MERRA Data

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MERRA U-WIND in June 1979
(Credit: Image from NASA)

MERRA is an abbreviation for Modern Era Retrospective-Analysis for Research and Applications. The dataset originates from the Global Modeling and Assimilation Office of NASA / Goddard Space Flight Center. The MERRA analysis are being conducted with the GEOS-5 Atmospheric Data Assimilation System(ADAS).

Resolution and Coverage

The model grid is 0.5 degree latitude and 2/3 degree longitude.
It holds 1 hourly values in a period from 1979 until present.
Coverage is global for land-areas and coastal regions.
Offshore coverage is only to be expected up to approximately 50 km from the coastline.

Data Availability

MERRA data is commonly available within WindPRO with a time-lag of 1-2 months. This is due to the processing time of the data at NASA and the subset-processing at EMD. When the data have been processed at EMD, then the following parameters are available from within the online-data services within WindPRO. Please note that the displacement height is the height at which the log wind profile projects the wind to be zero. See more at the MERRA-FAQ.

Table: Overview of MERRA Dataset Parameters.
Parameter Description
time UTC time stamp
pressure Sea level pressure
temperature Temperature at 2 m above the displacement height
wDir Wind direction at 50 m above surface
wSpeed Wind speed at 50 m above surface
dispHeight Displacement height

Data Experiences

Generally, the MERRA data is always considered when seeking for candidate reference wind datasets for a particular site. Correlation between local measurements and MERRA data is often high, see the figure below. For his particular study made in 2010, MERRA data was compared against NCEP/NCAR, 3Tier (commercial data) and SYNOP data.

Comparing Tall Mast data (Risø) to NCEP/NCAR, 3Tier, MERRA and SYNOP data

External Links

Acknowledgement

Credits: The Global Modeling and Assimilation Office (GMAO) for the MERRA-analysis and the GES DISC for the dissemination of MERRA.