Effects of New Data Types and Data Assimilation System Upgrades on Middle Atmosphere Dynamics in GEOS-5 Reanalyses

The NASA GMAO (Global Modeling and Assimilation Office) produced a long-term (35 year), ongoing, reanalysis, called MERRA (Modern-Era Retrospective analysis for Research and Applications) that has proven useful for studies of middle atmosphere transport and dynamics, in addition to many other applications. The use of an unchanging data assimilation system (DAS) over the entire time period allows for a consistent reanalysis. However, because the system is frozen, it is not possible to accommodate new data types or system improvements into MERRA. To allow such improvements, the GMAO has begun a new reanalysis, called MERRA-2, based on an updated data assimilation system. A continuous MERRA-2 data record, from 1979 to the present, is expected to be available in early 2015. Comparisons between MERRA-2 and MERRA products show the effects of these DAS and data changes on the middle atmosphere winds and temperatures. In particular, the additional temperature profiles provided by the Aura MLS (Microwave Limb Sounder) enables improvements to the bias correction of high altitude AMSU-A (Advanced Microwave Sounding Unit-A) channels, in turn leading to improved DAS temperatures near the stratopause.