Before doing anything, we need to make basic some assumptions about our atmosphere.

• The atmosphere is Thin

• The atmosphere is supported by pressure equilibrium (hydrostatic equilibrium)

• The atmosphere is isothermal

• The equation of state is the Ideal Gas Law

These assumptions allow us to treat the atmosphere is a thin, uniform slab of material at constant density and temperature.

The atmosphere is a physically complex system. While some of its behavior can be described with relatively simple physics, its dynamic nature means that the system is highly non-linear.

This class will try to build a physical foundation by which we can understand some of the more important atmospheric processes. Along the way, complexities will be introduced.

There are basically 8 generic items about the physical nature of the atmosphere. All of these items interact, in subtle and complex ways, to produce weather and climate.

1. The atmosphere is a differentially absorbing medium in terms of electromagnetic radiation. This leads to its vertical structure (see more below).

2. The atmosphere is an open, heterogeneous thermodynamic system so understanding thermodynamics is essential and this is where we will start in this class.

3. The atmosphere is a fluid system free to move and flex This is where the physics gets hard. We will not be discussing fluid dynamics in this class very much since that is beyond the math prerequisite.

4. The atmosphere is a system which rotates, with the rotation of Earth this sets up forces and equations of motion.

5. The atmosphere is a gaseous system containing at least one condensible gas (water vapor), at normally occuring conditions, which can additionally freeze to a solid form the behavior of water vapor is the single biggest influence on weather.

6. The atmosphere is subject to chemical transformations having profound influences like the CFC chemical depletion of the Ozone Layer

7. The atmosphere is subject to profound influences occuring at Earth's surface. This is dominated by the effects of 6 billion humans altering the surface.

8. The atmosphere is a coherently integrated, interactive scientific system such that all the above factors interact with each other to produce the behavior of the global weather and climate which we still can not model effectively.

Indeed, one of the big questions in modeling is whether large scale synoptic disturbances dominate the weather, or does a complex, linked network of small scale aspects dominate?