The atmosphere behind the forecast
Why air rises or refuses to: composition, stability, the adiabatic process and lapse rates, and where the heat goes when water changes state.
13 min read · IFR weather
After this lesson you can
- State what the atmosphere is made of, and why the smallest component drives the weather.
- Define stability as resistance to vertical motion, and predict what stable and unstable air each produce.
- Apply the three lapse rates - average, dry adiabatic, moist adiabatic - and say why the moist one is smaller.
- Explain latent heat of evaporation and sublimation, and how water carries energy through the atmosphere.
- Recognize an inversion and say what it traps.
An instrument pilot reads forecasts for a living, and a forecast is a conclusion. This lesson is the reasoning underneath it: why one afternoon builds towering cumulus and the next holds a smooth overcast, why a lapse rate predicts turbulence, and why moisture changes everything it touches.
The instrument ACS asks for it explicitly, under Weather Information: atmospheric composition and stability, and temperature and heat exchange. They are the two knowledge items that let a pilot disagree with a forecast for a reason.
The rest of this lesson
- 1.What the air is made of, and the one percent that matters
- 2.Stability: resistance to vertical motion
- 3.The adiabatic process and the three lapse rates
- 4.Temperature and heat exchange: where the energy goes
- 5.Inversions: when the profile turns upside down
- 6.Wind: what drives it, what bends it, and where it shears
- 7.Reading the winds aloft: the FB
- 8.Air masses and fronts: where the weather systems come from
- 9.Turbulence, frost, and the things that hide the ground
These 9 sections, their figures, the checks along the way and the end-of-lesson quiz come with the IFR track. Paid once, yours for good.
Key terms
Try to recall each definition before turning the card.