What is the aerosol optical depth?

What is the aerosol optical depth?

Aerosol Optical Depth (AOD) is the measure of aerosols (e.g., urban haze, smoke. particles, desert dust, sea salt) distributed within a column of air from the instrument. (Earth’s surface) to the top of the atmosphere.

How is aerosol depth calculated?

I(λ) = I0(λ)exp(-m(θ)*τ(λ)) Here, AOD is calculated at wavelengths of 368, 412, 500 and 862 nm as recommended by the World Climate Research Programme (WCRP) in a technical report (WCRP (1986)) in Tsukuba.

How is AOD measured?

Aerosol optical depth (AOD) is the measure of aerosols distributed within a column of air from the instrument or Earth’s surface to the top of the atmosphere. In this paper, we compared the AOD measured by the Raymetrics Lidar system and AERONET sunphotometer.

What is the unit of AOD?

Aerosol Optical Depth (AOD)

What is the aerosol index?

The Aerosol Index (AI) is a qualitative index indicating the presence of elevated layers of aerosols with significant absorption. The main aerosol types that cause signals detected in the AI are desert dust, biomass burning and volcanic ash plumes.

What does high aerosol optical depth mean?

An optical thickness of less than 0.1 (palest yellow) indicates a crystal clear sky with maximum visibility, whereas a value of 1 (reddish brown) indicates very hazy conditions. High aerosol amounts are linked to different process in different places and times of year.

How do you measure optical thickness?

The optical thickness of a light-absorbing medium is its geometrical thickness times its intensity attenuation coefficient. For example, an optical thickness of 1 implies that the transmitted power is reduced to 1/e (≈ 37%) of its original value.

What is Deep Blue algorithm Modis?

The Deep Blue aerosol optical depth (AOD) retrieval algorithm was introduced in Collection 5 of the Moderate Resolution Imaging Spectroradiometer (MODIS) product suite, and complemented the existing Dark Target land and ocean algorithms by retrieving AOD over bright arid land surfaces, such as deserts.

What does optical depth tell us?

Optical depth is a measure of the extinction coefficient or absorptivity up to a specific ‘depth’ of a star’s makeup. From the definition, it is also clear that large optical depths correspond to higher rate of obscuration. Optical depth can therefore be thought of as the opacity of a medium.

What is aerosol layer height?

The TROPOMI Aerosol Layer Height product focuses on retrieval of vertically localised aerosol layers in the free troposphere, such as desert dust, biomass burning aerosol, or volcanic ash plumes. Height information for aerosols in the free troposphere is particularly important for aviation safety.

What are aerosols?

Aerosols. Aerosols are extremely small solid particles, or very small liquid droplets, suspended in the atmosphere. Aerosols consisting of solid particles can be placed in the atmosphere primarily by large dust storms, volcanic eruptions, or the soot particles from large fires.

What is PM2 5 and why you should care?

PM2. 5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5 micrometers, which is about 3% the diameter of a human hair. Commonly written as PM2.5, particles in this category are so small that they can only be seen with a microscope.

What is aerosol optical depth (AOD)?

Aerosol Optical Depth (AOD) is the measure of aerosols (e.g., urban haze, smoke particles, desert dust, sea salt) distributed within a column of air from the instrument (Earth’s surface) to the top of the atmosphere.

What is the formula for the aerosol component?

The optical depth due to water vapor, Rayleigh scattering, and other wavelength-dependent trace gases must be subtracted from the total optical depth to obtain the aerosol component: τ(λ)Aerosol = τ(λ)TOT – τ(λ)water – τ(λ)Rayleigh – τ(λ)O3 – τ(λ)NO2 – τ(λ)CO2 – τ(λ)CH4 (1b)

How is the size distribution of aerosols estimated?

The size distribution of aerosols can be estimated from spectral aerosol optical depth, typically from 440nm to 870nm.

How do you determine the amount of water vapor in aerosol?

The optical depth due to water vapor, Rayleigh scattering, and other wavelength-dependent trace gases must be subtracted from the total optical depth to obtain the aerosol component: The total column water vapor amount determination uses three channels: 675nm, 870nm, and 940nm.