中国西部冬季降水年际与年代际变化的水汽输送差异

中国西部地区是著名的气候脆弱区,降水的多寡对其影响十分巨大。尤其是在全球变暖的背景下,西部地区的增暖、增湿异常显著,随之而来的西部地区气候变化也越来越受到关注。本研究主要分析了中国西部地区冬季降水的时空变化特征,结果表明:该地区冬季降水的最主要模态具有全区一致变化的特点,并且在20世纪80年代中期出现了一次显著的年代际突变,突变之后中国西部地区冬季降水明显增多。大气环流和水汽输送的分析结果显示,引起西部地区冬季降水年际和年代际变化的因子有着明显的差异。其中西风带水汽输送是影响西部地区冬季降水年代际变化的主要原因;而影响西部地区冬季降水年际变化的水汽则主要来自于阿拉伯海西南向的水汽输送;而且在不同年代际背景下,影响中国西部地区冬季降水的主要水汽输送通道是一致的。这些说明西部降水的预测必须要分不同时间尺度进行研究,短期气候预测需要综合考虑年际变化、年代际变化以及气候长期变化背景才会更为合理和可行。另外,西部降水年际变化因子在不同年代际背景下的稳定性,为建立该地区持续稳定的年际预测模型奠定了科学基础。

Difference of Water Vapour Transportation in the Interannual and Decadal Variations of Winter Precipitation over Western China

Western China is a highly climate-sensitive area, over which anomalous precipitation plays an important role. In this study, the temporal and spatial distribution features of winter precipitation over Western China are analyzed. The results show that the primary mode of winter precipitation over this area showed a homogeneous change and it underwent a significant decadal change around the mid-1980s, after which winter precipitation suddenly increased compared to the amounts before. Analyses of atmospheric circulation and water vapor transportation indicate that different factors influenced decadal variation and inter-annual variation of winter precipitation over Western China. The main cause for the decadal variation was westerly water vapor transportation at mid-to-high latitude; while the primary reason for the interannual variation was southwesterly water vapor transportation from the Arabian Sea. In two different decades, the channel of water vapor transportation for winter precipitation over Western China was consistent. These findings indicate that prediction of winter precipitation over Western China should be studied on different timescales, and it would be more reasonable to synthetically consider the interannual variation, decadal variation, and even long-term variation in climate predictions. In addition, the consistence of interannual influential factors in different decades provides a scientific basis for development of a stable interannual prediction mode for winter precipitation in Western China.