Brief Comparison with Interim Reanalysis

Recently the ECMWF Interim reanalysis has been released (see http://data.ecmwf.int/data/). We have a quick overlap and look at a comparison with MERRA at monthly time scales for January 1998.

The figure below shows two features of the MERRA system we have been tracking since the system was under development, 1) negative zonal wind bias in the tropics and extratropics and 2) dry bias in the lower troposphere, especially the tropics. These are apparent against each of the existing long reanalyses (see the quick look page for more comparisons). However, in comparing ERA40 and the new Interim reanalyses with MERRA, the magnitude of the differences is smaller compared to Interim.

At this time monthly files are not available on the ECMWF site. When those become available for download, we will integrate the Interim data into the quick look pages for comparisons.



(Gary Partyka, GMAO, downloaded the Interim data and performed the comparison and evaluation.)