基于多套再分析数据的全球山脉力矩计算及比较分析

Calculation and comparison of global mountain torque:A study based on three reanalysis data

山脉力矩是地球与大气角动量交换的重要途径之一,为了深刻地理解全球的大气环流变化,比较了NCEP再分析数据、欧洲中心中尺度天气预报的ECMWF再分析数据和NASA的MERRA再分析数据计算的1979—2012年的全球山脉力矩的时、空分布及其年际变化。研究发现三套数据计算的山脉力矩空间分布基本一致,均显示北半球的青藏高原、落基山脉以及南半球的安第斯山脉是对全球山脉力矩贡献最大的三个区域。NCEP再分析数据计算的山脉力矩空间差异和多年变化标准差明显高于其他两套数据,其在纬向上的积分廓线与其他两套数据也差异较大,但是全球积分以后其平均值与标准差与其他两套数据基本一致,而且其在欧亚、南美和北美区域的积分与其他两套数据也没有明显差别,因此,NCEP再分析数据适用于大尺度的山脉力矩模拟。在研究空间尺度较小的山脉力矩变化时,建议优先考虑ECMWF和MERRA再分析数据。三套数据对北美地区山脉力矩计算的一致性较高,其次是欧亚地区,对南美区域山脉力矩计算的一致性则较差,表明北美地区气象数据质量要高于亚洲,南美洲气象数据质量较差。欧亚地球山脉力矩与大西洋—欧洲环流有很强的相关,北美山脉力矩与太平洋区极涡面积关系密切。

Spatial and temporal variation characteristics of global mountain torque are of great importance for the atmospheric angular momentum change analysis. Considering uncertainties in the computation derived from different data source errors, three reanalysis datasets, i.e. NCEP reanalysis, ECMWF reanalysis and MERRA reanalysis data were used in this study to calculate global mountain torque series from 1979 - 2012, and the spatial and temporal variations of mountain torque were fur- ther discussed. At the spatial scale, the mountain torque in the Tibetan Plateau, the Rocky Mountains and the Andes Mountain have the greatest contributions to global variation. Standard deviation analysis showed that the results based on NCEP reanalys- is dataset are higher than that based on the other two datasets. However, the results from the NCEP reanalysis over Eurasian, South America, North America and the global integration are consistent with that from the other two reanalysis datasets. This result suggests that the NCEP data is suitable for large-scale mountain torque simulation while the ECMWF and MERRA data are appropriate for small spatial scale. It is worth noting that the mountain torques calculated from the three dataset have little difference in North America, but have great differences in South America. It may he because the quality of meteorological data in North America is better than that in Eurasian and South America.