青藏高原感热通量的时空变化及其对我国夏季区域降水的影响

发布时间：2018-10-05 08:25

【摘要】：在地气相互作用时,能量、物质和动量交换对全球大气环流及气候波动产生深远影响。其中,在近地层,感热通量通过湍流形式与大气发生地气相互作用。由于青藏高原平均海拔大于4000米以上被称为地球的"第三极",其矗立在高空中强大的感热加热称为感热驱动泵。高原的热力作用是亚洲季风更替的重要因子,它对东亚地区降水的重要性毋庸置疑。同时,在季风转变期间,高原感热通量作为加热高原及周边地区大气最重要的因子之一,对我国夏季降水的预测有重要意义。根据高原下垫面植被覆盖率差异,我们将海拨大于3000m青藏高原划分为7个子区域(A区一G区)。同时,利用青藏高原地区78个站点的观测资料、全国830个站点的观测资料,及NCEP提供的全球17层的资料,计算了高原和各分区感热通量。通过小波分析、相关分析、合成分析、EOF等分析方法,研究了高原感热通量的时空分布特征及变化规律,高原4月感热通量与我国夏季降水的关系,以及高原4月感热通量与我国长江以南夏季降水的关系。高原感热通量的时空变化特征。高原年平均、春季和夏季感热通量的变化周期均为3到4年,秋季、冬季为2到3年;高原最强感热加热位于在喜马拉雅地区,最弱加热区域位于高原西北部A区;高原春秋季节感热通量的空间分布均匀,冬夏季节有明显的梯度分布,夏季呈现自东向西的梯度,而冬季方向相反。高原10m风速的极值中心随季节北上南撤变化与地气温差的强弱变化共同决定了感热通量的季节变化。高原4月感热通量与我国长江以南夏季降水的关系。4月喜马拉雅地区(高原E区)是影响长江以南夏季降水的关键区,4月关键区感热通量和长江以南地区夏季降水具有相反的变化趋势,即负相关关系,且均有4年主周期和8年副周期,在1998、2011年前后分别出现转折。分析其降水异常的机理发现,高原关键区4月感热通量偏弱时,长江以南地区处于深槽槽前,配合有切变线系统,斜压性很强,空气相对湿度很大,有利于长江以南地区降水。反之,不利于降水。
[Abstract]:Energy, matter and momentum exchange have a profound effect on the global atmospheric circulation and climate fluctuations during the earth atmosphere interaction. In the near layer, sensible heat flux interacts with the atmosphere through turbulence. Because the Qinghai-Tibet Plateau has an average elevation of more than 4000 meters, it is called the "third pole" of the earth, and its powerful sensible heat heating in the upper air is called the sensible heat driving pump. The thermal action of the plateau is an important factor in the turnover of the Asian monsoon, and its importance to the precipitation in East Asia is beyond doubt. At the same time, during the monsoon transition, the sensible heat flux of the plateau is one of the most important factors in heating the atmosphere of the plateau and its surrounding areas, which is of great significance to the prediction of summer precipitation in China. According to the difference of vegetation coverage on the underlying surface of the plateau, we divide the Qinghai-Tibet Plateau over 3000m into seven sub-regions (area A and G). At the same time, the sensible heat fluxes of the plateau and regions are calculated by using the observational data of 78 stations in the Qinghai-Xizang Plateau, the observational data of 830 stations in China and the global 17 layers data provided by NCEP. By means of wavelet analysis, correlation analysis, synthetic analysis and EOF, the temporal and spatial distribution and variation of sensible heat fluxes over the plateau are studied, and the relationship between the sensible heat fluxes of the plateau and summer precipitation in China in April is studied. And the relationship between the April sensible heat flux and summer precipitation south of the Yangtze River in China. Temporal and spatial characteristics of sensible heat flux over the plateau. The mean annual, spring and summer sensible heat fluxes vary from 3 to 4 years in autumn and 2 to 3 years in winter, and the strongest sensible heat in the plateau lies in the Himalayan region and the weakest in the A region in the northwest of the plateau. The spatial distribution of sensible heat flux in spring and autumn is uniform and the gradient distribution is obvious in winter and summer. The gradient in summer is from east to west, but the direction is opposite in winter. The seasonal variation of sensible heat flux is determined by the extreme center of 10 m wind speed over the plateau and the variation of the temperature difference between the north and the south. The relationship between the April sensible heat flux of the plateau and the summer precipitation south of the Yangtze River in China. The Himalayan region (Plateau E region) in April is the key area affecting the summer precipitation in the south of the Yangtze River, and the sensible heat flux in the key area in April and the summer fall in the south of the Yangtze River. Water has the opposite trend. There is a negative correlation, and there are 4 years main cycle and 8 years sub period, respectively, and turn around in 1998 and 2011. By analyzing the mechanism of precipitation anomaly, it is found that when the sensible heat flux in the key area of the plateau is weak in April, the area south of the Yangtze River is in front of the deep trough with shear line system, the baroclinic is very strong, and the air relative humidity is very high, which is favorable to precipitation in the south of the Yangtze River. On the contrary, it is unfavorable to precipitation.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P426.6;P461

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