Humidity, Saturation, and Stability: Part 1 Flashcards
What does the saturation vapor mixing ratio of air depend on?
Pressure and temperature
What happens to the humidity and vapor mixing ratio of a saturated air parcel as its temperature falls?
Humidity does not change and the vapor mixing ratio decreases
What happens to the density and relative humidity of an unsaturated air parcel as its temperature and pressure do not change and its vapor mixing ratio increases?
Density decreases and relative humidity increases
If the vapor mixing ratio of a parcel of air is 2g/kg and its saturation mixing ratio is 6g/kg. What is its relative humidity?
33.3%
If the mixing ratio of a parcel of air is 6g/kg and the relative humidity is 25%. What is the saturation mixing ratio?
24g/kg
If the air is 12°C and the vapor mixing ratio is the same as the saturation vapor mixing ratio. Is the dewpoint temperature less than, equal to, or more than the temperature?
It is equal to the temperature
On a clear and calm day, what usually happens to the relative humidity between sunrise and early afternoon?
It falls
What soundings always indicate stable atmosphere conditions?
Temperature inversion, isothermal conditions, and either no change or an increase in temperature with altitude
What does conditional instability indicate in an air layer?
That it is unstable for saturated and stable for unsaturated air parcels
How does unstable air affect the vertical motion of air parcels?
It enhances it.
Why don’t rising parcels of saturated air not cool as rapidly as rising parcels of unsaturated air?
Because expansion cooling of saturated air is partially compensated for by the release of latent heat
What happens to the saturation mixing ratio as saturated air flows up the windward slopes of a mountain range?
It decreases
What happens when unsaturated air flows down the leeward slopes of a mountain range?
- Air temperature rises
- Relative humidity decreases
- Saturation vapor pressure increase
What happens when a clear parcel of air ascends dry adiabatically?
- Its relative humidity increases
- Its saturation vapor mixing ratio decreases
- Its temperature drops
Suppose the vapor mixing ratio of the cold outside air is the same as the vapor mixing ratio of the warm air indoors. What happens to the relative humidity indoors if the door was opened and the cold air replaces some of the warm air.
It becomes higher than before
Which pair of processes, working together, will make the atmosphere more unstable?
Warm the surface and cool the air aloft
A parcel of unsaturated air descends adiabatically without mixing. What happens to the temperature when it descends 800m?
It warms 8°C
What does 10% relative humidity mean?
10% of the mass of air consists of water vapor
Consider the case of very calm wind conditions near the ground. What happens to the relative humidity when the air temperature increases?
It decreases
What happens to the temperature of an air parcel when it rises without mixing with ambient air?
It decreases
What is vapor pressure?
The partial pressure exerted by water vapor alone
What is the mixing ratio?
The mass of vapor divided by the mass of dry air
What is humidity?
The amount of water vapor
What does saturation vapor pressure depend on?
Temperature
What is isobaric cooling?
When a system cools while the pressure remains constant
What is isothermal compression?
When pressure increases while the temperature remains constant
What is relative humidity?
The vapor pressure divided by saturation vapor pressure
-i.e. the amount of water vapor in the air vs the amount the air can hold
What happens when unsaturated air cools?
- Vapor pressure does not change
- Temperature decreases
- Saturation vapor pressure decreases
- Relative humidity increases
What happens when unsaturated air warms?
- Vapor pressure does not change
- Temperature increases
- Saturation vapor pressure increases
- Relative humidity decreases
What is a dewpoint?
The temperature at which air must be cooled at a constant pressure to reach saturation.
How can dewpoint be used?
Relative humidity = saturated vapor pressure at dewpoint / saturated vapor pressure at a temperature
What is the mixing ratio?
The mass of water vapor contained in 1kg of dry air
What is the saturated mixing ratio?
The max amount of water vapor 1kg of dry air can contain
What does saturated mixing ratio depend on?
Temperature and pressure
How can you calculate relative humidity with the mixing ratio and saturated mixing ratio?
Relative humidity = mixing ratio / saturated mixing ratio
What is precipitable water?
The amount of water content of a vertical column of air from the surface to the top of the atmosphere
How much water would be produced if you condensed all water vapor in the atmosphere?
2.5cm deep pool of water globally
