The role of northern Arabian Sea surface temperature biases in CMIP5 model simulations and future projections of Indian summer monsoon rainfall
The role of northern Arabian Sea surface temperature biases in CMIP5 model simulations and future projections of Indian summer monsoon rainfall
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DOI：
10.1007/s00382-012-1656-x
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发表时间：
2013-01
期刊：
影响因子：
4.6
通讯作者：
R. Levine;A. Turner;Deepthi Marathayil;G. Martin
中科院分区：
文献类型：
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作者：
R. Levine;A. Turner;Deepthi Marathayil;G. Martin
许多气候模式在模拟印度夏季季风降雨及其变率方面存在问题，导致未来预测存在相当大的不确定性。问题可能与许多因素有关，例如物理参数化方案的制定对当地的影响，而气候系统内其他地方形成的共同模式偏差也可能很重要。在这里，我们研究的程度和影响的冷海表面温度（SST）的偏差发展在北方阿拉伯海的CMIP 5多模式合奏，这种SST偏差被证明是常见的。这种偏见以前已被证明是减少季风降雨的气象局统一模型（MetUM）的减弱印度的水汽通量事件。CMIP 5模式中的阿拉伯海SST偏差在冬季持续发展，通过加强冬季风环流，并持续到春季和夏季。在CMIP 5模式中，阿拉伯海冷SST偏差和弱季风降雨之间存在明显的关系，与MetUM中的效果相似。这种影响的一部分也可能与其他因素有关，例如春季赤道降水过多对早期季风的强迫。大气只有未来的时间片实验表明，阿拉伯海冷SST偏差有可能削弱未来季风降水的增加，通过限制水分通量加速通过克劳修斯-克拉珀龙关系的非线性。CMIP 5模式未来情景模拟的分析表明，这种影响是小的其他来源的不确定性相比，虽然模型与大阿拉伯海冷SST偏差可能会抑制未来早期季风降雨变化的潜在结果的范围。
Many climate models have problems simulating Indian summer monsoon rainfall and its variability, resulting in considerable uncertainty in future projections. Problems may relate to many factors, such as local effects of the formulation of physical parametrisation schemes, while common model biases that develop elsewhere within the climate system may also be important. Here we examine the extent and impact of cold sea surface temperature (SST) biases developing in the northern Arabian Sea in the CMIP5 multi-model ensemble, where such SST biases are shown to be common. Such biases have previously been shown to reduce monsoon rainfall in the Met Office Unified Model (MetUM) by weakening moisture fluxes incident upon India. The Arabian Sea SST biases in CMIP5 models consistently develop in winter, via strengthening of the winter monsoon circulation, and persist into spring and summer. A clear relationship exists between Arabian Sea cold SST bias and weak monsoon rainfall in CMIP5 models, similar to effects in the MetUM. Part of this effect may also relate to other factors, such as forcing of the early monsoon by spring-time excessive equatorial precipitation. Atmosphere-only future time-slice experiments show that Arabian Sea cold SST biases have potential to weaken future monsoon rainfall increases by limiting moisture flux acceleration through non-linearity of the Clausius–Clapeyron relationship. Analysis of CMIP5 model future scenario simulations suggests that such effects are small compared to other sources of uncertainty, although models with large Arabian Sea cold SST biases may suppress the range of potential outcomes for changes to future early monsoon rainfall.