Characterizing the North American Monsoon in the Community Atmosphere Model: Sensitivity to Resolution and Topography
Characterizing the North American Monsoon in the Community Atmosphere Model: Sensitivity to Resolution and Topography
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DOI：
10.1175/jcli-d-18-0567.1
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发表时间：
2019-11
影响因子：
4.9
通讯作者：
A. Varuolo-Clarke;K. Reed;B. Medeiros
中科院分区：
文献类型：
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作者：
A. Varuolo-Clarke;K. Reed;B. Medeiros
本研究在一个大气环流模式的实验中，探讨了水平分辨率和地形对北美季风的影响。观测被用来评估社区大气模式第5版（CAM 5）模拟中季风代表的保真度，标准网格间距为1.0°，高分辨率网格间距为0.25°。模拟的季风有一些现实的特点，但两种配置也显示降水偏差。默认的1.0°网格间距配置模拟了在观测范围内具有年周期和降水强度的季风，但季风的开始和结束过于缓慢，并且没有到达足够远的北方。这项研究表明，在高分辨率（0.25°网格间距）配置中改进的地形表示改善了区域环流，因此与1.0°对应物相比，模拟季风的某些方面。在更高的分辨率下，CAM5模拟了美国西南部上空更强的低压中心，比1.0°配置更真实的低空气流。结果，季风降水量增加，降水年周期的幅度也增加。湿度分析揭示了季风动力学，表明焓平流和湿静态能量的变化驱动了CAM 5 1.0°与0.25°配置中季风降水之间的差异。附加的模拟证实，这些改进主要是由于地形对通过加州湾的低空气流的影响，而不仅仅是水平分辨率的增加。
This work examines the effect of horizontal resolution and topography on the North American monsoon (NAM) in experiments with an atmospheric general circulation model. Observations are used to evaluate the fidelity of the representation of the monsoon in simulations from the Community Atmosphere Model version 5 (CAM5) with a standard 1.0° grid spacing and a high-resolution 0.25° grid spacing. The simulated monsoon has some realistic features, but both configurations also show precipitation biases. The default 1.0° grid spacing configuration simulates a monsoon with an annual cycle and intensity of precipitation within the observational range, but the monsoon begins and ends too gradually and does not reach far enough north. This study shows that the improved representation of topography in the high-resolution (0.25° grid spacing) configuration improves the regional circulation and therefore some aspects of the simulated monsoon compared to the 1.0° counterpart. At higher resolution, CAM5 simulates a stronger low pressure center over the American Southwest, with more realistic low-level wind flow than in the 1.0° configuration. As a result, the monsoon precipitation increases as does the amplitude of the annual cycle of precipitation. A moisture analysis sheds light on the monsoon dynamics, indicating that changes in the advection of enthalpy and moist static energy drive the differences between monsoon precipitation in CAM5 1.0° compared to the 0.25° configuration. Additional simulations confirm that these improvements are mainly due to the topographic influence on the low-level flow through the Gulf of California, and not only the increase in horizontal resolution.