青藏高原地表感热通量变化特征及其对气候变化的响应

Characteristics of Surface Sensible Heat Flux over the Qinghai-Tibetan Plateau and Its Response to Climate Change

选取中国气象局在青藏高原(下称高原)地区常规气象观测站点中85个资料连续性较好的站点资料,基于CHEN-WENG感热交换系数方案计算了1981-2014年地表日均感热通量,并用M-K检验法分析了季节平均感热通量和年均感热通量的年际变化特征,结合经验正交函数法EOF(Empirical Orthogonal Function)、Pearson相关法,分析了年均感热通量的时空演变及异常分布特征以及不同地区站点感热通量与气候因子的相关性。结果表明,1981年以来,高原地表感热通量无论在年尺度还是季节尺度上的年际变化都表现为先下降后上升的趋势,其中春季和冬季由下降转变为上升的年份早于夏季和秋季,且夏季上升的幅度是四季中最弱的;1981-2003年间感热通量下降主要与地气温差和平均风速的减小有关,而2004-2014年间感热通量的上升主要与地气温差的显著增大有关。空间上,各站点感热通量的上升或下降并不同步,但存在一定的相互联系,感热通量上升的站点主要位于青海省;感热通量与各气候因子的相关性有明显的时空差异,整体上受地表温度影响显著,与地表温度变化呈正相关;与降水、日照时数、风速等气候因子的相关性在年尺度上存在较大的空间差异,在季节尺度上,感热通量与气象因子的季节相关性较好,尤其是夏季,感热通量与降水呈反相关,与日照时数、风速和气温呈正相关,其次是春季,秋、冬季相关性较差。

Using the conventional meteorological observation data of the Qinghai-Tibetan Plateau （QTP） offered by the China Meteorological Administration （CMA）, the average daily sensible heat flux from 1981 to 2014 was calculated on the basis of 85 stations which have continuously better data and the CHEN-WENG heat exchange parameterizeu scheme. The characteristics of seasonal average and annual average sensible heat flux and the con- nections between them and climate factors which include surface temperature, air temperature at 1. 5 m, wind speed, precipitation and sunshine duration were analyzed by using the methods of Mann-Kendall test, empirical orthogonal function （EOF）, and Pearson correlation. The results showed that both seasonal average and annual average sensible heat flux had risen after falling for more than 20 years since 1981 and the time of change hap- pened earlier in winter and spring than in summer and autumn. The decline of sensible heat flux between 1981 and 2003 was mainly caused by the decrease of land-air temperature difference and the average wind speed, while the raise between 2004 and 2014 was mostly due to the significantly increase of land-air temperature differ- ence, and not all stations had the same pace in decrease or increase. The stations which increased mostly locate in Qinghai province. In addition, the correlations between the sensible heat flux and climate factors are obviously temporal and spatial different. Almost the whole stations are significantly influenced by the surface temperature with positive correlation with sensible heat flux, while other climate factors are probably tend to have a better correlation with sensible heat flux in the growing season than in the whole year, especially in summer when the sensible heat flux mostly has a negative correlation with the precipitation and a positive correlation with wind speed, air temperature at 1. 5 m and sunshine duration.