav ity wave activities in middle atmosphere and their relation to lower atmospheric processes; (3) coupling between the stratosphere and troposphere.
基金supported by the Special Fund for Strategic Pilot Technology of the Chinese Academy of Sciences(Grant No.XDA05040300)
文摘The 10-year climatological features related to midlatitude double tropopause events (DTs) are examined using ERA- Interim data from 2003 to 2012. The analysis is based on tropopauses defined by lapse rate. Results show that DTs are permanent or semi-permanent in the midlatitudes, and high DT frequency bands move poleward in winter and equatorward in summer, which is consistent with the seasonal movement of the subtropical jet. Based on our statistics, the second tropopause is found at about 100 hPa in the subtropics and at slightly lower altitudes in sub-polar regions. The thickness between the first and second tropopause is smaller in the subtropics and increases with latitude. Next, the origin of air sandwiched between the first and second tropopause of DTs is studied with a revised version of the UK Universities Global Atmospheric Modelling Programme Offline Trajectory Code (Version 3) diabatic trajectory model. The results show that, in the lower or middle troposphere, air is transported into the DTs from lower latitudes, mainly in the tropics. The dominant source regions are mainly areas of deep convection and steep orography, e.g., the western Pacific and Himalayan Mountains, and they show strong seasonality following the seasonal shift of these strong upwelling regions.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Class A)(Grant No.XDA17010104)the National Natural Science Foundation of China(Grant Nos.4157685&91752103)。
文摘The Tibetan Plateau(TP)has unique atmospheric dynamics and thermal structures that originate from its giant terrain and complex climate.High vertical-resolution thermal radiosondes were launched near the central(Lhasa,91°06′E,29°36′N,3670 m above sea level(ASL))and marginal(Da Qaidam,95°21′E,37°51′N,3180 m ASL)areas of the TP during the summers of 2018 and 2020,respectively.Atmospheric turbulence parameters were calculated,and the characteristics of the atmospheric turbulent vertical structure at sunset in these two areas were analyzed and compared.Affected by TP thermal forcing and stably controlled by the summer monsoon anticyclone,the atmospheric refractive index structure constant(C_(n)^(2))tended to increase and then decrease with increasing height,reaching a maximum at the tropopause(~18 km ASL)at the Lhasa site.Although C_(n)^(2) at the Da Qaidam site also tended to increase at the tropopause,the position of the strong turbulent band(STB)(5–7 km ASL)was below the tropopause height corresponding to the potential temperature lapse rate minimum.The vertical distribution of C_(n)^(2) at the two sites,particularly regarding the position of the STB,was highly correlated with the atmospheric stability(Ri)and the thermal mixing scale(L_(T)).The significant correlations among the three parameters(STB,Ri,and L_(T))indicated that the strong fluctuations in temperature caused by thermal mixing were the dominant factor causing the Ri to be less than its critical value of 0.25.Moreover,the suppression strength involving the upward transport of the heat sources was the main reason for the different turbulent vertical structures and STB positions at the two sites.The zonal mean thermodynamic and dynamical fields derived from the reanalysis data also showed a height difference in the heat sources transported to the troposphere at the two sites.In the marginal TP,the material and energy in the lower troposphere were transported by the turbulent atmosphere upward along the slope of the mountain and converged at the central TP(28°N–35°N)with strong thermal forcing up to the tropopause.In the STB of the Lhasa site,the turbulent dissipation rate and eddy diffusion coefficient increased sharply,indicating that the turbulent atmosphere in this central site was highly diffused,and the small-scale turbulence transported the material and energy upward.