Atmosphere/vegetation feedbacks: A mechanism for abrupt climate change over northern Africa
Atmosphere/vegetation feedbacks: A mechanism for abrupt climate change over northern Africa
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DOI：
10.1029/2007jd009608
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发表时间：
2008-09
影响因子：
--
通讯作者：
C. Patricola;K. Cook
中科院分区：
文献类型：
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作者：
C. Patricola;K. Cook
[1]中全新世的模拟研究和古气候数据提供了北方非洲气候突变的有力证据。区域气候模式模拟被用来隔离和诊断植被和西非夏季风的动态之间的相互作用，在产生气候突变的作用。模拟固定和互动植被分布。当沙漠边界位于17.9°N以南时，模拟的气候对边界纬度基本不敏感。但当沙漠边界位于17.9°N以北仅180公里处时，气候相当敏感，撒哈拉沙漠的夏季降水率高出5倍，非洲东风急流弱50%。规定植被的阈值纬度以北的地方，潮湿的土壤下面的热低，增加了低层潮湿的静态能量和对流不稳定。大气模型异步耦合一个简单的植被模型，使植被响应和影响气候。当模式以10.0°N的沙漠边界为初始值时，得到的平衡植被分布与现在的相似。相比之下，当模型以20.9°N的沙漠边界初始化时，一个新的平衡植被分布结果是撒哈拉中部被植被覆盖。这两种稳定的气候和植被状态以及临界纬度的存在表明，植被（特别是通过土壤水分）和大气（通过非洲东风急流）之间的相互作用可能会造成气候突变。
[1] Modeling studies and paleoclimate data of the mid-Holocene provide strong evidence of abrupt climate change over northern Africa. Regional climate model simulations are used to isolate and diagnose the role of interactions between vegetation and the dynamics of the West African summer monsoon in generating abrupt climate change. Simulations with both fixed and interactive vegetation distributions are included. The modeled climate is largely insensitive to the latitude of the desert border when the border is located south of 17.9°N. But when the desert border is located only 180 km north of 17.9°N, the climate is quite sensitive, with summer precipitation rates a factor of 5 greater over the Sahara desert and an African easterly jet that is 50% weaker. Prescribing vegetation north of the threshold latitude places moist soil beneath the thermal low, increasing the low-level moist static energy and convective instability. The atmospheric model is asynchronously coupled with a simple vegetation model that allows the vegetation to respond to and influence climate. When the model is initialized with the desert border at 10.0°N, the resulting equilibrium vegetation distribution is similar to that of the present day. In contrast, when the model is initialized with the desert border at 20.9°N, a new equilibrium vegetation distribution results in which the central Sahara is vegetated. The existence of these two stable climate and vegetation states and the threshold latitude indicates that interactions between vegetation (specifically through soil moisture) and the atmosphere (through the African easterly jet) can produce abrupt climate change.