区域气候模式(PRECIS)对黄土高原降水模拟能力的评估

黄土高原水资源短缺,严重制约其社会经济发展;全球变暖背景下,需要对该区水资源状况进行详细的影响评估。区域气候模式可提供气候变化情景下的数据,但模式的模拟精度直接影响评估结果。为此利用ERA40再分析数据作为边界条件驱动PRECIS,从降水频率、降水量和极端事件3个方面,评估了PRECIS对黄土高原1960—2000年降水的模拟能力。结果表明,PRECIS能够模拟出各要素东南-西北方向变化的空间分布特征,还可模拟出整体的时间变化趋势,其中对非汛期的模拟较好,而汛期降水日数和降水量等被严重高估;并且涉及干旱的指标普遍偏低;还发现对于极端降水事件模式对强度指标的模拟能力优于频率指标。因此,还需要进一步探讨订正方法,才能更好的应用于气候变化水文效应评估。

Verifying the applicability of PRECIS-simulated precipitation on the Loess Plateau

The Loess plateau is primarily a rain-fed agricultural area in China, and water is one of the main factors affecting agricultural production in the region. As a result of global warming, precipitation is a critical variable affecting the water cycle and plant growth. The simulation accuracy of precipitation directly influences climate change projections and impact assessments. The regional climate model, PRECIS (Providing Regional Climates for Impacts Studies), has been widely used for climate change projection; however, its capability for impact studies has been rarely assessed. Using ERA40 reanalysis data as the boundary conditions, precipitation on the Loess Plateau during 1960-2000 was simulated and its applicability was evaluated through comparison with the observed precipitation frequency, amount, and extreme events. PRECIS simulated the spatial distribution of precipitation changes along the southeast-northwest direction; however, the wet days and precipitation amounts were overestimated by 1.8 times the recorded amounts, and the indices related to the drought index were greatly underestimated. PRECIS simulated the low values more accurately than the high values of each index. The model simulated the temporal changes more accurately in the dry season due to an overestimation of wet days and precipitation in the flood season. For extreme indices, PRECIS simulated intensity-related indices more accurately than those related to frequency. Overall, PRECIS cannot be directly used to assess the impacts of climate change on hydrology, and the model calibration method should be discussed further.