Comparison of convective parameters derived from ERA5 and MERRA2 with rawinsonde data over Europe and North America
Comparison of convective parameters derived from ERA5 and MERRA2 with rawinsonde data over Europe and North America
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DOI：
10.1175/jcli-d-20-0484.1
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发表时间：
2020-12
影响因子：
4.9
通讯作者：
M. Taszarek;Natalia Pilguj;J. Allen;Victor A. Gensini;H. Brooks;Piotr Szuster
中科院分区：
文献类型：
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作者：
M. Taszarek;Natalia Pilguj;J. Allen;Victor A. Gensini;H. Brooks;Piotr Szuster
在这项研究中，我们将欧洲和北美232个站点的370万次雷达探头观测数据与ERA5和MERRA2的近端垂直剖面进行了比较，以检验再分析对观测到的对流参数的描述程度。在热力理论包参量、低空递减率和低空风切变方面，实测结果与再分析结果差异较大。相比之下，再分析最能代表温度和湿度变量、对流层中层递减率和平均风。两种重新分析都低估了CAPE、低层湿度和风切变，特别是在考虑极值时。对低层递减率、对流层中层湿度和自由对流水平的估计过高。与最不稳定的包裹相比，混合层包裹总体上具有更好的准确性，特别是考虑到对流抑制和提升的凝结水平。在过去的39年里，对于几乎所有被分析的变量，两次重新分析的平均绝对误差都在稳步下降。与MERRA2相比，ERA5具有更高的相关性和更低的平均绝对误差。MERRA2在中欧和巴尔干半岛上空通常更干燥，更不稳定，而在俄罗斯西部则相反。两种重新分析都低估了大平原地区的CAPE和CIN。再分析对于低海拔站点和沿海地区和山脉等边界站点更为可靠。基于本研究和先前的研究结果，我们认为ERA5可能是最可靠的对流环境探测再分析之一，主要是因为它提高了分辨率。对于未来的研究，我们还建议对流变量的计算应该使用模型水平，与数量较少的压力水平相比，模型水平可以提供更准确的边界层条件采样。
In this study we compared 3.7 mln rawinsonde observations from 232 stations over Europe and North America with proximal vertical profiles from ERA5 and MERRA2 to examine how well reanalysis depicts observed convective parameters. Larger differences between soundings and reanalysis are found for thermodynamic theoretical parcel parameters, low-level lapse rates and low-level wind shear. In contrast, reanalysis best represents temperature and moisture variables, mid-tropospheric lapse rates, and mean wind. Both reanalyses underestimate CAPE, low-level moisture and wind shear, particularly when considering extreme values. Overestimation is observed for low-level lapse rates, mid-tropospheric moisture and the level of free convection. Mixed-layer parcels have overall better accuracy when compared to most-unstable, especially considering convective inhibition and lifted condensation level. Mean absolute error for both reanalyses has been steadily decreasing over the last 39 years for almost every analyzed variable. Compared to MERRA2, ERA5 has higher correlations and lower mean absolute errors. MERRA2 is typically drier and less unstable over central Europe and the Balkans, with the opposite pattern over western Russia. Both reanalyses underestimate CAPE and CIN over the Great Plains. Reanalyses are more reliable for lower elevations stations and struggle along boundaries such as coastal zones and mountains. Based on the results from this and prior studies we suggest that ERA5 is likely one of the most reliable available reanalysis for exploration of convective environments, mainly due to its improved resolution. For future studies we also recommend that computation of convective variables should use model levels that provide more accurate sampling of the boundary-layer conditions compared to less numerous pressure levels.