Fires

Aerosols absorb and scatter incoming sunlight, which reduces visibility and increases the optical depth. Aerosols have an effect on human health, weather and the climate. Sources of aerosols include pollution from factories, smoke from fires, dust from dust storms, sea salts, and volcanic ash and smog. Aerosols compromise human health when inhaled by people with asthma or other respiratory illnesses. Aerosols also have an affect on the weather and climate by cooling or warming the earth, helping or preventing clouds from forming.

Satellite-derived Aerosol Index products are useful for identifying and tracking the long-range transport of volcanic ash from volcanic eruptions, smoke from wildfires or biomass burning events and dust from desert dust storms, even tracking over clouds and areas of snow and ice.

Aerosol Optical Depth (AOD) (or Aerosol Optical Thickness) indicates the level at which particles in the air (aerosols) prevent light from traveling through the atmosphere. Aerosols scatter and absorb incoming sunlight, which reduces visibility. From an observer on the ground, an AOD of less than 0.1 is “clean” - characteristic of clear blue sky, bright sun and maximum visibility. As AOD increases to 0.5, 1.0, and greater than 3.0, aerosols become so dense that sun is obscured. Sources of aerosols include pollution from factories, smoke from fires, dust from dust storms, sea salt, and volcanic ash and smog. Aerosols compromise human health when inhaled by people, particularly those with asthma or other respiratory illnesses. Aerosols also have an effect on the weather and climate by cooling or warming the earth, helping or preventing clouds from forming. Since aerosols are difficult to identify when they occur over different types of land surfaces and ocean surfaces, Worldview provides several different types of imagery layers to assist in the identification.

Carbon Monoxide (CO) is a poisonous, odorless and colorless gas. CO is produced by incomplete combustion of fossil fuels and biomass burning. It is one of the longest-lived, naturally occurring atmospheric carbon compounds. CO is a trace gas produced by methane oxidation, fossil fuel consumption (emitted from factories and cars) and biomass burning (from forest fires and agricultural burning). These measurements are useful for analyzing the distribution, transport, sources and sinks of CO in the troposphere and can be used to observe how it interacts with land and ocean biospheres. CO hinders the atmosphere’s natural ability to rid itself of harmful pollutants.

MODIS and VIIRS Corrected Reflectance imagery are available only as near real-time imagery. The imagery can be visualized in Worldview and Global Imagery Browse Services (GIBS). More:

Information on MODIS Corrected Reflectance Imagery layers including

• Corrected Reflectance True Color (Bands 1-4-3)
• Corrected Reflectance (Bands 3-6-7)
• Corrected Reflectance (Bands 7-2-1)

Information on VIIRS Corrected Reflectance Imagery layers including

• Corrected Reflectance True Color (Bands I1-M4-M3)
• Corrected Reflectance (Bands M3-I3-M11)
• Corrected Reflectance (Bands M11-I2-I1)

Browse Corrected Reflectance imagery in Worldview

For more on the difference between Corrected Reflectance and Surface Reflectance Imagery

The VIIRS and MODIS Fire and Thermal Anomalies layer shows active fire detections and thermal anomalies, such as volcanoes, and gas flares. Fires can be set naturally, such as by lightning, or by humans, whether intentionally or accidentally. Fire is often thought of as a menace and detriment to life, but in some ecosystems it is necessary to maintain the equilibrium, for example, some plants only release seeds under high temperatures that can only be achieved by fire, fires can also clear undergrowth and brush to help restore forests to good health, humans use fire in slash and burn agriculture, to clear away last year’s crop stubble and provide nutrients for the soil and to clear areas for pasture. The fire layer is useful for studying the spatial and temporal distribution of fire, to locate persistent hot spots such as volcanoes and gas flares, to locate the source of air pollution from smoke that may have adverse human health impacts.

Land Surface Temperature layer shows the temperature of the land surface in Kelvin (K). This measurement differs from air temperature measurements as it provides the temperature of whatever is on the surface of the earth for example, bare sand in the desert, ice and snow covered area, a leaf covered tree canopy and even the temperature of man-made buildings and roads. Land Surface Temperature is useful for monitoring changes in weather and climate patterns and used in agriculture to allow farmers to evaluate water requirements for wheat, or determine frost damage in orange groves.

Sulfur Dioxide (SO₂), is a colorless gas with a pungent, suffocating odor that is water soluble to produce the acid, H₂SO₃. SO₂ is one of the US Environmental Protection Agency's (EPA) six major regulated criteria pollutants (Tropospheric Ozone, Nitrogen dioxide, Sulfur dioxide, Lead, PM2.5 and PM10 particulates). It irritates the eyes, nose, and lungs. High concentrations of SO₂ can result in temporary breathing impairment. It is produced by combustion of coal, fuel oil, and gasoline, since these fuels contain sulfur in the combustion, and in the oxidation of naturally occurring sulfur gases. It is a precursor to sulfuric acid (H₂SO₄), which is a major constituent of acid rain. SO₂ is injected into the stratosphere by volcanic eruptions. SO₂ also is a major precursor to PM2.5 (Particulate Matter up to 2.5 micrometers in size), which is a significant health concern, and a main contributor to poor visibility. These data are used by the Volcanic Ash Advisory Centers in advisories to airlines for operational decisions.