Plateau Meteorology

24 September 1988, Volume 7 Issue 3

TWO EXAMPLES OF USING A SINGLE WEATHER DOPPLER RADAR TO OBTAIN 2-D FLOW FIELD AND THERMAL ADVECTION ON THE NORMAL PLANE OF MESOSCALE RAIN BANDS
Zhuang Yinmo
1988 Vol. 7 (3): 197-205.
Abstract ( ) PDF (635KB) ( )
2-D flow fields and thermal advection on the normal plane of mesoscale rain bands in the winter polar air mass vortex have been calculated by using single Doppler radar data and the method following Browning and Hobbs and others. Results are qualitatively agreement with the existence of rain bands and their different developing stages, also basically agreement with radio sounding. However the value of vertical velocity obtained seems too large and cold and warm advection areas are not totally consistent. Results also change remarkably with the different methods of data processing.

THE DYNAMIC ANALYSES OF THE CENTRAL ASIA DEPRESSION MOVING EASTWARD
Sun Guowu;Wu Jicheng;Xu Hongbo
1988 Vol. 7 (3): 206-213.
Abstract ( ) PDF (480KB) ( )
According to the principle of the thermal wind adjustment, the problem of Central Asia depression moving to east have been discussed. The results show that the moving and non-moving depression are different in the thermal wind advection processes of both baroclinic development of temperature field disturbance and barotropic development of stream field disturbance.

A NUMERICAL EXPERIMENT OF THE FLOW WHICH CLIMBS OVER MOUNTAIN VALLEY
Qian Weihong
1988 Vol. 7 (3): 214-220.
Abstract ( ) PDF (425KB) ( )
A two-dimensional stationary model has been used to examine the dynamical effects produced by the flow which climbs over mountain valley. The results show that disturbance vortex is restricted by the basic flow(Ū), the depth(δ) and half-width(L) of the valley. For example, there are two disturbance vortexes if Ū=6m·s ^-1, δ/L<1 and there is only a disturbance vortex if Ū=6 m·s ^-1 while δ/L<1.

SOME BASIC FACTS OF THE HARMONIC ANALYSIS OF EACH HEIGHT FIELD IN THE STRATOSPHERE OVER THE NORTHERN HEMISPHERE
Qu Zhang;Lü Shihua;Zheng Guang;Lin Junfeng;Qiu Hailong
1988 Vol. 7 (3): 221-233.
Abstract ( ) PDF (804KB) ( )
Using the harmonic analysis method, we've calculated the amplitude of wave 1-3 of each latitude at 30, 50 and 100hPa level from Jan. to Dec. over the northern hemisphere. The, result shows that the amplitude of all the wave 1, 2 and 3 increases with latitude at each level and the maximum is in the belt of 50-70°N latitude; All amplitude of winter are 5-10 times that of Summer. The sum of amplitude of wave 1 and wave 2 occupies the mains of the sum of wave 1-4, especially wave 1 plays an important role in it. In summer, not only the maximum amplitude appears in 30-40°N latitude at 100 hPa level in troposphere but also "the secondary maximum amplitude" of wave 1 appears in 30-40°N latitude at 50 and 30 hPa and "the secondary maximum amplitude" of wave 2 appears at 50 hPa level in the stratosphere; It associates that the influence of Qinghai-Xizang High on the stratosphere. If we character the seasonal transition from winter to summer and the reversal with the increase and decrease of the amplitude of each wave in the stratospheve then the former occurs from March to April, the latter occurs from August to Sept., so the seasonal transition of the stratosphere is more than one month earlier than the troposphere.

A CASE STUDY OF THE EFFECT OF TIBETAN PLATEAU ON THE OUTBREAK OF COLD AIR
Luo Siwei;Chen Yuchun;Yu Xuequan
1988 Vol. 7 (3): 234-245.
Abstract ( ) PDF (803KB) ( )
In this paper we have discovered the following main effects of Tibetan Plateau on the intensity of cold-outburst and its trajectory through numerical experiments with orography and without orography for the case in the period of 10-13 April 1979.(1) Owing to the broken action of Tibetan Plateau, the cold air moves fast southeastward along its north and east periphery, the cold front reaches far to the southern area and brings more temperature drop and more rainfall in the plains of China which lies to the east of the Plateau.(2) The cold front reaching far low latitude is caused by the lateral boundary action of Tibetan Plateau which accelerates the cold air flows around its periphery.(3) If Tibetan Plateau did not exist, the cold air would straight rush to India and would bring strong temperature drop there.

ANALYSES ON THE CHARACTERISTICS OF WIND,TEMPERATURE FIELDS IN THE BOUNDARY LAYER OF YAN-AN (city) IN WINTER
Li Dinghua;Wu Jingzhi
1988 Vol. 7 (3): 246-253.
Abstract ( ) PDF (486KB) ( )
In this paper, by using the field observational data in the period from December 25, 1985 to January 9 , 1986, the characteristics of wind, temperature fields in the boundary layer of Yan-an in winter are analysed. The results show that, in the lower layer in winter, the sustaining time of temperature inversion is long and its strength is high. During the sustaining period, the atmospheric structure tens meters above the ground manifests itself as mixed layers. The wind field in the boundary layer is very complex and its time-space changes are large. The ground layer is often in a state of light breeze, and both the direction and velocity of wind show an evident shear along vertical direction, while in the lower layer, the flow field has a significant channel effect and the valley wind displays evidently.

SENSITIVITY STUDY OF RADIATIVE TRANSFER IN THE INFRARED WINDOW (10.5-11.5 MICRON AND 11.5-12.5 MICRON)
Wei Li;Zhong Qiang
1988 Vol. 7 (3): 254-263.
Abstract ( ) PDF (667KB) ( )
Surface temperature can be determined by using the infrared channels (10.5-11.5 micron and 11.5-12.5 micron) data of AVHRR with considering the atmospheric correction. In this paper, the sensitivity of upward radiance at the top of atmosphere in the infrared window to changes of atmosphere and surface state and emissive angle are investigated based on radiative transfer modeling with Midlatitude and Tibetan Plateau model atmospheres.

ON THE ANNUAL VARIATION OF THE BAROTROPIC AND BAROCLINIC KINETIC ENERGY OF MONTHLY MEAN CIRCULATION OVER THE MID-HIGH LATITUDE OF THE NORTHERN HEMISPHERE
Huang Jianping;Chou Jifan
1988 Vol. 7 (3): 264-268.
Abstract ( ) PDF (329KB) ( )
using secular monthly mean data, the annual variation of the barotropic and baroclinic kinetic energy for monthly mean circulation has been computed. It is showed that both barotropic and baroclinic kinetic energy have the obvious annual variation and the same tendency, but the contribution of barotropic kinetic energy to total kinetic energy is much more than that of baroclinic kinetic energy. The monthly mean circulation anomaly has the equivalent barotropic structure. These conclusions can be used to simplify the long-range numerical forecast model.

SOME STATISTICAL RESULTS OF WET SEASONS AND DRY SEASONS IN CHINA
Zhang Jian;Tang Maocang
1988 Vol. 7 (3): 274-278.
Abstract ( ) PDF (335KB) ( )
The seasonal anomaly maps of precipitation during 1954-1984 was analysed. It was discovered that. 1. There is a more(less) rain belt always occuring over the east side of Tibet Plateau(95-105°E), when the whole China is a less(more) rainy season. 2. The best persistence of season-to-season departure sign of precipitation is in spring to summer; the worst one is in autumn to winter. 3. There is a positive correlation between the sea surface temperature of kuroshio current and the numbers of more rainy seasons in the same year.