Current Issue

• THE EFFECTS OF LAND-SEA DISTRIBUTIONS AND TIBETAN PLATEAU ON THE MEAN MERIDIONAL CIRCULATIONS IN JANUARY AND JULY AND THEIR SEASONAL VARIATIONS
• Luo Siwei;Lu Shihua;Sun Liye
• 1984 Vol. 3 (4): 1-13. 
• Abstract ( ) PDF (1087KB) ( )
• In this paper the heating field and 13 vertical cross sections of circulation along meridian in the global latitude zone of 50°N-35°S are calculated with the grid point 5°×2.5° latitude and longitude by using the 10 year mean data of U.S GFDL.In these cross sections with 11 layers, the vertical velocity is calculated by observational wind and the heating field by the thermodynamic equation. Analysis point out: (1) there are two kinds of seasonal changes of the meridional circulation over the regions A and B.Region B is all of land or water, while in region A, the north part is land and the south part is ocean. In January in Northern Hemisphere the Hadley cells appear in the region A and B, but it is stronger in region A than in region B.In July the Hadley cell in region A is changed into anti-Hadley cell (Monsoon circulation) but that in region B still remains and even becomes stronger. (2) The opposite change of the meridional circulation in summer and winter is most evident along the 90°E near the main part of Tibetan Plateau. The Hadley cell becames weaker from the beginning of February, then in April the pre-monsoon circulation appears in the lower layer to the south side of Plateau and the compensating circulation cell appears in the upper layer, too.In June these two circulations develop and become typical monsoon circulation, and in October the Hadley cell appears again in the lower layer to the sonth side of plateau.All these changes are closely connected with the thermal effect of the Tibetan Plateau and this effect on the meridional circulation in the upstream and downstream is also discussed in this paper.

• THE CLIMATE OF LHASA IN THE EARLY 20th CENTURY
• Lin Zhenyao;Wu Xiangding
• 1984 Vol. 3 (4): 14-20. 
• Abstract ( ) PDF (548KB) ( )
• A former top officer to Tibet (Xizang), You Tai's diary (1904.2.9-1907.4.17)and other historical literatures are adopted here to study the climate of Lhasa in the early 20th century. From the records about the beginning and ending dates of ice-forming and frozen depth in ponds, snow and its cover and some phenological phenomena, it is concluded that Lhasa was much colder in the early 20th century than that at present. From analyzing the rainy days, rain intensities and the occurrence of flood and waterlogging, it is suggested that it was a rainy period from 1904-1906 in Lhasa. In addition, modern observations indicate that Lhasa is a city without any fog, while You Tai's dairy recorded that there were fog days in some years.

• CLIMATIC VARIATIONS OVER QI-LIAN MOUNTAIN AREA
• Tang Maocang;Xu Manchun
• 1984 Vol. 3 (4): 21-33. 
• Abstract ( ) PDF (796KB) ( )
• According to the data of last 500 years collected by liu etc. ^[1] and zhang ^[3],we have pointed out that tie phase of the climatic vibration scaled near 100 years over the Qilian mountain is about 15 years earlier than that over the eastern part of China.The interannual precipitations are always in opposite the tendencies between the western part and eastarn part of this mountain area. In the 1960s, the mountain area as a whole was cooler than in 1950s, but in the middle basin of all the eastward rivers, the case was just inverse, being warmer in that ten years.In the 1970s, the Plateau summer monsoon was stronger than in 1960s.The variability of temperature and precipitation of the inner part of mountain area is much less than the outer part around the mountain.This phenomena can be explained by the interannual variation of the Plateau monsoon's vertical cireulation system.

• A REVIEW OF DYNAMIC EFFECTS OF THE PLATEAU AND MOUNTAINS ON THE LARGE-SCALE PROCESSES
• Zhu Baozhen
• 1984 Vol. 3 (4): 34-44. 
• Abstract ( ) PDF (797KB) ( )
• The problems of the large-scale dynamic processes of orography are reviewed, including the asymmetric properties of the stationary planetary flow, the resonance and the multiple equilibria in orographic forced wave systems, the non-linear topographic forced instability, the vertical transfer of energy in stationary mountain waves, the atmospheric flow over and around large-scale plateau, as well as the lee-side cyclogesis.

• THE MECHANISM OF "LIGHTNING ELIMINATOR"
• Guo Changming
• 1984 Vol. 3 (4): 55-62. 
• Abstract ( ) PDF (580KB) ( )
• From analyzing the point discharge process, current flowing in the atmosphere, leader process and attachment process of lightning, it is concluded that the effect of any existing system with artificial points is nothing but to influence the local distribution of air earth current. The space charge layer formed during point discharge process is not enough to prevent the leader from marching, and can not prevent the forming of upward leader,either.The so called "lightning eliminator" can not elin inate lightning, on the contrary, it will trigger upward leader and get hit by lightning like an ordinary lightning rod does.