Diurnal cycle of summer precipitation over the North China Plain and associated land–atmosphere interactions: Evaluation of ERA5 and MERRA-2,International Journal of Climatology

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Diurnal cycle of summer precipitation over the North China Plain and associated land–atmosphere interactions: Evaluation of ERA5 and MERRA-2
International Journal of Climatology ( IF 3.5 ) Pub Date : 2021-04-30 , DOI: 10.1002/joc.7166
Yuanyuan Song _{1,

2} , Jiangfeng Wei _{1,

2}

Affiliation

The diurnal cycle of precipitation is influenced by the dynamic and thermodynamic processes of the land–atmosphere system and is a gateway for understanding land–atmosphere interactions. Here, we use satellite-based precipitation data from CMORPH and TRMM 3B42 to evaluate the ability of ERA5 and MERRA-2 reanalyses to depict the diurnal cycle of summer precipitation over the North China Plain (NCP). The observed diurnal cycles generally have a peak time in the afternoon or in the night to early morning, depending on the region. Both ERA5 and MERRA-2 can reproduce the observed night to early morning precipitation peak, but the observed afternoon precipitation peak is only shown in ERA5. Moisture flux convergence is the main driver for night and early morning precipitation, while local land surface evapotranspiration and moisture flux convergence jointly drive afternoon rainfall. Compared with ERA5, the land surface is more strongly coupled with the atmosphere in MERRA-2, and MERRA-2 precipitation is more sensitive to precipitable water. The low-level wind field is more divergent in MERRA-2 than in ERA5 during afternoon, which causes weaker ascending motions, less precipitable water, and lower precipitation efficiency. The less favourable atmospheric conditions for precipitation, exacerbated by the strong land–atmosphere coupling, lead to the absence of afternoon rainfall in MERRA-2.

中文翻译：

华北平原夏季降水日循环及其相关的陆-气相互作用：ERA5和MERRA-2的评价

降水的昼夜循环受陆地-大气系统的动力和热力学过程的影响，是理解陆地-大气相互作用的门户。在这里，我们使用来自 CMORPH 和 TRMM 3B42 的基于卫星的降水数据来评估 ERA5 和 MERRA-2 再分析的能力，以描述华北平原（NCP）夏季降水的昼夜循环。观察到的昼夜循环通常在下午或夜间至清晨出现高峰时间，具体取决于地区。ERA5 和 MERRA-2 都可以再现观测到的夜间到清晨的降水峰值，但观测到的下午降水峰值仅在 ERA5 中显示。水分通量汇聚是夜间和清晨降水的主要驱动力，而局部地表蒸散和水分通量的汇聚共同推动了下午的降雨。与ERA5相比，MERRA-2地表与大气耦合更强，MERRA-2降水对可降水更敏感。MERRA-2的低空风场在下午比ERA5的发散更大，导致上升运动减弱，可降水量减少，降水效率降低。由于强烈的陆地 - 大气耦合加剧了对降水不利的大气条件，导致 MERRA-2 没有下午的降雨。MERRA-2的低空风场在下午比ERA5的发散更大，导致上升运动减弱，可降水量减少，降水效率降低。由于强烈的陆地 - 大气耦合加剧了对降水不利的大气条件，导致 MERRA-2 没有下午的降雨。MERRA-2的低空风场在下午比ERA5的发散更大，导致上升运动减弱，可降水量减少，降水效率降低。由于强烈的陆地 - 大气耦合加剧了对降水不利的大气条件，导致 MERRA-2 没有下午的降雨。

更新日期：2021-04-30

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