1987 Vol. 4, No. 3
Display Method:
1987, 4(3): 249-263.
doi: 10.1007/BF02663596
Abstract:
Scale analyses for long wave, zonal ultralong wave (with zonal scale of disturbance L1~104 km and meridional scale L2~103 km) and meridional ultralong wave (L1~103 km, L2~104 km) are carried out and a set of approximate equations suitable for the study of these waves in a dry tropical atmosphere is obtained. Under the condition of sheared basic current, frequency analyses for the equations are carried out. It is found that Rossby waves and gravity waves may be separated for n ≥ l where n is the meridional wave number, whereas for n = 0 and L1~1000 km, the mixed Rossby-gravity wave will appear. Hence it is confirmed that the above results of scale analyses are correct. The consistency be-tween frequency analysis and scale analysis is established.The effect of shear of basic current on the equatorial waves is to change their frequencies and phase velocities and hence their group velocities. It increases the velocity of westward travelling Rossby waves and inertia-gravity and mixed waves, but decelerates the eastward inertia-gravity waves and the Kelvin wave. The recently observed low-frequency equatorial ocean wave may be interpreted as an eastward Kelvin wave in a basic current with shear.
Scale analyses for long wave, zonal ultralong wave (with zonal scale of disturbance L1~104 km and meridional scale L2~103 km) and meridional ultralong wave (L1~103 km, L2~104 km) are carried out and a set of approximate equations suitable for the study of these waves in a dry tropical atmosphere is obtained. Under the condition of sheared basic current, frequency analyses for the equations are carried out. It is found that Rossby waves and gravity waves may be separated for n ≥ l where n is the meridional wave number, whereas for n = 0 and L1~1000 km, the mixed Rossby-gravity wave will appear. Hence it is confirmed that the above results of scale analyses are correct. The consistency be-tween frequency analysis and scale analysis is established.The effect of shear of basic current on the equatorial waves is to change their frequencies and phase velocities and hence their group velocities. It increases the velocity of westward travelling Rossby waves and inertia-gravity and mixed waves, but decelerates the eastward inertia-gravity waves and the Kelvin wave. The recently observed low-frequency equatorial ocean wave may be interpreted as an eastward Kelvin wave in a basic current with shear.
1987, 4(3): 264-277.
doi: 10.1007/BF02915593
Abstract:
In this paper, the data collected during the Mesoscale Weather Experiments in East China are utilized to study the meso-α scale rain-bands of meiyu front heavy rain, its structural features as well as the mechanism of its development. It has been revealed that the precipitation band during the meiyu season is in the shape of ribbon, which is parallel to the surface quasi-stationary front. Sometimes two meso-α scale rain-bands are present. The meso-α scale rain-band is associated with meso-α scale convergence line. As shown by the two dimentional disturbance circulation, calculated through band-pass filtering, the single rain-band is quite different from the double rain-bands. The former is, to some extent, akin to the frontogenctical circulation in the vicinity of the high- and low-level frontal zones; the latter features roller-like circulations at middle and low-levels with their axes parallel to the rain-bands while at higher levels they run in the opposite direction. This kind of disturbance may be caused by the symmetric instability in the moist atmosphere.
In this paper, the data collected during the Mesoscale Weather Experiments in East China are utilized to study the meso-α scale rain-bands of meiyu front heavy rain, its structural features as well as the mechanism of its development. It has been revealed that the precipitation band during the meiyu season is in the shape of ribbon, which is parallel to the surface quasi-stationary front. Sometimes two meso-α scale rain-bands are present. The meso-α scale rain-band is associated with meso-α scale convergence line. As shown by the two dimentional disturbance circulation, calculated through band-pass filtering, the single rain-band is quite different from the double rain-bands. The former is, to some extent, akin to the frontogenctical circulation in the vicinity of the high- and low-level frontal zones; the latter features roller-like circulations at middle and low-levels with their axes parallel to the rain-bands while at higher levels they run in the opposite direction. This kind of disturbance may be caused by the symmetric instability in the moist atmosphere.
1987, 4(3): 278-286.
doi: 10.1007/BF02663598
Abstract:
By utilizing the denser upper-air observations from the Okinawa region and Japanese islands during August 17－23, 1975, the vertical transports of heat and moisture by cumulus convection in the typhoon No. 7507 have been calculated. It is found that there exist a large apparent heat source (Q1) and a mois-ture sink (Q2) in the southern part of the typhoon at the disturbance, growing and mature stages. The magnitudes of the apparent heat source and moisture sink ace rather small, or turn into the apparent heat sink in the northern sector of the typhoon. In the southern part of the typhoon, the total cloud mass flux (Mc) is positive, whereas in the northern part of the typhoon Mc is negative. The above-mentioned distributions of Q1, Q2 and Mc agree well with the major cloud patterns.In the southern part of the typhoon, Q2 is positive because the drying effect is always larger than the evaporative cooling, whereas in the northern part of the typhoon, the opposite case is true because both the drying and evaporating effects of liquid water make a negative contribution to Q2.
By utilizing the denser upper-air observations from the Okinawa region and Japanese islands during August 17－23, 1975, the vertical transports of heat and moisture by cumulus convection in the typhoon No. 7507 have been calculated. It is found that there exist a large apparent heat source (Q1) and a mois-ture sink (Q2) in the southern part of the typhoon at the disturbance, growing and mature stages. The magnitudes of the apparent heat source and moisture sink ace rather small, or turn into the apparent heat sink in the northern sector of the typhoon. In the southern part of the typhoon, the total cloud mass flux (Mc) is positive, whereas in the northern part of the typhoon Mc is negative. The above-mentioned distributions of Q1, Q2 and Mc agree well with the major cloud patterns.In the southern part of the typhoon, Q2 is positive because the drying effect is always larger than the evaporative cooling, whereas in the northern part of the typhoon, the opposite case is true because both the drying and evaporating effects of liquid water make a negative contribution to Q2.
1987, 4(3): 287-299.
doi: 10.1007/BF02663599
Abstract:
By using multiple scale analysis method, two coupled models of gravity wave-mean flow interactions m a three-dimensional stratified atmosphere are derived. One model can be applied to the inertio-gravity wave-mean flow interactions in a global scale. The other one treats the meso-scale gravity wave forcing in a local region.
By using multiple scale analysis method, two coupled models of gravity wave-mean flow interactions m a three-dimensional stratified atmosphere are derived. One model can be applied to the inertio-gravity wave-mean flow interactions in a global scale. The other one treats the meso-scale gravity wave forcing in a local region.
1987, 4(3): 300-312.
doi: 10.1007/BF02663600
Abstract:
A numerical model is used to study the properties of pollutant dispersion over a large uniformly-sloped surface in the stable atmospheric boundary layer. By simulating the structure of boundary layer flow to improve the advective wind field and vertical eddy diffusivities included in the advection-diffusion equa-tion, this numerical model permits an estimation of the distribution of pollutant concentration for more real-istic atmospheric diffusion conditions.
A numerical model is used to study the properties of pollutant dispersion over a large uniformly-sloped surface in the stable atmospheric boundary layer. By simulating the structure of boundary layer flow to improve the advective wind field and vertical eddy diffusivities included in the advection-diffusion equa-tion, this numerical model permits an estimation of the distribution of pollutant concentration for more real-istic atmospheric diffusion conditions.
1987, 4(3): 313-322.
doi: 10.1007/BF02663601
Abstract:
A numerical model for the study of the regional acid precipitation is developed. The model consists of five parts: the distribution patterns of SO2 concentration, the mesoscale flow fields, the parameteriza-tion of SO2, transformation into SO4=, the parameterization of precipitation scavenging process, and the relationship between SO2 content in precipitation and ground level concentration of SO2 in the air. The distribution of SO2, SO2= and pH for all precipitations in Chongqing area during the period of July to October 1982 are simulated with the model. A comparison of the simulated results with experimental data shows that high SO2 concentration centres correspond to low pH centres. The source of the acid rain in Chongqing area is local air pollution which is due to the lower effective stack height, low wind velocity in the area, basin topography, and the use of coal with high sulphur content. The mechanism for the formation of the acid precipitation here may be different from that in the United States of America and the Western Europe, where acid rain appears in the area far from pollution source.
A numerical model for the study of the regional acid precipitation is developed. The model consists of five parts: the distribution patterns of SO2 concentration, the mesoscale flow fields, the parameteriza-tion of SO2, transformation into SO4=, the parameterization of precipitation scavenging process, and the relationship between SO2 content in precipitation and ground level concentration of SO2 in the air. The distribution of SO2, SO2= and pH for all precipitations in Chongqing area during the period of July to October 1982 are simulated with the model. A comparison of the simulated results with experimental data shows that high SO2 concentration centres correspond to low pH centres. The source of the acid rain in Chongqing area is local air pollution which is due to the lower effective stack height, low wind velocity in the area, basin topography, and the use of coal with high sulphur content. The mechanism for the formation of the acid precipitation here may be different from that in the United States of America and the Western Europe, where acid rain appears in the area far from pollution source.
1987, 4(3): 323-331.
doi: 10.1007/BF02663602
Abstract:
On the basis of the data of concentrations as well as wind and temperature, simultaneously observed in the north suburb of Beijing, measurements have been made of the dry deposition velocities of suspended particles. Results show that, over such an environment, the dry deposition velocities for suspended par-ticles vary from 0.15 to 10.62 cm s-1, which are comparable with those over forests, that the average surface resistance in the transfer process of particles is about four times as large as the aerodynamic resis-tance, and that the dry deposition velocity is well related to the frictional velocity in terms of positive cor-relation function.
On the basis of the data of concentrations as well as wind and temperature, simultaneously observed in the north suburb of Beijing, measurements have been made of the dry deposition velocities of suspended particles. Results show that, over such an environment, the dry deposition velocities for suspended par-ticles vary from 0.15 to 10.62 cm s-1, which are comparable with those over forests, that the average surface resistance in the transfer process of particles is about four times as large as the aerodynamic resis-tance, and that the dry deposition velocity is well related to the frictional velocity in terms of positive cor-relation function.
1987, 4(3): 332-342.
doi: 10.1007/BF02663603
Abstract:
On the basis of a three year record of Radiosonde observations over Indian region, the autocorrelation function and structure function of the humidity mixing ratio (r) were computed for 850 hPa level. These are necessary for the construction of a suitable objective analysis scheme for humidity over Indian region using optimum interpolation method. The statistics were derived for the monsoon period (June through September) for 850 hPa level.In order to model the humidity correlation for Indian region, two types of curves were fitted: (i) μ(ρ) = a exp (-bρ), (ii) μ(ρ) = A exp (-Bρ2) where μ is the autocorrelation function － a function of distance ρ－between two observing stations. It was found that the best description of humidity correla-tion function was given by Eq. (1). The value of ‘a’ gives a quantitative impression of the observation error. Further, the mean random errors were computed from structure functions, the weighting factors for the observing stations with respect to each grid point were calculated, and objective analyses were made for the humidity mixing ratio.
On the basis of a three year record of Radiosonde observations over Indian region, the autocorrelation function and structure function of the humidity mixing ratio (r) were computed for 850 hPa level. These are necessary for the construction of a suitable objective analysis scheme for humidity over Indian region using optimum interpolation method. The statistics were derived for the monsoon period (June through September) for 850 hPa level.In order to model the humidity correlation for Indian region, two types of curves were fitted: (i) μ(ρ) = a exp (-bρ), (ii) μ(ρ) = A exp (-Bρ2) where μ is the autocorrelation function － a function of distance ρ－between two observing stations. It was found that the best description of humidity correla-tion function was given by Eq. (1). The value of ‘a’ gives a quantitative impression of the observation error. Further, the mean random errors were computed from structure functions, the weighting factors for the observing stations with respect to each grid point were calculated, and objective analyses were made for the humidity mixing ratio.
1987, 4(3): 343-348.
doi: 10.1007/BF02663604
Abstract:
The observational data of global sea surface temperature and the 500 hPa geopotential height field in the Northern Hemisphere are used to get two teleconnection patterns. The time interval of the data is from January 1950 to December 1979. The results show that the sea surface temperature anomalies in the Indian Ocean have evident positive correlation with the SSTA in the eastern Pacific and obvious teleconnection with the 500 hPa geopotential height field in the Northern Hemisphere.
The observational data of global sea surface temperature and the 500 hPa geopotential height field in the Northern Hemisphere are used to get two teleconnection patterns. The time interval of the data is from January 1950 to December 1979. The results show that the sea surface temperature anomalies in the Indian Ocean have evident positive correlation with the SSTA in the eastern Pacific and obvious teleconnection with the 500 hPa geopotential height field in the Northern Hemisphere.
1987, 4(3): 349-362.
doi: 10.1007/BF02663605
Abstract:
The paper presents a review of the success and failure of the practical results from summer drought and flood forecasts and seasonal precipitation forecasts in the period from 1976 to 1985. An analysis is made on the anomaly of the general circulation winch gives rise to summer precipitation and drought-flood occurrences in the country. It is proposed that the subtropical high over the West Pacific, the South Asia high and middle-latitude westerlies are the major synoptical regimes producing summer weather in China. The analysis focuses on the features of low-frequency oscillation and abnormality of the West Pacific sub-tropical high in the monthly 500 hPa mean charts, and on their interactions with the sea temperature of the North Pacific and the Equatorial Pacific. The result shows that there exist quasi-cycles of 3－4 years, 11 years and 19 years or so in the subtropical high with the feature of strong persistence and seasonal changes. There is a rather good correlation between the behaviour of the subtropical high and changes in the cold current area in the East Pacific, and especially during the El Nino period, there is an ob-vious coupling with abnormal changes of the intensity of the subtropical high. Analysis is also made on the effect of the thermal condition of the Tibetan Plateau, the Northern Hemisphere westerly circulation and the astronomical factors on the West Pacific subtropical high, the South Asia high and precipitation in the rainy season in China.
The paper presents a review of the success and failure of the practical results from summer drought and flood forecasts and seasonal precipitation forecasts in the period from 1976 to 1985. An analysis is made on the anomaly of the general circulation winch gives rise to summer precipitation and drought-flood occurrences in the country. It is proposed that the subtropical high over the West Pacific, the South Asia high and middle-latitude westerlies are the major synoptical regimes producing summer weather in China. The analysis focuses on the features of low-frequency oscillation and abnormality of the West Pacific sub-tropical high in the monthly 500 hPa mean charts, and on their interactions with the sea temperature of the North Pacific and the Equatorial Pacific. The result shows that there exist quasi-cycles of 3－4 years, 11 years and 19 years or so in the subtropical high with the feature of strong persistence and seasonal changes. There is a rather good correlation between the behaviour of the subtropical high and changes in the cold current area in the East Pacific, and especially during the El Nino period, there is an ob-vious coupling with abnormal changes of the intensity of the subtropical high. Analysis is also made on the effect of the thermal condition of the Tibetan Plateau, the Northern Hemisphere westerly circulation and the astronomical factors on the West Pacific subtropical high, the South Asia high and precipitation in the rainy season in China.
1987, 4(3): 363-374.
doi: 10.1007/BF02663606
Abstract:
In the light of the idea of fuzzy neartude, a fuzzy procedure of verifying weather forecast and climate simula-tion is demonstrated. Several verification indices used in weather forecast, such as hit ratio, Heidke score, Brier score, correlation coefficient and information entropy score, are unified under fuzzy neartude and a new verifica-tion index is proposed on the basis of Hamming distance neartude. Further, D2-statistics used in climate sim-ulation verification is derived from a weighted Euclidean distance neartude. The “January climate” generated by general circulation model (GCM) is also numerically verified.
In the light of the idea of fuzzy neartude, a fuzzy procedure of verifying weather forecast and climate simula-tion is demonstrated. Several verification indices used in weather forecast, such as hit ratio, Heidke score, Brier score, correlation coefficient and information entropy score, are unified under fuzzy neartude and a new verifica-tion index is proposed on the basis of Hamming distance neartude. Further, D2-statistics used in climate sim-ulation verification is derived from a weighted Euclidean distance neartude. The “January climate” generated by general circulation model (GCM) is also numerically verified.
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