MERRA-2 Data

Example of MERRA-2 mean wind speeds at 50 m. Screen shot from http://www.windprospecting.com/

Observations assimilated in MERRA2 (top) and MERRA (bottom) datasets for the period 01.1980 until 12.2014. Units are millions per 6 hours. From Bosilovich et al.

Introduction

MERRA-2 is the recent version of the popular MERRA dataset modelled and distributed by the Global Modeling and Assimilation Office of NASA / Goddard Space Flight Center. The original MERRA dataset is discontinued in early 2016. After this point MERRA-2 is the most recent and updated MERRA dataset. MERRA-2 uses a newer version of the modelling system and also incorporates newer data sources and observations.

At EMD, we have done a comprehensive evaluation of the performance of the MERRA2 dataset for wind-energy applications. Please consult the paper by Thøgersen et al, "Is MERRA2 Able to Replace MERRA as a Trusted Reference Wind Dataset?". The paper is available from the windPRO knowledgebase, here.

Resolution and Coverage

The model grid is 0.5 degree latitude and 0.625 degree longitude. This is slightly different from the original MERRA dataset.
It holds 1 hourly values in a period from 1992 until present.
Coverage is global for land-areas and coastal regions.
Offshore coverage is only to be expected up to approximately 300 km from the coastline.

Dataset Overview

• Content:: Renewable energy focused data subset of MERRA2 data.
• Spatial Resolution:
  • 0.5 degree latitude
  • 0.625 degree lontigude
• Temporal Resolution: Hourly values.
• Coverage:
  • Coverage is global for land-areas and coastal regions.
  • In windPRO, offshore coverage is at a distance of approximately 300 km from any known coastlines.
• Period: 25+ years. The EMD databases will hold data back to 1992.
• Update schedule:
  • EMD updates the dataset once a month - with data being aviailable with a 1-2 month delay from real-time due to NASA/MERRA data availability.

Usage Notes and User Notifications

2020-11-03: NASA has notified us about an issue with the September 2020 data (released from NASA on October 20th 2020). The MERRA-2 science team at NASA do not recomment to use the data - and are currently reprocessing the data. In the windPRO online-data services, September 2020 data has now been removed as of November 3rd. If you have downloaded the MERRA-2 data in the period between October 24th to November 3rd, we recomment that you disable or remove the MERRA2-data for the month of September 2020. The actual nature of the issue is unknown to the windPRO online-data team, but we will send out a notification when new data has been released from NASA. Read the original statement from NASA here.

Data Availability

MERRA-2 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.

Table: Overview of MERRA-2 Dataset Parameters.

Parameter	Description
time	UTC time stamp
psfc	Surface pressure
msl	Mean Sea Level pressure
wSpeed.50	Wind speed at 50 m above surface
wDir.50	Wind direction at 50 m above surface
wSpeed.850hpa	Wind speed at 850 hpa
wDir.850hpa	Wind direction at 850hpa
temperature.10	Temperature at 10 m above surface
temperature.50	Temperature at 50 m above surface
dispHeight	Displacement height
precIceWater	Total precipitable ice water
precLiqWater	Total precipitable liquid water
precWaterVapor	Total precipitable water vapor
specHumidity.10	Specific humidity at 10 m

External Links

• The MERRA-2 project page at: http://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/

Acknowledgement

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