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Full catalog/M2TCNXLTM
M2TCNXLTM·v2·dataset

Long-term average weather conditions (1991-2020 model)

MERRA-2 tavgC_2d_ltm_Nx: 2d, Single-Level, Long Term Mean Diagnostics based on 1991-2020 V2 (M2TCNXLTM) at GES DISC
atmosphere NASA GES_DISC Level 4
In plain English

What it measures. Long-term average weather conditions for each calendar month, based on three decades (1991-2020) of data. It includes things like air temperature, wind, surface and sea-level pressure, rainfall, evaporation, and water vapor, plus how much each varies year to year.

How it's made. Computed from MERRA-2, NASA's blended record that combines satellite observations with a weather model to fill in a consistent global picture, then averaged over the 30-year period.

How & where you'd use it. A baseline for comparing whether a given month was wetter, warmer, or windier than normal, and a reference for climate studies and modeling.

What's measured

ATMOSPHERE › ATMOSPHERIC TEMPERATURE › SURFACE TEMPERATURE › AIR TEMPERATUREATMOSPHERE › PRECIPITATION › PRECIPITATION RATE

Coverage & cadence

  • Time span1991-01-01 → 2020-12-31
  • Measured byMERRA-2 (NOT APPLICABLE)
  • Processing levelLevel 4
  • Spatial extent-180, -90, 180, 90
  • StatusCOMPLETE

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

M2TCNXLTM (or tavgC_2d_ltm_Nx) is a 2-dimensional monthly data collection for climatological long term mean and standard deviation representing the interannual variability on a monthly timescale, derived from monthly Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) datasets. V2 of this data collection is calculated with data from January 1991 to December 2020. In contrast, V1, the original version, is computed with data from an earlier 30-year time of 1981-2010. This collection consists of meteorological diagnostics, such as air temperature (maximum, mean, and minimum at 2-meter), wind components at different vertical levels (2-meter, 10-meter, 50-meter, 850 hPa, 500hPa, and 250 hPa), sea level pressure, surface pressure, and total precipitation, evaporation, and total precipitable water vapor. MERRA-2 is the latest version of global atmospheric reanalysis for the satellite era produced by the 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 a latency of ~3 weeks after the end of the previous 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 filename. MERRA-2 Mailing List: Sign up to receive information on reprocessing of data, changes to 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 the "MERRA-2 File Specification Document'', “MERRA-2 Data Access – Quick Start Guide”, and FAQs linked from the ”Documentation” tab on this page for more information. If these documents do 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

m2tcnxltm_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="M2TCNXLTM",
    version="2",
    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.