1971—2012年青藏高原春季风速的年际变化及对气候变暖的响应

The interannual variation of wind speed in the Tibetan Plateau in spring and its response to global warming during 1971-2012

利用青藏高原73个气象台站的观测资料和日本气象厅JRA-55再分析资料,通过引入年际增量和动能收支方程,分析了1971—2012年高原春季风速的年际变化特征及其对气候变暖的响应。结果表明,在气候变暖的背景下高原风速呈减弱的趋势,随着变暖趋缓风速的变化也趋于平稳。春季高原风速与气温的线性趋势是相反的,但在年际尺度上二者表现出同位相的变化,当青藏高原、中南半岛和印度半岛的地面气温偏高,北亚和东亚地区的地面气温偏低时,有利于高原地面风速增大,反之风速减小。20世纪末青藏高原及其周边地区的升温速率表现为北快南缓,高原南、北侧气温差异减小,而东、西向的气温差异增大,风速趋于减弱;21世纪初高原中部及其南侧地区以升温为主,高原东北侧和东亚地区以降温为主,南、北向气温差异较小,高原风速的变化也趋于平缓,东、西向气温差异有减小的趋势,对应高原东部风速有所增大。青藏高原及其邻近地区的热力差异及其变化速率的不均衡改变了对流层大气的斜压性,进而通过两种途径影响青藏高原的风速,一方面是近地面层气压梯度力的直接作用,另一方面是高层动能向低层的输送。此外,还指出JRA-55再分析风速资料比ERA-Interim和NCEP/NCAR资料在青藏高原的适用性更强。

Based on the daily observed data of 73 stations in the Tibetan Plateau and the JRA-55 reanalysis data,by using yearto-year differences and the equation of kinetic energy budget,the variation of wind speed in the Tibetan Plateau in spring during the period of 1971-2012 and its response to global warming are investigated.It is indicated that there is a statistically significant decrease trend of spring wind speed in the Tibetan Plateau as the climate is warming,while the variation tends to be steady as a hiatus of warming occurs at the beginning of the 21 st century.Although the climatic trend of wind speed is contrary to surface temperature,they exhibit a homothetic phase on an inter-annual scale,in which case the spring wind speed in the Tibetan Plateau increases when the surface temperature increases in the Tibetan Plateau,Indo-China Peninsula and India Peninsula but decreases in the north and east of Asian.A decline trend of spring wind speed in the Plateau at the end of the 20 th century due to more rapid warming in the North Asia than in the South Asia,and an increasing trend of wind speed in the years followed is accompanied by warming in central Plateau and South Asia while cooling in North and East Asia.The asymmetrical thermal condition of both the Tibetan Plateau and its purlieus make an impact on atmospheric baroclinicity by which the variation of wind speed in the Plateau can be influenced in two ways：one is changing directly the pressure gradient force near surface,and another is affecting the transportation of kinetic energy from the upper levels to the middle levels.Meanwhile,the applicability of the three different reanalysis wind data to the Tibetan Plateau is investigated,respectively.