Meteorology: Water in the Atmosphere
Station 1: Changing Relative Humidity in a Parcel of Air
1. Start off with the provided amount of water in the large beaker. This is a WARM AIR PARCEL (we will call it
28oC). This is roughly 33% RH.
a. What is its water vapor content if it is about 1/3 full? This will be our standard in which we compare
cooler air parcels to.
2. Pour the water into the 2nd Beaker (smaller beaker). The smaller beakers represent COOLER PARCELS of air than
the original ‘x-tra large’ beaker.
a. What happens to the Relative Humidity as the air cools?
b. Approximately, what is the new Relative Humidity in this beaker if the parcel of air temperature is 18oC?
3. Pour the water into the 3rd Beaker. This represents an air parcel that is 11oC.
a. What is the RH of this beaker?
b. What is the difference of Capacity vs. Saturation Point of this parcel of air?
4. Pour the water into the 4th and final Beaker. This represents an air parcel that is 0oC.
a. What is the capacity at 0oC?
b. How much water condenses out of this parcel?
c. If this air were to descend 3000 meters, what would be the RH at the new elevation?
Station 2: Cloud Making 101
Procedure: Use warm tap water out of the faucet to fill the container to the recommended line. Light a match and blow
out the match leaving the ash, dust, and soot in the air within the container(s). The ash, dust, and soot represent
condensation nuclei, aerosols particulates in the atmosphere already that allow for water vapor to condense around.
This is what happens in the atmosphere naturally, particulates provide the initial location for vapor to condense into
droplets of precipitation as air rises, cools, and reaches its Dew Point. Screw the lid on quickly. Squeeze and release…
1. Squeeze the container. Does this represent high or low pressure?
2. Release the container. Does this represent high or low pressure?
3. What is a general rule about high and low pressure related to cloudy or clear conditions?
4. Which of the scenarios did you create a cloud? Why did the cloud form?
5. Which scenario represents descending, dry air?
6. Which scenario represents ascending, cooling air?
7. When would you expect to get precipitation, high or low pressure conditions? Why?
8. What are 2 ways in which we could increase the RH of an air parcel?
Station 3: Adiabatic Lapse Rate (Dry and Wet)
As air warms at the surface of the Earth (conduction, then convection) it rises in altitude/elevation. This rise leads to a
decrease in temperature. The decrease in temperature increases a parcel of air’s Relative Humidity, but since it is most
likely to be below the Dew Point, it increases its temperature at roughly 10oC per 1000m. This is called the Dry Adiabatic
Lapse Rate. Once the parcel of air reaches its Dew Point, it continues to rise yet cools at a different rate, 5oC per 1000m,
called the Wet Adiabatic Lapse Rate. The temperature change/difference is due to the release of latent heat during the
phase change (gas to liquid) that slows the temperature change process.
Scenario: Air at sea level is 28oC and has a relative humidity of 30%. This air is forced to rise 6,000m over a mountain
and descends to a 1500m plateau on the leeward side of the mountain.
1. What is the sea level air’s capacity?
2. What is the Water Content?
3. What is the Dew Point Temperature?
4. At what elevation do clouds form on the windward side of the mountain?
5. What will be the temperature of the rising air at the summit of the mountain?
6. How much water vapor (g/kg) will be condensed out from the rising air after it reaches the summit?
7. What will be the changed conditions of the leeward side of the moutain AT THE PLATEAU?
8. What are the general climate conditions of BOTH sides of the moutain?
Station 4: Finding the Relative Humidity and Dew Point:
Procedure: Use TWO thermometers to find the RH and Dew Point of the Classroom AND outside of X-hall. Complete the
following data table: Inside Room Outside Building
Dry-bulb temperature (°C)
Wet-bulb temperature (°C)
Temperature difference (°C)
Relative humidity (%)
Dew-point temperature (°C)
Analysis: Based on the RH and Temperature of the inside classroom AND outside:
1. What amount of temperature decrease/increase (oC) would cause saturation
2. What amount of water vapor to be condensed out/needed to cause saturation (g/kg)?
Station 5: Relative Humidity and Dew Point
Water Vapor Content (g/kg) Dew Point Temperature (°C) Relative Humidity (%)
Water Vapor Content Temperature (°C) Amount of Temperature Amount of Water Vapor to
(g/kg) Decrease or Increase (°C) to be Condensed Out or
Cause Saturation Needed to Cause
Station 6: Geographical and Geological Barriers that influence atmospheric conditions…
Use the handout and complete ‘what you already know’ about conditions that influence atmospheric conditions. It is
important that you consider information that you already bring in with you before adding more to your understanding.
Complete the handout with your group members.
Table 8-3. Relative humidity measure chart (%).
Table 8-4. Dew-point temperature chart (°C).