Lecture 5 Flashcards
The density of air increases as altitude increases.
Is this stable?
Unstable!
Less dense air will rise!
What determines the stability of the atmosphere?
Density of air
The density of air decreases as altitude increases.
Is this stable?
Yes!
Denser air is near the ground. Air at any point neither sinks or rises.
What is the determinant of air density?
Temperature
What is dry Adiabatic Lapse rate?
10°c/km
Meaning that the temperature of a parcel of air drops by 10°C when the air rises in the atmosphere by 1 km.
What happens to the temp and pressure of a parcel of fluid when it is compressed?
Its temperature rises.
Its pressure increases.
What happens to the temperature and pressure of a parcel of fluid when it is expanded?
The temperature falls.
The pressure decreases.
What is the first law of thermodynamics?
The internal energy of a system can be changed only by performing work on the system or by adding or removing heat.
What does “adiabatic” mean?
Changes in temperature due to changes in volume (or density) and internal energy.
NOT due to gain or loss of heat from or to the surroundings.
Change in heat is 0.
If the air is saturated with water, how is the adiabatic lapse rate compared to that of dry air?
Smaller.
Meaning that wet air cools slower than dry air as it rises up the altitude.
What is adiabatic lapse rate?
The rate of decline (lapse) in the temperature of air as it rises up the altitude.
Wet air cools slower than dry air as it rises up in the atmosphere.
Why?
As wet air cools, the water vapor condenses, releasing latent heat of evaporation.
So more energy is require to change the temperature of wet air than dry air.
