RAPID: Evaluation of Climate Models in the Southeast Pacific Marine Stratocumulus Region

这是由一封亲爱的同事来信(NSF 11-006)资助的16个快速反应(RAPID)项目之一，该信鼓励对为政府间气候变化专门委员会第五次评估报告(IPCC AR5)准备的气候模型模拟进行诊断分析。在这些项目中进行的研究有望导致更详细的模型相互比较，更好地理解稳健的模型行为，以及更好地理解和量化未来气候模拟中的不确定性。海洋层积云(MSC)出现在大陆西侧的副热带海洋地区，由于它们对传入的太阳辐射的强烈反射，对地球气候产生冷却作用。由MSC云主导的区域已被证明是气候模式中热带云反馈的巨大不确定性的重要驱动因素，并导致模式模拟与观测之间的巨大差异。在这笔赠款下进行的研究考虑了模式模拟中的MSC属性，并将它们与最近从包括CloudSat剖面仪在内的卫星仪器中观察到的云属性进行了比较。研究了短波云辐射强迫对海表面温度变化的响应，并将模式云诊断变量与卫星观测进行了比较，以确定导致低云反馈不确定性的潜在过程。该项目更广泛的影响在于它对IPCC AR5的支持，该AR5旨在向世界各地的决策者提供有关气候变化及其后果的信息。云反馈可以在确定温室气体浓度预期增加在多大程度上导致全球变暖方面发挥重要作用，因此，研究有助于更好地理解云反馈，并在气候模型中更好地表示云，这将有助于理解人为气候变化可能造成的严重程度。

This is one of 16 Rapid Response (RAPID) projects funded as the result of a Dear Colleague Letter (NSF 11-006) encouraging diagnostic analyses of climate model simulations prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Research conducted in these projects is expected to lead to more detailed model intercomparisons, better understanding of robust model behaviors, and better understanding and quantification of uncertainty in future climate simulations.Marine stratocumulus (mSc) clouds occur in subtropical oceanic regions off the west sides of continents, and have a cooling effect on the earth's climate because of their strong reflection of incoming solar radiation. Regions dominated by mSc clouds have been shown to be an important driver of the large uncertainties in tropical cloud feedbacks in climate models, and are responsible for the large differences between model simulations and observations. Research conducted under this grant considers mSc properties in model simulations, and compares them with cloud properties found in recent observations from satellite instruments including the CloudSat Profiling Radar. The response of shortwave cloud radiative forcing to changes in sea surface temperature is examined, and model cloud diagnostic variables are compared to satellite observations to determine the underlying processes responsible for uncertainties in low-cloud feeback. The broader impact of the project lies in its support of the IPCC AR5, which is intended to provide information on climate change and its consequences to decision makers worldwide. Cloud feedbacks could play an important role in determining how much global warming comes from the expected increases in greenhouse gas concentrations, so research leading to better understanding of cloud feedbacks and better representation of clouds in climate models would be beneficial for understanding the likely severity of anthropogenic climate change.