Current Issue

• SPECTRAL ANALYSES OF DIABATIC EFFECTS ON THE CIRCULATION SYSTEMS AND THEIR SEASONAL VARIATION OF THE EAST TIBETAN PLATEAU IN 1979
• Lu Shihua
• 1983 Vol. 2 (3): 1-9. 
• Abstract ( ) PDF (642KB) ( )
• The multichannel maximum entropy spectral estimation is used to analyse the influences of thermal effects on the circulation systems and their seasonal changes of the East Tibetan Plateau in 1979. The statistical results seem to be very interesting.It points out that all of parameters have oscillations with the quasi-biweekly period and the quasi-weekly period during the spring, summer, autumn, winter.The phase relations of the oscillations between the thermal parameters and the circulation parameters change with the seasonal variations.When there is a heat source in the atmosphere, the oscillation change with two weekly period in the low level atmosphere is earlier than in the upper atmosphere and when there is a heat sink in the upper atmosphere the oscillation change is earlier than the lower atmosphere.The sensible heat and the latent heat make some contributions to the formation and maintenance of the Tibetan high on 100 mb over the East Tibetan Plateau.The changes of the surface sensible heat are the earliest among the oscillations of all the parameters.

• ON VERTICAL INTERPOLATION OF METEOROLOGICAL ELEMENTS AND INITIAL DATA PROCESSING IN NUMERICAL MODELS
• Qian Yongfu
• 1983 Vol. 2 (3): 10-20. 
• Abstract ( ) PDF (722KB) ( )
• Detailed discussions of vertical interpolation and initial processing of meteorological elements are given in this paper.Three kinds of temperature -pressure distributions in vertical direction are tested to determine their suitabilities in numerical models.The better interpolations are obtained when we assume that temperature changes with logarithm of pressure or with height.Experiments show that large and irregular errors of initial processing result from assuming unchanged temperature lapse rate below surf ace. Using local isothermal or local equal temperature Laplacian assumptions, we can obtain better extrapolations and much less errors of ca-lculation of pressure gradient force.

• THE CLIMATOLOGICALLY SYNOPTIC CHARACTERISTICS OF THE SHEAR LINE ON THE 700mb SURFACE TO THE EAST OF THE QINGHAI-XIZANG PLATEAU
• Xu Guochang
• 1983 Vol. 2 (3): 21-25. 
• Abstract ( ) PDF (351KB) ( )
• The shear line on the 700mb surface to the east of the Qinghai-Xizang Plateau is a climatic system with synoptic scale in the boundary layer stream fields.It is located at the most south in winter and at the most north in summer.It has the usual temperature gradient, but different vor-ticity, divergence and vertical velocity fields from other shear lines. It is caused primarily by the orographically dynamic effect. To each side of the shear line, there is a meridional vertical circulation and in the vicinity of the shear line, there are great gradients of humidity, cloudiness, precipitation and sunshineetc.

• A CALCULATION OF THE MECHANISM OF THE ELECTRIFICATION BY POLARIZED PRECIPITATION IN THUNDERSTORM
• Yan Muhong;Ge Zhengmo
• 1983 Vol. 2 (3): 26-39. 
• Abstract ( ) PDF (954KB) ( )
• A numerical model relating to time with the mechanism of the electrification by polarized precipitation is employed(in this paper) to simulate the growth process of the electric field in thunderstorm and hailstorm. Assuming hydrometeores are of Marshall-Palmer distribution, the integrally separated probability and the cosine of the coalescence-angle are reasonably adopted in the caleulation in accordance with List's experimental records. It is shown from calculations that the charging rate due to the collision between hailstones and icd crystals is the highest, the electric field which is large enough to trigger lightning can be produced within about 250-750 seconds after the hailfall rate reaches 2-26mm/hour and its maximum may even grow up to 7000v/cm, the charging rate by the collision between rain drops and cloud droplets is weaker,the electric field of about 4000v/cm, however, would also appear if the charging time is long enough.The critical rainfall rate which may induce sufficient electric field to trigger lightning is 3mm/hour.This result is coincident with the observations.The eletrification by the collision between hailstones and cloud drop- lets may produce high charging rate when high concentration of droplets exists in clouds.Charging rates with great differences may happen depending upon different concentrations of droplets and under the condition of low concentration, lightning would not be stimulated even if the rainfall rate is high.This coincides also with the data of observations. As the practical maximum of electric field, about 4000v/cm, is formed in cloud, the hydrometeors may still keep falling with large speed instead of suspensing.The suppression effects of the force of the electric field on the growth of the electric field and the reversion-current effects of small ice crystals can be neglected.It is found from the calculation that the charge amount may reach about -100--400pc for single hail-particles(rad-ius 2-3mm)and-3--10pc for raindrops(radius 0.8mm).All these are similar to the data from aircraft measurements. In addition, the time of forming maximum of electric field may vary depending upon the initial state of cloud which has little effect on the electric field value, however.

• VERTICAL AIRFLOW CHARACTERISTICS OF SQUALL-LINE HAILSTORM AT DIFFERENT DEVELOPMENTAL STAGES
• Zhang Peiyuan
• 1983 Vol. 2 (3): 40-48. 
• Abstract ( ) PDF (621KB) ( )
• This paper analyses the squall-line hailstorm synthetically in Zhangjia-kou area on July 20th, 1980, by radar echo and meteorological factors at ground and high altitude, discusses its vertical airflow characteristics at different developmental stages, gives streamline field patterns of hailstorms at developmental and stable. It is shown that there are obvious differences between streamline field patterns of different developmental stages of squall-line hailstorm.