Uncertainties due to transport-parameter sensitivity in an efficient 3-D ocean-climate model
Uncertainties due to transport-parameter sensitivity in an efficient 3-D ocean-climate model
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DOI：
10.1007/s00382-004-0508-8
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发表时间：
2005-03-01
期刊：
影响因子：
4.6
通讯作者：
Marsh, R
中科院分区：
文献类型：
--
作者：
Edwards, N;Marsh, R
一个简化的气候模式，其中包括一个完整的3-D，摩擦地转（FG）的海洋组件，但保留了集成效率大大高于现有的气候模式与3-D，连续方程海洋表示（20 kyears的集成可以在一天左右的PC上完成）。该模式还包括一个能量和水分平衡大气和一个动态和热力学海冰模式。使用1，000个模拟的半随机系综，我们解决了参数估计的逆问题以及量化混合和传输参数引起的不确定性的直接问题。我们的研究结果代表了第一次尝试调整一个3-D气候模式的严格定义的程序，但认为整个适当的参数空间。模式估计的纬向翻转和大西洋热量输送是很好地再现，而误差减少只有适度的分辨率增加一倍。模型参数仅受数据的弱约束，而平均误差和参数值之间的强相关性大多被认为是单参数研究的假象，不表明全球模型的行为。因此，单参数敏感性研究可能具有误导性。假设一个单一的、说明性的二氧化碳增加情景。通过对控制极其简单的辐射参数化的多项式系数的分析，在100年强迫作用后，模式预测的仅由输送参数引起的全球平均变暖的扩散约为一度，尽管在一个典型的4,000年集合体模拟中，深太平洋变暖的峰值出现在强迫作用开始后的400年。100年后大西洋倾覆的相应不确定性约为5 Sv，长期崩溃的可能性很小，但不可忽略。
A simplified climate model is presented which includes a fully 3-D, frictional geostrophic (FG) ocean component but retains an integration efficiency considerably greater than extant climate models with 3-D, primitive-equation ocean representations (20 kyears of integration can be completed in about a day on a PC). The model also includes an Energy and Moisture Balance atmosphere and a dynamic and thermodynamic sea-ice model. Using a semi-random ensemble of 1,000 simulations, we address both the inverse problem of parameter estimation, and the direct problem of quantifying the uncertainty due to mixing and transport parameters. Our results represent a first attempt at tuning a 3-D climate model by a strictly defined procedure, which nevertheless considers the whole of the appropriate parameter space. Model estimates of meridional overturning and Atlantic heat transport are well reproduced, while errors are reduced only moderately by a doubling of resolution. Model parameters are only weakly constrained by data, while strong correlations between mean error and parameter values are mostly found to be an artefact of single-parameter studies, not indicative of global model behaviour. Single-parameter sensitivity studies can therefore be misleading. Given a single, illustrative scenario of CO2 increase and. xing the polynomial coefficients governing the extremely simple radiation parameterisation, the spread of model predictions for global mean warming due solely to the transport parameters is around one degree after 100 years forcing, although in a typical 4,000-year ensemble-member simulation, the peak rate of warming in the deep Pacific occurs 400 years after the onset of the forcing. The corresponding uncertainty in Atlantic overturning after 100 years is around 5 Sv, with a small, but non-negligible, probability of a collapse in the long term.