The synchronous NCEP/NCAR summer reanalysis data are verified by comparing with the intensive observation boundary layer wind speed and direction of TIPEX at Damxung station indicate a distinctive phenomenon that there exists and low in the south modon of pressure field in Qinghai-Xizang Plateau boundary layer. The drought formation of on the northeast side of Qinghai-Xizang Plateau has been studied by introducing stationary heat force and transient heat force, which determined by continuos evolution of sensible heat flux (May 31 to June 4, 1998). The main results are there exist (1) advection transportation of to upstream anticyclone vortex through westerly basic flow, (2) southern cyclonic energy dispersion, (3) anticyclon system intesifying caused by Qinghai-Xizang Plateau heat forcing.
The 500 hPa Subtropical High over the West Pacific (SHWP) is one of the members of summery monsoon systems in Eastern Asia, it has the important influence on the main rain belt in China summer. In this paper to seek the forecast precursors for medium- and short-range forecast of the SHWP moving southward and northward suddenly, the impacts on the SHWP moving southward and northward and associated rain belt of the Qinghai-Xizang Plateau (QXP) vortexes moving eastward, the 100 hPa Southern Asia High (SAH) moving southward and northward, as well as the cold air invading from the North have been analyzed, utilizing the daily weather maps from June to August in 1998 and 1991, and the observational data from the Second Meteorology Science Test on the QXP, and the daily averaged gridded reanalysis data (e. g. u, v, h) on 2.5 degree x 2.5 degree from NCEP/NCAR. The main conclusions are as follows: 1) If the air-column thickness between 300 and 500 layers over the eastern QXP is greater than or equal to 392 gp-dm, the
It is very important to know and master the status of atmosphere vapor in operation of artificial precipitation enhancements. The principle of dynamical meteorology is used to calculate the vapor transportation, convergence and divergence in spring over northeast Qinghai, the total vapor content and liquid water are observed by the microwave radiometer. The calculated result shows that the input of vapor in northwest Qinghai is more than output, and the vapor about 83 percent can pass the area and then move out Qinghai, and it has bigger potential water resource. From the liquid water content, though the vapor content is less than the area of plain, but the liquid water content is more than that one. Otherwise, according to calculations of tatal cloud condensation water and precipitation efficiency from the third dekad of March to the first dekad of May 1997, the atmospheric total condesation water is obtained to be 284 x 10 super(8)t, but actual precipitation is about 34 x 10 super(8)t, the average precipita
Using the vertical measurement data of urban and suburb in kunming which located at low-latitude plateau, the characteristics of vertical distribution of city climate at low-latitude plateau city were analyzed. Through comparing analyses, the primary results are as follows: The findings indicate that urban heat island lie in not only near the ground but also upper atmosphere, the intensity of night (influenced height >50 m) go beyond daytime (influenced height <50 m), near the ground exceed upper atmosphere. In urban area, the air temperature decrease with height increasing in daytime and temperature at night is inversion distribution, the center of urban heat island shifts with height increasing. This distribution would have an effect on the diffusion of urban contamination, architecture design and energy saving.
The characteristics of April mean general circulation between more and less sandstorm years in Ningxia are compared with each other. The results show that the intensity of the pole eddy at 500 hPa and the latitudinal west wind in North China are stronger in more sandstorm years and weaker in less sandstorm years. Also the longitudinal general circulation is stronger in more sandstorm years and weaker in less sandstorm years in April. Furthermore, the anomaly of geopotential height on the north side of West Pacific subtropical high in more sandstorm years is contrary to that of the less sandstorm years. It shows that the sandstorms in North China including Ningxia maybe have important relations to low-latitude circulation.
Statistical analyses are made of morning sounding data and ground flash data from June to August 1997 and 1998, the latter was obtained with a 3-station lightning direction finder network installed in Pingliang. The results show that there is good correlation between total ground flash number of convective storm and environmental stratification factors. Atmospheric instability, ambient temperature at altitude with residual instability of 5 degree C and mean relative humidity in the middle layer are important factors, which affect the ground flash frequency of storm, therefore can be used for lightning activity forecast.
The diurnal and seasonal varying characteristics of solar ultraviolet radiation and the ratio ( eta ) of UV to total radiation during the plant growing season were analysed by observed radiation data in the area of Haibei alpine meadow of Qilian mountain in 2000. Ultraviolet radiation was higher in this area. The instant maximum ultraviolet radiation was 77 W times m super(-2), the total maximum ultraviolet radiation in a day was more than 1.8 MJ times m super(-2), the accumulated ultraviolet radiation in a month was 41. 620 MJ times m super(-2) (May) under the real weather condition; the total accumulated ultraviolet radiation was 218. 651 MJ times m super(-2) during the plant growing season (from April to October). The ultraviolet radiation had obvious diurnal and seasonal changing pattern in this area. The diurnal variation of ultraviolet radiation showed as a single peak curve which was related with the total radiation change caused by the change of sun's altitude. The change of eta in a sunny day was hig
Using 0.8 m monthly soil temperature over China and NCAR sea surface temperature data, the land-sea temperature difference of China with the East Asia summer monsoon circulation anomaly index were analyzed initially. The correlation analysis between the East Asia summer monsoon circulation anomaly index and the land-sea temperature difference is notable. And there is distinguished heterogeneity of temporal-spatial distribution of annual variation trend, the distinguished differences exist in correlation distribution in various area. Dynamic analysis further proved the effect of the land-sea temperature contrast on the East Asia Summer monsoon.
By using the results of the radiative energy budget calculated by CRM/CCM3, we studied the seasonal characteristics of the radiative energy budget in earth-troposphere system over the Qinghai-Xizang (Tibet) plateau in winter and summer, the relationship of the radiative energy budget in earth-troposphere system and in earth-atmosphere system, and compared them with that over the plain in the eastern china and the arid region in the north-western china. The cloud radiative forcing and the effects of surface snow-cover on the radiative energy budget in winter, and the contributions of the radiative heating and surface sensible heat flux on the atmospheric heat source over the plateau in summer were discussed.
It is impotent that understanding the parameters of size, density, type and moving of hydrometeors and the process of microphysics change of these hydrometeors within clouds in real-time for weather modification, because these parameters and process reveal the different evolution stages of cloud and precipitation, and they are very useful for estimating the potential increase precipitation of cloud and correctly select the area and time of artificial seeding. It provide the basis for raising effect of weather modification. According to the successful application examples of polarization weather radar, the application problem of the polarization weather radar in weather modification was discussed and especially the methods of identify the type was introduced, density of hydrometeors and monitor the microphysics change process within clouds and estimating the effect after artificial seeding. These methods will be useful for developing ourselves polarization weather radar and raising application level of weather
The Chinese temperature change in the past 2000 years was simulated using the sunspot number and the sunspot cycle length. The trend of simulated temperature, especially in the past 700 years, basically consists with that in the previous studies. In addition, the temperature change over the Northern Hemisphere in the past 120 years is also simulated. The results indicate that the solar activity is the basic factor influencing the temperature change over 10 year time scale, and the action of greenhouse gas may not be overlooked in the past 10 years or more.
Using the Arctic sea-ice data during the period 1953-1998, the sea level pressure in North Hemisphere, and the temperature in 22 stations of North-East China, we analyzed interannual and decadal climatic changes with statistical method. The results are as follows: (1) Obvious reduce of the sea-ice extent was appeared in high latitude. In latitude band to the north of 60 degree N, the variance of the tendency term is larger then 50% of total variance, and larger than period variation. (2) Since 1990, the sea-ice extent decrease was suddenly appeared in the Barents Sea, Greenland Sea, Lablador Sea and to the north of 50 degree N. The Arctic sea ice is very sensitivity to climatic variation of the warm in the world. (3) There exist period variation about 11-15 years in the high latitude ocean, but the sea ice decrease trend is dominant scale. The variance of decrease tend is larger than the period variation in he high latitude ocean, therefor the sea-ice extent decrease is main character in sea-ice variation dur
The variation of East Asia summer monsoon circulation in different periods of ENSO cycle has been analyzed by using meteorological data from NCEP/NCAR and sea surface temperature data from NCAR. The normalized relative intensity, correlation and difference between the circulation of each year and the mean circulation are calculated and their relation with SST anomalies are discussed. The results show that there are obvious annual and decadal changes in East Asia summer monsoon circulation, and there are quiet good negative correlation between the normalized relative intensity of the summer monsoon circulation and SST in East Equatorial Pacific. Especially, the negative correlation between the summer monsoon circulation and SST in March and April is best. The northward extended latitudes of the south wind component at 850 hPa and the meridional circulation in East Asia summer monsoon region in June and July in the cool period of Nino1 + 2 SST is much different from those in the warm period of Nino1 + 2 SST. Th
The test is 6-group time integral in total 4-5 model day for studying the influence of typhoon on subtropical high location and intensity using a shallow water model. The results show that the interactions between typhoon and subtropical high strengthen subtropical high and move it westward, by which potential theories lie in statistic relationship between typhoon action and drought over the east part of northwest China is discussed.
Short-range climatic prediction factors of summer server drought and flood in Guizhou were analysed. The forecast signal of summer sever drought and flood using different combinations of the East Asian and North American troughs in spring obtained five main prediction factors. The two short-range climatic prediction models of summer sever drought and flood in Guizhou are established using the forecast signal and prediction factors. The model forecast results of independent sample in 1997-2000 are satisfactory.
A simplified probability density function (PDF) which is applied to description surface heterogeneity is presented in this paper. The PDF may be directly used in LSPM to carry out the numerical experiment of the land-air physical exchange over subgrid scale area, and the accuracy of the calculated flux is not influenced by this simplified method. Thus, the method has certain generality. But, only a symmetrical simplified PDF distribution is researched in this paper. The cases for calculations of net flux of infrared radiation over the heterogeneous land surface are virified by using the simplified PDF.
The variance similarities of wind velocity (u, v and w), air temperature and air humidity over the grassland surface of Qinghai-Xizang Plateau are analyzed with the data observed in the IOP of GEWEX Asian Monsoon Experiment in Qinghai-Xizang Plateau (GAME/Tibet). In addition, they are compared with the results for the land surface of HEIFE and South China sea surface. Some new concepts about the variance similarity for the high altitude area are obtained.
The sand and dust storm is a disastrous weather phenomenon which often occurs in the northwest of China spring. The diagnostic analysis of a sand-dust storm case, which occurred on 16 May 1995, is studied by using of the PSU/NCAR non-hydrostatic mesoscale model MM5 improved by NMC. The results show that the dust storm is a process of strong frontogenesis when the cold front move to the northwest China region. The sensible heat flux is very greater than the latent heat flux in the PBL air. The case study also indicates that the thermal factor play an important role on the producing process of the dust storm through removing the surface flux from the MM5.
Using the maximum and minimum temperature data from 1961 to 1990 at 70 stations in Northwest China, the departure values are caculated and analysed. The result shows that the temperature change at nighttime in Northwest China is obvious, the variation trend is consistent with the global changs. Moreover, it is found that the maximum and minimum temperature variation in Northwest China is more significant in higher elevation areas, but the maximum and minimum temperature variation in Wulumuqi, Delinha is the best significant in the whole Northwest China in recent 30 years.
The method of remote sensing dust storm with TOMS Aerosol Index(AI) is discussed in this paper. Then this method is used to remote sensing a dust storm occurred on April 15, 1998. The result shows that this method can detect the occurrence, development, transfer and coverage of the dust storm successfully. It is almost not influenced by cloud and is a new and useful method in dust storm research.