青藏高原大气蕴含潜热时空分布特征研究

Study on Temporal Spatial Distribution Characteristics of Latent Heat over the Qinghai-Tibetan Plateau

利用ECMWF(欧洲中期天气预报中心)月平均比湿资料,通过直接对比湿q进行多年平均计算、气候倾向率分析、EOF分解等,研究了1979-2015年青藏高原(下称高原)地区大气蕴含潜热的时空分布特征及年际、年代际变化特征。结果表明,高原大气蕴含潜热从低层向高层逐渐减少,且夏季蕴含潜热最多,其次为春、秋,且两季分布特征大致相似,冬季蕴含潜热最少,各季大值均集中在高原东南部及南部;蕴含潜热整体呈增长的趋势,夏季增长最快,冬季最慢;高原西部和云贵高原地区大气蕴含潜热均有不同程度的减小,夏季减小最快,冬季减小最慢;EOF分析中,各积分层以及整层[地表到500 hPa积分(第一积分层);500~400 hPa积分(第二积分层);400~300 hPa积分(第三积分层);地表到300 hPa积分(整层)]在第一模态下均大致呈正分布;在第二模态下均呈“正-负”的偶极子分布(其中第一积分层和整层为西南—东北“正-负”分布,其余两层为东—西“正-负”分布),说明蕴含潜热在这两种分布状态中的变化趋势均存在反相关系);在第三模态下均在西北—东南方向为“正-负-正”的分布。各积分层以及整层除第二模态年际变化相对明显外,其他两个模态年际变化均不明显。

Using monthly mean specific humidity reanalysis data provided by ECMWF (European Centre for Medium-Range Weather Forecasts). We study the spatio-temporal distribution, interannual and interdecadal variation of latent heat from 1979-2015 over Qinghai-Tibetan Plateau (QTP) by using the methods such as annual average analysis of q, climate tendency rate analysis of q at each layer, EOF analysis and so on. The results show that latent heat over QTP decreases from lower layer to upper layer, the amount of latent heat is the most in summer, the second is autumn, distribution characteristics of spring and autumn are similar, and the amount of latent heat is the least in winter. The max values are all located in the southeast and the south side of QTP;Specific humidity increases sharply in summer and the region where specific humidity grow fastest is located in the northeast of QTP. Specific humidity grows slowest in winter and the fastest growing area is also located in the northeast. Generally speaking, there is a positive growth rate of specific humidity over QTP, but the growth rate of specific humidity is negative in the west of QTP and the Yunnan-Guizhou Plateau at lower layers, and that decreases fastest in summer;As for the EOF analysis, the first EOF mode of the four integral layers[from the surface to 500 hPa (the first integral layer), from 500 hPa to 400 hPa (the second integral layer), from 400 hPa to 300 hPa (the third integral layer), from the surface to 300 hPa (the whole integral layer)] generally shows a positive distribution. And the second EOF mode shows a "positive negative" dipole distribution. The third EOF mode of the four integral layers is a "positive-negative-positive" distribution, and the inter-annual variation of all EOF modes are not obvious except the second EOF mode.