Simulating Study On The Characteristics Of Climate Change And Over Tibet Plateau

In the past several decades, the Tibetan Plateau climate has significant change, mainly as follows:the temperature increased, and the minimum temperature rose faster than the maximum temperature, there is an asymmetric change between minimum temperature and maximum temperature; the precipitation and snow also increased, and the frozen ground was degradation; the variables change has seasonal differences and regional differences. In this paper, we made a detailed analysis and research on the climate change by EOF, wavelet analysis and mutation; and calculated the relationships between climate change and atmospheric circulation and sea surface temperature in the past few decades over Tibetan Plateau; regional climate model (RegCM3) was used over Qinghai-Tibet Plateau for the simulation analysis, the simulation results are revised and the climate change of next 90 years were predicted over Tibetan Plateau.Firstly, we analyze the changes of temperature, precipitation, snow and permafrost over Tibetan Plateau in the past 46 years by EOF, wavelet analyse and mutation. The results showed that:1) The temperature, minimum temperature and maximum temperature increased in the past few decades over Tibetan Plateau, and there was a significant change around 1986, the rate of temperature increased of northern was greater than the southern over Tibetan Plateau; the precipitation also increased, the rate of precipitation increased was larger in southern; snow cover increased, and has a significant increased after 1986, snow decreased in the Tarim Basin West, the Hexi Corridor region, Tanggula pulse Bayan Har Mountains and increased in the Junggar Basin, Tianshan Mountains, the Tarim Basin, the southern Tibetan Plateau, the huge area of Qilian Mountains; the permafrost degradated, the sensitive area of degradation mainly in the seasonal frozen area; the regional change of snow and permafrost were more sensitive than temperature and precipitation.2) The principal component analysis of temperature and precipitation showed that:the first eigenvector of temperature showed the same feature which was consistent positive, indicating that the change of temperature was consistent, the corresponding time coefficients increased, the time coefficients has a obvious change around 1986; the second eigenvector of temperature showed a northwest-southeast (positive -negative) distribution pattern in the study area, but no significant rised or declined in the corresponding time coefficients; the first eigenvector of precipitation was positive, indicating that the change of precipitation was consistent, the corresponding time coefficient rose, and the dividing point was also 1986; the second eigenvector was negative in the study region, the corresponding time coefficient is not significantly increased or decreased.3) The mutation and cycle analysis of temperature and precipitation showed that the temperature mutation started in 1986, which was corresponding to the first time coefficient of the temperature of EOF analysis, while the precipitation was not mutation; the wavelet analysis of temperature and precipitation showed that, quasi-3-year cycle was more obvious at analysis duration, the oscillation about 5-8 years was more remarkable duiring 1980 to 1990.The changes of temperature and precipitation over Tibetan Plateau was closely related to atmospheric circulation, there was a positive correlation in the atmospheric circulation of the northern Tibetan Plateau, North Pacific, Western Pacific and warm pool, and a negative correlation in the north Tibetan Plateau, corresponding to the westerly jet and the equatorial easterly jet. A significant association among Tibetan Plateau warming and tropospheric adjustment of the whole layer of the atmospheric circulation and the atmospheric circulation of the Pacific warm pool, accompanied by the changes of geopotential height field and the water vapor. The westerly jet in north Qinghai-Tibet Plateau enhanced, easterly jet in south Qinghai-Tibet Plateau weaked, the east wind of the low latitudes and western Pacific weaked, the geopotential height of the equatorial and Tibetan Plateau increased, the water vapor increased in the Western Pacific and decreased in The Indian Ocean and Pacific water.There was a high positive correlation between temperature and precipitation over Tibetan Plateau and sea surface temperature of the Western Pacific and Indian Ocean. The numerical results revealed that the increase of SST would cause the changes of the mid-latitude jet stream and low-latitude westerly wind. However, the warm pool SST and the temperature over Tibetan Plateau was not directly related, the results further showed that the warm SST caused changes in the intensity and scope of tropical easterly wind, the location and intensity of tropical easterly wind caused the entrance (the north ridge of Xinjiang) of mid-latitude westerly jet and the easterly wind over India continent by some mechanism. The easterly and westerly jet changes of middle and low latitudes caused the changes of the minimum temperature and temperatureover the Tibetan Plateau.The simulation study of Tibetan Plateau climate using RegCM3 found that, compared to MICRO3.2(SRES A1B), RegCM3 significant improvemented the GCM simulation results. The distribution of temperature and precipitation on the details of the simulation better than GCM simulation results in the Tianshan, Tarim Basin, Junggar Basin, the Kunlun Mountains, Qinghai-Tibet Plateau Gangdise Mountains. Removed to improve GCM simulation results, the underlying surface topography of the regional model was still needed to be studied, this paper results showed that the simulation of winter precipitation was better than the two transition seasons (spring and autumn), which has soil freezing- thawing, snow and snowmelt over Tibetan Plateau.Although the totally featurs simulated was consistent with observed over Tibetan Plateau, but there was a systematic deviations in temperature and precipitation, especially in complex terrain, simulated results has error. Therefore, the simulation results are revised, the revised results showed that the absolute error of temperature and precipitation decreased after revising, the correlation coefficient increased. In the future 90 years, the climate warming is dominant, the temperature increase with 0.28癈/10a, and there is a turning point in 2052; precipitation increase, and there is a turning point in 2047. The temperature increase throughout the Tibetan Plateau, increase of temperature in northern is larger than in southern, north of Tianshan Mountains is a high value area. The precipitation increase over Qinghai-Tibet Plateau, decrease in the Taklimakan Desert, the Junggar Basin and the Brahmaputra fed up with pagodas, increase of temperature in sorthern is larger than in nouthern. Snow decrease over the Tibet Plateau, there is a high value of decreasing in the Tianshan, Kunlun, Qilian Mountains, Bayan Har, Gangdise mountains, the Nu and Jinsha River in the future 90 years.