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Please place all new topic requests/questions within the "Comments" section below. Your request will be moderated and, once approved, added to the forum as a new thread for comment/discussion. 
Note: To comment within the forums, an Earthdata Login is required. 

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  1. Hello, I am attempting to attain hourly wind speed readings for offshore locations around the UK. Preferably, i could attain this data in hourly timestamps for each specific long/lat co-ordinate. I can currently attain each hours data and analyse this data in Panoply, yet each download is rather large, at 360MB, and the method for analysing through Panoply is unwieldy. I understand i can somehow use WGET to download smaller files, and have attempted to understand, although am finding little success.
    Is there a more straight forward process for requesting a specific long/lat co-ordinates hourly data over a long period of time? i am aiming for data from 2013-2017. Thanks for any help rendered. 

    1. Hi Daniel,

      There are several ways to download the data and/or plot/visualize the MERRA-2 wind data.

      The service you mentioned, MERRA-2 data subsetter, allows you to go through a simple click interface to generate subset URLs that can then be called using wget to download the data. We also offer this same service through our website and here is an instructional HowTo on how to use it: How to use the Level 3 and 4 Subsetter and Regridder

      You need an Earthdata account to download any data, here are the instructions to set up the account and to link GES DISC in your applications (see step 1 & 2):

      In the link provided for setting up the account you also see the instructions for how to use wget.

      We also have multiple HowTo pages that describe how you can download the data through multiple tools and services depending on your comfort with coding or how you want to download the data (multiple files, single file etc). You can see the HowTo pages here:

      For example, this one is using Python to calculate wind speed, direction for a given area:

      How to calculate and plot wind speed using MERRA-2 wind component data

      There is also this one that describes how to download time series for a single point using GDS:

      How to Download Hourly MERRA-2 Time Series at a Single Point

      If you want a simple download URL for a single point you can also use the OPeNDAP service, you will still have to use wget to download the URLs. For the product you mentioned, here is the OPeNDAP url to start:

      We'd be more than happy to walk you through further steps if needed.

      Dana Ostrenga

      1. This is exactly what i was after, thanks for your help, this is an excellent and seemingly underutilised resource.
        For anyone seeking to solve a similar problem, I used the level 3,4 subsetter, downloaded in ASCII format, merged and copied into excel, took about 1 hour to organise each years data.

  2. problems about TRMM Processing naming rules

    Recently, I looked up a lot of documentation about TRMM, but couldn't find information about TRMM Processing Level naming rules. Take TRMM 2A25 for example, I just know the first number '2' means product level, but how about the remain means?

    I hope to receive your reply, thank you!

    1. 2A25: The average rainfall rate between the two pre-defined altitudes is calculated for each
      beam position. Other output data include parameters of Z-R relationships, integrated rain rate
      of each beam, range bin numbers of rain layer boundaries, and many intermediate parameters.

      File names involve some combination of the following attributes:

       The date is always in a format with the last 2 digits of the year following by the month and the day, always with a leading zero. An example for 4 August 2009 would be: 090804.

       This is the 5 digit orbit number.

       This is the product version. The most recent version is 7.

      2A25 2A25.<date>.<orbit_number>.<product_version>.HDF.Z Compressed HDF4

      README Document for the Tropical Rainfall Measurement Mission (TRMM) Version 7 by NASA


      with more detail naming rules, hope can help you more

  3. Hi Wenjia,

    Right, in TRMM 2A25, ‘2’ is the data processing level defined in,

    A is for a single instrument (and B for multiple instruments). 25 is for the PR algorithm.

    Please note that V8 TRMM products are a part of the GPM product suite now,

    Their naming convention has been changed:

    For example, a variable-size alphanumeric short name or acronym for algorithm name is used.

    Hope these help.



    1. I already understand, thank you very much!

  4. Can we get latest update on marine linkage.

  5. I am working in a research of aerosols and I need the boundary layer heigh. I have and specific question about MERRA Is the boundary layer heighfrom above terrain or from the sea level or somenthing?.... Cna you help me please with this information. 

  6. Ivan,

    Hello.  This forum is not our preferred mode of user communication at this time;  we anticipate having a much better multi-DAAC forum this summer.  For now, please send your question to our Help Desk, so that we can provide a full answer.  The Help Desk address is  The brief answer to your question is that the boundary layer height is the height above the surface. 

    1. Thank you so much Dr. Acker