Land-Ocean Warming Contrast over a Wide Range of Climates: Convective Quasi-Equilibrium Theory and Idealized Simulations
Land-Ocean Warming Contrast over a Wide Range of Climates: Convective Quasi-Equilibrium Theory and Idealized Simulations
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DOI：
10.1175/jcli-d-12-00262.1
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发表时间：
2013-06-01
影响因子：
4.9
通讯作者：
O'Gorman, Paul A.
中科院分区：
文献类型：
--
作者：
Byrne, Michael P.;O'Gorman, Paul A.
在全球变暖的模拟和观测中，陆地表面温度的上升速度高于海洋。此前有人提出，由于陆地可用水分有限，这种陆地-海洋变暖对比与陆地和海洋递减率的不同变化有关。这里发展了陆地-海洋变暖对比的简单理论，其中递减率是由对流准平衡的假设决定的。该理论预测，随着气候变暖或陆地变得更加干旱，陆地和海洋温度之间的差异会单调增加。然而，在相对湿度恒定的情况下，陆地和海洋的差异变暖比率随温度非单调变化，并在大约 290 K 处达到最大值。该理论适用于理想化大气环流模型的模拟，其中大陆构造和气候系统地变化。当气候因长波光学厚度的变化而变化时，模拟的变暖对比仅限于 50 度以下的纬度。变暖对比取决于土地干旱度，并且地带性陆地带的变暖对比大于地带性范围有限的大陆。在高纬度地区，陆地表面干旱可能会导致陆地-海洋温度对比，但其幅度相对较小。尽管包含陆地-海洋反照率对比会导致理论高估陆地温度，但该理论总体上很好地描述了变暖对比。讨论了该理论的扩展，包括大规模涡流对温带热分层的影响，并解释了表面空气和表面皮肤温度的变暖对比。
Surface temperatures increase at a greater rate over land than ocean in simulations and observations of global warming. It has previously been proposed that this land-ocean warming contrast is related to different changes in lapse rates over land and ocean because of limited moisture availability over land. A simple theory of the land-ocean warming contrast is developed here in which lapse rates are determined by an assumption of convective quasi-equilibrium. The theory predicts that the difference between land and ocean temperatures increases monotonically as the climate warms or as the land becomes more arid. However, the ratio of differential warming over land and ocean varies nonmonotonically with temperature for constant relative humidities and reaches a maximum at roughly 290 K.The theory is applied to simulations with an idealized general circulation model in which the continental configuration and climate are varied systematically. The simulated warming contrast is confined to latitudes below 50 degrees when climate is varied by changes in longwave optical thickness. The warming contrast depends on land aridity and is larger for zonal land bands than for continents with finite zonal extent. A land-ocean temperature contrast may be induced at higher latitudes by enforcing an arid land surface, but its magnitude is relatively small. The warming contrast is generally well described by the theory, although inclusion of a land-ocean albedo contrast causes the theory to overestimate the land temperatures. Extensions of the theory are discussed to include the effect of large-scale eddies on the extratropical thermal stratification and to account for warming contrasts in both surface air and surface skin temperatures.