Vol.8, NO.2, 1997

Display Method:
A Study of Atmospheric CO2 Concentration Variations and Emission from the Soil Surface at Mt. Waliguan
Wen Yupu Tang Jie Shao Zhiqing, Shao Zhiqing, Zhang Xiaochun, Zhao Yucheng
1997, 8(2): 129-136.
By using non-dispersive infrared (NDIR) method, continuous measurements of atmospheric CO2 were carried out at Mt. Waliguan where the environment is unaffected directly by local anthropogenic pollution. The characteristics of the atmospheric background CO2 concentration variation for the inland Plateau of China were presented in this paper. The results show that is has clearly diurnal and seasonal variations related to the grown cycle of the land vegetations, and that the pattern of seasonal variation correspond with the global geographical distribution of atmospheric CO2. It is found that the increase of CO2 concentration was at a lower rate in 1993, but at a great rate in 1994. Furthermore, the emission rates of CO2 from the Plateau grassland soil were also measured. The results show that the CO2 emission rate from the soil surface increases relatively in winter with the largest value of above 170 mg/m2·h when the photosynthesis of vegetation is essentially stagnant.
The Seasonal Rapid Changes of Global Potential Energy at Different Latitudes
Wei Min Qiu Yongyan
1997, 8(2): 137-146.
Utilizing the data of monthly mean of the zonal potential energy (PZ) over the entire globe at different latitudes and levels, the seasonal rapid changes (SRC) in the entire circulation in terms of these potential energy modes have been investigated. The results show that seasonal rapid changes of PZ take place generally in April and October at every latitude, and the rapid changes in June also are analysed by using daily data. As to upper and lower levels, the seasonal rapid changes of PZ at lower level (500 hPa) are more obviously than those at upper level (100 hPa) of the Northern Hemisphere, and it is opposite to the Southern Hemisphere
A Study of Atmospheric Water Vapour Retrieval Approach from TOVS Observations and Its Experiment
Zhang Fengying, Wang Chao, Ran Maonong, Hu Xiaoxin
1997, 8(2): 147-156.
The paper presents a new approach for the satellite retrieval of atmospheric humidity form TIROS-N Operational Vertical Sounder (TOVS) observations with 6-hour numerical forecasts from the National Meteorological Center (NMC) as the first guess of the Simultaneous Physical Retrieval Model (SPRM). It is shown that the RMS error of SPRM retrievals is about 20%, and the results for the summer time is slightly better than those for the winter time. As compared to the first guess. The SPRM retrievals have greatly improved especially for the lower level (1000 hPa) and higher levels (above 500 hPa). Also, the SPRM results are much better (about 10%) than those from the statistic regression method. This research will lay the foundation for establishment of a cycle system of interaction among the satellite retrieval, data assimilation and numerical prediction.
Numerical Experiments on Calculating Scheme of Water Equation
Zhang Qinghong Zhang Yuling
1997, 8(2): 157-166.
Easter’s scheme, which is the modified version of Bott’s forward- in-time and positive definite numerical advection scheme, is described in this paper. Two groups of comparable experiments show that Easter’s scheme exhibits less numerical diffusion than the original scheme of LAFS, and therefore it won’t give excessive precipitation, which is consistent with observations, but needs 16% more CPU time.
A Study on the Criterion for Interpreting Typhoon Heavy Rain Location
Wang Shujing, Zhou Liming, Chen Gaofeng
1997, 8(2): 167-174.
Under the heavy rain criterion (MPV10), which are deduced from developing theory of slantwise vorticity, the several examples of landing typhoon with different tracks and structures have been interpreted on the heavy rain location. On the base of summing up the operational criterion, it is found that horizonal component of the wet potential vorticity MPV2 had better be replaced by the non-geostrophic component MPV2’ of it. Meanwhile, it is also mentioned that the top of typhoon inverted trough is the most active area of the typhoon interacting with westerly belt system, where the sub-synoptic scale and mesoscale disturbances appear frequently. Furthermore, it is shown that owing to rapid increasing of the vertical component of wet potential vorticity MPV1 and MPV2’, sudden heavy rain will probably happen in this area
Statistical-diagnostic Analysis of Cause for the Change of China’s Temperature Field During the Last 100 Years
Jiang Zhihong Ding Yuguo Jin Lianji
1997, 8(2): 175-185.
The cause for the changes of China’s temperature fields during the recent 100 years (1881~1992) is diagnosed by using CCA method. The results show that (1) the enhanced greenhouse effect due to the increase of CO2 is more closely correlated with the linear trend of warming in China’s temperature fields and the relationship appears more obviously since 1980s; (2) the sensitive regions of greenhouse effect are located in the northern North China, Northeast China, western Northwest China and the mid-lower reaches of Changjiang River, respectively; (3) the effect caused by volcanism is of relative importance in the fluctuation superposing the long trend, and the sensitive region lies to the south of 35oN, the center is in southwestern China, (4) the warming from 1920s to 1940s seems to be the joint results of the greenhouse effect, volcanism and solar activity, and that by the end of 1970s may be mainly caused by enhanced greenhouse effect.
Climatological Characteristics of Evolution of East Asian Winter Monsoon
Wang Qiyi, Wang Qiyi Ding yihui
1997, 8(2): 186-196.
Characteristics of evolution of East Asia winter monsoon and cold surge were discussed and compared with those in South Asia. It is found that there exist an abrupt change of meridional circulation in East Asia during middle October, which represents the onset of East Asia winter monsoon circulation. Three abrupt changes of temperature occur in lower troposphere in the early September, middle November and late January. However, the change of the circulation in South Asia is not as strong as in East Asia. The change of meridional wind in upper troposphere is earlier than that in lower troposphere. There exist two abrupt changes of the temperature in lower troposphere, which are weaker than in East Asia longitudinally. Furthermore, in East Asia, the frequency of cold surges has its maximum in South China Sea in December, but in west Pacific in January. On the other hand, in South Asia, the cold surges occur most frequently still in December, but much less than in East Asia, and they decrease quickly with time. Another different aspect is that the clod surge frequencies decrease upward in East Asia, but increase in South Asia
Variation of Temperature and Precipitation During the Last Forty Years in Jilin Province
Lian Yi, An Gang, Wang Qi, Ni Chaoyu, Xi Zhuxiang
1997, 8(2): 197-204.
Using data set of ten representative stations in Jilin Province for 40 years and the power spectral method, the seasonal variations of precipitation and temperature were analyesed, respectively. The results show that the period of a short-term climatic change in Jilin is almost consistent with that of the interannual oscillation of quasi-3.5-year (QTO) and quasi-biennial (QBO) of East Asia monsoon. Furthermore, it is found that the seasonal temperature got warm clearly about 2oC higher than that of the 1950s in winter, but weakly in summer. As compared with the low temperature period in summer from the 1950s to the 1970s, the temperature was a relative warm during the period of 1980s. Also, progression or retrogression of subtropical summer monsoon has a great effect on the temperature and precipitation of the summer in Jilin.
The Effects of Non-phase Change Diabatic Heating Process in Short Term Forecast
Zhou Tianjun Qian Yongfu
1997, 8(2): 205-211.
Numerical experiments are made on the effect of non-phase change diabatic heating process in short term forecast. The results show that its effect on quantitative precipitation forecast is significant. If omitting the process, the forecasts of rainfall amount and its distribution have obvious departure from observation. And, the rain belt in some region of the main land disappears or appears in error, the rainfall amount decreases evidently.
Estimating Farmland Soil Moisture in Eastern Gansu Province Using NOAA Satellite Data
Guo Ni, Chen Tianyu, Lei Jianqin, Yang Lanfang
1997, 8(2): 212-218.
Some statistical models established by using vegetation index data calculated from NOAA satellite visible and infrared data, brightness temperature data from satellite channel No.4 and soil moisture data observed at agricultural meteorological stations in the farmland of the eastern Gansu Province. The results show that vegetation index could reflect a part of moisture information, and there is some relationship between brightness temperature and soil moisture. Therefore, vegetation index and brightness temperature can be used to monitor drought regime.
A New Retrieval Technique for Single-Doppler Radar
Jiang Haiyan Ge Runsheng
1997, 8(2): 219-223.
This paper presents a new method called Vorticity-Divergence method (V-D method) for retrieving horizontal wind field from single-Doppler radar PPI. Retrieval experiments are conducted using the Doppler radar observational data on July 12, 1994 with the V-D method. The results are compared with the actual synoptic situation. It is shown that the V-D method is a effective one for the single-Doppler radar wind field retrieval
A Study of the Prediction of Agroclmatic Harvest and Decision Service System
Wei Li
1997, 8(2): 224-229.
The agroclimatic harvest prediction and decision service system (ACHPDS) consists of three parts. They are agrometeorological disaster prediction (AMDP), crop yield harvest prediction (COHP) and crop planting area arrangement decision system (CAAD). The approach and application of the system are discussed in detail.
The Change of Northern Hemisphere Snow Cover and Its Impact on Summer Rainfalls in China
Zhai Panmao Zhou Qinfang
1997, 8(2): 230-235.
Based on the Northern Hemispheric snow cover data from 1973 to 1995, climatologic characteristics and changes of snow cover extent over the Northern Hemisphere, Eurasia and North America are studied. It is found that 1970s is a period of snow cover expansion with the maximum in 1978. After 1980s, snow cover decreased significantly. Correlation analysis shows that East Asia winter snow cover is negatively correlated to summer precipitation in the areas from the Mid-lower reaches of the Yangtze River to south of it. Spring snow cover is significantly correlated to rainfalls in northern Xinjiang and northern Northeast China. Significant reverse correlations were found between East Asia winter snow cover and the Meiyu duration when ENSO years are excluded.
A Study on Radiation Budget of the Winter Wheat Field in Tibet Plateau
Zhang Xianzhou, Wang Huimin, Zhang Yiguang
1997, 8(2): 236-241.
The components of radiation budget in the winter wheat field in Tibet Plateau were measured from June to August, 1995, and then their diurnal variations were analysed. The results showed that the average net radiation was 75% of the global radiation in daytime or 67.4% of the global radiation including day and night during the measuring period. A linear relationship between net radiation and global radiation which can used to calculate net radiation from global radiation was established
The Effect of Topographic Forcing on the Instability of Inertia Gravitational Waves in Basic Flow of Vertical Shear
Wu Hong Lin Jinrui
1997, 8(2): 242-246.
By using the shallow-water wave equation and WKB method (small parameter method), the local frequency equation of the inertia gravitational waves is obtained, which includes the effects of the basic flow with vertical shear and the mountain range with east-west direction. The instability of the waves is discussed through the equation under different environment conditions.
A Case Study of Typhoon Torrential Rain
1997, 8(2): 247-251.
In this paper, a case of typhoon torrential rain over North China is analysed using synoptic and Dynamic diagnostic method. The analysis reveals that a southeasterly low level jet between typhoon and West Pacific subtropical high is evidently characterized by supergeostrophic wind, and it is a key system for the typhoon torrential rain over North China. The Q-vector analysis shows that the regions where Q is convergent coincide with torrential rainfall area