merradownload 1.0.2

Download and process MERRA-2 meteorological data from NASA GES DISC

merradownload

A Python package for downloading, cleaning, and aggregating meteorological data from NASA's MERRA-2 database.

Adapted from Emily Laiken's merradownload, which builds on Jan Urbansky's opendap_download and the Open Power System Data notebook. Edited and maintained by Anemona.

Installation

pip install merradownload

Prerequisites: NASA Earthdata account

1. Register at https://urs.earthdata.nasa.gov/
2. Go to Applications → Authorized Apps → Approve More Applications
3. Approve NASA GESDISC DATA ARCHIVE

Quick start

Python API

from opendap_download.multi_processing_download import DownloadManager

dm = DownloadManager(
    username='your_earthdata_username',
    password='your_earthdata_password',
    links=['https://...'],       # list of OPeNDAP query URLs
    download_path='data/output', # where to save .nc4 files
)
dm.start_download(nr_of_threads=5)

CLI

merradownload \
  --username YOUR_USER \
  --password YOUR_PASS \
  --urls-file urls.txt \
  --output-dir data/output \
  --threads 5

urls.txt should contain one OPeNDAP query URL per line. See examples/merra_scraping.py for how to generate these URLs for a given location, year range, and variable set.

Example script

examples/merra_scraping.py shows a complete end-to-end workflow: coordinate translation → URL generation → download → xarray/pandas processing → CSV and plot outputs.

Dependencies

Package	Purpose
requests	HTTP downloads
urllib3	Retry logic
tqdm	Progress bar
pyyaml	Optional credential file support

Processing dependencies (used in the example script only, not required by the core package):

pip install numpy pandas xarray netCDF4 matplotlib

Features

• Parallel downloads via ThreadPoolExecutor
• Automatic retry on HTTP 5xx errors (3 retries, exponential backoff)
• Skips already-downloaded files — safe to resume interrupted runs
• Progress bar
• Credential file support (yaml)