1985 Vol. 2, No. 1
Display Method:
1985, 2(1): 1-7.
doi: 10.1007/BF03179731
Abstract:
In this paper, the influences of orography on the boundary layer flow with the approximation of geostrophic momentum are studied. The wind velocity at the lower boundary will not always be zero when the orography exists. So the structure of the boundary layer flow, as well as the vertical velocity at the top of the boundary layer, is affected. There are three factors affecting the vertical motion at the top of the boundary layer: lifting due to orography; divergence due to Ekman flow, and advection of the geostrophic momentum. These effects and the features of the flow within the boundary layer are discussed in detail.
In this paper, the influences of orography on the boundary layer flow with the approximation of geostrophic momentum are studied. The wind velocity at the lower boundary will not always be zero when the orography exists. So the structure of the boundary layer flow, as well as the vertical velocity at the top of the boundary layer, is affected. There are three factors affecting the vertical motion at the top of the boundary layer: lifting due to orography; divergence due to Ekman flow, and advection of the geostrophic momentum. These effects and the features of the flow within the boundary layer are discussed in detail.
1985, 2(1): 8-19.
doi: 10.1007/BF03179732
Abstract:
Using conventional two-dimensional nonlinear storm model, the storm surges caused by the six ty-phoons with different kinds of tracks which hit the coast of Zhejiang and Jiangsu Provinces including Shanghai during the period from 1953 to 1974 are computed numerically. To avoid the nonlinear and linear computational instabilities, a finite-difference scheme with the quadratic conservation (or the semi-momentum) is adopted and a criterion for linear computational stability is derived. The basic parameters used in this computation are: the space step Δs=30km, the time step Δt=200sec, the coefficient of the wind stress = 2.6 "10-> and the coefficient of the bottom friction v&2=2.0x 10-'. The pressure and surface wind distribution for typhoon are assumed to be characterized by Fujita's pressure formula and Uerto's wind model, respectively.
Using conventional two-dimensional nonlinear storm model, the storm surges caused by the six ty-phoons with different kinds of tracks which hit the coast of Zhejiang and Jiangsu Provinces including Shanghai during the period from 1953 to 1974 are computed numerically. To avoid the nonlinear and linear computational instabilities, a finite-difference scheme with the quadratic conservation (or the semi-momentum) is adopted and a criterion for linear computational stability is derived. The basic parameters used in this computation are: the space step Δs=30km, the time step Δt=200sec, the coefficient of the wind stress = 2.6 "10-> and the coefficient of the bottom friction v&2=2.0x 10-'. The pressure and surface wind distribution for typhoon are assumed to be characterized by Fujita's pressure formula and Uerto's wind model, respectively.
1985, 2(1): 20-27.
doi: 10.1007/BF03179733
Abstract:
Transfer of radiation through cirrus consisting of non-sphericalice crystals randomly oriented in a plane (2D model) is solved by using the discrete-ordinates method. The model is employed to determine the radiative flux properties and the intensity distribution of cirrus for both solar and thermal infrared ra-diation. Comparison of the 2D cloud model with the conventional 3D cloud model, i.e., randomly oriented in a three- dimensional space, shows that the preferential orientation of ice crystals has a substantial effect on the cloud solar albedo. The difference in the cloud albedo computed from the two models can be as large as 8% for a cirrus of 2 km thickness. On the thermal infrared side, although the flux emission for cirrus is less affected by the orientation of ice crystals, the difference in the upward radiance using 2D and 3D models is also significant.
Transfer of radiation through cirrus consisting of non-sphericalice crystals randomly oriented in a plane (2D model) is solved by using the discrete-ordinates method. The model is employed to determine the radiative flux properties and the intensity distribution of cirrus for both solar and thermal infrared ra-diation. Comparison of the 2D cloud model with the conventional 3D cloud model, i.e., randomly oriented in a three- dimensional space, shows that the preferential orientation of ice crystals has a substantial effect on the cloud solar albedo. The difference in the cloud albedo computed from the two models can be as large as 8% for a cirrus of 2 km thickness. On the thermal infrared side, although the flux emission for cirrus is less affected by the orientation of ice crystals, the difference in the upward radiance using 2D and 3D models is also significant.
1985, 2(1): 28-34.
doi: 10.1007/BF03179734
Abstract:
The absorption characteristics of the atmospheric window in the microwave band (λ=8.5 mm and 3.2 cm) are studied. The results measured in Beijing by using both solar radiation method and atmospheric radiation method are compared with the values calculated from the radiosonde data so as to analyze their correlativity. The relationship between atmospheric window absorption and total column water vapour content is also discussed. The effects of clouds on the absorption are described.
The absorption characteristics of the atmospheric window in the microwave band (λ=8.5 mm and 3.2 cm) are studied. The results measured in Beijing by using both solar radiation method and atmospheric radiation method are compared with the values calculated from the radiosonde data so as to analyze their correlativity. The relationship between atmospheric window absorption and total column water vapour content is also discussed. The effects of clouds on the absorption are described.
1985, 2(1): 35-44.
doi: 10.1007/BF03179735
Abstract:
An experiment is performed to simulate the drag effect of raindrops on the air motion in the atmos-phere by means of fine sand particles precipitating through a liquid fluid. The results suggest that the drag effect of the precipitating particles may cause the downward motion in the column where sand particles (or raindrops) precipitate, and produce the updraft around, thus forming a vertical vortex flow pattern around the precipitation area. This effect is also found to be propagating outward, resulting in a multi-vortex flow field. In the stratified fluid, vortexes can be observed at 2 or 3 levels. In the lower layer, the rotating direc-tion of vortexes varies periodically. In addition, the whole flow field induced by the drag effect of precipitat-ing particles is characterized by clear vacillation. The experimental results obtained in this paper can be used to explain the phenomena of multi-layer clouds and multi-belt rainfall around the severe rain.
An experiment is performed to simulate the drag effect of raindrops on the air motion in the atmos-phere by means of fine sand particles precipitating through a liquid fluid. The results suggest that the drag effect of the precipitating particles may cause the downward motion in the column where sand particles (or raindrops) precipitate, and produce the updraft around, thus forming a vertical vortex flow pattern around the precipitation area. This effect is also found to be propagating outward, resulting in a multi-vortex flow field. In the stratified fluid, vortexes can be observed at 2 or 3 levels. In the lower layer, the rotating direc-tion of vortexes varies periodically. In addition, the whole flow field induced by the drag effect of precipitat-ing particles is characterized by clear vacillation. The experimental results obtained in this paper can be used to explain the phenomena of multi-layer clouds and multi-belt rainfall around the severe rain.
1985, 2(1): 45-53.
doi: 10.1007/BF03179736
Abstract:
On the basis of analysis and study of the growth of ice crystals, the inadequacy and thus a necessity for improvement of the Kohayashi-Pruppacher model are discussed. Be experimenting with a new wedge-shaped chamber of ice thermal diffusion which provides a stable environment and a wide range of control, a great amount of quantitative data from three-dimensional size measurements have been obtained. A quantitative research method is established, yielding, for the first time, satisfactory quantitative results in the region of low ice supersaturation. These results show that the Kobayashi-Pruppacher inference is inade-quate, and reveal new characteristics of ice-crystal growth in the Wulff growth region, the region of abrupt change of crystal forms and that of low ice supersaturation.
On the basis of analysis and study of the growth of ice crystals, the inadequacy and thus a necessity for improvement of the Kohayashi-Pruppacher model are discussed. Be experimenting with a new wedge-shaped chamber of ice thermal diffusion which provides a stable environment and a wide range of control, a great amount of quantitative data from three-dimensional size measurements have been obtained. A quantitative research method is established, yielding, for the first time, satisfactory quantitative results in the region of low ice supersaturation. These results show that the Kobayashi-Pruppacher inference is inade-quate, and reveal new characteristics of ice-crystal growth in the Wulff growth region, the region of abrupt change of crystal forms and that of low ice supersaturation.
1985, 2(1): 54-62.
doi: 10.1007/BF03179737
Abstract:
By using the power spectrum analysis, the interannual variation of medium-range oscillation charac-teristics in the upper troposphere over the subtropical region in China during June-August, 1966－1981 is studied. The quasi-two and quasi-one week oscillations are the two major oscillations generally existing in the subtropical region, and their intensities have obvious quasi-triennial variation period. These medium-range oscillation characteristics are closely related to the South Asian high, and in some degree to the summer precipitation in China. The quasi-two week oscillation is probably a display of the inherent oscillation of the south Asian high itself, and the quasi-one week oscillation is probably that of the forced oscillation from westerly disturbances.
By using the power spectrum analysis, the interannual variation of medium-range oscillation charac-teristics in the upper troposphere over the subtropical region in China during June-August, 1966－1981 is studied. The quasi-two and quasi-one week oscillations are the two major oscillations generally existing in the subtropical region, and their intensities have obvious quasi-triennial variation period. These medium-range oscillation characteristics are closely related to the South Asian high, and in some degree to the summer precipitation in China. The quasi-two week oscillation is probably a display of the inherent oscillation of the south Asian high itself, and the quasi-one week oscillation is probably that of the forced oscillation from westerly disturbances.
APPLICATION OF SODAR SOUNDING TO ATMOSPHERIC DISPERSION-MIXING DEPTH AND CONCENTRATION AT THE GROUND
1985, 2(1): 63-71.
doi: 10.1007/BF03179738
Abstract:
It is the intent of this paper to illustrate how to apply acoustic radar data on the variation of mixing depth in the study of atmospheric dispersion. The box model, as an example of the routine usage of acoustic sounding, has been modified. A case of the development of the structure of mixed layer, resulting from some synoptic process is discussed and the results show that the ordinary model calculations regarding atmospheric dispersion will mislead the assessment of air quality if no remote techniques, such as the acoustic radar, are associated with.
It is the intent of this paper to illustrate how to apply acoustic radar data on the variation of mixing depth in the study of atmospheric dispersion. The box model, as an example of the routine usage of acoustic sounding, has been modified. A case of the development of the structure of mixed layer, resulting from some synoptic process is discussed and the results show that the ordinary model calculations regarding atmospheric dispersion will mislead the assessment of air quality if no remote techniques, such as the acoustic radar, are associated with.
1985, 2(1): 72-80.
doi: 10.1007/BF03179739
Abstract:
By using a two-dimensional axisymmetrical PEM in which two physical processes (the Ekman pumping and the vertical transportation of cumulus momentum) are included, the genesis and development of typhoons have been simulated. The results of numerical simulation show that the generation and structure of the typhoon simulated by the model involving both the physical processes are much close to a real one in the atmosphere as compared with that involving either the Ekman pumping or the cumulus momentum transport. Therefore, it can be suggested that the cumulus momentum transport and Ekman pumping together play an important role in the genesis and development of typhoons through the CISK mechanism.
By using a two-dimensional axisymmetrical PEM in which two physical processes (the Ekman pumping and the vertical transportation of cumulus momentum) are included, the genesis and development of typhoons have been simulated. The results of numerical simulation show that the generation and structure of the typhoon simulated by the model involving both the physical processes are much close to a real one in the atmosphere as compared with that involving either the Ekman pumping or the cumulus momentum transport. Therefore, it can be suggested that the cumulus momentum transport and Ekman pumping together play an important role in the genesis and development of typhoons through the CISK mechanism.
1985, 2(1): 81-92.
doi: 10.1007/BF03179740
Abstract:
In this paper, a quasi-geostrophic, 34-level spherical coordinate model with Rayleigh friction, New-tonian cooling and the horizontal eddy thermal diffusivity is used to simulate the three-dimensional teleconnection in the summer circulation over the Northern Hemisphere.The computed results show that the change of the heat source over the Tibetan Plateau may cause the change of the atmospheric circulation over the middle and high latitudes in the Northern Hemisphere. When the heat source over the Tibetan Plateau is enhanced, it may cause the Tibetan high to enhance over South Asia and cause the change of the atmospheric circulation over East Asia and North America, i. e. Northeast China and North Japan will be controlled by a trough, which brings about a cold summer in this area. In the same way, an anticyclone will be enhanced over the Okhotsk sea. Moreover, another trough will be formed over Alaska, while another ridge will develop to the northeast of North America. Besides, the Pacific subtropical high will be weakened. These results are in good agreement with those obtained from the observed data.
In this paper, a quasi-geostrophic, 34-level spherical coordinate model with Rayleigh friction, New-tonian cooling and the horizontal eddy thermal diffusivity is used to simulate the three-dimensional teleconnection in the summer circulation over the Northern Hemisphere.The computed results show that the change of the heat source over the Tibetan Plateau may cause the change of the atmospheric circulation over the middle and high latitudes in the Northern Hemisphere. When the heat source over the Tibetan Plateau is enhanced, it may cause the Tibetan high to enhance over South Asia and cause the change of the atmospheric circulation over East Asia and North America, i. e. Northeast China and North Japan will be controlled by a trough, which brings about a cold summer in this area. In the same way, an anticyclone will be enhanced over the Okhotsk sea. Moreover, another trough will be formed over Alaska, while another ridge will develop to the northeast of North America. Besides, the Pacific subtropical high will be weakened. These results are in good agreement with those obtained from the observed data.
1985, 2(1): 93-103.
doi: 10.1007/BF03179741
Abstract:
This paper describes the retrieval procedure of liquid water content (LWC) in cloud or rainfall distri-bution by a combination of microwave radiometry and radar and its numerical simulation. The per-formance of a combined dual-wavelength (35.0& 9.375 GHz) radar-radiometer system for the remote sensing of cloud LWC and rainfall is given. During the two summers of 1980 and 1981, the preliminary obser-vations of different clouds and storms by the combined system and combined radar-radiometric cloud and rain parameter retrievals are carried out. Research results show that by the use of the combined radar-radiometric method, improvement are obtained in accuracy of rms LWC and rainfall over the pure radio-metric technique or the radar alone.
This paper describes the retrieval procedure of liquid water content (LWC) in cloud or rainfall distri-bution by a combination of microwave radiometry and radar and its numerical simulation. The per-formance of a combined dual-wavelength (35.0& 9.375 GHz) radar-radiometer system for the remote sensing of cloud LWC and rainfall is given. During the two summers of 1980 and 1981, the preliminary obser-vations of different clouds and storms by the combined system and combined radar-radiometric cloud and rain parameter retrievals are carried out. Research results show that by the use of the combined radar-radiometric method, improvement are obtained in accuracy of rms LWC and rainfall over the pure radio-metric technique or the radar alone.
1985, 2(1): 104-111.
doi: 10.1007/BF03179742
Abstract:
The equations for calculating the echo power from meteorological targets and the energy distribution within radar beam were derived, by taking the earth curvature, atmospheric refractivity gradient, reflection factor and the roughness of the earth's surface into consideration. The estimation based on these equations shows that the rain echo power may deviate from its normal value by a factor of －3 to +6 db depending on the radar height, antenna elevation, wave length, beam width, surface reflectivity and roughness.
The equations for calculating the echo power from meteorological targets and the energy distribution within radar beam were derived, by taking the earth curvature, atmospheric refractivity gradient, reflection factor and the roughness of the earth's surface into consideration. The estimation based on these equations shows that the rain echo power may deviate from its normal value by a factor of －3 to +6 db depending on the radar height, antenna elevation, wave length, beam width, surface reflectivity and roughness.
1985, 2(1): 112-123.
doi: 10.1007/BF03179743
Abstract:
Using the wind data at mountain stations, gravity waves on the axis of low level jet and their relation to rain clusters have been studied by means of the spectrum method. It is found that the spectrum densities of both wind and rainfall reach their maximums at the period of 8 h and the module between wind and rainfall also reach the maximum in that range. Both observation and theoretical study give the same con-clusion that the unstable development of gravity waves depends not only on the atmospheric stratification but also on the vertical shear of the environmental wind. The appearance of the jet-shape vertical profile of wind is favourable for the unstable development of gravity waves. The lower the height of the axis, the larger the growth rate of amplitude.
Using the wind data at mountain stations, gravity waves on the axis of low level jet and their relation to rain clusters have been studied by means of the spectrum method. It is found that the spectrum densities of both wind and rainfall reach their maximums at the period of 8 h and the module between wind and rainfall also reach the maximum in that range. Both observation and theoretical study give the same con-clusion that the unstable development of gravity waves depends not only on the atmospheric stratification but also on the vertical shear of the environmental wind. The appearance of the jet-shape vertical profile of wind is favourable for the unstable development of gravity waves. The lower the height of the axis, the larger the growth rate of amplitude.
1985, 2(1): 124-128.
doi: 10.1007/BF03179744
Abstract:
This paper discusses the possible error of the calculation of the atmospheric extinction coefficient by the Koschinieder visibility formula. An analysis of the problem shows that an error of 10% can be in-troduced in the measurement if the target used is a non-blackbody. By using the telephotometer as a tool of measurement, such an error can be markedly reduced.
This paper discusses the possible error of the calculation of the atmospheric extinction coefficient by the Koschinieder visibility formula. An analysis of the problem shows that an error of 10% can be in-troduced in the measurement if the target used is a non-blackbody. By using the telephotometer as a tool of measurement, such an error can be markedly reduced.
1985, 2(1): 129-131.
doi: 10.1007/BF03179745
Abstract:
Iteration procedure have been applied to obtain the scattering phase function from measurements of sky brightness on solar almucantar. The principle and calculating examples have been discussed.
Iteration procedure have been applied to obtain the scattering phase function from measurements of sky brightness on solar almucantar. The principle and calculating examples have been discussed.
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