AIRS Rapid Response:
Latest Sulfur Dioxide and
Dust Detection

Detection Time: 2024/05/03, UTC 21:29:21

Region plotted represents one AIRS data granule.


About | KMZ | GeoTIFF

Sulfur dioxide brightness temperature difference is calculated by differencing the values reported between two AIRS channels, one that is sensitive to SO2 and one that is not. Larger differences imply greater SO2 absorption, which in turn implies a stronger volcanic signal. Please refer to the opening paragraph on this page for a better understanding of what this measurement implies.


About | KMZ | GeoTIFF

Dust score is determined from multiple tests that compare radiances. Higher scores indicate more certainty that dust is present. Dust is probable when the score is above 380.


Total Cloud Fraction
About | KMZ

The cloud fraction reported by AIRS is the product of cloud emissivity and areal coverage. Low fraction can indicate either small, highly emissive clouds or more extensive but less emissive clouds. The cloud fraction shown here has a spatial resolution of 45 km at nadir. AIRS can sense up to two cloud decks in a column of atmosphere, and this plot shows the cloud fraction of all cloud decks present.

Cloud Top Altitude
About | KMZ

Cloud top altitude is calculated from the natural logarithm of the AIRS cloud top pressure assuming a surface pressure of 1000 hPa and a scale height of 6 km. The cloud altitude shown here has a spatial resolution of 45 km at nadir. AIRS can sense up to two cloud decks in a column of atmosphere, but in this plot only the higher of the two decks is depicted.


Visible Image (daytime only)

This image is created using data from AIRS’ visible/near-infrared light sensor, Vis/NIR, and is available for daytime acquisitions only. Please note the green rectangular border defines the area of one granule of AIRS data on Earth’s surface that is observed by AIRS’ primary set of IR sensors. The viewing area for the Vis/NIR instrument is slightly different than the primary sensors, which explains the misalignment of the visible image and the green border.

Infrared Image

AIRS' infrared sensor measures radiometric temperature (brightness temperature) at the top of the atmosphere over a wide spectral range, allowing determination of air temperature throughout the atmospheric column either above the clouds or at Earth's surface when not blocked by cloud. Useful for assessing cloud cover (clouds are colder than the underlying surface).


  • Use this tool to overlay sulfur dioxide (SO2), dust, cloud fraction, and cloud top height derived from AIRS data plus AIRS visible light and infrared imagery.
  • Set the visibility and opacity of individual layers to see where quantities intersect and to facilitate interpretation.
  • Clouds can obscure the AIRS SO2 signal. By combining SO2, cloud fraction, and cloud height you can see can where meteorological clouds interfere with AIRS detections of SO2.