MODIS Terra Near-Real-Time Aerosol Optical Depth Gridded Product

NASA's Terra satellite, launched in 1999, provides near-global daily coverage of aerosol optical depth (AOD). The Naval Research Laboratory and University of North Dakota produce this value-added, gridded Level-3 dataset from MODIS Level 2 aerosol products, with stringent filtering and bias corrections. Granules are produced every six hours with a three-hour observation window around timestamps of 00:00, 06:00, 12:00, and 18:00 UTC.

Use Cases

• Assimilating gridded AOD values and their quantitative uncertainty estimates into atmospheric chemistry and transport models for improved air quality forecasts.
• Validating aerosol model outputs against spatially averaged AOD data points that have undergone empirical corrections for systematic biases over land and ocean.
• Monitoring regional aerosol plumes (e.g., from dust storms or wildfires) using the near-real-time, six-hourly production cycle and cloud-contamination filtering.
• Analyzing diurnal aerosol patterns by comparing AOD values from the four daily timestamps (00:00, 06:00, 12:00, 18:00 UTC) which each aggregate three hours of observations.

Strengths

• Near-real-time production with granules generated every six hours via the LANCE system.
• Includes quantitative estimation of uncertainty for each AOD data point.
• Applies stringent filtering to reduce outliers and cloud contamination, and empirical corrections to reduce systematic biases.

Limitations

• Spatial resolution is limited to the 1 km grid of the underlying Level 2 MODIS data, which may not capture fine-scale aerosol features.
• The three-hour observation window for each granule may smooth or miss short-lived aerosol events.
• Specific row counts, geographic coverage bounds, and data volume details are not provided in the source description.

Provenance

Source

NASA's Earth Observing System (EOS) Terra satellite MODIS instrument, processed by the Naval Research Laboratory and University of North Dakota.

Collection Method

Derived from MODIS Level 2 aerosol products, with value-added processing including filtering, bias correction, spatial averaging, and uncertainty estimation.

Time Range

Data available from April 2000 onward, with continuous near-real-time production.

Freshness

Near-real-time; granules produced every six hours.

Geography

Near-global coverage from the MODIS instrument's 2330 km viewing swath, providing almost daily observations.