Small Group Activity: Optical depth of atmosphere

Contemporary Challenges 2021
In this activity students estimate the optical depth of the atmosphere at the infrared wavelength where carbon dioxide has peak absorption.

This activity follows Temperature of the Earth.

Estimate the optical depth for infrared light with wavelength 15 \(\mu\)m when it travels through our atmosphere at standard temperature and pressure \(STP\). The number density of air molecules at STP can be found from \(pV=Nk_BT\).

Our air is 0.041% CO2 (410 ppm).

Absorption cross sections \(\sigma_a\). The graph is from Fundamentals of Atmospheric Radiation by Craig Bohren, a highly recommended book.

Learning Outcomes