Atmospheric transmittances for the AVHRR channels

Area of Science:

• Atmospheric Science
• Remote Sensing
• Radiometry

Background:

• Accurate atmospheric transmittance is crucial for satellite remote sensing.
• The Advanced Very High Resolution Radiometer (AVHRR) is a key instrument for Earth observation.

Purpose of the Study:

• To compute vertical path atmospheric transmittances for AVHRR channels.
• To identify key atmospheric absorbers and scatterers impacting transmittance spectra.

Main Methods:

• Utilized a line-by-line transmittance model.
• Incorporated gaseous absorption, molecular scattering, and aerosol scattering.
• Analyzed contributions from various atmospheric constituents per channel.

Main Results:

• Channels 1 and 2 transmittance dominated by aerosol scattering.
• Channel 3 transmittance influenced by water vapor lines/continuum and minor gases (CH(4), N(2)O, N(2)).
• Channels 4 and 5 transmittance dominated by water vapor continuum, with CO(2), HNO(3), and CFCs also significant.

Conclusions:

• Aerosol properties are critical for understanding transmittance in lower AVHRR channels.
• Water vapor is a primary absorber across multiple channels.
• Increasing concentrations of chlorofluorocarbons (CFCs) will impact future transmittance, particularly in channels 4 and 5.