The MERRA-2 data set, produced by the Global Modeling and Assimilation Office (GMAO), is now available from the Goddard Earth Sciences Data and Information Services Center (GESDISC)!
- GMAO and GES DISC would like to inform the science community that MERRA-2 data is available at the GES DISC:
- There is also a new MERRA-2 subsetter that was developed to provide additional functionality, including regridding:
- The New MERRA-2 Web page at GMAO is available, but much of the content is still being developed:
- A draft of the Initial Climate Evaluation is also now available:
- In using the data, you will want to refer to the MERRA-2 File Specification Document:
The MERRA-2 File Specification Document is important because while the nominal resolution of MERRA-2 is still ~0.5°, the grid is slightly different from MERRA.
In addition to the grid, there are a few other changes to note. There is a difference between MERRA and MERRA-2 over land surfaces, where MERRA-2 uses observation-based precipitation data as forcing for the land surface parameterization. This approach is similar to the gauge-based precipitation forcing developed for MERRA-Land ( Reichle et al., 2011; Reichle, 2012; Reichle and Liu, 2014 ). The precipitation forcing data derived from this approach is archived as the output variable called PRECTOTCORR in the MERRA-2 FLX and LFO collections (see Section 6 in the MERRA-2 File Specification Document). Note that the forcing precipitation is not purely gauge observations, as it tapers back to MERRA-2 model generated precipitation poleward of 42.5° latitude, and is completely MERRA-2 precipitation poleward of 62.5°. Also, over continental Africa, the observations change to the CMAP gauge-satellite product, due to limitations in the available gauge observations. Care must be taken in mass balance studies, as the difference between the observation-based and model-generated precipitation will affect the water budget when land and atmosphere budgets are combined.
Along with the enhanced use of satellite observations in MERRA-2, a secondary motivation was to include more aspects of the Earth System. An important aspect of this is the assimilation of aerosol information, based on the off-line “MERRAero” dataset that was integrated using meteorological fields from MERRA. MERRA-2 aerosol variables are included in additional file collections, which use the tags AER, ADG and GAS in their file names, similar to the MERRAero data file (Da Silva et al., 2015).
Reflecting the broader scope of the assimilation system, there are several other new file collections. MERRA-2 includes a mass balance over glaciated land surfaces, which is written in the GLC collection. Several surface variables have additional daily statistics written in a separate collection called statD.
Regarding the quality of the data, several documents and presentations are being finalized and will be added to the MERRA-2 Web pages over time — thank you for your patience.
Lastly, it is important to inform the community that the computing platform MERRA is produced on will no longer be supported. When it is gone, real-time MERRA data will no longer be produced. While this date is not presently fixed, we expect to stop the MERRA production on February 29, 2016. When we know the end date, it will be shared on this list and the GMAO and GESDISC Web pages.
Two other examples of MERRA-2 data are shown in the images below. Thank you for your interest and use of the MERRA data products!
Above: Time-averaged maps of MERRA-2 Dust Column Mass Density for the period April 4-14, 2001. During this period, one of the largest dust storms ever observed originating in China transported dust over the North Pacific Ocean to North America. The dust from this storm affected air clarity across the United States, from California to Maryland. Click on the image to view it full-size.
Above: Image of MERRA-2 eastward and northward wind speed at 2 meters above the Earth surface on August 28, 2012. On this date, while Hurricane Isaac approached the northern Gulf Coast of the United States, Typhoon Bolaven was located in the Yellow Sea between China and the Korean Peninsula. Typhoon Bolaven was the most powerful typhoon to strike the Korean Peninsula in a decade. Click on the image to view a much larger version.
Questions or comments? Email the NASA GES DISC Help Desk: firstname.lastname@example.org