A month ago, NASA notified about an issue with the MERRA2 data from a four month period ranging from June 2021 to September 2021:
The issue was caused by an error in the MERRA2 pre-processing of ocean buoys observations of near-surface temperatures and resulting in significant near-surface temperature biases in various regions.
At the time of the notification, it was unclear how much the wind-speeds were influenced. As a result, MERRA2 data from the affected period was removed from the online-data services of windPRO and EMD-API: read more at our knowledgebase or our newsletter.
This issue has now been resolved and updated MERRA2 data from June to November has been made available.
We can confirm that the wind fields are also influenced by the issue (see the map below). Thus, if you have downloaded and used MERRA2 data for months June-September 2021 and the data was downloaded before November 30th, then we recommend replacing the erroneous data and re-do any calculations and analysis’.
Image: Showing the difference (in percent) in average wind-speed for erroneous MERRA2 vs corrected MERRA2 data from July 2021.