青藏高原湿池的气候特征及其变化

Characteristics of the Moist Pool over the Qinghai-Tibetan Plateau and Its Variation

利用ERA-Interim再分析资料研究了青藏高原湿池的气候特征及其变化,得出以下主要结论:气候平均状态下,6—9月,整个青藏高原上空相对于全球中高层地区而言是一个垂直深厚的高湿区,称之为青藏高原湿池。利用比湿的相对纬偏值研究了高原湿池的垂直分布特征,通过分析发现,6—9月高原湿池相对于全球同高度地区来说是一个垂直深厚的水汽含量最大值区,不同高度层的水汽含量数值可达纬圈平均值的1倍以上到3倍以上;随着高度的增加,湿池内部比湿相对纬偏值大值区明显地向下游地区倾斜延伸,能从高原上空一直向下游延伸到120°E及以东地区,表明了高原上空的大气水汽含量对周边地区的重要影响。夏季高原湿池主要有三种空间变化模态:全区一致型,东西反向型,南北反向型。定义了一个夏季高原湿池强度指数,分析发现1979—2011年以来夏季高原湿池整体表现出显著的增强趋势,在1997年前后发生了年代际变化,33年期间主要具有3~4年、7~8年左右的振荡周期。夏季青藏高原湿池的增强趋势具有明显的区域差异,总体来说,高原西部增湿强于东部,而对高原西部来说,高空增湿强于近地面,增湿幅度最大值区域主要位于400~200 h Pa附近。最后,综合多种再分析资料以及其他研究学者采用探空观测资料、卫星资料的相关研究结果,分析了所选研究资料的适用性,结果表明ERA-Interim再分析资料对于本研究是适用的,基于该资料得出的研究结论是可信的。

Characteristics of the Moist Pool over the Qinghai-Tibetan Plateau and its variation are analyzed by using ERA-Interim reanalysis data from 1979 2011. The result shows that, under the climate average state, to the global middle-high levels, there exists an entire layer of high humidity area over the Tibetan Plateau from June to September, which is known as the Qinghai-Tibetan Plateau Moist Pool in this paper. The vertical features of the Plateau Moist Pool are studied through the relative zonal difference of specific humidity. It is found that, during June and September, the Plateau Moist Pool is a vertical, deep and maximum center of the water vapor content to other parts of the globe at the same latitude. The value of water vapor content at different level inside the Moist Pool is above one time to three times of the zonal average. The high value areas of the relative zonal difference of specific humidity inside the Plateau Moist Pool are obviously extending obliquely to the downstream regions with the increase of the altitude and can reach 120°E and the areas east to it. The empirical orthogonal function （EOF） analysis shows that the Plateau Moist Pool in summer has three modes in spatial distribution as follows： the same signs in the whole, the reverse signs in the western and eastern, and the reverse signs in the southern and northern. The summer intensity index of the Plateau Moist Pool is defined in this paper, and it is found the Moist Pool has a significant increase trend in summer from 1979 to 2011, mainly with the oscillation cycle of 3-4 years and 7-8 years. The Plateau Moist Pool in summer has changed significantly around 1997. Since 1998, the Plateau Moist Pool in summer enhanced significantly, and the increase trend in the western is more stronger than that in the eastern. In the west of the Moist Pool, the increase trend of the upper air is stronger than that near the surface, and the maximum center is located near the 400- 200 hPa. Finally, the results with three kinds of reanalysis data and the relating researches using sounding data and satellite data are integrated to analyze the applicability of the data in the study, and the analysis shows that the data for this study is applicable, and the results based on ERA-Interim reanalysis data in this paper are credible.