Takacs Lawrence L, Suárez Max J, Todling Ricardo
Science Systems and Applications, Inc., Lanham, USA.
Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, USA.
Q J R Meteorol Soc. 2016 Apr;142(697):1565-1573. doi: 10.1002/qj.2763. Epub 2016 Feb 8.
This study describes the modifications made to the Goddard Earth Observing System (GEOS) Atmospheric Data Assimilation System (ADAS) to conserve atmospheric dry-air mass and to guarantee that the net source of water from precipitation and surface evaporation equals the change in total atmospheric water. The modifications involve changes to both the atmospheric model and the analysis procedure. In the model, sources and sinks of water are included in the continuity equation; in the analysis, constraints are imposed to penalize (and thus minimize) analysis increments of dry-air mass. Finally, changes are also required to the Incremental Analysis Update (IAU) procedure. The effects of these modifications are separately evaluated in free-running and assimilation experiments. Results are also presented from a multiyear reanalysis (Version 2 of the Modern Era Retrospective-Analysis for Research and Applications: MERRA-2) that uses the modified system.
本研究描述了对戈达德地球观测系统（GEOS）大气数据同化系统（ADAS）所做的修改，以守恒大气干空气质量，并确保降水和地表蒸发产生的净水源等于大气总水量的变化。这些修改涉及大气模型和分析程序两方面的改变。在模型中，水的源和汇被纳入连续性方程；在分析中，施加约束以惩罚（从而最小化）干空气质量的分析增量。最后，对增量分析更新（IAU）程序也需要进行更改。在自由运行和同化实验中分别评估了这些修改的效果。还给出了使用改进系统进行的多年再分析（现代时代回顾性分析研究与应用版本2：MERRA - 2）的结果。
