SNPP VIIRS Fire and Smoke Imagery
eIDEA shows the Suomi National Polar-orbiting Partnership (SNNP) Visible Infrared Imaging Radiometer Suite (VIIRS) smoke mask in shades of pink (light pink for thin smoke and bright pink for thick smoke; see scale on the top) overlaid on the true color image (also called as RGB for Red Green Blue wavelengths). Because the RGB image is derived from visible wavelengths, it looks like a picture. Areas of white are clouds and the surface is evident in cloud-free regions. The opacity of the RGB image and smoke mask can be adjusted using the RGB Opacity and Smoke Products Opacity slider bars, respectively, in the menu to the right of the imagery.
The pink-colored smoke mask is a qualitative indicator of smoke originating from burning fires in the region or transported smoke from upwind regions. The smoke mask is derived using spectral and spatial threshold tests based on VIIRS measurements in the visible and infrared wavelengths. More information on the smoke mask algorithm is available in the Documents link in the menu bar on the left side of the eIDEA homepage.
Red dots on the image are fire hot spots, which indicate the locations of fires sensed by VIIRS. The quantitative measure of "fire temperature" is given by the Fire Radiative Power (FRP), which is indicated by the size of the dots (scale on the top); larger dots correspond to larger values of FRP. The FRP hot spots can be turned on/off by clicking on the FRP button in the menu to the right of the imagery.
The default settings for eIDEA have the VIIRS smoke mask, RGB, and FRP hot spots turned on. Additional quantitative information about how much aerosol is present in the atmosphere can be obtained by clicking on the Aerosol Optical Thickness (AOT) and Satellite Derived PM2.5 buttons in the menu to the right of the imagery. AOT is a unitless measure of the scattering and absorption of visible light in a vertical column of the atmosphere; values typically range from 0 to 1 in the U.S. (see scale at top). AOT is related to concentrations of fine particulate matter (PM2.5) in the atmosphere. PM2.5 is a criteria pollutant that causes acute and chronic human health effects. High areas of AOT (red, orange, and yellow colors in the image) correspond to high concentrations of PM2.5 due to aerosols in the atmosphere. Cool colors (blues and greens) indicate low AOT and correspondingly low concentrations of PM2.5. Aerosols can be smoke, urban/industrial haze, dust, volcanic ash, and/or sea salt. Note that clouds block the measurement of AOT, so no AOT is available in cloud-covered regions.
The Satellite Derived PM2.5 button indicates an estimate of surface PM2.5 concentrations (in μg/m3; see at the top) derived from AOT. Also available are the AIRNOW PM2.5 measurements from the U.S. EPA AirNow network of surface PM2.5 monitors. By clicking on the AirNow PM2.5 button, users can see areas where smoke indicated by VIIRS is reaching the ground and causing high readings of PM2.5 (orange and red colored AirNow PM2.5 dots). The AOT-estimated PM2.5 and AirNow PM2.5 datasets use the same color coding scale, so the agreement/disagreement between satellite and ground observations indicate how well the VIIRS instrument is capturing surface aerosol concentrations.
The user can zoom in to an area of interest using the Zoom in Zoom out button on the top left of the image or by clicking on the imagery. Clicking on the County button in the menu to the right of the imagery adds an overlay of county boundaries to the imagery. Likewise, clicking on the Labels button turns the national and state borders/labels on and off. To save an imagery configuration as a graphics file, click on the Save Image button. To change the date of the imagery, click on the date next to "Select Date" at the top of the imagery, or use the arrows to go back/forward one day at a time.