Wind Turning in the Planetary Boundary Layer in CMIP6 Models
Wind Turning in the Planetary Boundary Layer in CMIP6 Models
复制标题
CMIP6 模型中行星边界层的风转向
DOI：
10.1175/jcli-d-22-0705.1
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发表时间：
2023
影响因子：
4.9
通讯作者：
Svensson, Gunilla
中科院分区：
文献类型：
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作者：
Pyykkö, Joakim;Svensson, Gunilla
针对行星边界层 (PBL) 上的风转向和相应的交叉等压质量通量评估了一组 CMIP6 模型。批量理查森数方法用于计算 PBL 的高度，以便与 Lindvall 和 Svensson 基于综合全球无线电探空仪档案中的 800 多个站记录的观测到的风转向角的气候学进行比较。发现所有模型中的风转向角都被低估，其中 GFDL CM4 模型的分布与观测结果最接近。在所有模型和 ERA 中期再分析中，在高地形区域和北大西洋风暴路径区域都发现了大的负交叉等压质量通量（流向更高压力）。在挪威地球系统模型、中等大气-中等海洋分辨率 (NorESM2-MM) 中，基于体理查森数的 PBL 特别浅，这可能是由于与使用相同大气模型的 CESM2 模型相比，湍流和云方案的变化造成的，导致风转向角和跨等压质量通量较小。使用 850 hPa 水平作为上边界可以拓宽风转向角分布，并增加所有模型的交叉等压质量通量。这使得模型更接近观察结果，尽管仍然存在实质性差异。整个 PBL 中地转风恒定的假设可能会影响计算的质量通量。
A set of CMIP6 models is evaluated for the turning of the wind over the planetary boundary layer (PBL) and the corresponding cross-isobaric mass flux. The bulk Richardson number method is used to calculate the height of the PBL to allow for comparisons with a climatology of observed wind-turning angles documented by Lindvall and Svensson based on more than 800 stations in the Integrated Global Radiosonde Archive. Wind-turning angles are found to be underestimated in all models, with the GFDL CM4 model having the closest distribution to the observations. Large, negative cross-isobaric mass fluxes (flow toward higher pressure) are found over high-terrain areas and the North Atlantic storm-track region in all models and the ERA-Interim reanalysis. Bulk Richardson number–derived PBLs are particularly shallow in the Norwegian Earth System Model, medium atmosphere-medium ocean resolution (NorESM2-MM), likely caused by a change in the turbulence and cloud scheme as compared to the CESM2 model that uses the same atmospheric model, leading to small wind-turning angles and cross-isobaric mass fluxes. Using the 850-hPa level as the upper boundary broadens the wind-turning angle distribution and increases the amount of cross-isobaric mass flux for all models. This makes the models closer to the observations, although substantial differences are still present. The assumption of a constant geostrophic wind throughout the PBL possibly affects the calculated mass fluxes.