Local atmospheric decoupling in complex topography alters climate change impacts
Local atmospheric decoupling in complex topography alters climate change impacts
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DOI：
10.1002/joc.2007
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发表时间：
2010-10-01
期刊：
影响因子：
--
通讯作者：
Unsworth, Michael H.
中科院分区：
文献类型：
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作者：
Daly, Christopher;Conklin, David R.;Unsworth, Michael H.
在许多山谷中，特别是在夜间和冬季，会发生冷空气的排水和汇集。与频繁冷空气汇集相关的局部气候制度对物种物候、分布和多样性具有重大影响。然而，人们对冷空气排放和汇集的程度和频率将如何响应气候变化知之甚少。有证据表明，由于冷池与自由大气解耦，这些局部气候的响应方式可能与粗网格环流模式估计的区域尺度气候不同。事实上，最近的研究表明，历史变化（天气条件的频率）在地面气候变化中产生了复杂的空间变化。在俄勒冈瀑布的山地地形中，我们发现，在相对暴露的山坡和山脊顶部位置，气温与700 hpa水平的天气环流模式变化高度耦合，而在隐蔽的山谷底部，夜间和冬季的冷空气聚集导致气温在很大程度上与700 hpa的变化脱钩，并且相对不敏感。结果是一个复杂的温度景观，由陡峭的时间变化梯度组成。主要受海拔梯度和地形位置的控制。当将预估的气候变暖2.5℃与天气环流频率分布的可能变化相结合时，在间隔较近的地点模拟的温度变化相差很大（最多相差6℃），其差异等于或超过了实际的区域温度变化。因为冷空气汇集和随之而来的大气解耦发生在许多山谷中，特别是在高纬度地区。这一现象可能是了解气候变化对山区影响的一个重要考虑因素。版权所有(C) 2009皇家气象学会
Cold air drainage and pooling occur in many mountain valleys, especially at night and during winter. Local climate regimes associated with frequent cold air pooling have substantial impacts on species phenology, distribution and diversity. However, little is known about how the degree and frequency of cold air drainage and pooling will respond to a changing climate. Evidence suggests that, because cold pools are decoupled from the free atmosphere, these local climates may not respond in the same way as regional-scale climates estimated from coarse-grid general circulation models. Indeed, recent studies have demonstrated that historical changes M the frequency of synoptic conditions have produced complex spatial variations in the resulting climatic changes on the ground. In the mountainous terrain of the Oregon Cascades, we show that, at relatively exposed hill slope and ridge top locations, air temperatures are highly coupled to changes in synoptic circulation patterns at the 700-hPa level, whereas in sheltered valley bottoms, cold air pooling at night and during winter causes temperatures to be largely decoupled from, and relatively insensitive to, 700-hPa How variations. The result is a complex temperature landscape composed of steep gradients in temporal variation. controlled largely by gradients in elevation and topographic position. When a projected climate warming of 2.5 degrees C was combined with likely changes in the frequency distribution of synoptic circulation, modelled temperature changes at closely spaced locations diverged widely (by up to 6 degrees C), with differences equalling or exceeding that of the imposed regional temperature change. Because cold air pooling and consequent atmospheric decoupling occur in many mountain valleys, especially at high latitudes. this phenomenon is likely to he an important consideration in understanding the impacts of climate change in mountainous regions. Copyright (C) 2009 Royal Meteorological Society