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What you will learn in Atmospheric Circulation and Weather Systems

1. Pressure makes wind
Air moves because pressure differs from place to place, not because it is high or low. On a planet that does not turn it runs straight from high to low; turn the planet and the same push ends up along the isobars.
2. Add rotation
One flight seen twice: straight from space, curved from the ground. The Coriolis effect is what a turning observer sees, and it turns moving air right in the north, left in the south and not at all along the equator.
3. How big is the effect, really
The Rossby number compares the flow's own acceleration with the Coriolis one. A bathtub scores over three thousand and an ocean gyre about a thousandth, and the bathtub story dies on the number.
4. Three cells, six belts
Heating contrast and rotation together give three cells in each hemisphere, and the trade winds, the westerlies, the pressure belts and the subtropical deserts follow from them. The measured atmosphere sits beside the model.
5. Jets and fronts
The jet stream runs along the boundary between polar and tropical air. When it meanders, cold air spills south under the troughs and warm air pushes north under the ridges, and the waves drift east or stall depending on their length.
6. A depression passes overhead
Stand still while a mid-latitude depression crosses: the barometer falls and rises, the wind veers or backs depending on which side of the track you are, and the warm and cold fronts arrive in an order you can predict from the chart.
7. Tropical cyclones, and the limits of forecasting
Warm water fuels tropical cyclones and the equator, with no rotation to spin them, almost never makes one. Then the limit on every forecast: two runs of one perfect model, started a hair apart, stop agreeing, and the climate they share is a different thing from the weather they disagree about.

What you will learn in Atmospheric Circulation and Weather Systems

1. Pressure makes wind

Air moves because pressure differs from place to place, not because it is high or low. On a planet that does not turn it runs straight from high to low; turn the planet and the same push ends up along the isobars.

2. Add rotation

One flight seen twice: straight from space, curved from the ground. The Coriolis effect is what a turning observer sees, and it turns moving air right in the north, left in the south and not at all along the equator.

3. How big is the effect, really

The Rossby number compares the flow's own acceleration with the Coriolis one. A bathtub scores over three thousand and an ocean gyre about a thousandth, and the bathtub story dies on the number.

4. Three cells, six belts

Heating contrast and rotation together give three cells in each hemisphere, and the trade winds, the westerlies, the pressure belts and the subtropical deserts follow from them. The measured atmosphere sits beside the model.

5. Jets and fronts

The jet stream runs along the boundary between polar and tropical air. When it meanders, cold air spills south under the troughs and warm air pushes north under the ridges, and the waves drift east or stall depending on their length.

6. A depression passes overhead

Stand still while a mid-latitude depression crosses: the barometer falls and rises, the wind veers or backs depending on which side of the track you are, and the warm and cold fronts arrive in an order you can predict from the chart.

7. Tropical cyclones, and the limits of forecasting

Warm water fuels tropical cyclones and the equator, with no rotation to spin them, almost never makes one. Then the limit on every forecast: two runs of one perfect model, started a hair apart, stop agreeing, and the climate they share is a different thing from the weather they disagree about.