Modern-Era Retrospective analysis for Research and Applications (MERRA)

MERRA - Known Issues

May 2, 2012 - TPSNOW diagnostic error: On rare occasions, the top layer snow temperature diagnostic (TPSNOW) can exceed 273.16K due to an error in the timing of its calculation. In the MERRA and MERRA-Land systems, TPSNOW is set to the tile average land surface temperature (TSURF) if snow is absent at the beginning of a time step and present at the end of the time step. This occurs rarely and has a minimal impact on the system.

May 2, 2012 - TWLAND baseline: MERRA's total land water storage variable (TWLAND) occasionally contains negative values, typically in desert areas, because of a suboptimal reference baseline used for computing TWLAND from the Catchment model's soil moisture excess and deficit variables. This has been changed in MERRA-Land. For details see Appendix C in the MERRA-Land Data Product documentation.

Sep. 15, 2009 - SPSNOW Diagnostic Error: During the MERRA production, the variable SPSNOW was found to be producing incorrect values, and was patched in the middle of production. Incorrect SPSNOW data occur during the following periods:

19790101-19840101
19890101-19931201
19980101-20011001

SPSNOW is the spurious snow source used to maintain stability and balance in the mass budget. In general it should be a very small term and is included in the output to provide more accurate water budgets.

This error exists in the data in the MERRA archives, but there are plans to correct the files.

Jan. 29, 2009 - Stream 2: The ERS surface wind data was inadvertently suspended after 31 January 1994 instead of 31 March 1994. The data was re-introduced, as intended, on 6 April 1994.

Nov. 13, 2008: An issue was noticed regarding the GPROF rain rate data, beginning January 1, 2000. In the first 100 days a bug in the bufr processing of the GPROF data throws out 21-03Z data (so data counts drop), and data at other times are counted twice (proper time). After day 100, the data are handled correctly. This was a Y2K bug that was corrected, but MERRA was not rewound. Processing after 2003 did not have this problem. An investigation indicated that the impacts on monthly means of precip, q850, total column water and the analysis increments are extremely small.