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Full catalog/VJ121A1D
VJ121A1D·v002·dataset

How hot the land surface gets, daytime (NOAA-20, daily, 1 km)

VIIRS/JPSS1 Land Surface Temperature/Emissivity Daily L3 Global 1km SIN Grid Day V002
land NASA LPCLOUD Level 3 active HDF-EOS5
In plain English

What it measures. How hot the land surface gets during the daytime, plus a related property (emissivity) that describes how the surface gives off heat. It's the actual skin temperature of the ground, roads, and rooftops, not the air temperature.

How it's made. Compiled daily from the VIIRS instrument on the NOAA-20 satellite, averaging clear-sky daytime readings onto a 1-km grid, designed to match the older MODIS temperature record.

How & where you'd use it. Used to study heat waves and urban heat, monitor droughts and water stress, and track long-term land surface temperature trends.

What's measured

LAND SURFACE › SURFACE RADIATIVE PROPERTIES › EMISSIVITYLAND SURFACE › SURFACE THERMAL PROPERTIES › LAND SURFACE TEMPERATURE

Coverage & cadence

  • Time span2018-01-01 → ongoing
  • Measured byNOAA-20 (VIIRS)
  • Processing levelLevel 3
  • Spatial extent-180, -90, 180, 90
  • FormatsHDF-EOS5
  • StatusACTIVE

What you can do with it

  • Track deforestation, fire scars and land-cover change
  • Monitor crop and vegetation health (NDVI/EVI)
  • Map how built-up vs. green an area is over time
Official description

The NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) Day Version 2 product (VJ121A1D) is compiled daily from daytime Level 2 Gridded (L2G) intermediate products. The L2G process maps the daily [VJ121](https://doi.org/10.5067/VIIRS/VJ121.002) swath granules onto a sinusoidal MODIS grid and stores all observations overlapping a gridded cell for a given day. The VJ121A1 algorithm sorts through all these observations for each cell and estimates the final LST value as an average from all cloud-free observations that have good LST accuracies. The daytime average is weighted by the observation coverage for that cell. Only observations having observation coverage more than a certain threshold (15%) are considered for this averaging. The 1 kilometer dataset is derived through resampling the native 750 meter VIIRS resolution in the input product. The VJ121A1D product is developed synergistically with the Moderate Resolution Imaging Spectroradiometer (MODIS) LST&E Version 6.1 product ([MOD21A1D](https://doi.org/10.5067/MODIS/MOD21A1D.061)) using the same input atmospheric products and algorithmic approach. The overall objective for NASA VIIRS products is to ensure the algorithms and products are compatible with the MODIS Terra and Aqua algorithms to promote the continuity of the Earth Observation System (EOS) mission. Additional details regarding the method used to create this Level 3 (L3) product are available in the Algorithm Theoretical Basis Document (ATBD). The VJ121A1D product contains seven Science Datasets (SDS) variables: LST, quality control, emissivity for bands M14, M15, and M16, view zenith angle, and time of observation. A low-resolution browse image for LST is also available for each VJ121A1D granule. Known Issues * For complete information about known issues please refer to the [MODIS/VIIRS Land Quality Assessment website](https://landweb.modaps.eosdis.nasa.gov/knownissue?sensor=VIIRS) and the User Guide.

Get the data

vj121a1d_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="VJ121A1D",
    version="002",
    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 LPCLOUD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.