Current Issue

• NUMERICAL STUDY ON THE LEEWARD SIDE OROGRAPHIC EFFECTS OF QINGHAI-XIZANG PLATEAU ON A SOUTHWEST VORTEX PROCESS
• Zheng Qinglin;Wang Bizheng;Song Qingli
• 1997 Vol. 16 (3): 225-234. 
• Abstract ( ) PDF (413KB) ( )
• Based on a typhoon numerical model with horizontally threefold structure, a numerical model, in which the Qinghai-Xizang Plateau and its leeward side different scale orographic effects can been considered, is developed to study on a southwest vortex process during the period from 20:00 BST 12 to 20:00 BST 14 July, 1981. Comparison of the three numerical experiment results——with real orography, one third orography and without orography——shows:the features of the southwest vortex such as its movement, development, shape and domain, as well as the distribution and centres of its precipitation can be well simulated in the experiment with real orography.however, in other two experiments, it is failed to simulated out these features.Furthermore, the axis of the jet stream takes northward direction in the experiment with real orography, but it takes eastward either in the experiment with one third orography or in that without orography.Instead of appearing the shear-convergence flow pattern in the experiment with real orography, the wind field appears a deep trough pattern in that case without orography, so the massive northwest colder air mass moved southward.

• THE VALIDATION AND ANALYSES OF SYSTEMATIC ERRORS OF MODELING SUMMER CLIMATE WITH p-σ INCORPORATED COORDINATE GLOBAL MODEL
• Zhang Yaocun;Qian Yongfu;Wang Shiyu
• 1997 Vol. 16 (3): 235-242. 
• Abstract ( ) PDF (318KB) ( )
• The model evaluation and systematic errors are analyzed by using a p-σ incorporated coordinate global model in this paper, which is developed from zonal domain model. The comparisons are made between modeling monthly mean results and GFDL analyzed data in summer. The results show that this model can simulate the summer monthly mean climate conditions and can improve the simulated results to some extent compared with that of zonal domain model. The statistical tests indicate that modeling results over land are better than that over ocean. These results can provide climatic bases for improving and utlizing the model.

• SENSITIVITY EXPERIMENTS OF SOUTHWEST VORTEX RAIN TO VEGETATIVE COVER AND SOIL MOISTURE
• Wang Geli;Chen Wanlong;Zhou Suoquan
• 1997 Vol. 16 (3): 243-249. 
• Abstract ( ) PDF (262KB) ( )
• A limited area mesh model developed by Yan Hong et al including Deardorff's scheme of vegetative parameterization is used to investigate the sensitivity of southwest vortex rain(SWVR) to vegetative cover and soil moisture(VCSM) in the Qinghai-Xizang Plateau and its neighbouring areas(QXPA). The stress is on the sensitivities of SWVR, ascending motion, sensible heat and water vapour fluxes near the underlying surface to VCSM in QXPA during the period of both "82.7" and "81.7" southwest votexes heavy rain processes. It is shown that SWVR is very sensitivity to VCSM. Ascending motion in the lower atmospheric layer and surface heat flux are also sensitive to VCSM in QXPA.

• EFFECTS OF SURFACE TEMPERATURE AND ITS TAKING VALUES ON ATMOSPHERIC LONGWAVE RADIATION COOLING OVER THE QINGHAI- XIZANG PLATEAU
• Jiang Hao;Wang Keli;Wu Guoxiong
• 1997 Vol. 16 (3): 250-257. 
• Abstract ( ) PDF (277KB) ( )
• In order to achieve the goal of using the atmospheric radiative transfer model over the Qinghai-Xizang Plateau region, taking values of surface temperature in the model and effects of that on the calculation results of atmospheric longwave radiation cooling are analysed with the Liou-Ou one dimension radiative transfer model based on the data set of surface, radiosonde and satellite observation over the Qinghai-Xizang Plateau during period from August 1982 to July 1983. The effects of both underlying surface temperature( T _g) and near-surface air temperature( T _a) are distinguished in the radiative transfer model and the effectiveness is verified by using satellite observation data. The diurnal cycle and seasonal cycle of T _g and T _a are analysed and a simple method to calculate the T _g from the T _a is presented.

• THE SIMILARITY OF VERTICAL WIND VELOCITY VARIANCE σ _W/U ^* IN THE STABLE ATMOSPHERE SURFACE LAYER
• He Jianlin;Wang Jiemin
• 1997 Vol. 16 (3): 258-264. 
• Abstract ( ) PDF (240KB) ( )
• Based on the similarity theory and assuming that the variance of vertical velocity σ _W is a feeble function of height Z, some relations are derived for σ _W/U ^* as function of Z/L in the stable atmospheric surface layer, which can explain the facts of σ _W/U ^* being not constant in stable stratification.

• CLIMATIC CHARACTERISTICS OF RADAR ECHO OF CLOUD AND PRECIPITATION IN PINGLIANG REGION
• Liu Liping;Qian Yongfu;Wang Zhijun
• 1997 Vol. 16 (3): 265-273. 
• Abstract ( ) PDF (334KB) ( )
• Based on the radar data measured by dual linear polarization radar in Pingliang Radar Station, Lanzhou Institute of Plateau Atmospheric Physics, Chinese Academy of Sciences, we analysed the Z _H and Z _DR figures for thunderstorm and hail storm, studied the daily and monthly variation and spatial distribution of precipitation, thunderstorm and hail storm by EOF method, researched the relationship between these parameters and orography and effects of Liupanshan Mountain on the precipitation and cloud. This work has laid the foundation of research of cloud and precipitation by dual linear polarization radar and model simulation in the region.

• CHARACTERISTICS OF WATER VAPOUR TRANSFER IN UPPER TROPOSPHERE OVER QINGHAI-XIZANG PLATEAU IN SUMMER
• Zheng Xinjiang;Xu Jianmin;Li Xianzhou
• 1997 Vol. 16 (3): 274-281. 
• Abstract ( ) PDF (300KB) ( )
• With GMS-5 water vapour images and meteorological data, water vapour transfer in upper troposphere over Qinghai-Xizang Plateau in June and July of 1995 is analysed. The results show that there are three types of circulation pattern for water vapour transfering toward Qinghai-Xizang Plateau in upper troposphere. They are west side ridge pattern, east side ridge pattern and out of phase pattern. The relationship between them and precipitation in the Qinghai-Xizang Plateau is also analysed.

• SPATIAL AND TEMPORAL CHARACTERISTICS AND VARIATION TREND OF AIR TEMPERATURE IN NORTHWEST CHINA AND MONGOLIA IN LAST 40 YEARS
• Ma Xiaobo;Gao Youxi
• 1997 Vol. 16 (3): 282-291. 
• Abstract ( ) PDF (371KB) ( )
• In this paper, monthly mean air temperature data of 59 stations (EOF analysis is 25 stations) in Northwest China and Mongolia from 1951 to 1990 are analysed by use of EOF method to find out its spatial and temporal characteristics. There are three kinds of spatial distributions:(1) seasonal variation in all areas is identical, (2) north-south distribution, (3) west-east distribution. Main variation periods are 2~4, 5~8 and 10~13 years, shorter periods dominate in summer, and longer periods are in winter and whole year. Spatial distribution of air temperature trends are nonuniform. Annual and winter mean air temperature rises, maximum is 0.56℃/10a, falls in summer, maximum is -0.60℃/10a over the middle and east parts of Southern Xingjiang, rises or falls in spring and autumn, but variation amplitude is small. Variation trends which warmes in whole year and winter, cooles in summer in Northwest China are maximum in the China, it is also larger than that in Northern Hemisphere and its variation trend is the most significant.

• RESEARCH ON THE CHARACTERISTICS AND REGIONALIZATION OF SUMMER- DROUGHT IN GUIZHOU
• Liu Xuemei;Song Guoqiang;Cheng Pingshun;Gu Xiaoping;Wu Junming
• 1997 Vol. 16 (3): 292-299. 
• Abstract ( ) PDF (278KB) ( )
• Drought is one of the main meteorological disasters in Guizhou province. Based on the systematic studying about the types, the happening frequency, the duration, the regional distribution, the easy happening stage and the vertical change characteristics of summer-drought in Guizhou by utilizing the summer-drought intensity index, the amended Palmer-index and rainfall etc., the main characteristics of summer-drought are summarized in this paper. Lastly, the regionalization of summer-drought was presented.

• FURTHER STUDY ON THE SEMI-CIRCLE THEOREM FOR BAROTROPIC QUASI-GEOSTROPHIC MOTION ON SPHERICAL SURFACE
• Lin Naishi
• 1997 Vol. 16 (3): 300-305. 
• Abstract ( ) PDF (207KB) ( )
• In this paper, the Howard semi-circle theorem of unstable wave in a barotropic quasi-geostrophic motion on spherical surface has been further studied. It is shown that the theorem can be developed into circle arc theorem under special basic flow distribution, and a more accurate growth rate estimation formula is obtained.

• THE NUMERICAL EXPERIMENTS OF INFLUENCE OF SHEAR LINE OVER QINHAI-XIZANG PLATEAU ON A SHARP HEAVY RAIN IN WEST SICHUAN BASIN
• Yu Shuhua;He Guangbi;Teng Jiamo
• 1997 Vol. 16 (3): 306-311. 
• Abstract ( ) PDF (229KB) ( )
• By using the ETA model, a numerical simulations was done for a sharp heavy rain in the west Sichuan basin on 24 August, 1995 and the numerical experiments without shear line over Qinghai -Xizang Plateau and Xichang small high were also done for the heavy rain. The results of numerical experiments are as follws: (1) The activity of the shear line over the Plateau can strengthen the heavy rain in west Sichuan Basin, but it will be weaken when there is the Xichang small high. (2) The main mechanism of strengthening heavy rain caused by the activity of the shear line over the Plateau is that strengthening of the convergence of vapour flux and flow field, positive vorticity, ascending motion in lower troposphere and convergence of vapour flux and flow field in middle troposphere over the heavy rain area. (3) The vapour and dynamic conditions in lower troposphere are very important for the development of heavy rain.

• THE CLIMATOLOGICAL CHARACTERISTICS OF TEMPERATURE VARIATION MORE THAN FORTY YEARS IN LHASA
• Zhang Shunli;Huang Xiaoqing
• 1997 Vol. 16 (3): 312-319. 
• Abstract ( ) PDF (260KB) ( )
• The 44 years variational characteristics of Lhasa temperature are analysed by using the monthly mean temperature data from 1952 to 1995. It shows that in the recent 44 years, there are warm-cold-warm-cold-warm evolution processes for Lhasa temperature. A long cold period is in the 1960's and a warm period is from 1980's ~1990's. Temperature of Lhasa has a good persistence in spring and summer. It's persistence is easy change in August~September and December~January. The 3-year, 11-year and 22-year periods are significant. Lhasa temperature is mainly affected by middle latitude circulation and sunspot.

• THE CHARACTERISTICS OF URBAN CLIMATE OF KUNMING IN LOW LATITUDE AND PLATEAU AREA
• Zhang Yiping;Peng Guifen;Li Yulin
• 1997 Vol. 16 (3): 320-325. 
• Abstract ( ) PDF (264KB) ( )
• The microclimatic observation was carried out over ground in the city and suburbs of Kunming City of China. The main results obtained in this paper are summarized as follows: (1) The wind speed in the suburbs are larger than in the city, and its differences are notable at daytime. (2) In the city, the air temperatures are higher than suburbs. Its differences are larger at nighttime. Because the influences by different factors, in the day when the urban heat island is appeared, the urban cool island may appear too. This shown complicated characteristic of thermodynamics in the city. (3) In the city, the humidity is littler than in the suburbs, but its differences are different for different time and sky and surface conditions. (4) Because the characteristic and the variation of meteorological element are different in the city and the suburbs, therefore the characterisitics of the urban climate are different. The urban climate complexities are shown up.

• LONG-TERM TREND OF SUMMER PRECIPITATION IN SHAANXI PROVINCE
• Pang Wenbao;Yang Wenfeng;Li Zhaoyuan
• 1997 Vol. 16 (3): 326-330. 
• Abstract ( ) PDF (184KB) ( )
• Based on summer precipitation data at stations of Yulin, Xi'an and Hanzhong, the trend of summer precipitation is predicted with the method of grey topology in this paper. Aanlyses show that there are obvious droughts at beginning and middle of the summer in Guanzhong area. It is found that the mean summer precipitation in Xi'an(semi-moisture area) is less than in Yulin(semi-drought area). Trends of summer precipitation decrease in Guanzhong and south part since 1951, while decreasing trend didn't change obviously in north part. Beside, the features are apparent that more rain or less rain happened successively in Guanzhong and south part, and high oscillation happened frequently in north part.

• A VERIFICATION OF WEATHER SIGNIFICANCE OF PBL WIND FIELD EVOLUTION AT CHENGDU
• Li Yueqing;Peng Hu;Zhang Bo
• 1997 Vol. 16 (3): 331-336. 
• Abstract ( ) PDF (222KB) ( )
• By using the enhanced observation radiosonde data during the period from April 25 to May 4, 1993 in Sichuan Basin(SB), the relationship between wind field evolution in planetary boundary layer(PBL) at Chengdu and the widespread high wind, hail and heavy rain processes in SB on April 30~May 1, 1993 are analyzed. It is further confirmed that Chengdu station near the Qinghai-Xizang Plateau is a information point for the weather variation in SB. It shows the important observation fact that under the effect of specific topography of the Plateau-Basin, the wind field in PBL over SB is regular variation. Its holographic image is that when it is blowing northeast wind, the PBL over SB maintains easterly cyclonic flow field with convergence, positive vorticity and ascending motion, and it will be strong convection weather such as heavy rain. When blowing non-northeast wind, especially southwest wind, the PBL over SB maintains southerly anticyclonic flow field with divergence, negative vorticity and descending motion, and it will be rainless weather.