MODIS/Aqua MYD21: Daily Land Surface Temperature and Emissivity at 1km Resolution

MYD21 Version 6.1 provides daily land surface temperature and emissivity data in five-minute increments from the MODIS/Aqua satellite. The algorithm uses a physics-based Temperature/Emissivity Separation technique on thermal infrared bands, differing from the split-window method used in the heritage MYD11 product. This Level 2 product is produced by NASA with a swath of approximately 2,030 by 1,354 pixels at a nadir resolution of 1,000 meters.

Use Cases

• Monitoring diurnal land surface temperature cycles based on five-minute temporal increments.
• Validating physics-based temperature/emissivity separation algorithms against split-window techniques.
• Studying thermal anomalies like fires or lava flows based on the retention of high-temperature values.
• Assessing atmospheric correction under humid conditions using the improved Water Vapor Scaling scheme.
• Analyzing the impact of dust and cloud contamination on thermal retrievals over desert regions.

Strengths

• Algorithm uses a physics-based Temperature/Emissivity Separation technique on three MODIS thermal bands (29, 31, 32).
• Data is produced daily in five-minute temporal increments of satellite acquisition.
• Swath dimensions are approximately 2,030 pixels along track and 1,354 pixels per line.
• Includes an improved Water Vapor Scaling atmospheric correction scheme for stable retrieval in warm, humid conditions.

Limitations

• Known issue of extreme high temperature outliers, especially over desert regions like the Sahara, due to undetected cloud and dust.
• Contaminated pixels are retained in the output product, requiring users to apply Quality Control filtering, unlike the MYD11 product which flags them.
• Column-level documentation is absent; field semantics must be inferred after download.

Provenance

Source

National Aeronautics and Space Administration

Collection Method

Produced from MODIS/Aqua satellite observations using the MYD21 Land Surface Temperature and Emissivity algorithm.

Time Range

Daily production.

Freshness

Last updated 2026-03-13 00:23:40.904299; freshness should be verified.

Geography

Global coverage from satellite swaths.