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Through analyzing the yearly average data obtained from 123 regular meteorological observatories located in the Tibetan Plateau (T-P), this article studies the characteristics of climate change in T-P in the last 40 years. From the distribution of the linear trend, it can be concluded that the southeastern part of T-P becomes warmer and wetter, with an obvious increase of rainfall. The same characteristics are found in the southwestern part of T-P, but the shift is smaller. In the middle of T-P, temperature and humidity obviously increase with the center of the increase in Bangoin-Amdo. The south of the Tarim Basin also exhibits the same tendency. The reason for this area being humid is that it gets less sunshine and milder wind. The northeastern part of T-P turns warmer and drier. Qaidam Basin and its western and southern areas are the center of this shift, in which the living environment is deteriorating. Analyzing the characteristics of the regional average time series, it can be found that in the mid-1970s, a significant sudden change occurred to annual rainfall, yearly average snow-accumulation days and surface pressure in the eastern part of T-P. In the mid-1980s, another evident climatic jump happened to yearly average temperature, total cloud amount, surface pressure, relative humidity, and sunshine duration in the same area. That is, in the mid 1980s, the plateau experienced a climatic jump that is featured by the increase of temperature, snow-accumulation days, relative humidity, surface pressure, and by the decrease of sunshine duration and total cloud amount. The sudden climatic change of temperature in T-P is later than that of the global-mean temperature. From this paper it can be seen that in the middle of the 1980s, a climatic jump from warm-dry to warm-wet occurred in T-P.

Using the dataset of 1998 TIPEX, the data of 6 automatic heat balance observational stations (AWS) from May to August 1998, a dataset of 52 surface observational stations over the Tibetan Plateau (TP) and its adjacent region, the daily rainfall amounts from about 300 stations in China, the outgoing longwave radiation (OLR) data received by the National Satellite Meteorological Center(NSMC) of China, and TBB data from GMS remote sensing of Japan, the characteristics of the seasonal variation of the surface total heating over TP and its surrounding area in summer 1998 and its relationship with the convection over the subtropical area of the western Pacific is studied in this paper. The results show that the surface total heating over TP had a close relationship with the onset of the rainy season, and after the onset of the rainy season, the regional mean surface total heating over TP decreased distinctly. Furthermore, the regional mean surface total heating over TP had very good negative correlation with TBB over the subtropical area of the western Pacific along 20–30°N, which shows that the surface total heating over TP was able to affect the convection over the subtropical area of the western Pacific.

A preliminary study is given on the bulk transfer coefficients and surface fluxes over the Tibetan Plateau, on the basis of data from four sets of AWS in Tibet from July 1993 to March 1999 according to P.R. China-Japan Cooperation Research Project on Asian Monsoon Mechanism. The surface roughness lengths are decided by the logarithmic wind law under neutral conditions using the least square method, the value at each station is scattered and seasonal mean is obtained. The bulk transfer coefficients for momentum and heat are estimated using the flux-profile relationships, means of the bulk transfer coefficients for momentum and heat are 4.44×10-3∼4.75×10-3 and 6.02×10-3∼6.40×10-3, respectively. The surface fluxes of momentum, sensible heat and latent heat are computed by bulk transfer formulations, sum of sensible and latent heat at each station is about 100 W/m2. In addition, diurnal and seasonal variations of the bulk transfer coefficients and surface fluxes as well as the relations among bulk transfer coefficients, bulk Richardson number and surface wind speed are discussed in detail using a composite method. A possible relationship between surface fluxes and monsoon over the Tibetan Plateau is suggested, i.e., the surface heat transfer on the Eastern Tibetan Plateau is dominated by the sensible heat flux and latent heat flux jointly in the pre-monsoon and latent heat flux mainly during the monsoon.

Estimates of the time and space variability of the atmospheric heat source over Tibet are presented for the summer of 1979. These estimates rely on new data from the People's Republic of China allowing a better assessment of the surface heat fluxes, and on new satellite data from Nimbus-7 giving the radiation balance at the top of the atmosphere. The estimates of the atmospheric heat source turned out to be considerably smaller than those provided earlier in the literature, mainly because of different assumptions of the drag coefficient. The atmospheric heat source over Tibet is mainly modulated by the release of latent heat. Over the southeastern and southwestern plateau regions the heat source appears to be in phase with the precipitation yield of the Indian summer monsoon, whereas central Tibet reveals an out-of-phase behavior. Over western Tibet there appears to be hardly any net import of moisture from outside the region, whereas the maintenance of the hydrological cycle over eastern Tibet requires moisture flux convergence from outside the region of up to 40 percent of the mean rainfall, in agreement with what is known about the surface hydrology of Tibet.

The atmospheric heat source strength over western Tibet has been computed for the period beginning with the last ten days in May, 1979 and extending through August, 1979. Our results show a significantly smaller heat source than that obtained by other authors. The discrepancy is mainly due to adjustments in the drag coefficient suggested by observations and numerical modeling experiments. We subdivided western Tibet into northern and southern parts. In the north sensible heating,SH, provides the dominant input into the atmospheric heat source, whereas in the southern part latent heat,LP, offers a significant contribution after the start of the rainy season.

For better understanding the mechanism of monsoon formation and designing the numerical simulation of the general atmospheric circulation, a new approach of calculating atmospheric radiation is proposed to investigate the distribution of the atmospheric heat source, and the budget of heat component is recalculated. The results show that there is a tremendous atmospheric heat source region over central India, northeast of the Bay of Bengal, east of the South China Sea and about 10 °N at the west Pacific, among which the heating center with a maximum heating rate of 8 °C/day is located over the Bay of Bengal and the average rate in the Plateau is about 1 °C/day.