Reanalyses integrate tremendous amounts of satellite observations from numerous instruments with Earth system models through data assimilation.
The resulting data, continuous in space and time, has proven to be a useful research tool for many fields. While progress has been made in all aspects of the reanalysis technology, further work and development is needed to fully realize the potential for satellite data reanalyses in climate research and applications. In this talk, we review the Modern-Era Retrospective analysis for Research and Application (MERRA) project and some recent results. Advances over previous generations of reanalyses will be discussed, along with some issues that need to be addressed in future research (such as model bias and the changing observing system). We will also discuss the potential application of reanalyses in climate monitoring and the next steps in the development of reanalyses for NASA.