MERRA-2 wind speed data

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simranm
Posts: 2
Joined: Thu Apr 09, 2020 9:31 am America/New_York

MERRA-2 wind speed data

by simranm » Wed Apr 15, 2020 11:44 am America/New_York

Hello
I am interested to plot a vertical wind speed profile making use of the MERRA-2 data. With regards to that, I had the following queries, and I would really appreciate if anyone could provide some clarification.

1) The vertical grid variables are the 42 pressure levels. While converting these pressure levels to altitude values, I have referred to the ISA standards. I would like to know, what would be the accurate method for the conversion, and whether there is a latitude dependency involved?
2) A significant number of wind speed component magnitudes in the MERRA-2 datasets have values greater than 140m/s, which is comparative to (or appears to be greater than) the highest wind speeds ever recorded. Is it correct to consider the values for the eastward and northward wind components as it is from the files downloaded, or there might be some error in the interpretation of these variables?

Thank you

mbosilov
Posts: 4
Joined: Thu Apr 16, 2020 9:03 am America/New_York

Re: MERRA-2 wind speed data

by mbosilov » Thu Apr 16, 2020 9:15 am America/New_York

Hi,

Just to be sure you have the appropriate information, MERRA-2 Documentation is at: https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/docs/. Also, be aware that the GMAO maintains a help email for science and technical questions regarding the MERRA-2 data. merra-questions@lists.nasa.gov

1 The pressure level data also has height levels. So, if you are working with point data, you can interpolate height, temperature, winds using log P. Alternatively, the hydrostatic equation and hypsometric equation also allow for getting height from pressure.

2 you haven't provided enough information to allow us to check these values. Please use the merra-questions email above to send exact coordinates of the values and we will double check the source files. such values are not uncommon in the mesosphere. Have you double checked how you are reading the vertical layers? For example, inadvertently inverting the orientation of the vertical coordinate?

Thanks for your interest in MERRA-2 data! Be safe!

Mike

simranm
Posts: 2
Joined: Thu Apr 09, 2020 9:31 am America/New_York

Re: MERRA-2 wind speed data

by simranm » Mon Apr 20, 2020 8:46 am America/New_York

Hi!
Many thanks for all the information and for guiding me to the correct email address for technical queries.

My vertical plots cover data up to altitudes of 20km. So those high wind values are noticeable both in the troposphere and lower stratosphere layers, which seems uncommon. I have double-checked the way the values are accessed from the files. To my understanding, it seems correct. Thank you once again for your response. I will followup on this question at the email provided.


Regards,
Simran

minousoso
Posts: 1
Joined: Tue Apr 21, 2020 6:34 am America/New_York

Re: MERRA-2 wind speed data

by minousoso » Tue Apr 21, 2020 2:55 pm America/New_York

specific location in Alaska. One of the community I am trying to download for is Cordova, Alaska (Lat: 60.489, Lon: -145.451). Please let me know if it is possible or where I should be looking for these information. Thank you!!

GES DISC - jimacker
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Posts: 157
Joined: Mon Sep 30, 2019 1:57 pm America/New_York
Answers: 2

Re: MERRA-2 wind speed data

by GES DISC - jimacker » Tue Apr 21, 2020 4:13 pm America/New_York

Hello,

You can obtain MERRA-2 data from the NASA GES DISC:
https://disc.gsfc.nasa.gov/datasets?pag ... %20MERRA-2

and from Giovanni, which allows easy regional selection:
https://giovanni.gsfc.nasa.gov/giovanni ... 20Model%3B

Please reply if you have additional questions.

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