Current Issue

• Comparison of Cloud Observed by Ground Based Doppler Radarwith TRMM PR in Qinghai-Xizang Plateau, China
• FENG Jin-ming;LIU Li-ping;WANG Zhi-jun;CHU Rong-zhong
• 2001 Vol. 20 (4): 345-353. 
• Abstract ( ) PDF (412KB) ( )
• By analyzing Doppler radar data and TRMM PR data of Qinghai-Xizang Plateau in 1998, we compare the difference and similarity of cloud observation by ground based Doppler radar and TRMM PR in many different aspects, such as echo structure, echo intensity and precision of rainfall measuring. Some causes are given to interpret these deviations.Generally, the echo structure observed by TRMM PR is very similar with that observed by ground based Doppler radar, but the echo intensity observed by TRMM PR is greater than that observed by ground based Doppler radar. Echo intensity observed by TRMM PR has systematic deviation of 23 dB with that observed by ground based Doppler radar.Because of the different observational mode and transmittal wavelength of TRMM PR and ground based Doppler radar, the scatter property for those cloud particle of the different phase and spatial direction is also different. Therefore, the deviations of cloud observation is caused.

• Numerical Simulation of Local Climatic Effect of Heterogeneous Underlying Surface
• GAO Yan-hong;Lü Shi-hua
• 2001 Vol. 20 (4): 354-361. 
• Abstract ( ) PDF (414KB) ( )
• The local climatic effect of heterogeneous underlying surface was simulated through the MM5V3 meso-scale model. The simulations reappear the some typical characteristics of the oasis-desert interaction such as mountain valley wind, "oasis effect" in the summer, and "inverse humidity" on desert and oasis-desert vertical circulation which are caused by the thermodynamic distinctions of different underlying surfaces and reveal the physical mechanicsm of the interaction between the land surface and wind field, temperature and humidity in atmospheric boundary layer over heterogeneous land surface. Namely, the results of the numerical simulations in the paper have well tested the ones in field experiments.

• A Preliminary Study on Trends and Interannual Variaration of Precipitation in Central and Western Portions of Northwest Region of China
• XIE Jin-nan;ZHOU Jia-ling
• 2001 Vol. 20 (4): 362-367. 
• Abstract ( ) PDF (245KB) ( )
• The trends and interannual variation of precipitation in Northwest China are studied by using the trend coefficient and moving t-test technique based on the(1951-1998) observation data at 22 stations located in the Northwest Region of China. The results show that there exists descending trends of precipitation on the northeast side of Qinghai-Xizang Plateau during recent half a century, especialy during recent 10 years.

• Climatic Condition and Chinese History(Ⅰ):SCL and Chinese Climate
• TANG Mao-cang;LIU Yan-xiang;GUO Wei-dong
• 2001 Vol. 20 (4): 368-373. 
• Abstract ( ) PDF (260KB) ( )
• In the past over 2500 years, it is divided into Good Climatic Condition(GCC) and Bad Climatic Condition(BCC) with sunspot cycle length(SCL) data. The result shows that drought in BCC is obviously more than it in GGT. GGT is corresponding warm(cold) on climate. At last, the paper gave a chain reaction of climate change influenced by solar activity.

• Numerical Simulation Experiment for Interactions of Different Scale and Arranged Vortexes
• LI Chun-hu;HUANG Fu-jun;LUO Zhe-xian
• 2001 Vol. 20 (4): 374-380. 
• Abstract ( ) PDF (281KB) ( )
• The tests are 8 groups time integrations upto total 48 hours for studying behavior of multi-eddy interaction using barotropic primitive equation model. The results show that the 5 initial linear arraying-keeping eddy with different scales, intensity and arraying directions reveal 3 type terminative space pattern by multi-eddy interaction, namely, the original linear arraying-like patterns, the Northwest-Southeast linear arraying eddy ones and the polygon arraying eddy ones.

• Heat Sources over Qinghai-Xizang Plateau and Surrounding Areasand Their Relationships to Onset of SCS Summer Monsoon in 1998
• JIAN Mao-qiu;LUO Hui-bang
• 2001 Vol. 20 (4): 381-387. 
• Abstract ( ) PDF (374KB) ( )
• Using the twice daily routine rawinsonde data in the domain 90°~130°E, -2.5°~42.5°N from 1 May to 31 August 1998, the heat source and moisture sink are computed, and the evolution of the temperature in themiddle-to-upper level of the troposphere over the SCS monsoon area and its thermal mechanisms around the onset of SCS summer monsoon are analyzed. The results show that the onset of SCS summer monsoon is closely linked to the inversion of meridional temperature gradent in the middle\|to-upper level of the troposphere over SCS monsoon area. The inversion of meridional temperature gradient occurrs first over the region to the east of Bay of Bengal in the fifth pentad of May, and then over the India subcontinent and its western part area half month later. The abrupt warming in the middle-to-upper level of the troposphere over northern part of Indo-China is caused by both the sensible heat flux and the latent heating before the monsoon onset. However, the warming over South China and the northern part of South China Sea results mainly from the warm advection. The marked warming over the eastern part of Qinghai-Xizang Plateau during the period of May and June, which is primarily due to the diabatic heating in the atmosphere, is very important to the northward extending of East Asian monsoon and its maintenance. The sensible heat flux is the main contributor to heat source over eastern Plateau from May to June. During the period of July and August, the latent heat plays a samerole as the sensible heat flux for the tropospheric heating over eastern part of Qinghai-Xizang Plateau.

• The Influence of Sudden Change of Ural Blocking High on Heavy Rainstorm Processes in the Middle-Lower Reaches of Yangtze River in JuneJuly of 1998 and 1999
• CHEN Ju-ying;WANG Yu-hong;WANG Wen
• 2001 Vol. 20 (4): 388-394. 
• Abstract ( ) PDF (344KB) ( )
• The heavy rainstorm processes occurred in the middle-lower reaches of Yangtze River in 1998 and 1999. To understand the large-scale circulation background of the heavy rainstorm system in the middle-lower reaches of Yangtze River in 1998 and 1999, and explore the precursor factors of producing heavy rainstorm, we analyzed and studied that the day-to-day changes of Ural Blocking High(UBH) and show they have a great influence on the heavy rainstorm processes in the middle-lower reaches of Yangtze River. The daily 12:00 UTC UBH intensity indexes(UBHII) at 500 hPa over the area 45°~65°N, 30°~100°E in June~July 1998 and 1999 are calculated by using the observed data. The UBHII before and after the heavy rain in the middle-lower reaches of Yangtze River in recent two years and the daily circulation change feature are mainly analyzed. We find that the persistent heavy rainstorm processes in the middle-lower reacher of Yangtze River in 1998 and 1999 occurred usually in the descending periods of the daily UBHII. When the UBH sets up and intensifies, Asian-European circulation is stable, there is a little rainfall in the middle-lower reaches of Yangtze River. The result shows that the abrupt turnning of UBH changing from devoloping period into weaken period is one of the precursor factors producing heavy rain in the middle-lower reaches of Yangtze River. The day-to-day evolution processes of height field at 500 hPa and its mechanism are also discussed in this paper.

• Analyese on Some Features of Ground Flashes in Chinese Inland Plateau
• QIE Xiu-shu;YU Ye;WANG Huai-bin;ZHANG Cui-hua
• 2001 Vol. 20 (4): 395-401. 
• Abstract ( ) PDF (285KB) ( )
• Characteristics of both positive and negative ground flashes in Chinese inland plateau were measured and analyzed by recording the electric fields generated by the whole flash in microsecond resolution. The ratio of positive ground flash to total flash had a tendency of increasing with total ground flash number. It is 16% in average which fallen between winter thunderstorm of Japan and summer thunderstorm of United States. For negative ground flashes the geometric and arithmetic mean of the interstroke intervals were 64.3 ms and 46.6 ms. It was found that 54% of the negative multiple-stroke ground flashes had at least one subsequent stroke with a peak electric field larger than that of the first return stroke. Furthermore, about 20% of the subsequent stroke had peak electric field amplitudes larger than those of the first return strokes. The geometric mean of the ratio of the subsequent stoke peak field to the first return stroke peak field was 0.46. The mean number of stokes per flash was 3.76 and 39.8% of the flash were single-stroke flashes. For the positive flashes, only 13.0% of the flash were multi-stroke flashes, and the interstroke interval is 91.7 ms.

• Climatic Character Analyese of Snow Disasters in East Qinghai-Xizang Plateau Livestock Farm
• DONG Wen-jie;WEI Zhi-gang;FAN Li-jun
• 2001 Vol. 20 (4): 402-406. 
• Abstract ( ) PDF (211KB) ( )
• The data set of snow disasters from 1967 to 1996 in 25 stations on the Qinghai-Xizang Plateau livestock farm is analyzed. The results show that the period of snow disasters last 8 months from last October to May. March and April are two high frequency months of snow disasters. The snow disaster on the Qinghai-Xizang Plateau livestock farm is mainly to the south and east of the Bayankalashan mountains and has an increasing trend in recent 30 years. The winter and spring snow disasters were little from 1968 to 1976, had three high periods and two low periods from 1977 to 1992 and have been in a new high period since 1993. There is an obvious 5~6 year cycle and a weak 2~3 year cycle of the snow disaster. We define snow disasters from January to May as the latter winter snow disaster and ones from October to December as the former winter snow disaster. We found that there was high former winter snow disaster in 1970s and was high latter winter snow disaster in the period from the end of 1980s to 1990s. The inter-annual anomaly of the subtropical high in the West Pacific Ocean is a main factor that the snow disaster varies.

• The Forming and Forecasting of Autumn Snow-Disaster Weather inEasten Pastoral-Area of Qinghai-Xizang Plateau
• MA Lin;MA Yuan-cang;WANG Wen-ying;LI Xi-fu;ZHANG Qing-mei;ZHAO Chun-ning
• 2001 Vol. 20 (4): 407-414. 
• Abstract ( ) PDF (352KB) ( )
• The forming and forecasting analysis of autumn snow disaster weather in the easten pastoral area of Qinghai-Xizang Plateau(hereafter EPAQXP) during the period of 1967-1996 has been made. The Eurasian weather situations on large scale of forming sonw disaster weather in the EPAQXP are sumed up and classified. The Arctic Ocean trough and subtropical high ridge are pointed out to be dominant and steady factors. The three kinds of weather patterns are sumed up in the forming snow disaster weather, andthe ageostrophic wind near southwest lower-level jet is analyzed in the plateau, and they are showed that the lower-level jet is major snow-produced system and the strong convergence is one of reasons causing heavy snow. The effect of the ageostrophic wind on snowing and creating minimum temperature are discussed. Eventually, some of the indexes for snowing weather forecast are given.

• South China Sea AXBT Data and Four Dimension Analysis of Assimilation by Ocean Model in May 1995
• CHEN Yu-chun;Lü Shi-hua;Peter C Chu
• 2001 Vol. 20 (4): 415-420. 
• Abstract ( ) PDF (634KB) ( )
• In the study we used U.S. Princeton University Ocean Model with observation data assimilated in the South China Sea in May 1995. The method of assimilation used the optimum interpolation scheme to approach from analysis to observation. When Princeton Ocean Model have run to the fourth year by restore surface boundary, the wind stress and net heat fluxes of COADS were used for forcing ocean. And when the model have run to the fifth year, the AXBT and MISST data were inputted for assimitating to integrate 30 d from May 1995. Results showed that the simulation temperature and current field ware improved with assimilation, there are warm-core and cool-core eddies in South China Sea on May 1995.

• Feature Analysis of Summer Water Resource in North China and Its Response to Climate Change(Ⅰ):Summer Water Resource Feature Analysis Near40 Years in North China
• FAN Guang-zhou;Lü Shi-hua;CHENG Guo-dong
• 2001 Vol. 20 (4): 421-428. 
• Abstract ( ) PDF (329KB) ( )
• Recently, the shortage of the fresh water resource is becoming the serious problem that is concerned by the people all over the world. North China is the center of the politics, economy and culture of China and its water resource is severe insufficient. The improvement of the people living standard and the development of the economy are puzzled by the lack of the water. By using the 40 year reanalysis data of NCEP/NCAR we find that there are some surpluses of the annual mean water resource during the near 40 years. But its distribution is not very even during one year. The months that the water resource is superfluous during one year are only June, July, August and September, and the other months are all deficit. The result of EOF analysis for the North China water resource in summer, in which season the water resource is the most enough, shows that the main space distribution characteristics of the water resource variables, are accordant all over the area. The main time variation directions of them are continually decreasing from 60s to 80s and are increasing a little after the middle of 80s. The result of MK catastrophe test for the variables shows that every variable sudden changed at the middle of 60s, but the time of the sudden change is not the same.

• A "Diqi" Map Method of Qualitative Prediction in Annual Precipitation with Geothermal Anomaly in China
• CHEN Wen-hai;LIU Yan-xiang;TANG Mao-cang
• 2001 Vol. 20 (4): 429-434. 
• Abstract ( ) PDF (270KB) ( )
• A new method, "Diqi" map(or earth-atmospheric map), is used in annual precipitation with qualitative prediction. The relations between the variation of climate data, the earth rotation speed and the axes direction of geothermal vortex cluster are analyzed during 1955-1996. The result shows that the axes direction and wet-belts in East China are similar, namely, wet(dry)-belt and axes of geothermal(cold) vortex are almost coincident. As axis is north-south direction, wet-belt is north-south, vice versa. Rain-belt is often south-north in the slow year of earch rotation.

• Numerical Simulation of Oasis-Desert Circulation in HEIHE Area
• YAN Yu-ping;WANG Jie-min;Massimo Menenti;SU Zhong-bo
• 2001 Vol. 20 (4): 435-440. 
• Abstract ( ) PDF (309KB) ( )
• It is very important to study the interaction of land surface and atmosphere for predicting the future climatic change. The oasis-desert mesoscale circulationin the Heihe area, which deduced by the strong hydrological and the rmodynamic distinction between oasis and desert/Gobi, has much effecton the exist and developmentof oasis ecosystem. In this paper, RAMS is utilized to successfully reproducethe oasis-desert circulation in the Heihe area. At thesame time, the numerical simulations of the field of air temperature and specific humidity indicate that the oasis-desert circulation is directly dependent on the thermodynamic discrepancy of heterogeneous land surface. It is strong in daytime and disappearsat night. The circulation is so important for the maintaining of oasis ecosystem because the mass and energy balancecan be kept.

• A Multi-timeseries Forecast Model of Monthly Climate Change in Yunnan
• DUAN Xu;LI Min;YOU Wei-hong
• 2001 Vol. 20 (4): 441-446. 
• Abstract ( ) PDF (233KB) ( )
• In order to make full use of the accumulative huge data of climate monitor so far, this paper establishes a multi-timeseries forecast mode1 of monthly climate change for Yunnan province. By using over 20 time series which there is a certain physical relations with the monthly climate change of Yunnan province, an actual monthly climate change forecast model for Yunnan province has been established. In the case of two month ahead, the verifications of precipitation and temperature forecasts for Yunna province show that the operational forecast average scores of this model can reach 66.7% and 79.0% during the period of January 1995-October 1999, respectively. These scores are sharply superior over the present operational level of Meteorological Observatory of Yunnan province and achieve the goal of studies of the ninth five-year plan. This newly established model is important for actual short-range climate forecast.

• Radar Discrimination and Verification of Forecast Index of Severe Convection Weather in the Plain of Ningxia
• FENG Jian-ming;XU Yang-chun;LI Feng-xia;SHEN Yang
• 2001 Vol. 20 (4): 447-452. 
• Abstract ( ) PDF (246KB) ( )
• Using the way of regression probability and Chi-square test, the type to discriminate severe convection weather classifiably set up in the plain of Ningxia, and we found out some direct, simply and practicable forecast indexes. Some return tests have been also done based on historical date and so we got some regular and practical conclusions.

• On Influence of Mesoscale Motion on Grid-Averaged Subgrid-ScaleFluxes of Large-Scale Model
• ZHANG Qiang;CAO Xiao-yan;HU Yin-qiao
• 2001 Vol. 20 (4): 453-460. 
• Abstract ( ) PDF (408KB) ( )
• The influence of mesoscale motion on grid-averaged subgrid-scale fluxes of large-scale model is systematically expounded.The ideas of parameterization of mesoscale fluxes and surface subgrid-scale fluxesare presented. The defects of the present parameterization are preliminarily analyzed. The key factors to be considered for parameterizing the mesoscale fluxes and surface subgrid-scale fluxesare suggested. Finally, the new ideas and questions on parameterization of grid-averaged subgrid-scale fluxesof atmosphere of heterogeneous large-scale grid are discussed.

• A Expert System of Suppressing and Decreasing Hailstone Disaster
• WANG Zhi-jun;FENG Jin-ming;CHU Rong-zhong;ZHANG Tong;SONG Xin-min;LI Xiao-ping;JIA Wei
• 2001 Vol. 20 (4): 461-467. 
• Abstract ( ) PDF (281KB) ( )
• The suppressing and decreasing hailstone disaster is an important work. In order to raise its efficiency and guide it with science and technology we develop this expert system. It includes a lot of theory and technology of artificially suppressing hailstone and can be used easily by worker. The main discussion of this paper is about these theory and technology which include the forecasting of hailstone, monitoring of hail-cloud with weather radar and lighting detection system, artificially suppressin hailstone and so on. The efficiency of the work of artificially suppressing and decreasing hailstone disaster will be greatly increased using this expert system.

• Potential Vorticity and Potential Vorticity Inversion
• ZHANGShu-wen;WANG Shi-gong
• 2001 Vol. 20 (4): 468-473. 
• Abstract ( ) PDF (259KB) ( )
• The history of potential vorticity developments is reviewed and the invertibility principle for potential vorticity is presented. We discuss the various versions of potential vorticity and the Lagrangian conservation properties in the differently approximate models. Some new properties of potential vorticity are summarized. Several methods of potential vorticity inversion are discussed and compared. A lot of examples are examined and their disadvantage are also investigated. We conclude the remark by predicting some possible applications of the IPV concept and potential vorticity inversion.