The response of US summer rainfall to quadrupled CO2 climate change in conventional and superparameterized versions of the NCAR community atmosphere model
The response of US summer rainfall to quadrupled CO2 climate change in conventional and superparameterized versions of the NCAR community atmosphere model
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DOI：
10.1002/2014ms000306
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发表时间：
2014-09-01
影响因子：
6.8
通讯作者：
Somerville, Richard C. J.
中科院分区：
文献类型：
--
作者：
Kooperman, Gabriel J.;Pritchard, Michael S.;Somerville, Richard C. J.
观测和区域气候模拟（RCM）研究表明，全球气候模式（GCM）是不可靠的预测极端降水的变化。然而，区域气候模型的气候变化模拟受大气环流模型提供的边界条件的约束，不与可能对整个区域响应至关重要的大尺度动态反馈相互作用。全球和区域模拟方法的局限性对未来降雨预测造成了很大的不确定性。进步需要一个能够捕捉到的降雨强度的区域尺度的变化，而不牺牲行星尺度的建模框架。在这里，美国夏季降雨量的CO2气候变化的四倍进行了调查，使用常规（CAM）和超参数化（SPCAM）版本的NCAR社区大气模型。超参数化方法，其中云解析模式阵列嵌入在GCM网格列，提高了降雨统计和对流变率在全球模拟。一组5年的时间切片模拟，规定的海表温度和海冰边界条件收获的前工业化和突然四倍CO2耦合社区地球系统模式（CESM/CAM）模拟，比较CAM和SPCAM。这两种模式产生非常不同的变化，平均降水模式，这是从大尺度环流异常与行星尺度的变暖反应的差异。CAM显示整体降雨强度略有下降，从较弱的参数化对流和大尺度降水减少的贡献增加。SPCAM有相反的反应，一个显着的转变，降雨发生向更高的降水率，包括更激烈的传播美国中部中尺度对流系统在四倍的CO2气候。
Observations and regional climate modeling (RCM) studies demonstrate that global climate models (GCMs) are unreliable for predicting changes in extreme precipitation. Yet RCM climate change simulations are subject to boundary conditions provided by GCMs and do not interact with large-scale dynamical feedbacks that may be critical to the overall regional response. Limitations of both global and regional modeling approaches contribute significant uncertainty to future rainfall projections. Progress requires a modeling framework capable of capturing the observed regional-scale variability of rainfall intensity without sacrificing planetary scales. Here the United States summer rainfall response to quadrupled CO2 climate change is investigated using conventional (CAM) and superparameterized (SPCAM) versions of the NCAR Community Atmosphere Model. The superparameterization approach, in which cloud-resolving model arrays are embedded in GCM grid columns, improves rainfall statistics and convective variability in global simulations. A set of 5 year time-slice simulations, with prescribed sea surface temperature and sea ice boundary conditions harvested from preindustrial and abrupt four times CO2 coupled Community Earth System Model (CESM/CAM) simulations, are compared for CAM and SPCAM. The two models produce very different changes in mean precipitation patterns, which develop from differences in large-scale circulation anomalies associated with the planetary-scale response to warming. CAM shows a small decrease in overall rainfall intensity, with an increased contribution from the weaker parameterized convection and a decrease from large-scale precipitation. SPCAM has the opposite response, a significant shift in rainfall occurrence toward higher precipitation rates including more intense propagating Central United States mesoscale convective systems in a four times CO2 climate.