Over twenty thousand lightning location data obtained by using Lightning Location System(LLS) from Lanzhou and Beijing regions have been analysed to ascertain the characteristics of ground flashes in both regions. The...Over twenty thousand lightning location data obtained by using Lightning Location System(LLS) from Lanzhou and Beijing regions have been analysed to ascertain the characteristics of ground flashes in both regions. The strength of positive flashes is 5 times higher in Lanzhou than in Beijing. The strength of positive flashes is 3 times and 2.2 times as large as negative flashes in Beijing and in Lanzhou respectively. It has been found that the strength of positive and negative flashes is submitted to the normal distribution, and is independent of the characteristics of thunderstorm. So the lightning strength obtained by DF may be used to forecast the coming of thunderstorm. Although the stroke number in both regions decreases as exponent regulation, the maximum number of return stroke for one lightning in Beijing is more than that in Lanzhou. The peak flash rate occurs in late afternoon for both regions, but the maximum and minimum flash rate appeared an hour earlier in Beijing than in Lanzhou.The relationship between DF display and lightning radiation electric field, discharge current is obtained.展开更多
In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, a...In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, and the forecasting and simulating of 4 sets of Meiyu onset of the year have finally been run utilizing the global model at UK Me-leorological Office. The results show: 1) Meiyu fronts are different from Baiu ones in temperature, humidity and stratification fields in lower atmosphere; and the possibly reasons for it are explained. 2) The Bay of Bengal is the main moisture source for Meiyu front, the South China Sea and the Pacific, for Baiu ones; and some existed arguments on it are also discussed. 3) The onset of Meiyu and its rainfall and rain belts are sensitive to the Tibetan Plateau, and the water vapour conditions over the Bay of Bengal and the South China Sea, but not sensitive to the SST over the equatorial area or to the East of Japan.展开更多
Ⅰ.INTRODUCTION We have discovered that there exists a good corresponding relationship between theanomalous axes of soil temperature at a depth of 1.6m in winter (December to February) andprecipitations in following f...Ⅰ.INTRODUCTION We have discovered that there exists a good corresponding relationship between theanomalous axes of soil temperature at a depth of 1.6m in winter (December to February) andprecipitations in following flood season (Tang et al., 1982a). We have also designed a simplethermodynamical model and applied it to the forecasting of precipitations in the flood season(Tang et al., 1982 b,c). The practical forecast started from 1975. Before 1980, however, therewere only 40-50 stations in China for measuring the soil temperature at a 1.6m depth. Since1980, the stations have been increased to a total of about 180, but no available mean valueshad been obtained from newly added stations before 1982. Therefore the analysis and map-ping of anomalies of soil temperature was not performed until 1983, and from then on theprecision of analysis has been greatly improved. The following is the actual situation of forecast in five years from 1983 to 1987.展开更多
The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern par...The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south- ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.展开更多
The Tibetan Plateau has experienced a number of processes of uplift and planation alternately since about 45 Ma B. P. when it began to raise. A differential equation model for describing the Plateau altitude variation...The Tibetan Plateau has experienced a number of processes of uplift and planation alternately since about 45 Ma B. P. when it began to raise. A differential equation model for describing the Plateau altitude variation with time is formulated on the basis of previous field studies and a theoretical hypothesis: if palaeomagnetic polarity is positive, the convective activity in the earth is strong; orogenic movement is violent; and the raising velocity of the Plateau is high and vice versa . The analytical solution of the equation is obtained. The altitude variation from the beginning of the Plateau uplift to present is computed through using the geomagnetic polarity reversals timing series and interstellar atomic hydrogen concentration data. A comparison between the model results and the field studies indicates that the former is quite similar to the latter. The model results are able to basically reproduce the alternating processes of uplift and planation of the plate geological history. In the present model, the influences of the denudation and the geomagnetic polarity and interstellar atomic hydrogen concentration on the raising velocity of the Plateau altitude are mainlv considered.展开更多
After analyzing the mean pressure, dominant wind and temperature data of 40 observation sta- tions in Mongolia from 1961 to 1990, we reach some conclusions as below: (a) The warm advec- tion in the free atmosphere har...After analyzing the mean pressure, dominant wind and temperature data of 40 observation sta- tions in Mongolia from 1961 to 1990, we reach some conclusions as below: (a) The warm advec- tion in the free atmosphere hardly reaches the ground in the west in winter. Because of thermody- namic differences of various meso- and micro-topography, there are 'multi-centers' in the pressure field, and the dominant wind field is 'disordered': the temperatures on the convexi-concave orog- raphy and sun-shady slope are different significantly. There is cold advection in the east side, which can reaches the ground and the air pressure field is a 'unity'. The wind field is dominated by the west wind. The temperature differences of various slope directions are small, and become smaller with height. (b) In summer, the upper control flow (planetary west wind) becomes weak- er, and the orographic air pressure centers in the east develop. Over the windward side of the mountain high pressure prevails, and over the lee side low pressure does. These areas become deserts for dryness and lack of rainfall. Air temperature in summer can be expressed by latitude, longitude and elevation.展开更多
A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to compute the atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 19...A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to compute the atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 1988.Some characteristics of atmospheric radiative heating fields during the autumn in Zhangye area have been analysed,and some questions that merit attention in the future observation are also discussed in this paper.展开更多
The combination of field experiments and satellite observations is the fundamental way to understand the characteristics of spatial-temporal variation in surface albedo over the Tibetan (Qinghai-Xizang) Plateau. Under...The combination of field experiments and satellite observations is the fundamental way to understand the characteristics of spatial-temporal variation in surface albedo over the Tibetan (Qinghai-Xizang) Plateau. Under the condition without snow cover, the relatively regular annual variation cycle of the surface albedo can be expressed by an empirical formula. The effect of snow cover on the surface albedo in winter can be expressed by introducing two variables of snow forcing and sensitivity parameter. The existing satellite retrieved results of surface albedo may provide the digital grid data for describing the geographical distribution. However, some satellite retrieved surface albedos available over the Tibetan Plateau are obviously too low in winter. Taking the satellite derived results in summer as the background field representative of geographical distribution and combining the empirical formula of annual cycle based on the surface observations, a dynamic model of surface albedo is developed for the need of modeling the climatic influence of the underlying surface forcing of the Tibetan Plateau.展开更多
Investigating all the Great Ice Age events throughout the Earth’s history, each was found to follow a strong mountain-making process. Therefore, a hypothesis was put forward with its causality chain as: strong mounta...Investigating all the Great Ice Age events throughout the Earth’s history, each was found to follow a strong mountain-making process. Therefore, a hypothesis was put forward with its causality chain as: strong mountain-making process→great disparity in topography on the Earth surface→introducing efficient atmospheric circulation system (plateau monsoon)→increase in global atmospheric heat engine efficiency →generating more atmospheric kinetic energy → enhancing the planetary westerly (under the condition that the huge relief is longitudinal on the whole )→widening the temperature difference between the equator and the polar regions (restrained by the thermal wind law)→sharp cooling in high latitudes and the polars (supposing the solar radiation was approximately constant)→forming a Great Ice Age event.展开更多
In this paper an ideal model for the formation and development of the Qinghai-Xizang Plateau vortex is presented by a large number of statistical data and typical case studies. It points out that the Plateau vortex is...In this paper an ideal model for the formation and development of the Qinghai-Xizang Plateau vortex is presented by a large number of statistical data and typical case studies. It points out that the Plateau vortex is shallow and thermal originated from a strong heat source near the surface of the west of the Plateau. Then moving eastward , it develops and becomes stronger and thicker with larger upward vertical velocity, and causes great precipitation in the middle Plateau. But at this time the heat source in the vortex becomes weaker, and even the heat sink occurs near the surface. Consequently, it disappears in a cold trough with a strong heat sink in the east of the Plateau. The heat source (sink) is mainly determined by the vertical eddy flux convergence (divergence) of the sensible heat caused by the cumulus convection and turbu-lance. Both the nonuniform heating (cooling) at the surface and the convergence (divergence) of the eddy kinetic energy coact and play an important role in the genesis (disappearance) of the Plateau vortex in the west (east) Plateau. The transformation value from the mean kinetic energy to the eddy kinetic energy increases when the Plateau vortex moves eastward, helping the formation of the cold trough and the increase in.+ξ and large-scale precipitation in the east Plateau.展开更多
In this paper the statistical analysis is carried out on the correlation between lightning strokes and atmospheric stratification factors.It is shown that the total number of strokes in lightning process is mainly dec...In this paper the statistical analysis is carried out on the correlation between lightning strokes and atmospheric stratification factors.It is shown that the total number of strokes in lightning process is mainly decided by environmental temperature at altitude with the residual instability of 5℃(T_r).The instability should also affect the total number of strokc in lightning process.A forecasting equation of stroke in light- ning process has been deduced and two interesting preliminary conclusions have been obtained.展开更多
To better analyse and understand the causes of Northwest China(NW China)arid climate formation,firstly the dry and wet standards were chosen and the yearly dry and wet grades on the north side of Qinghai-Xizang Platea...To better analyse and understand the causes of Northwest China(NW China)arid climate formation,firstly the dry and wet standards were chosen and the yearly dry and wet grades on the north side of Qinghai-Xizang Plateau(hereafter NSQXP)in summers were classified utilizing the rainfall data of five stations over the area in June-August of 1952—1990.Then the differences between the vertical motion over the Qinghai-Xizang Plateau(QXP)and NSQXP in dry and wet summers were comparatively analyzed using the ECMWF's gridded data of June—August of 1979 —1986.Finally the connection between the QXP surface thermal condition and the dry and wet summers on the NSQXP was discussed as well. The main results are the following:(1)the dry and wet standards taking the rainfall standard deviation as criterion are suitable for the arid climate area;(2)the QXP may be,to some extent. responsible for the environment background of Middle Asia,NW China and North China arid climate areas;(3)there are the striking differences between the dominant vertical motion over the QXP and NSQXP in the dry and wet summers of NSQXP:(4)the QXP surface thermal condition is.to a great extent,responsible for the year—to—year variation of NW China arid climate as well.展开更多
By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the 'World Survey of climatology, Vol. 1-15', the distributions of the maximum precipitation months (MPM...By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the 'World Survey of climatology, Vol. 1-15', the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types(continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east-and-wcst shift.展开更多
In this paper,we simulate the regional climate in summer and winter in northwestern part of China and the Qinghai-Xizang Plateau with regional climate model(MM4)nested with GFDL data,and compare the simulated results ...In this paper,we simulate the regional climate in summer and winter in northwestern part of China and the Qinghai-Xizang Plateau with regional climate model(MM4)nested with GFDL data,and compare the simulated results with observed data and GFDL data.The results show that the regional model reproduces the regional climate systems,such as the high pressure on the plateau and the low pressure in the north of the plateau in winter,the warm-low pressure over the plateau and pressure ridge in south and north of the Qinghai-Xizang Plateau in summer.These regional climate features could not be distinguished by the GCM.The simulations of precipitation distribution are reasonable.But differences between the simulated and observed precipitation values in some places are obvious.The precipitation in south of the Qinghai-Xizang Plateau is underestimated,and in north of the Qinghai-Xizang Plateau,the precipitation is overestimated. The simulation of height field is better than temperature field.展开更多
In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed res...In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed results during 4—19 September 1988 in the Pilot Observation Period of the HEIFE.The results show that the atmosphere is in superadiabatic unstable state and there is a phenomenon of inverse humidity to form negative water vapour flux.The sensible heat flux on the surface energy budget is in majority,but the latent heat flux may be neglected over the Gobi and desert surface in the cloudless daytime in the summer.展开更多
The research indicates that there is a positive correlation between the negative CG flash rate and the area of radar echo with its reflectivity being equal to or greater than 30 dBz in the mesoscale convective system ...The research indicates that there is a positive correlation between the negative CG flash rate and the area of radar echo with its reflectivity being equal to or greater than 30 dBz in the mesoscale convective system in Beijing area.A max- imum of the positive CG flash rate exists at both the initial and the dissipating stages.The CG flashes are usually located near but not within the high reflectivity center.The negative flashes are associated with.the positions of the updraft re- gion,and with the regions of wind convergence and wind shear.Generally,the negative CG flashes are concentrative and the positive ones are dispersive.展开更多
Using ground temperature data from meteorological stations as well as earthquake, ground tilt and precipitation data, the spatial-temporal distribution of "Underground Hot Vortex" ( UHV) in China was analyze...Using ground temperature data from meteorological stations as well as earthquake, ground tilt and precipitation data, the spatial-temporal distribution of "Underground Hot Vortex" ( UHV) in China was analyzed in detail. The results show that concerning an "Underground Hot Vortex" cell, its life-span is 3-8 seasons, 1.5 years on average; the mean horizontal scale is 600 km and its characteristic velocity is about 400 km/a; UHV is likely to appear in some areas where the crustal movement is intense and the absolute value of vertical deformation rate is relatively high; its activity could hardly be detected in the area where the crust is stable and the vertical deformation is weak; most of "Underground Hot Vortex Groups" originate from the edge of Indian Plate, then migrate eastwards with a leaping-frog style. 5-10 years are needed for their arrival in the eastern border of China. Their horizontal migrating velocity is 200-500 km/a which is nearly equal to the characteristic velocity of a single UHV.展开更多
Based on the previous results, the relationship between 'Underground Hot Vortex' (UHV) and earthquake was analyzed. Some results show that concerning a UHV with a larger horizontal scale or longer duration, th...Based on the previous results, the relationship between 'Underground Hot Vortex' (UHV) and earthquake was analyzed. Some results show that concerning a UHV with a larger horizontal scale or longer duration, the accompanied earthquake will be surely stronger while no earthquake or only minor shocks appear with a weak UHV; the strong earthquakes during recent 14 years in China (Ms>5. 5 in East China, Ms>6. 5 in West China) concentrated on two belts; i. e. within the scope of UHV radius ratio r/R = 0. 32-0. 61 and r/R = 0. 73-0. 79. No strong earthquake was detected when r/R >0.80; the horizontal angle of the earthquake is to the north or northeast of UHV which lies in the central ascending region of crustal vertical deformation except for those in Guizhou Province; the earthquake occurred to the southeast or west of UHV located in central descending region except for those in Fen-Wei River Valley; the seismic magnitude is directly dependent on the lag time between the appearance of UHV (the beginning time of T'3.2≥0. 5℃ ) and the occurrence of earthquakes. A preliminary conception model indicating coupling between lithosphere and atmosphere is put forward on the basis of the previous analyses and this paper.展开更多
Based on the HEIFE 1988 and 1990 pilot observations,an analysis on the turbulence structure of Gobi surface layer,mainly on the similarity formulations of wind and temperature variances,the spectra and cospectra chara...Based on the HEIFE 1988 and 1990 pilot observations,an analysis on the turbulence structure of Gobi surface layer,mainly on the similarity formulations of wind and temperature variances,the spectra and cospectra characteristics,is presented.The phenomenon of downward water vapor flux over Gobi desert in daytime is confirmed in both observations,this and the well-known‘oasis effect’are two sides of a local mesoscale circulation.展开更多
At present, in numerical weather prediction models (e. g. [1] ), general circulation or climate models (e. g. [2, 3] ) or meso-scale models (e. g. [4, 5] ), the influence of the water vapor source/sink term (WVST) in ...At present, in numerical weather prediction models (e. g. [1] ), general circulation or climate models (e. g. [2, 3] ) or meso-scale models (e. g. [4, 5] ), the influence of the water vapor source/sink term (WVST) in the continuity equation (CE) of moist air has not been taken into account generally. Though Hansen et al. listed source and sink terms in the CE ( Eq. T2 ), they still neglected these terms in the approximate form employed in computations ( Eq. T6 ). In the real atmosphere there exist condensation and evaporation, sometimes strong condensation. In this note the role of the WVSTs in the CE and its related equations of numerical models and their influences on forecast results are discussed.展开更多
文摘Over twenty thousand lightning location data obtained by using Lightning Location System(LLS) from Lanzhou and Beijing regions have been analysed to ascertain the characteristics of ground flashes in both regions. The strength of positive flashes is 5 times higher in Lanzhou than in Beijing. The strength of positive flashes is 3 times and 2.2 times as large as negative flashes in Beijing and in Lanzhou respectively. It has been found that the strength of positive and negative flashes is submitted to the normal distribution, and is independent of the characteristics of thunderstorm. So the lightning strength obtained by DF may be used to forecast the coming of thunderstorm. Although the stroke number in both regions decreases as exponent regulation, the maximum number of return stroke for one lightning in Beijing is more than that in Lanzhou. The peak flash rate occurs in late afternoon for both regions, but the maximum and minimum flash rate appeared an hour earlier in Beijing than in Lanzhou.The relationship between DF display and lightning radiation electric field, discharge current is obtained.
文摘In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, and the forecasting and simulating of 4 sets of Meiyu onset of the year have finally been run utilizing the global model at UK Me-leorological Office. The results show: 1) Meiyu fronts are different from Baiu ones in temperature, humidity and stratification fields in lower atmosphere; and the possibly reasons for it are explained. 2) The Bay of Bengal is the main moisture source for Meiyu front, the South China Sea and the Pacific, for Baiu ones; and some existed arguments on it are also discussed. 3) The onset of Meiyu and its rainfall and rain belts are sensitive to the Tibetan Plateau, and the water vapour conditions over the Bay of Bengal and the South China Sea, but not sensitive to the SST over the equatorial area or to the East of Japan.
文摘Ⅰ.INTRODUCTION We have discovered that there exists a good corresponding relationship between theanomalous axes of soil temperature at a depth of 1.6m in winter (December to February) andprecipitations in following flood season (Tang et al., 1982a). We have also designed a simplethermodynamical model and applied it to the forecasting of precipitations in the flood season(Tang et al., 1982 b,c). The practical forecast started from 1975. Before 1980, however, therewere only 40-50 stations in China for measuring the soil temperature at a 1.6m depth. Since1980, the stations have been increased to a total of about 180, but no available mean valueshad been obtained from newly added stations before 1982. Therefore the analysis and map-ping of anomalies of soil temperature was not performed until 1983, and from then on theprecision of analysis has been greatly improved. The following is the actual situation of forecast in five years from 1983 to 1987.
文摘The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south- ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.
基金Project supported by the National Climbing Project "A Study on the Uplift,Evolution and Ecosystem of the Tibetan Plateau"and the CAS"(Chinese Academy of Sciences)Foundations for Returned Scholars
文摘The Tibetan Plateau has experienced a number of processes of uplift and planation alternately since about 45 Ma B. P. when it began to raise. A differential equation model for describing the Plateau altitude variation with time is formulated on the basis of previous field studies and a theoretical hypothesis: if palaeomagnetic polarity is positive, the convective activity in the earth is strong; orogenic movement is violent; and the raising velocity of the Plateau is high and vice versa . The analytical solution of the equation is obtained. The altitude variation from the beginning of the Plateau uplift to present is computed through using the geomagnetic polarity reversals timing series and interstellar atomic hydrogen concentration data. A comparison between the model results and the field studies indicates that the former is quite similar to the latter. The model results are able to basically reproduce the alternating processes of uplift and planation of the plate geological history. In the present model, the influences of the denudation and the geomagnetic polarity and interstellar atomic hydrogen concentration on the raising velocity of the Plateau altitude are mainlv considered.
基金This study is supported by the National Climbing Plan of China under Grant KJ85-03-03
文摘After analyzing the mean pressure, dominant wind and temperature data of 40 observation sta- tions in Mongolia from 1961 to 1990, we reach some conclusions as below: (a) The warm advec- tion in the free atmosphere hardly reaches the ground in the west in winter. Because of thermody- namic differences of various meso- and micro-topography, there are 'multi-centers' in the pressure field, and the dominant wind field is 'disordered': the temperatures on the convexi-concave orog- raphy and sun-shady slope are different significantly. There is cold advection in the east side, which can reaches the ground and the air pressure field is a 'unity'. The wind field is dominated by the west wind. The temperature differences of various slope directions are small, and become smaller with height. (b) In summer, the upper control flow (planetary west wind) becomes weak- er, and the orographic air pressure centers in the east develop. Over the windward side of the mountain high pressure prevails, and over the lee side low pressure does. These areas become deserts for dryness and lack of rainfall. Air temperature in summer can be expressed by latitude, longitude and elevation.
文摘A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to compute the atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 1988.Some characteristics of atmospheric radiative heating fields during the autumn in Zhangye area have been analysed,and some questions that merit attention in the future observation are also discussed in this paper.
基金This work was sponsored by the State ScienceTechnology Commission of China under GrantsKJ85-07 and PD-26
文摘The combination of field experiments and satellite observations is the fundamental way to understand the characteristics of spatial-temporal variation in surface albedo over the Tibetan (Qinghai-Xizang) Plateau. Under the condition without snow cover, the relatively regular annual variation cycle of the surface albedo can be expressed by an empirical formula. The effect of snow cover on the surface albedo in winter can be expressed by introducing two variables of snow forcing and sensitivity parameter. The existing satellite retrieved results of surface albedo may provide the digital grid data for describing the geographical distribution. However, some satellite retrieved surface albedos available over the Tibetan Plateau are obviously too low in winter. Taking the satellite derived results in summer as the background field representative of geographical distribution and combining the empirical formula of annual cycle based on the surface observations, a dynamic model of surface albedo is developed for the need of modeling the climatic influence of the underlying surface forcing of the Tibetan Plateau.
文摘Investigating all the Great Ice Age events throughout the Earth’s history, each was found to follow a strong mountain-making process. Therefore, a hypothesis was put forward with its causality chain as: strong mountain-making process→great disparity in topography on the Earth surface→introducing efficient atmospheric circulation system (plateau monsoon)→increase in global atmospheric heat engine efficiency →generating more atmospheric kinetic energy → enhancing the planetary westerly (under the condition that the huge relief is longitudinal on the whole )→widening the temperature difference between the equator and the polar regions (restrained by the thermal wind law)→sharp cooling in high latitudes and the polars (supposing the solar radiation was approximately constant)→forming a Great Ice Age event.
文摘In this paper an ideal model for the formation and development of the Qinghai-Xizang Plateau vortex is presented by a large number of statistical data and typical case studies. It points out that the Plateau vortex is shallow and thermal originated from a strong heat source near the surface of the west of the Plateau. Then moving eastward , it develops and becomes stronger and thicker with larger upward vertical velocity, and causes great precipitation in the middle Plateau. But at this time the heat source in the vortex becomes weaker, and even the heat sink occurs near the surface. Consequently, it disappears in a cold trough with a strong heat sink in the east of the Plateau. The heat source (sink) is mainly determined by the vertical eddy flux convergence (divergence) of the sensible heat caused by the cumulus convection and turbu-lance. Both the nonuniform heating (cooling) at the surface and the convergence (divergence) of the eddy kinetic energy coact and play an important role in the genesis (disappearance) of the Plateau vortex in the west (east) Plateau. The transformation value from the mean kinetic energy to the eddy kinetic energy increases when the Plateau vortex moves eastward, helping the formation of the cold trough and the increase in.+ξ and large-scale precipitation in the east Plateau.
文摘In this paper the statistical analysis is carried out on the correlation between lightning strokes and atmospheric stratification factors.It is shown that the total number of strokes in lightning process is mainly decided by environmental temperature at altitude with the residual instability of 5℃(T_r).The instability should also affect the total number of strokc in lightning process.A forecasting equation of stroke in light- ning process has been deduced and two interesting preliminary conclusions have been obtained.
基金This work was supported by both the National Natural Science Foundation of China under Grant 49605067 Prominent Young Scientist Project in West China of Chinese Academy of Sciences.
文摘To better analyse and understand the causes of Northwest China(NW China)arid climate formation,firstly the dry and wet standards were chosen and the yearly dry and wet grades on the north side of Qinghai-Xizang Plateau(hereafter NSQXP)in summers were classified utilizing the rainfall data of five stations over the area in June-August of 1952—1990.Then the differences between the vertical motion over the Qinghai-Xizang Plateau(QXP)and NSQXP in dry and wet summers were comparatively analyzed using the ECMWF's gridded data of June—August of 1979 —1986.Finally the connection between the QXP surface thermal condition and the dry and wet summers on the NSQXP was discussed as well. The main results are the following:(1)the dry and wet standards taking the rainfall standard deviation as criterion are suitable for the arid climate area;(2)the QXP may be,to some extent. responsible for the environment background of Middle Asia,NW China and North China arid climate areas;(3)there are the striking differences between the dominant vertical motion over the QXP and NSQXP in the dry and wet summers of NSQXP:(4)the QXP surface thermal condition is.to a great extent,responsible for the year—to—year variation of NW China arid climate as well.
文摘By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the 'World Survey of climatology, Vol. 1-15', the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types(continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east-and-wcst shift.
文摘In this paper,we simulate the regional climate in summer and winter in northwestern part of China and the Qinghai-Xizang Plateau with regional climate model(MM4)nested with GFDL data,and compare the simulated results with observed data and GFDL data.The results show that the regional model reproduces the regional climate systems,such as the high pressure on the plateau and the low pressure in the north of the plateau in winter,the warm-low pressure over the plateau and pressure ridge in south and north of the Qinghai-Xizang Plateau in summer.These regional climate features could not be distinguished by the GCM.The simulations of precipitation distribution are reasonable.But differences between the simulated and observed precipitation values in some places are obvious.The precipitation in south of the Qinghai-Xizang Plateau is underestimated,and in north of the Qinghai-Xizang Plateau,the precipitation is overestimated. The simulation of height field is better than temperature field.
基金This paper is one of the results of HEIFE subject which is supported by the National Natural Science Foundation of China.
文摘In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed results during 4—19 September 1988 in the Pilot Observation Period of the HEIFE.The results show that the atmosphere is in superadiabatic unstable state and there is a phenomenon of inverse humidity to form negative water vapour flux.The sensible heat flux on the surface energy budget is in majority,but the latent heat flux may be neglected over the Gobi and desert surface in the cloudless daytime in the summer.
基金supported by grants from State Planning Commission under Grants No.75-09-02-19
文摘The research indicates that there is a positive correlation between the negative CG flash rate and the area of radar echo with its reflectivity being equal to or greater than 30 dBz in the mesoscale convective system in Beijing area.A max- imum of the positive CG flash rate exists at both the initial and the dissipating stages.The CG flashes are usually located near but not within the high reflectivity center.The negative flashes are associated with.the positions of the updraft re- gion,and with the regions of wind convergence and wind shear.Generally,the negative CG flashes are concentrative and the positive ones are dispersive.
基金Project sponsored by the National Climbing Project and Key Project of the Chinese Academy of Sciences
文摘Using ground temperature data from meteorological stations as well as earthquake, ground tilt and precipitation data, the spatial-temporal distribution of "Underground Hot Vortex" ( UHV) in China was analyzed in detail. The results show that concerning an "Underground Hot Vortex" cell, its life-span is 3-8 seasons, 1.5 years on average; the mean horizontal scale is 600 km and its characteristic velocity is about 400 km/a; UHV is likely to appear in some areas where the crustal movement is intense and the absolute value of vertical deformation rate is relatively high; its activity could hardly be detected in the area where the crust is stable and the vertical deformation is weak; most of "Underground Hot Vortex Groups" originate from the edge of Indian Plate, then migrate eastwards with a leaping-frog style. 5-10 years are needed for their arrival in the eastern border of China. Their horizontal migrating velocity is 200-500 km/a which is nearly equal to the characteristic velocity of a single UHV.
基金Project sponsored by the National Climbing Project and Key Project of the Chinese Academy of Sciences
文摘Based on the previous results, the relationship between 'Underground Hot Vortex' (UHV) and earthquake was analyzed. Some results show that concerning a UHV with a larger horizontal scale or longer duration, the accompanied earthquake will be surely stronger while no earthquake or only minor shocks appear with a weak UHV; the strong earthquakes during recent 14 years in China (Ms>5. 5 in East China, Ms>6. 5 in West China) concentrated on two belts; i. e. within the scope of UHV radius ratio r/R = 0. 32-0. 61 and r/R = 0. 73-0. 79. No strong earthquake was detected when r/R >0.80; the horizontal angle of the earthquake is to the north or northeast of UHV which lies in the central ascending region of crustal vertical deformation except for those in Guizhou Province; the earthquake occurred to the southeast or west of UHV located in central descending region except for those in Fen-Wei River Valley; the seismic magnitude is directly dependent on the lag time between the appearance of UHV (the beginning time of T'3.2≥0. 5℃ ) and the occurrence of earthquakes. A preliminary conception model indicating coupling between lithosphere and atmosphere is put forward on the basis of the previous analyses and this paper.
基金The HEIFE program is supported by National Natural Science Foundation of China,the Chinese Academy of Sciences,the Special Committee for WCRP of the Geodesy Council,Japanese Ministry of Education,Science and Culture.
文摘Based on the HEIFE 1988 and 1990 pilot observations,an analysis on the turbulence structure of Gobi surface layer,mainly on the similarity formulations of wind and temperature variances,the spectra and cospectra characteristics,is presented.The phenomenon of downward water vapor flux over Gobi desert in daytime is confirmed in both observations,this and the well-known‘oasis effect’are two sides of a local mesoscale circulation.
基金Project supported by the National Major Project of Science and Technology 75-09-01.
文摘At present, in numerical weather prediction models (e. g. [1] ), general circulation or climate models (e. g. [2, 3] ) or meso-scale models (e. g. [4, 5] ), the influence of the water vapor source/sink term (WVST) in the continuity equation (CE) of moist air has not been taken into account generally. Though Hansen et al. listed source and sink terms in the CE ( Eq. T2 ), they still neglected these terms in the approximate form employed in computations ( Eq. T6 ). In the real atmosphere there exist condensation and evaporation, sometimes strong condensation. In this note the role of the WVSTs in the CE and its related equations of numerical models and their influences on forecast results are discussed.
