Data

Downloading Datasets from Earthdata

Shell Script (More Time-Consuming; doesn't require python)

1. Register for an account on https://urs.earthdata.nasa.gov. In order to create a profile, you will be prompted to provide a username, password, email address, and data about your title/role/institution. You'll receive an e-mail asking you to confirm account activation, don't forget to click on the link in that e-mail to fully activate your account!

$~~~~$

2. Locate the dataset you would like to download on https://search.earthdata.nasa.gov/ and click on it. Once selected, press the green "Download Data" button.

$~~$

$~~~~$

3. Wait until the download is 100% ready.

$~~$

$~~~~$

4. Click the "Download Script" tab. Create a path on the Remote Directory to store your data. In the desired folder, create a shell (.sh) file (called download.sh, for example). Copy and paste the provided script into your shell (.sh) file. $~~$

$~~~~$

5. In the terminal, run the command chmod 777 download.sh (replace "download" with whatever you named your shell file). This command just allows you to access and run the shell file.

$~~~~$

6. In the terminal, run the command ./download.sh (once again, replace "download" with whatever you named your shell file). You will be prompted to type your Earthdata username and password.

$~~~~$

7. The download will begin! :D

Downloading through Podaac (needs python >= 3.7)

1. Register for an account on https://urs.earthdata.nasa.gov. In order to create a profile, you will be prompted to provide a username, password, email address, and data about your title/role/institution. You'll receive an e-mail asking you to confirm account activation, don't forget to click on the link in that e-mail to fully activate your account!

$~~~~$

2. Locate the dataset you want to download. Click the download button under Capabilities and jot down the PO.DAAC Data Subscriber code. For example, the GRACE dataset is located in GRACE website and the PO.DAAC Data Subscriber code is podaac-data-subscriber -c TELLUS_GRAC_L3_CSR_RL06_LND_v04 -d ./data/TELLUS_GRAC_L3_CSR_RL06_LND_v04 --start-date 2002-04-05T00:00:00Z

$~~~~$

3. Now, we can follow the instruction to download the data from PODAAC's Github page. Note the following command works on Macbook, Windows users should consult the Github page for more detail. First, run the following command in terminal pip install podaac-data-subscriber. This requires Python >= 3.7.

$~~~~$

4. Run echo $HOME, then pwd. Make sure the two locations are the same.

$~~~~$

5. Create and write a .netrc file by running the following commands at the same location touch .netrc, then nano .netrc. In the .netrc file, you should put in the following information: machine urs.earthdata.nasa.gov login <your username> password <your password> The username and password is your login information from https://urs.earthdata.nasa.gov. Then, save and close the file using control+o, enter, and then control+w

$~~~~$

6. Then, download the dataset you want by entering the PO.DAAC Data Subscriber code in step 2 to the terminal. If you want to "download PO.DAAC data once in a while or prefer to do it 'on-demand'", instead of "continuously pulling the latest data from the PO.DAAC archive", change the subscriber in the command line to downloader and add an end date to the data you want to download. For example, for GRACE data, you can change the command line from podaac-data-subscriber -c TELLUS_GRAC_L3_CSR_RL06_LND_v04 -d ./data/TELLUS_GRAC_L3_CSR_RL06_LND_v04 --start-date 2002-04-05T00:00:00Z to podaac-data-downloader -c TELLUS_GRAC_L3_CSR_RL06_LND_v04 -d ./data/TELLUS_GRAC_L3_CSR_RL06_LND_v04 --start-date 2002-04-05T00:00:00Z --end-date 2017-10-19T00:00:00Z

Commands to download data

CSR

GRACE CSR

podaac-data-downloader -c TELLUS_GRAC_L3_CSR_RL06_LND_v04 -d ~/remoteData/GRACE/TELLUS_GRAC_L3_CSR_RL06_LND_v04 --start-date 2002-04-05T00:00:00Z --end-date 2017-10-19T00:00:00Z

GRACE-FO CSR

podaac-data-downloader -c TELLUS_GRFO_L3_CSR_RL06.1_LND_v04 -d ~/remoteData/GRACE/TELLUS_GRFO_L3_CSR_RL06.1_LND_v04 --start-date 2018-05-22T00:00:00Z --end-date 2023-06-23T00:00:00Z

GFZ

GRACE GFZ

podaac-data-downloader -c TELLUS_GRAC_L3_GFZ_RL06_LND_v04 -d ~/remoteData/GRACE/TELLUS_GRAC_L3_GFZ_RL06_LND_v04 --start-date 2002-04-05T00:00:00Z --end-date 2017-10-19T00:00:00Z

GRACE-FO GFZ

podaac-data-downloader -c TELLUS_GRFO_L3_GFZ_RL06.1_LND_v04 -d ~/remoteData/GRACE/TELLUS_GRFO_L3_GFZ_RL06.1_LND_v04 --start-date 2018-05-22T00:00:00Z --end-date 2023-06-23T00:00:00Z

JPL

GRACE JPL

podaac-data-downloader -c TELLUS_GRAC_L3_JPL_RL06_LND_v04 -d ~/remoteData/GRACE/TELLUS_GRAC_L3_JPL_RL06_LND_v04 --start-date 2002-04-05T00:00:00Z --end-date 2017-10-19T00:00:00Z

GRACE-FO JPL

podaac-data-downloader -c TELLUS_GRFO_L3_JPL_RL06.1_LND_v04 -d ~/remoteData/GRACE/TELLUS_GRFO_L3_JPL_RL06.1_LND_v04 --start-date 2018-05-22T00:00:00Z --end-date 2023-06-23T00:00:00Z

Datasets & Technical Notes

GRACE & GRACE-FO

• GRACE goes until Oct 2017; GRACE FO starts in May 2018
• After 2018, they shut the accelerometer off on one of the satellites, resulting in degradation of data quality.
• There are 3 processing centers and the documentation suggests averaging all three.

Questions with GRACE data:

• What's the difference between Mascon solution data and spherical harmonic solution?

  • Spherical harmonic solutions are used to account for the Earth not being perfectly spherical and oblate. Mascon solutions bin the earth into a grid and by binning you can get more precise measurements within the bin. So use mascon data for more granular analysis. Because mascon solution and spherical harmonic solutions use different models with different assumptions, use the mascon solution for Hydrology applications. More details on site

• When should we apply the scale factor?

• What does uncertainty mean?

• How should we think about aggregating over a region？

• Do we still need to average over different processing centers for Mascon data?