Current Issue

• ANALYSIS OF THE CHARACTERISTICS OF THE LOW LEVEL JETS AND THE NIGHTTIME DRAINAGE WINDS IN HEIHE REGION
• Wang Qiang;Zhu Ping;Wang Bangzhong;Jiang Ruibin
• 1995 Vol. 14 (3): 257-263. 
• Abstract ( ) PDF (403KB) ( )
• According to the data obtained in HEIFE experiments, in this paper, we analyze the developing process of the nighttime drainage winds and the low level jets. Under normal condition, the characteristics of low level jets in Heihe region are quite similar to those of the low level jets caused purely by nocturnal oscillations. Due to the influence of the Qilianshan Mountain, the nighttime drainage wind occurs along the Gobi slope. When nighttime drainage wind exists before midnight, it has influence on the development of the low level jet. In this situation, the height of the low level jet often drops to the height just near the top of the surface layer. This characteristics may affect the structure of PBL and the exchange between land and atmosphere in Heihe region.

• ANALYSIS OF THE MEASURING ACCURACY FOR THE TETHERSONDE SYSTEMS IN HEIFE EXPERIMENTS
• Wang Qiang;Yang Zhiyong;Chen Shaoyou;Wang Bangzhong;Zhu Ping
• 1995 Vol. 14 (3): 264-269. 
• Abstract ( ) PDF (413KB) ( )
• During IOP-2 and IOP-3 in HEIFE experiments three tethersonde systems are used to observe the structure of PBL at Gobi, Oasis and Desert observation stations at the same time. This paper gives a detailed analysis for the measuring accuracy of the tethersonde systems and the method of the data handling procedure. The results show that the errors caused by the measuring method are larger than those caused by the inaccuracy of the system itself at normal conditions. The reliable results could be obtained using the correct method of operation and the data handling procedure. Little difference among the equipments at three observation stations is found in HEIFE experiments.

• MESOSCALE NUMERICAL SIMULATION OF DEVELOPING STRUCTURE AND EVOLUTION FOR VORTEX WITH HEAVY RAIN IN JIANGHUAI AREAS DRUING 4-7 JULY 1991
• Cheng Linsheng;Peng Xindong;Ma Yan
• 1995 Vol. 14 (3): 270-280. 
• Abstract ( ) PDF (474KB) ( )
• Mesoscale numerical simulation of heavy rain event due to the vortex with shear line is conducted to use verified and improved MM4 with high resolution PBL parameterization. The control simulative results revealed the Jiang-Huai heavy rain event has close relation to the genesis and development of the mesoscale vortex and its special dynamic and thermodynamic structure. The intensive ascending motion of coupling development with the column of cyclonic vorticity is a necessary vertically secondary circulation condition for maintaining persistent development of the vortex and accomplishing the exchange and transport of the fluxes at upper and lower levels. The coexisting structure of three forming an organic whole, which consists of the deep moist tongue and the intensive ascending motion as well as the column of cyclonic vorticity, is a typical structure of persistent developing vortex with convective cloud system and continuous heavy rain. The development and maintenance of the SW lower levels jet are not only an important dynamic condition of the genesis and persistent development of the vortex, but also a main medium of moistureneeded for heavy rain event. The formation and maintenance of the deep unstable stratification in the lower troposphere are an necessary thermal stratification condition for the vortex with persistent convective activity and convective precipitation. The north side of the central axis of the strong warm-moist band at 850 hPa and adjacent moist baroclinic zone are basically consistent with the precipitation band of the vortex with shear line. Within the PBL of the vortex, the sensible heat flux is the positive flux at day-time and the negative flux at night-time. But the latent heat flux is always positive flux both day-and nigth-time, and larger than the sensible heat flux of corresponding time. This fact implies that the upward transferring moisture and latent fluxes are more important than that of the sensible heat flux during the heavy rain.

• THE CONTRAST EXPERIMENTS BETWEEN THE σ-COORDINATE AND THE η-COORDINATE WITH STEP MOUNTAIN REPRESENTATION
• Teng Jiamo;He Guangbi;Xiao Yuhua
• 1995 Vol. 14 (3): 281-288. 
• Abstract ( ) PDF (430KB) ( )
• The contrast experiments between the σ-coordinate and the q-coordinate with step mountain representation are made based on the ETA Model in which the coordinate is changeable. The results show that many problems can be avoided by using η-coordinate with step mountain representation instead of σ-coordinate, and the predictions by η-coordinate conform basically to the observations, much better than that by σ-coordinate.

• THE PROPAGATION AND THE STABILITY OF THE WAVES IN GEOSTROPHIC BASIC FLOW OVER THE OROGRAPHY
• Zhong Zhong;Zhang Jinshan
• 1995 Vol. 14 (3): 289-295. 
• Abstract ( ) PDF (784KB) ( )
• In this paper, the propagation and stability of waves in the geostrophic basic flow over orography were studied with a linear model considering the effects of inclination of the mean surface height of the low layer fluid. The studies show that the most instability waves appear in the easterlies over northern slope of orography, only in the westerlies the waves can appear obviously to propagate eastward or westward. The gravity waves and the Rossby wave in the strong westerlies over the southern slope greater than 10‰ are all instability, and the features of propagation and stability of the Rossby wave have no great changes with wave number.

• INFLUENCE OF OROGRAPHY ON THE MONTHLY NUMERICAL PREDICTION
• Wu Jun;Zheng Qinglin
• 1995 Vol. 14 (3): 296-304. 
• Abstract ( ) PDF (478KB) ( )
• In this paper, a numerical research of the influence of orography on the monthly numerical prediction has been made by comparison of the different simulations of the northern hemispheric circulations in September 1992 with and without incorporation of the orography, utilizing the improved T42L10 monthly numerical prediction model. The results show that the model forecasts turn out to be better if the orographic effects are considered. The correlation coefficient between the predicted with orography and the observed northern hemisphere 500 hPa geopotential height anomaly can arrive at 0.73 which is 0.08 higher than that without orography when with the orography, the forcasted averaged root mean square decreases by 10 gpm. The orographic effect appears more obvious in East Asia. The predicted 500 hPa circulations with orography is in good agreement with the observed. When the orography is removed from the model, the forecasts deviate a lot from the observed. The polar vortex centre splits and the fluctuations in the mid-latitude weaken apparently and the subtropical highs weaken and locatesd far south. We also find a cyclogenesis on the lee side of the Tibetan Plateau and an anticyclogenesis over the Taiwan in a large area due to the orographic effects of the Tibetan Plateau.

• MESOSCALE NUMERICAL SIMULATION OF A MIDTROPOSPHERIC VORTEX WITH HEAVY RAINFALL OVER MIDDLE REACH OF YELLOW RIVER
• Li Xiaoli;Hui Xiaoying;Cheng Linsheng
• 1995 Vol. 14 (3): 305-313. 
• Abstract ( ) PDF (398KB) ( )
• In this paper, we have investigated the mesoscale system, which caused the strong heavy rainfall event in the middle reach of the Yellow River during the late stage of July 29-August 21982, through mesoscale numerical simulations by using the improved MM4. The results show that the mesoscale vortex was not the result of transforming of the landing typhoon but the generating and developing mesoscale vortex under the influence of the peripheral southeast jet of the landing typhoon. It was a deep asymmetry midtropospheric vortex with clear baroclinic structure and strong warm advection at low level. The main mechanism caused the development of the mesoscale vortex was adiabatic moist process. Latent heat release was possessed of the dominant role in the diabatic moist force. The positive feedback between latent heat release and vertical motion was the essential energy source for the development of the vortex and the persistence of the heavy rainfall. The surface energy fluxes are not the decisive factor affecting development of mesoscale system. The thermal structure of model atmosphere was affected without the surface heat fluxes, in turn the intensity of development of vortex and precipitation were also affected however, the development of mesoscale system was still maintained.

• THE NUMERICAL SIMULATION OF CLIMATE MEAN STATES FOR JANUARY AND JULY
• Zhou Yajun;Zhu Shu
• 1995 Vol. 14 (3): 314-324. 
• Abstract ( ) PDF (576KB) ( )
• In this paper, We simulated January and July global climate utilizing the modified T21L7 model. The sea-surface temperature, the sea-ice distribution and solar zenith angle are constant in each simulation. Land surface temperature are solved by land surface energy equilibrium equation. Vertical diffusion and land water cycle are also considered. The latitude-height distribution of the zonal wind is successfully simulated. The model can show westerly jets between in the troposphere and stratosphere in winter hemisphere, and the location and strength of jets centers are basically consistent with real. The latitude-height distribution of the temperature is similar with real, only the horizontal temperature gradients below 500 hPa in summer hemisphere polar area are not evident. The sea-level pressure and surface air temperature shows, the model can clearly discriminate the different climate systems caused by large scale ocean and continent.

• NUMERICAL EXPERIMENTS OF THE EFFECTS OF LAND SURFACE CHARACTERS ON REGIONAL ENERGY BALANCE
• Zhang Yaocun;Qian Yongfu
• 1995 Vol. 14 (3): 325-333. 
• Abstract ( ) PDF (616KB) ( )
• The different land surface characters would lead to large differences in exchanges of surface energy, as a result exert substantial influence on regional climate. This paper puts emphasis on the regulation mechanisms of land surface characters by the surface energy fluxes on regional climate. By utilizing a 3-D regional climate model, the surface energy budget is modeled in North China. The results show that the energy fluxes from different underlying surfaces transfered into atmosphere are significantly different. Therefore it is possible to improve the climate condition and ecological environment in regional scale by modifying the land surface characters.

• MEASUREMENTS AND ANALYSES OF SO ₂ AND O ₃ NEAR THE GROUND SURFACE IN "THE FIRST ECO-AGRICULTURE VILLAGE"-XIAOZHANGZHUANG AND HEFEI AREAS
• Yao Keya;Chen Yuejuan;Zhang Hong;Huang Meiyuan;Shen Zhilai;Shi Liqing
• 1995 Vol. 14 (3): 334-341. 
• Abstract ( ) PDF (660KB) ( )
• The concentrations of SO ₂ and O ₃ near the ground surface were measured in "Global 500"——Xiaozhangzhuang Eco-agriculture village and Hefei areas from 14 to 26 October and from 28 October to 6 November 1993, respectively. Some average characteristics and variation with time are presented in this paper. The results show that: the atmosphere over Xiaozhangzhuang and Hefei areas is clear for SO ₂ and O ₃ during the measurements the concentration of NO _x is higher in both areas in comparison with that of SO ₂ the influence of wind direction on the concentrations of SO ₂ in Xiaozhangzhuang area is not apparent the scavenging of SO ₂ and O ₃ by rain and fog is important in both areas.

• EOF ANALYSIS OF SUMMER PRECIPITATION IN NORTHWEST CHINA AND THE RELATION BETWEEN IT AND 500 hPa HEIGHT FIELD
• Wang Baoling;Dong Anxiang;Wang Ling
• 1995 Vol. 14 (3): 342-347. 
• Abstract ( ) PDF (628KB) ( )
• Based on the precipitation data of 140 stations in Northwest China from 1960 to 1990, the characteristics of monthly precipitation from July to September in this region are analysed by use of EOF method. The relation between the precipitation and 500 hPa monthly mean height is also discussed. The results show that: (1) A strong precipitation center of monthly precipitation from July to September for first eigenvector appears on the northeast side of Qinghai-Xizang Plateau. (2) Simultaneous relationships between first eigenvector of precipitation in July and August and 500 hPa height field in 20°-40°N,100°-130°E and 55°-70°N, 50°-85°E are better.

• AIR TEMPERATURE VARIATIONS IN MONGOLIA AND NORTHERN HEMISPHERE FOR RECENT 50 YEARS
• Ma Xiaobo
• 1995 Vol. 14 (3): 348-358. 
• Abstract ( ) PDF (510KB) ( )
• In this paper, monthly mean air temperature variations(1940-1991) at 25 stations in Mongolia are studied and are compared with Northern Hemisphere air temperature(NHT) from 1940 to 1987. It is found that annual mean air temperature(52 years) in Mongolia increases at the rate of 0.0190 ℃/year. Mean temperatures in winter, spring and autumn were on the increase, the maximum is in winter(0.0540℃/year), mean temperature in summer was on the decrease (-0.0110 ℃/year). The linear correlation coefficient of annual mean air temperature between Mongolia and NH is 0.34, and 0.41 in winter. NHT increases at the rate of 0.0003 ℃/year, winter and spring were on the increase, the maximum is in winter (0.0033 ℃/year): summer and autumn were on the decrease, the maximum is in autumn(-0.0032℃/year). There are three kinds of variation in Mongolia: warm, west warm and east cool, north warm and south cool. 1950's is the cool period in Mongolia, others are warm periods. But in NH, 1960's-1970's cool, 1940's and 1980's warm. Climate warmed mainly shows in winter. Warmer winter and cooler summer are one of the climate characteristics for recent 50 years not only in China, but also in Mongolia and Northern Hemisphere.

• THE WAVELET ANALYSIS OF AIR TEMPERATURE DATA IN SHANGHAI
• Bian Weilin;Lin Zhenshan;Deng Ziwang
• 1995 Vol. 14 (3): 359-364. 
• Abstract ( ) PDF (356KB) ( )
• It is an important problem how to analysis the structure and character of climate system in different levels. In this paper, wavelet analysis and diagnosis of annual mean air temperature in Shanghai from 1881 to 1980 using Mexican cap wavelet and solitary wave wavelet are made. The results show that either wavelet reveals obviously the singular point, singular valure, high-resolution structure in different levels. The catastrophes in different levels revealed by Mexican cap wavelet are zero-anomaly cusps, while those by solitary wave are nonequideparture cusps. The merits of wavelet analysis as mentioned above are not possessed of classical statistical methods (for example, moving average) and Fourier transforn.

• THE QUASI-GEOSTROPHIC FRONTOGENESIS FUNCTION ANALYSES FOR A STATIONARY COLD FRONT IN THE SOUTHWEST OF CHINA
• Yang Yang;Yu Yiming
• 1995 Vol. 14 (3): 365-372. 
• Abstract ( ) PDF (662KB) ( )
• A quasi-stationary cold front, which happened in the Southwest of China from 23 to 26 March 1990, was analysed in this paper by using the quasi-geostrophic frontogenesis function and Q-vector divergence, and routine synoptic sounding data. When the cold air on the north side of the front is strengthened, the frontogenesis of the stationary front is occurred, and the front moves southward. At the low level (850 hPa) along the front, the area of the quasi-geostrophic motion upward is zone distribution from northeast to southwest. The divergence field of the Q-vector can well reflect the variation of the precipitation along the front.

• THE CORRELATION BETWEEN DROUGHT FLOOD AND EARTHQUAKES IN YUNNAN PROVINCE DURING RECENT 43 YEARS
• Guo Weidong;Tang Maocang
• 1995 Vol. 14 (3): 373-378. 
• Abstract ( ) PDF (364KB) ( )
• Based on the data of precipitation and earthquakes from 1951 to 1993, the relationship between precipitation in flood season in Yunnan Province and earthquake activity in different geological units was analysed. It was concluded that most of the inner-plate earthquakes are accompanied by abundant precipitation, but the earthquakes near the edge of Plate are accompanied by less rain. So, the former can be called as "wet earthquake" and the edge-plate earthquake can be called as "dry earthquake". Finally, the inner mechanism between earthquakes and drought/flood was disscussed briefly.

• WHERE IS THE CENTER LOCATION OF ASIAN HIGH PRESSURE IN WINTER?
• Tang Maocang;Gao Xiaoqing;Zhang Jian
• 1995 Vol. 14 (3): 379-384. 
• Abstract ( ) PDF (468KB) ( )
• After a comprehensive analysis on pressure reduction methods being used at present, some shortcomings of the methods had been pointed out when these methods were used in high altitude area. And the writer proposed a "wind-conserved projection method" to analysize sea-level air pressure field is more accurate. This method was used to analysize Asian high in winter. The result shows that Mongolian Plateau, Tibetan Plateau and Loess Plateau are under the control of high pressure with three centers in winter, the highest center is on the south part of Tibetan Plateau, and the other two centers locate on northwest part of Mongolia and Qilian mountain area, respectively. Based on the result above, the writer proposed that it is more reasonable to call "Mongolian high" as "Asian high" or "Plateau high".