What are the six phase changes of water?
- Melting (S->L), 2. Freezing (L->S), 3. Evaporation (L->G), 4. Condensation (G->L), 5. Sublimation (S->G), 6. Deposition (G->S)
During which phase changes is energy (latent heat) ABSORBED by water?
Melting, Evaporation, Sublimation. These are ‘cooling’ processes for the environment.
During which phase changes is energy (latent heat) RELEASED by water?
Condensation, Freezing, Deposition. These are ‘warming’ processes for the environment.
What is ‘Latent Heat’?
The ‘hidden’ energy absorbed or released during a phase change, without a change in temperature.
Why is evaporation a ‘cooling process’?
Because the water molecules with the highest kinetic energy escape as vapor, lowering the average kinetic energy (temperature) of the remaining liquid.
What is the relationship between kinetic energy and the phase of water?
Higher kinetic energy means molecules move faster, favoring gas phase (water vapor). Lower kinetic energy means slower molecules, favoring liquid or solid phase.
What are the five ways humidity is expressed?
- Absolute Humidity, 2. Specific Humidity, 3. Mixing Ratio, 4. Vapor Pressure, 5. Relative Humidity
Which measure of humidity is the most commonly used in weather reports?
Relative Humidity (%)
How is Relative Humidity changed? (Two main ways)
- Change the amount of moisture in the air (add or remove water vapor). 2. Change the air temperature (warming lowers RH, cooling raises RH).
Which humidity measures are a direct measure of the actual amount of water vapor in the air?
Absolute Humidity, Specific Humidity, and Mixing Ratio.
If the water vapor content in the air remains the same but the temperature rises, what happens to the Relative Humidity?
It decreases.
What is the Dew Point temperature?
The temperature to which air must be cooled to become saturated. A direct measure of the air’s moisture content.
What does it mean if the air temperature and dew point are very close together?
The air is very humid and likely foggy or precipitating.
What is a Stüve Diagram?
A chart used to plot temperature and dew point data from a weather balloon to analyze atmospheric stability, clouds, and more.
On a Stüve Diagram, what does the line that starts warm at the bottom and cools with height represent?
The Temperature profile of the atmosphere.
On a Stüve Diagram, what does the line that follows the temperature line but deviates represent?
The Dew Point profile. Where they meet is the LCL.
What is the LCL (Lifted Condensation Level) on a Stüve Diagram?
The height where the air becomes saturated and a cloud begins to form (where the temperature and dew point lines meet).
What is an inversion on a Stüve Diagram?
A layer where temperature increases with height. It appears as a line bending to the right.
What does a large gap between the temperature and dew point lines indicate?
Dry air.
What is the tropopause on a Stüve Diagram?
The point where the temperature stops decreasing with height and becomes constant or starts increasing; the ‘top’ of the weather-producing layer.
How would you identify a thick cloud layer on a Stüve Diagram?
A layer where the temperature and dew point lines are very close together or on top of each other.
How do you find the air temperature at 3 miles altitude on a Stüve Diagram?
Follow the 3-mile altitude line to the temperature profile line, then read straight down to the temperature axis.
How do you find the 500 mb level on a Stüve Diagram?
Find the 500 mb isobar (pressure line) and follow it to the temperature profile line to get the temp at that pressure level.
What is an isobar on a Stüve Diagram?
A line of constant pressure (the horizontal lines).
