Plateau Meteorology

24 September 1987, Volume 6 Issue 3

THE BUDGET EQUATION OF ENERGY POTENTIAL VORTICITY AND ITS APPLICATION TO DIAGNOSIS OF HEAVY RAIN
Li Dingmin
1987 Vol. 6 (3): 193-207.
Abstract ( ) PDF (958KB) ( )
A new physical variate, energy potential vorticity (EPV) which combines the energy synoptical meteorolgy with the dynamics, is derived from the Ertel's general potential vorticity equation and the concept of atmospheric energy. As a natural extension, the quasi-EPV (Q-EPV) is given. The simplification of the above two variates and their physical background are discussed. Then, the budget equation of the EPV is derived according to its definition. When applying the EPV, Q-EPV and high pass filter technique to the diagnosis of a heavy rain case, we have found that the area of heavy rain was in accordance with the positive center of EPV and the negative center of Q-EPV. Further analysis of the budget equation shows that the equation can be use to analyse the interaction of different scale in the heavy main and that the EPV can describe the dynamical and energy condition rhich is necessary for heavy rain. Combining with the water vapour convergence, EPV and Q-EPV are veluable for the diagnosis of heavy rain in numerical prediction model.

AN OBSERVATIONAL STUDY ON THE CHARGE-SIZE OF RAINDROPS FROM WARM CLOUDS
Wang Caiwei;T. Takahashi
1987 Vol. 6 (3): 208-216.
Abstract ( ) PDF (585KB) ( )
The size and electric charge of more than 35,000 raindrops from 30 warm cloud showers were measured. Data were analyzed by examining charge spectra with respect to drop size. The result shows that the percentage of positive drops increased with drop size as well as the intensity of rain showers. The distribution of raindrop charge was asymmetric in electric sign:it was always broader in positive side, and negative drops were predominant when the magnitude of electric charge was small. But positive drops obviously prevailed as the drop charge became larger. During part of the observational period the volcano near the observational site erupted. It's effects on the drop charge were that the charge spectra became narrower and the percentage of drops with large electric charge decreased. The results are discussed and explained in terms of the electric-f ica tion mechanism through ion-drop interaction during the formation of raindrops in warm clouds.

THE OBSERVATIONAL RESEARCH OF THE THERMAL FLUX AND EVAPOTRANSPIRATION IN HEXI REGION
Su Congxian;Hu Yinqiao;Jiang Hao;Zhang Yongfeng;Wei Guoan
1987 Vol. 6 (3): 217-224.
Abstract ( ) PDF (501KB) ( )
The action of the plants for the adjustment on the hydrologic balance and the thermal balance has been developed from analysis of the meteorological elements gradient observation and thermal radiation observation in the surface layer over Hexi Region. The evapotranspiration of the mid growing period of the wheat in Hexi Region has been calculated by the energy balance method.

DYNAMIC EFFECTS OF LARGE SCALE ENVIRONMENT FIELD ON EASTWARD MOVING AND DEVELOPMENT OF LOWS OVER THE QINGHAI-XIZANG PLATEAU
Sun Guowu;Chen Baode;Wu Jicheng;Liu Donghan
1987 Vol. 6 (3): 225-233.
Abstract ( ) PDF (532KB) ( )
In this paper, the observation facts of the relationship between large scale environment field and eastward moving and local disappearing of lows over Qinghai-Xizang Plateau had been analysised. Dynamic effects of large scale environment field on eastward moving and development of lows over Qinghai-Xizang Plateau had been computed. The above facts and computations show whether a plateau low will move eastward and develop or disappear locally, it depend some what on the different contributions of both(f+ξ)▽·V and 1/acoφ?ω/?λ·?v/?p-1/α?ω/?φ ?u/?p and terms in vorticity equation.

ELECTRIC FIELD AND CHARGE DISTRIBUTION MODEL OF THUNDERSTORMS
Ye Zongxiu;Shao Xuanmin;Liu Xinsheng
1987 Vol. 6 (3): 234-243.
Abstract ( ) PDF (696KB) ( )
This Paper analyses the variation of electric field and radar echo of a thunderstorm in Pingliang, Gansu. The results show that the electric charge structure of thunderstorms in Pingliang is generally positive charge above, negative charge in the middle layer and another positive charge in the lower region of storms, over-head thunderstorms with heavy rain or hail often cause intensive positive electric field at surface and lightning flashes take place between lower positive charge region and negative charge region above. A model of charge distribution in the form of disc and column is proposed and compared with observations.The result shows basically mutual agreement. Specially, the rapid change of surface electric field from positive to negati'e value when precipitation stops falling or passes over observation station can be explained by the model.

A PRIMARY METHOD FOR PREDICTING THE SPRING RAINFALL BY THE WINTER SOIL TEMPERATURE DEPTH 80CM
Tang Maocang;Wang Jingxiang;Zhang Jian
1987 Vol. 6 (3): 244-255.
Abstract ( ) PDF (824KB) ( )
According to the vapor transport and precipitation systems, China can be divided into 10 zones. Based upon the comparison among these zones, the departure of soil temperature was classed into 5 degrees (High, Subhigh, Moderate, Sublow, Low).There is a very good correla tionship between the 0.8m soil temperature degree of winter season and precipitation anomaly of spring season in each zones. A regression equation was established for predicting the spring precipitation. Finally, two predicted cases of 1984 and 1985 was described.

THE INFLUENCE OF SNOW COVER OVER EURASIA ON THE GENERAL CIRCULATION OVER EAST ASIA AND THE SPRING RAINS OVER NORTHWEST CHINA
Li Shan;Xu Guochang
1987 Vol. 6 (3): 256-264.
Abstract ( ) PDF (554KB) ( )
The influence of snow cover ever Eurasia on the general circulation over East Asia and the weather over Northwest China is analysed with snow cover data of NOAA satellite from 1967 to 1980 and snow cover chart from 1979 to 1984. It is found that atmospheric cooling caused by abnormal snow cover is very clear.The snow cover which is far above than usual will lead to the decrease of both the temperature in troposphere and geopotential in mid-and upper troposphere and, therefore affect the circulation and weather. This cooling effect has a time lag with about one or two months and is more evident in melting snow season (from March to May).

AN ENERGY ANALYSIS OF EXPLOSIVE THUNDERSTORM AND HAILSTORM PROCESS IN LARGE AREA
X u wenjun;Li Jinlong;Wang Zhaoda
1987 Vol. 6 (3): 265-273.
Abstract ( ) PDF (570KB) ( )
In this paper, we used the total temperature of surface and unstable energy to study the explosive thunderstorm and hailstorm in large area of Northwest China on 30 June 1974. It is pointed out that unstable energy and its variation are closely related to both the thunderstorm and thunderstorm area. Through analyzing the physical composition and vertical distribution of unstable energy, we find that the energy accumulation of environmeut air column other than surface is the major contributor to unstable energy increasing, distributions of unstable energy in every vertical layer are different, energy accumulations of each layer are different from one another in time order, and the accumulation of lower layer is earlier than of upper layer.