青藏高原降水季节分配的空间变化特征

青藏高原是全球气候变化影响的敏感区域。在全球气候变暖的背景下,其水文气候过程发生了显著的变化,直接影响到区域水资源演化。然而,目前对该区域水文气候过程的时空演变规律仍认识不足。本文以青藏高原气象站点降水观测数据为基准,结合水汽通量资料,对13种不同源降水数据集质量进行对比分析;并选用质量较好的IGSNRR数据集识别了青藏高原降水季节分配特征的空间分布格局。结果表明,青藏高原东南、西南以及西北边缘地区降水集中度和集中期较小,夏季降水占全年降水比例不足50%;随着逐渐向高原腹地推进,降水集中度和集中期逐渐增大,雨季逐渐缩短且推迟,雨季降水占全年降水比例逐渐增大。降水季节分配的空间分布格局与水汽运移方向保持一致,即主要是由西风和印度洋季风的影响所致。基于此,识别出西风的影响区域主要位于高原35°N以北,印度洋季风的影响区域主要位于高原约30°N以南,而高原中部(30°N~35°N)降水受到西风和印度洋季风的共同影响。该结果有助于进一步理解和认识青藏高原水文气候过程空间差异性。

Spatial variability in the seasonal distribution of precipitation on the Tibetan Plateau

Hydroclimate process on the Tibetan Plateau (TP) is sensitive to global climate change, and its variability and change would directly affect the evolution of regional water resources in the region. However, there is not enough knowledge of the spatial-temporal characteristics of hydroclimate process on TP so far. In this article, based on the precipitation data measured at 80 meteorological stations and the water vapor flux data over the Tibetan Plateau, the quality of 13 types of remotely sensed and reanalysis-based precipitation datasets was analyzed and compared. The IGSNRR (Institute of Geographic Sciences and Natural Resources Research) precipitation dataset performs the best, and it was used to identify the spatial pattern of seasonal distribution of precipitation on the plateau. The results show that the concentration degree (PCD) and concentration period (PCP) of monthly precipitation were relatively small in the southeastern, southwestern, and northwestern parts of the Tibetan Plateau; correspondingly, summer precipitation accounted for less than 50% of annual precipitation in these regions. As going toward the hinterland of the plateau, the PCD and PCP values increased gradually, the rainy season became shorter and delayed, and the ratio between rainy season precipitation and annual precipitation increased. The spatial pattern of seasonal distribution of precipitation on the plateau was clearly consistent with the direction of water vapor transport, which is mainly determined by the Westerlies and the Indian Ocean monsoon. Based on this, it is identified that precipitation process in the areas north of 35°N was mainly influenced by the Westerlies, but that south of 30°N was influenced by the Indian Ocean monsoon; in the central plateau (30°N~35°N), precipitation process was under the control of both the Westerlies and the Indian Ocean monsoon.The study results are helpful for further understanding the spatial difference in hydroclimate variability on the Tibetan Plateau.