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Full catalog/M2IUNXGAS
M2IUNXGAS·v5.12.4·dataset

Daily haze thickness in the air (weather model)

MERRA-2 instU_2d_gas_Nx: 2d,diurnal,Instantaneous,Single-Level,Assimilation,Aerosol Optical Depth Analysis 0.625 x 0.5 degree V5.12.4 (M2IUNXGAS) at GES DISC
atmosphere NASA GES_DISC Level 4 active
In plain English

What it measures. Monthly, time-of-day snapshots of how thick the haze of airborne particles is (aerosol optical depth), capturing how much these particles dim the view through the atmosphere worldwide.

How it's made. Produced by NASA's MERRA-2 reanalysis, which blends a weather-and-climate model (GEOS) with satellite observations rather than reading from one instrument, reported every three hours as monthly means.

How & where you'd use it. Helps researchers study haze and air clarity and provides a long, consistent record of airborne-particle thickness back to 1980.

What's measured

ATMOSPHERE › AEROSOLS › AEROSOL OPTICAL DEPTH/THICKNESS

Coverage & cadence

  • Time span1980-01-01 → ongoing
  • Measured byMERRA-2 (NOT APPLICABLE)
  • Processing levelLevel 4
  • Spatial extent-180, -90, 180, 90
  • StatusACTIVE

What you can do with it

  • Map air pollutants — NO₂, aerosols, ozone
  • Track greenhouse gases and Earth's energy budget
  • Feed weather and air-quality analysis
Official description

M2IUNXGAS (or instU_3d_gas_Nx) is an instantaneous 2-dimensional monthly diurnal means data collection in Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2). This collection consists of assimilation of aerosol optical depth analysis and aerosol optical depth analysis increment. It consists of the monthly mean of the data fields every three hour starting from 00:00 UTC, e.g.: 00:00, 03:00, … , 21:00 UTC. MERRA-2 is the latest version of global atmospheric reanalysis for the satellite era produced by NASA Global Modeling and Assimilation Office (GMAO) using the Goddard Earth Observing System Model (GEOS) version 5.12.4. The dataset covers the period of 1980-present with the latency of ~3 weeks after the end of a month. Data Reprocessing: Please check “Records of MERRA-2 Data Reprocessing and Service Changes” linked from the “Documentation” tab on this page. Note that a reprocessed data filename is different from the original file. MERRA-2 Mailing List: Sign up to receive information on reprocessing of data, changing of tools and services, as well as data announcements from GMAO. Contact the GES DISC Help Desk (gsfc-dl-help-disc@mail.nasa.gov) to be added to the list. Questions: If you have a question, please read "MERRA-2 File Specification Document", “MERRA-2 Data Access – Quick Start Guide”, and FAQs linked from the ”Documentation” tab on this page. If that does not answer your question, you may post your question to the NASA Earthdata Forum (forum.earthdata.nasa.gov) or email the GES DISC Help Desk (gsfc-dl-help-disc@mail.nasa.gov).

Get the data

m2iunxgas_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="M2IUNXGAS",
    version="5.12.4",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from GES_DISC
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.