evsc 100 week 8 - Atmospheric Aerosol Loading

Atmospheric Aerosol Loading and the Planetary Boundary

control variable for atmospheric aerosol loading

Control variable: Aerosol optical depth (AOD) 

explain why we can not yet quantify the planetary boundary. 

Planetary boundary: Not yet quantified

• It's complicated because aerosols can both warm and cool the planet

• Hard because a boundary is set based on its effect on the earth’s system, if we set a boundary and it's wrong, then it's confusing

Describe what atmospheric aerosols are

they are are tiny solid particles or liquid droplets suspended in the atmosphere [atmospheric particulates]

why are atmospheric aerosols important to monitor

They affect climate, clouds, precipitation, air quality, health, and ecosystems.

• Monitoring them through measurements like AOD is crucial to predict climate impacts, guide policy, and protect human and environmental health.

natural sources of atmospheric aerosols

• Volcanic ash 

• Desert (mineral) dust 

• Forest fire smoke 

• Sea salt and Forest (trees) emissions 

  • Key - direct injection

anthropogenic sources of atmospheric aerosols

• Gases from burning fossil fuels 

• Volcanic gases 

  • Key - secondary reactions

How are aerosols detected and measured?

aerosols are detected and measured primarily through satellite observations using the Aerosol Optical Depth (AOD)

• AOD < 0.05: Very clear skies

• AOD ≈ 0.1: Hazy conditions

• AOD > 1: Very high aerosol concentrations

how do satellites detect aerosols

by observing how sunlight is scattered and absorbed as it passes through the atmosphere, using these measurements to calculate AOD and infer aerosol properties.

Describe, using a map, the patterns of aerosols in the atmosphere. 

darker means more aerosols - typically near the equator

Absorption

retains energy in the atmosphere, leading to atmospheric heating, and prevents energy from reaching the surface, leading to surface cooling

Scattering

prevents radiation from reaching Earth’s surface, leading to surface cooling

indirect effects of aerosols on climate and the hydrologic cycle

CDNC: “Cloud droplet number concentration.”

• More aerosols → more condensation nuclei on which clouds can form → more interactions between clouds and both shortwave/longwave radiation

direct effects of aerosols on climate and the hydrologic cycle

• How much radiation is scattered or absorbed depends on the chemical and physical characteristics of the aerosol material 

  • Particles in the atmosphere react to the solar radiation from the sun; therefore, it’s a direct effect

direct vs indirect effects of aerosols

Direct effects = aerosols directly scatter or absorb radiation

Indirect effects = aerosols modify clouds, which then influence radiation and precipitation.

effects of aerosols on human health.

Because aerosols are small, they can have an outsized impact on health (when we breathe them in and they react or accumulate in our bodies) and atmospheric composition (when aerosol-driven chemical reactions change the make-up of the atmosphere)

what bands of UV are filtered out!

• Ozone screens all of the most energetic, UV-C, radiation, and most of the UV-B radiation.

• Ozone only screens about half of the UV-A radiation.

• Excessive UV-B and UV-A radiation can cause sunburn and can lead to skin cancer and eye damage.