Earth Data School
About
Full catalog/OMMYDCLD
OMMYDCLD·v003·dataset

Combined cloud measurements (Aura + Aqua)

OMI/Aura and MODIS/Aqua Merged Cloud Product 1-Orbit L2 Swath 13x24 km V003 (OMMYDCLD) at GES DISC
atmosphere NASA GES_DISC Level 2 active
In plain English

What it measures. Cloud information for each satellite pass, merging cloud properties measured by the OMI instrument on Aura with matching statistics from the MODIS instrument on Aqua.

How it's made. Created by lining up near-simultaneous observations from two NASA A-Train satellites that fly close together, then attaching MODIS cloud statistics to each OMI viewing pixel.

How & where you'd use it. Used to improve cloud detection, spot multi-layer clouds, and clear clouds from other measurements, taking advantage of having two sensors look at the same scene at nearly the same time.

What's measured

ATMOSPHERE › CLOUDS › CLOUD MICROPHYSICS › CLOUD LIQUID WATER/ICEATMOSPHERE › CLOUDS › CLOUD MICROPHYSICS › CLOUD OPTICAL DEPTH/THICKNESSATMOSPHERE › CLOUDS › CLOUD PROPERTIES › CLOUD FRACTIONATMOSPHERE › CLOUDS › CLOUD PROPERTIES › CLOUD HEIGHTATMOSPHERE › CLOUDS › CLOUD PROPERTIES › CLOUD TOP PRESSUREATMOSPHERE › CLOUDS › CLOUD PROPERTIES › CLOUD TOP TEMPERATUREATMOSPHERE › CLOUDS › CLOUD RADIATIVE TRANSFER › CLOUD EMISSIVITYATMOSPHERE › CLOUDS › CLOUD RADIATIVE TRANSFER › CLOUD RADIATIVE FORCING

Coverage & cadence

  • Time span2004-10-01 → ongoing
  • Measured byAura (OMI) · Aqua (MODIS)
  • Processing levelLevel 2
  • 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

The OMI/Aura and MODIS/Aqua Merged Cloud Product 1-Orbit L2 Swath 13x24 km (OMMYDCLD) is a Level-2 orbital product that combines cloud parameters retrieved by the Ozone Mapping Instrument (OMI) on the Aura satellite with collocated statistical information for cloud parameters retrieved by the Moderate Resolution Imaging Spectrometer (MODIS) on the Aqua spacecraft. This product is designed to take advantage of the synergy between OMI and MODIS, which both fly on satellites in the NASA A-Train constellation of Earth-observing satellites that follow similar orbital tracks and collect near-simultaneous observations. This product can be used for cloud-clearing, detection of multi-layered clouds, and other applications that may exploit these multi-spectral measurements. The algorithm for the OMMYDCLD product co-locates daytime cloud parameters from MODIS onto the OMI visible (VIS) pixel for a given OMI orbit and generates statistical information from the collocated MODIS pixels. For each OMI granule, the orbit start and end times are used to select the corresponding 5-minute MODIS granules for processing. A contiguous list of MODIS granules spanning the full duration of the OMI orbit are selected based on the relative time lag between Aqua and Aura. The algorithm lead for this product is NASA OMI scientist Dr. Joanna Joiner. The OMMYDCLD data files are stored in the version 5 EOS Hierarchical Data Format (HDF-EOS5) using the swath model, and follows the same conventions used by the other OMI Level-2 data products. Each file contains data from the day lit portion of an orbit (about 53 minutes). There are approximately 14 orbits per day. The file size for the OMMYDCLD data product is about 8 Mbytes.

Get the data

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

results = earthaccess.search_data(
    short_name="OMMYDCLD",
    version="003",
    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.