Global scale palaeoclimate reconstruction of the middle Pliocene climate using the UKMO GCM: initial results
Global scale palaeoclimate reconstruction of the middle Pliocene climate using the UKMO GCM: initial results
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DOI：
10.1016/s0921-8181(00)00028-x
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发表时间：
2000-08
期刊：
影响因子：
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通讯作者：
A. Haywood;P. Valdes;B. Sellwood
中科院分区：
文献类型：
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作者：
A. Haywood;P. Valdes;B. Sellwood
本文概述了一项新的上新世（约3 Ma）气候模拟研究的结果。这项工作是使用英国气象局GCM （UKMO， 3.0版）进行的，这是一个网格点模型，使用纬度为2.5°，经度为3.75°的网格。该模型利用了美国地质调查局上新世解释和天气制图组（PRISM）提供的新的PRISM2 2°×2°增强型中上新世边界条件数据集。与目前相比，模式模拟预测全球年平均变暖1.9°C。高纬度地区的变暖最为严重，导致赤道到极点的温度梯度降低了6°C，大气环流减少。总降水量（mm/day）的年平均值增加了6%，高云分量略有增加。在低地和赤道地区，温度最多下降8°C（例如东非），而降水增加，与哈德利环流的扩大有关，促进了更大的蒸发和进一步的冷却。将我们的结果与先前研究上新世中期气候特征的模拟研究相比较，揭示了模型之间的广泛一致模式，但在细节上观察到显著差异。造成这些差异的原因是：(a)与其他模式相比，UKMO GCM使用了更高的空间分辨率和不同的物理参数化；(b)与原始的8°×10°或早期建模研究中使用的PRISM1 2°×2°数据集相比，PRISM2数据集存在差异。将模拟的古气候与现有的地质资料进行比较，结果表明两者基本一致。然而，在检查一些地质资料所显示的上升流的明显加强，与UKMO GCM所预测的大气环流强度的模拟减弱时，确实存在差异。此外，关于上新世中期南极东部冰盖范围的地质记录有充分的不确定性，这使得强加的PRISM2边界条件的总体精度难以真正评估，因此UKMO GCM的预测也难以真正评估。
This paper outlines the results of a new climate modelling study for the middle Pliocene (ca. 3 Ma). The work was carried out using the UK Meteorological Office GCM (UKMO, Version 3.0) which is a grid point model using a grid of 2.5° in latitude by 3.75° in longitude. The model utilised the new PRISM2 2°×2° enhanced data set of boundary conditions for the middle Pliocene supplied by the U.S. Geological Survey's Pliocene Interpretations and Synoptic Mapping Group (PRISM). By comparison with the present, the model simulation predicted a 1.9°C annual mean warming over the globe. Warming was at its greatest in high latitudes and resulted in a reduced equator-to-pole temperature gradient of 6°C and a reduction in the general circulation of the atmosphere. Annual mean values for total precipitation (mm/day) increased by 6% with a minor increase in the high cloud component. In low and equatorial regions, temperature decreases by a maximum of 8°C (e.g. over East Africa), whilst precipitation increases, associated with a broadening of the Hadley Cell, promoted greater evaporation and further cooling. Comparison of our results with previous modelling studies, which have examined the character of the middle Pliocene climate, reveal a broad pattern of agreement between the models, but with significant differences observed in detail. These differences are caused by: (a) the greater spatial resolution and different physical parameterisations used in the UKMO GCM compared to other models and (b) variations in the PRISM2 data set compared to the original 8°×10°, or the PRISM1 2°×2° data set used in earlier modelling studies. Comparison of the simulated palaeoclimate to available geological data shows a broad accordance. However, disparities do exist when examining the apparent strengthening of upwelling suggested by some geological data, against the simulated reduction in strength of the general circulation of the atmosphere predicted by the UKMO GCM. Furthermore, the well-documented uncertainty of the geological record concerning the extent of the East Antarctic ice sheet during the middle Pliocene makes the overall accuracy of the imposed PRISM2 boundary conditions, and hence the predictions of the UKMO GCM, difficult to truly assess.