1988 Vol. 5, No. 1
Display Method:
1988, 5(1): 1-14.
doi: 10.1007/BF02657341
Abstract:
In this paper, a tropical limited numerical prediction p.e. model in sigma coordinate is developed. The predicted variables are deviations from a rest reference atmosphere. This transformation is of benefit in reducing truncation error and guarantees computational stability after the very steep real topography is introduced into the model. The numerical tests with this model show that the large-scale obstacle of the Tibetan Plateau is not negligible in forecasting tropical systems like the South China Sea typhoon.
In this paper, a tropical limited numerical prediction p.e. model in sigma coordinate is developed. The predicted variables are deviations from a rest reference atmosphere. This transformation is of benefit in reducing truncation error and guarantees computational stability after the very steep real topography is introduced into the model. The numerical tests with this model show that the large-scale obstacle of the Tibetan Plateau is not negligible in forecasting tropical systems like the South China Sea typhoon.
1988, 5(1): 15-26.
doi: 10.1007/BF02657342
Abstract:
Monte-Carlo method is applied to simulate the intensities and degrees of polarization in twilight sky after the eruption of the El Chichon volcano and during the 1977 volcanically quiet period, respectively. The results coincide well with the observations. It is found that the significance of multiple scattering is com-pletely different in these two periods; the background concentration of stratospheric aerosols has probably increased since the 1960s. It is necessary to study the cause of the increase and its impact on climate.
Monte-Carlo method is applied to simulate the intensities and degrees of polarization in twilight sky after the eruption of the El Chichon volcano and during the 1977 volcanically quiet period, respectively. The results coincide well with the observations. It is found that the significance of multiple scattering is com-pletely different in these two periods; the background concentration of stratospheric aerosols has probably increased since the 1960s. It is necessary to study the cause of the increase and its impact on climate.
1988, 5(1): 27-34.
doi: 10.1007/BF02657343
Abstract:
The nonlinear discriminant function, when covariance matrixes of each population are not equal to each other, is discussed on the basis of Bayes criterion, and by using the stepwise discriminant method, a method for calculating the nonlinear discriminant function is provided, which is called stepwise nonlinear discriminant analysis. In addition, an appropriate discriminant analysis model is selected by testing whether the covariance matrixes of each population are equal, which was proposed by Box. The calculations show that, the discrimi-nant effects of this method are superior not only to linear discriminant analysis, but also to nonlinear discrimi-nant analysis in which the stepwise discriminant algorithm is not used when covariance matrixes of each popu-lation are not equal to each other. Satisfactory results have been obtained in applying this method. This is an important improvement on the linear discriminant analysis used in the weather typing prediction at present.
The nonlinear discriminant function, when covariance matrixes of each population are not equal to each other, is discussed on the basis of Bayes criterion, and by using the stepwise discriminant method, a method for calculating the nonlinear discriminant function is provided, which is called stepwise nonlinear discriminant analysis. In addition, an appropriate discriminant analysis model is selected by testing whether the covariance matrixes of each population are equal, which was proposed by Box. The calculations show that, the discrimi-nant effects of this method are superior not only to linear discriminant analysis, but also to nonlinear discrimi-nant analysis in which the stepwise discriminant algorithm is not used when covariance matrixes of each popu-lation are not equal to each other. Satisfactory results have been obtained in applying this method. This is an important improvement on the linear discriminant analysis used in the weather typing prediction at present.
1988, 5(1): 35-46.
doi: 10.1007/BF02657344
Abstract:
The monthly mean sea surface temperature data of 6 areas are used to study the El Nino/Southern Oscillation signals in the global tropical ocean. These areas are in the 5oN-5oS latitude zone at 1) eastern Pacific (110o-l40oW), 2) western Atlantic (30o-50oW), 3) eastern Atlantic (10oW-10oE), 4) western Indian Ocean (30o-50oE), 5) central Indian Ocean (70o-90oE) and 6) far western Pacific (120o-140oE), and the data cover the 120-month period of December 1968 to November 1978.A power spectrum analysts shows that the characteristic time of the El Nino/Southern Oscillation (about 3-4 years) appears not only in the eastern Pacific but also in other areas of the tropics except for the western Pa-cific, where the spectrum is of white noise. The amplitude of oscillation in the eastern Pacific is about 4 times larger than the others, making the El Nino/Southern Oscillation signal the strongest in this area. According to a cross-spectrum analysis, there is no time lag between the variation in the central Indian Ocean and that in the eastern Pacific. These two areas oscillate simultaneously and comprise the main feature of the El Nino/ Southern Oscillation. Other tropical areas are related with time lags, as shown by correlation and coherence calculations.It should be noted that the sea surface temperature in the eastern Pacific oscillates in phase with that in the Indian Ocean, while the pressure oscillations in these two areas are out of phase with each other, according to the Southern Oscillation definition. It is suggested that the Southern Oscillation cannot be explained simply by the sea surface temperature anomalies.Variations in the far western equatorial Pacific do not have the time scale of the El Nino/Southern Oscilla-tion, perhaps because it is a buffer zone between the monsoon system and the trade wind system.
The monthly mean sea surface temperature data of 6 areas are used to study the El Nino/Southern Oscillation signals in the global tropical ocean. These areas are in the 5oN-5oS latitude zone at 1) eastern Pacific (110o-l40oW), 2) western Atlantic (30o-50oW), 3) eastern Atlantic (10oW-10oE), 4) western Indian Ocean (30o-50oE), 5) central Indian Ocean (70o-90oE) and 6) far western Pacific (120o-140oE), and the data cover the 120-month period of December 1968 to November 1978.A power spectrum analysts shows that the characteristic time of the El Nino/Southern Oscillation (about 3-4 years) appears not only in the eastern Pacific but also in other areas of the tropics except for the western Pa-cific, where the spectrum is of white noise. The amplitude of oscillation in the eastern Pacific is about 4 times larger than the others, making the El Nino/Southern Oscillation signal the strongest in this area. According to a cross-spectrum analysis, there is no time lag between the variation in the central Indian Ocean and that in the eastern Pacific. These two areas oscillate simultaneously and comprise the main feature of the El Nino/ Southern Oscillation. Other tropical areas are related with time lags, as shown by correlation and coherence calculations.It should be noted that the sea surface temperature in the eastern Pacific oscillates in phase with that in the Indian Ocean, while the pressure oscillations in these two areas are out of phase with each other, according to the Southern Oscillation definition. It is suggested that the Southern Oscillation cannot be explained simply by the sea surface temperature anomalies.Variations in the far western equatorial Pacific do not have the time scale of the El Nino/Southern Oscilla-tion, perhaps because it is a buffer zone between the monsoon system and the trade wind system.
1988, 5(1): 47-56.
doi: 10.1007/BF02657345
Abstract:
In this paper, a numerical experiment of the motion in the PBL (planetary boundary layer) is perform-ed with geostrophic momentum approximation, in which a nonlinear eddy transfer coefficient is used. Some results are obtained for the boundary layer winds in cyclone-anticyclone and trough-ridge systems. This treat-ment improves W-Bs work. The effects of geostrophic wind tendency and the advection of the geostrophic wind on the winds in the PBL are also discussed.
In this paper, a numerical experiment of the motion in the PBL (planetary boundary layer) is perform-ed with geostrophic momentum approximation, in which a nonlinear eddy transfer coefficient is used. Some results are obtained for the boundary layer winds in cyclone-anticyclone and trough-ridge systems. This treat-ment improves W-Bs work. The effects of geostrophic wind tendency and the advection of the geostrophic wind on the winds in the PBL are also discussed.
1988, 5(1): 57-66.
doi: 10.1007/BF02657347
Abstract:
A method has been developed to determine the surface albedo over the Qinghai-Xizang Plateau region from NOAA polar orbiter AVHRR (Advanced Very High Resolution Radiometer) data. The empirical rela-tionship between clear-sky planetary and surface albedos is established the basis of surface global radiation measurements and the specified ratio between atmospheric reflection and absoption of solar radiation. The method is applied to the Qinghai-Xizang region with several measurements during the period of Sep. to Nov., 1985. A comparison is presented between the estimated surface albedos and that of surface observation. The results show that the presented method is suitable to detecting the spatial and temporal variation of surface albedo and is relevant for climatologies studies. The possible error sources and improvements are discussed as well.
A method has been developed to determine the surface albedo over the Qinghai-Xizang Plateau region from NOAA polar orbiter AVHRR (Advanced Very High Resolution Radiometer) data. The empirical rela-tionship between clear-sky planetary and surface albedos is established the basis of surface global radiation measurements and the specified ratio between atmospheric reflection and absoption of solar radiation. The method is applied to the Qinghai-Xizang region with several measurements during the period of Sep. to Nov., 1985. A comparison is presented between the estimated surface albedos and that of surface observation. The results show that the presented method is suitable to detecting the spatial and temporal variation of surface albedo and is relevant for climatologies studies. The possible error sources and improvements are discussed as well.
1988, 5(1): 67-74.
doi: 10.1007/BF02657346
Abstract:
The technique using a ground-based infrared broad-band scanning radiometer to measure temperature pro-files in the boundary layer is suggested. The methods for retrieving and reducing its errors are discussed, and that of correction to water vapour absorption is also given.
The technique using a ground-based infrared broad-band scanning radiometer to measure temperature pro-files in the boundary layer is suggested. The methods for retrieving and reducing its errors are discussed, and that of correction to water vapour absorption is also given.
1988, 5(1): 75-86.
doi: 10.1007/BF02657348
Abstract:
This paper describes a geopotential thickness difference method for computing instability energy E. EP1P2 =g0 ( HsP1P2-HP1P2 , where HP1P2 is the geopotential thickness of P1-P2 level; HsP1P2 is called adia-batic geopotential thickness, based on which a computational method for high resolution of instability energy is proposed. E(x,y)g0(A(x,y) - B(x,y)), where A is interpolating polynomial of HSP2P2 and it is afunction ofe, of surface observing stations (x, y); B(x,y) is the thickness over corresponding stations (x, y) obtained using surface fitting method. Therefore, data of METAR can be used by computer to produce hourly horizontal distribution chart of E of surface observing station density. With the result that the temporal and spatial resolution of stability analysis has been improved. Practical use has shown that this method is an effective tool for very short range forecast of severe convective storms.
This paper describes a geopotential thickness difference method for computing instability energy E. EP1P2 =g0 ( HsP1P2-HP1P2 , where HP1P2 is the geopotential thickness of P1-P2 level; HsP1P2 is called adia-batic geopotential thickness, based on which a computational method for high resolution of instability energy is proposed. E(x,y)g0(A(x,y) - B(x,y)), where A is interpolating polynomial of HSP2P2 and it is afunction ofe, of surface observing stations (x, y); B(x,y) is the thickness over corresponding stations (x, y) obtained using surface fitting method. Therefore, data of METAR can be used by computer to produce hourly horizontal distribution chart of E of surface observing station density. With the result that the temporal and spatial resolution of stability analysis has been improved. Practical use has shown that this method is an effective tool for very short range forecast of severe convective storms.
1988, 5(1): 87-96.
doi: 10.1007/BF02657349
Abstract:
The relationship between tropical cyclones developing in the Northwest Pacific and El Ni?o is analysed and the triggering mechanism of the near-equatorial cyclones on El Ni?o is proposed. It is pointed out that the near-equalorial tropical cyclones developing equatorward of 10oN can intensify equatorial westerlies and produce Kelvin waves, which propagate to the South American Coasts in about 2-3 months, inducing SST to rise there. The near-equatoral cyclones play an essential role in El Ni?o. The beginning period of El Ni?o ranges from January to May. The number of near-equatorial cyclones developing in this period determines whether El Ni?o can be generated or not. The persistence period is from June to September. El Ni?o can not continue developing unless there are adequate near-equatorial cyclones. If there are not, the developed El Ni?o will be broken down. The period from October to December is called the developing period. During this period El Ni?o may approach its culmination only when adequate near-eqatorial cyclones have been developed east of 140oE, especially east of 160oE.
The relationship between tropical cyclones developing in the Northwest Pacific and El Ni?o is analysed and the triggering mechanism of the near-equatorial cyclones on El Ni?o is proposed. It is pointed out that the near-equalorial tropical cyclones developing equatorward of 10oN can intensify equatorial westerlies and produce Kelvin waves, which propagate to the South American Coasts in about 2-3 months, inducing SST to rise there. The near-equatoral cyclones play an essential role in El Ni?o. The beginning period of El Ni?o ranges from January to May. The number of near-equatorial cyclones developing in this period determines whether El Ni?o can be generated or not. The persistence period is from June to September. El Ni?o can not continue developing unless there are adequate near-equatorial cyclones. If there are not, the developed El Ni?o will be broken down. The period from October to December is called the developing period. During this period El Ni?o may approach its culmination only when adequate near-eqatorial cyclones have been developed east of 140oE, especially east of 160oE.
1988, 5(1): 97-106.
doi: 10.1007/BF02657350
Abstract:
Based on the 1979 FGGE Level III b data, calculation is made of the transfer of sensible and latent heat and momentum due to a quasi-40-day periodic oscillation (QDPO) on a cross-equatorial meridional ver-tical cross-section, and analysis is done of the characteristics of the transfer at all phases of QDPO, with the following results obtained:1) During the monsoons QDPO activation and break phases, a strong transfer of sensible heat to the SH is felt in the upper troposphere over the Asian monsoon region; the conversion of perturbation effective potential into its kinetic energy attains its maximum at 500-300 hPa (15oN), serving as the source of kinetic energy for the quasi-40-day periodic perturbation; an intense transfer of potential energy is found above 200 hPa from the monsoon area to the SH to maintain the QDPO at the tropical latitudes;2) During the QDPO activation-break (and reverse) transitional phase the conversion of perturbation effective potential into kinetic energy reaches its maximum in the middle and lower troposphere over the SH middle latitudes and an appreciable lower transfer of potential energy occurs towards the SH tropical latitudes and the NH.3) The upper-tropospheric powerful transfer of westerly momentum caused by QDPO is discovered from the SH tropical latitudes to the NH, and the resulting momentum divergence and convergence are unfavorable for the maintenance of the seasonal mean fields of the NH tropical easterly and SH subtropical westerly winds.Finally possible synoptical processes responsible for QDPO are discussed together with its relation to the interaction between the circulations of both the hemispheres. It is found that QDPO is both the result of and medium for the interaction.
Based on the 1979 FGGE Level III b data, calculation is made of the transfer of sensible and latent heat and momentum due to a quasi-40-day periodic oscillation (QDPO) on a cross-equatorial meridional ver-tical cross-section, and analysis is done of the characteristics of the transfer at all phases of QDPO, with the following results obtained:1) During the monsoons QDPO activation and break phases, a strong transfer of sensible heat to the SH is felt in the upper troposphere over the Asian monsoon region; the conversion of perturbation effective potential into its kinetic energy attains its maximum at 500-300 hPa (15oN), serving as the source of kinetic energy for the quasi-40-day periodic perturbation; an intense transfer of potential energy is found above 200 hPa from the monsoon area to the SH to maintain the QDPO at the tropical latitudes;2) During the QDPO activation-break (and reverse) transitional phase the conversion of perturbation effective potential into kinetic energy reaches its maximum in the middle and lower troposphere over the SH middle latitudes and an appreciable lower transfer of potential energy occurs towards the SH tropical latitudes and the NH.3) The upper-tropospheric powerful transfer of westerly momentum caused by QDPO is discovered from the SH tropical latitudes to the NH, and the resulting momentum divergence and convergence are unfavorable for the maintenance of the seasonal mean fields of the NH tropical easterly and SH subtropical westerly winds.Finally possible synoptical processes responsible for QDPO are discussed together with its relation to the interaction between the circulations of both the hemispheres. It is found that QDPO is both the result of and medium for the interaction.
1988, 5(1): 107-116.
doi: 10.1007/BF02657352
Abstract:
According to the time cross-section of SST in the equatorial eastern Pacific and the historical data on typhoon actions over the western Pacific (including the South China Sea), a composite analysis of the actions of typhoon over the western Pacific in El Nino year (SST in the equatorial eastern Pacific are continuously higher than normal) and in the inverse El Nino year (there are continuative negative anomalies of SST in the equatorial eastern Pacific) is carried out. The results show that the actions of typhoon are in close rela-tion with El Nino: The annual average number of typhoons over the western Pacific and South China Sea is less than normal in El Nino year and more in the inverse El Nino year; The annual average number of the landing typhoon on the continent of China bears the same relationship with El Nino; The anomalies of typhoon actions mainly occur during July-November and their starting are behind the anomaly of SST in the equatorial eastern Pacific.Based on the generation and development conditions of typhoons, the circulations and state of the tropical atmosphere and SST in the western Pacific are respectively analysed in El Nino year and in the inverse El Nino year. Then some possible influence mechanisms of El Nino on the actions of typhoons are discussed.
According to the time cross-section of SST in the equatorial eastern Pacific and the historical data on typhoon actions over the western Pacific (including the South China Sea), a composite analysis of the actions of typhoon over the western Pacific in El Nino year (SST in the equatorial eastern Pacific are continuously higher than normal) and in the inverse El Nino year (there are continuative negative anomalies of SST in the equatorial eastern Pacific) is carried out. The results show that the actions of typhoon are in close rela-tion with El Nino: The annual average number of typhoons over the western Pacific and South China Sea is less than normal in El Nino year and more in the inverse El Nino year; The annual average number of the landing typhoon on the continent of China bears the same relationship with El Nino; The anomalies of typhoon actions mainly occur during July-November and their starting are behind the anomaly of SST in the equatorial eastern Pacific.Based on the generation and development conditions of typhoons, the circulations and state of the tropical atmosphere and SST in the western Pacific are respectively analysed in El Nino year and in the inverse El Nino year. Then some possible influence mechanisms of El Nino on the actions of typhoons are discussed.
1988, 5(1): 117-126.
doi: 10.1007/BF02657351
Abstract:
On the basis of analysis of the microclimate characteristics over a reservior in the Hexi Region, a new concept for the effect of the lake cold island is advanced. The physical mechanism and practical significance of the effect have also been analyzed.
On the basis of analysis of the microclimate characteristics over a reservior in the Hexi Region, a new concept for the effect of the lake cold island is advanced. The physical mechanism and practical significance of the effect have also been analyzed.
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