A comparison of downscaled and raw GCM output: implications for climate change scenarios in the San Juan River basin, Colorado
A comparison of downscaled and raw GCM output: implications for climate change scenarios in the San Juan River basin, Colorado
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DOI：
10.1016/s0022-1694(99)00136-5
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发表时间：
1999-11
影响因子：
6.4
通讯作者：
R. Wilby;L. Hay;G. Leavesley
中科院分区：
文献类型：
--
作者：
R. Wilby;L. Hay;G. Leavesley
统计缩小尺度的基本理由是，来自大气环流模式的气候变化实验的原始输出不足以在区域尺度上评估气候变化对陆面过程的影响。这是因为GCM的空间分辨率太低，无法分辨重要的次网格尺度过程(最明显的是与水文循环有关的过程)，而且GCM的输出在单个和次网格框尺度上往往不可靠。通过建立网格尺度环流指数(如大气涡度和散度)与次网格尺度地面预报(如降水)之间的经验关系，统计降尺度被认为是弥合这种空间差异的一种实用手段。这项研究比较了当前和未来三套降雨径流情景。这些情景的构建使用了：(1)统计上缩减的GCM输出；(2)原始GCM输出；以及(3)修正了海拔偏差的原始GCM输出。从英国气象局海洋-大气耦合模式(HadCM2)的输出中提取了大气环流指数和湿度变量，以缩小科罗拉多州圣胡安河流域阿尼玛斯河的日降水量和温度序列。在模拟的三种未来气候情景的积雪和流动状况之间出现了重大差异。总体而言，GCM的原始输出表明，相对于当前条件，冬季/春季积雪和夏季径流的减少幅度大于缩小尺度。需要进一步研究，以确定对其他区域的水资源影响、全球气候变化框架产出和缩小的情景的普遍性。
The fundamental rationale for statistical downscaling is that the raw outputs of climate change experiments from General Circulation Models (GCMs) are an inadequate basis for assessing the effects of climate change on land-surface processes at regional scales. This is because the spatial resolution of GCMs is too coarse to resolve important sub-grid scale processes (most notably those pertaining to the hydrological cycle) and because GCM output is often unreliable at individual and sub-grid box scales. By establishing empirical relationships between grid-box scale circulation indices (such as atmospheric vorticity and divergence) and sub-grid scale surface predictands (such as precipitation), statistical downscaling has been proposed as a practical means of bridging this spatial difference. This study compared three sets of current and future rainfall-runoff scenarios. The scenarios were constructed using: (1) statistically downscaled GCM output; (2) raw GCM output; and (3) raw GCM output corrected for elevational biases. Atmospheric circulation indices and humidity variables were extracted from the output of the UK Meteorological Office coupled ocean-atmosphere GCM (HadCM2) in order to downscale daily precipitation and temperature series for the Animas River in the San Juan River basin, Colorado. Significant differences arose between the modelled snowpack and flow regimes of the three future climate scenarios. Overall, the raw GCM output suggests larger reductions in winter/spring snowpack and summer runoff than the downscaling, relative to current conditions. Further research is required to determine the generality of the water resource implications for other regions, GCM outputs and downscaled scenarios.