基于微波探测资料的全球大气亮温长期变化趋势研究

本文使用1978—2013年美国大气海洋局NOAA研发的STAR V3.0版本的MSU/AMSUA逐月亮温格点数据,引入集合经验模式分解(EEMD)方法,研究了高空大气亮温的非线性变化趋势,尤其注重亮温气候趋势的时间演变特征,并与传统线性回归(CLR)方法做了对比研究。结果表明,在全球对流层增温、平流层降温的大背景下,基于EEMD的亮温非线性趋势演变特征表现为:近10 a对流层中、高层全球平均增暖趋势放缓,甚至出现轻微的降温趋势;北半球对流层增暖首先出现在北极,随后向低纬度方向延伸。北极对流层增暖向上影响高层大气,最高可以扩展到平流层低层。南半球对流层中低纬度地区受北半球大气影响也出现增温。另外,近10 a南极地区出现显著的独立增温现象。平流层变冷北半球最早从中纬度地区开始发生,变冷逐渐增强的同时向极地和低纬度两侧扩张。南极上空平流层大气早期也出现显著变冷,然而随着2000年以后南极大范围增暖,平流层变冷逐渐转移到中低纬地区。

Long-term trends of brightness temperature based on microwave sounding data

By using the STAR MSU/AMSU version 3.0 monthly brightness temperature data developed by National Oceanic and Atmospheric Administration(NOAA) during 1978 to 2013, with the Ensemble Empirical Mode Decomposition(EEMD) method, the nonlinear trend of monthly global mean brightness temperature of the upper air and time evolution characteristics of brightness temperature climatic trend are estimated, moreover, the result is compared with that using the Classical Linear Regression(CLR) method. Results show that under the background of warming troposphere and cooling stratosphere, the nonlinear evolution features of the brightness temperature derived by EEMD reveal that the warming trend of the troposphere at mid-high level slows down and even there exists a reverse trend in recent years. The tropospheric warming first occurs in the Arctic, and then gradually extends to the lower latitudes in the northern hemisphere. The tropospheric warming in the polar region even extends up to the lower stratosphere. In the southern hemisphere, the troposphere warming in the mid-low latitude is mainly affected by the atmospheric circulation. In addition, there has been an independent warming phenomenon in the Antarctic in recent decade. The stratospheric cooling first appeared in the middle latitude and then extended gradually equatorward and poleward. A significant cooling of the stratosphere has been found in the Antarctic, and then extended to the lower atmosphere. However, since 2000, with the appearance of a more extensive warming in the Antarctic, the stratosphere cooling has been gradually moving to the middle and low latitude regions.