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AIRMASSES
An air mass is a large volume of air in the atmosphere that is mostly uniform in temperature
and moisture.
Air masses can extend thousands of kilometers across the surface of the Earth, and can reach
from ground level to the stratosphere—16 kilometers (10 miles) into the atmosphere.
Air masses form over large surfaces with uniform temperatures and humidity, called source
regions.
Low wind speeds let air remain stationary long enough to take on the features of the source
region, such as heat or cold. When winds move air masses, they carry their weather conditions
(heat or cold, dry or moist) from the source region to a new region.
When the air mass reaches a new region, it might clash with another air mass that has a
different temperature and humidity. This can create a severe storm.
- Airmasses are labeled by a two letter code a. What does m and c stand for? _________________________________________________________ _________________________________________________________ b. What does A, P, T, Estand form?
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- Label the 18 Airmasses using the 2 letter codes (m, c) and (A, P, T)
- An air mass that develops over northern Canada is called a _______________________ air mass and is warm/cold and humid/dry.
- An air mass that develops over the Indian Ocean is called a ____________________ air mass and is warm/cold and humid/dry.
List the 3 Airmasses that affect the Mid-Atlantic region (i.e. Virginia). Which season do they impact. What type of weather do they generate; 1 Airmass ___________ Season: ________________________ Weather Type: _______________
2 Airmass ___________ Season: ________________________ Weather Type: _______________
3 Airmass ___________ Season: ________________________ Weather Type: _______________
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In the space provided, write the Front that best matches the description. A Cold front B Warm Front C Stationary Front D Occluded Front Description Front A front of air masses that moves either very slowly or not at all The front edge of a moving mass of cold air that pushes beneath a warmer airmass like a wedge The front edge of an advancing warm air mass that replaces colder air with warmer air A front that forms when a cold air mass overtakes a warm air mass and lifts the warm air mass off the ground and over the other airmass
HUMIDITY, TEMPERATURE AND DEWPOINT
At sea level pressure, air can hold 9 g H2O/cubic foot of air at 10 °C 17 g H2O/cubic foot of air at 20 °C 30 g H2O/cubic foot of air at 30 °C
- A cubic foot of air with 17 grams (g) of water vapor at 20 °C is at saturation, or ________% relative humidity.
- A cubic foot of air with 17 grams (g) of water vapor at 20 °C is at saturation.
- What is the dewpoint for this situation ____°C.
- If this cubic foot of air cooled it condensation will occur resulting in what weather phenonena: _____________, _________________, or ______________
- A cubic foot of air with 17 grams (g) of water vapor at 20 °C is at saturation. If the temperature is lowered to 10 °C, the air can hold only _________ g of water vapor.
- What happens to remaining 8 g of water. It will _____________________ as water droplets.
- Once that happened, the relative humidity will still be at 100%.
- A cubic foot of air with 17 grams (g) of water vapor at 20 °C is at saturation. If the same cubic foot of air warms to 30 °C, the capacity for water vapor os ______________g. Therefore the 17 g of water vapor will produce a relative humidity of __________________ CLOUD FORMATION As moist, unstable air rises, clouds often form at the altitude where temperature and dew point reach the same value.
When lifted, unsaturated air cools at a rate of 5.4 °F per 1,000 feet and the dew point temperature decreases at a rate of 1 °F per 1,000 feet. This results in a convergence of temperature and dew point at a rate of 4.4 °F. Apply the convergence rate to the reported temperature and dew point to determine the height of the cloud base. The process is as follows: Given Temperature (T) = 85 °F Given Dew point (DP) = 71 °F Given Convergence Rate (CR) = 4.4° T – DP = Temperature Dew Point Spread (TDS) = 14 °F TDS ÷ CR = 3. 3.18 × 1,000 feet = height of cloud base AGL 14 °F With an outside air temperature (OAT) of 85 °F at the surface, and dew point at the surface of 71 °F, the spread is 14°. Divide the temperature dew point spread by the convergence rate of 4.4 °F, and multiply by 1,000 to determine the approximate height of the cloud base.
Solve the following problem. What is the height of the cloud base at the airport when: T = 80 °F DP = 61 °F Convergence Rate (CR) = 4.5° TDS= T- DP = ________________________ TDS ÷ CR = ____________________ (TDS ÷ CR ) × 1,000 = ______________________________ feet AGL The height of the cloud base is ______________________ feet AGL. DEW & FROST On cool, calm nights, the temperature of the ground and objects on the surface can cause temperatures of the surrounding air to drop below the dew point. When this occurs, the moisture in the air condenses and deposits itself on the ground, buildings, and other objects like cars and aircraft. True of False:
- Dew poses no threat to an aircraft TRUE/FALSE
Advection Fog Conditions Geographic Location Physics
Upslope Fog Conditions Geographic Location Physics
Steam Fog, or Sea Smoke Conditions Geographic Location Physics
CLOUDS
For clouds to form, there must be adequate water vapor and condensation nuclei, as well as a method by which the air can be cooled. When the air cools and reaches its saturation point, the invisible water vapor changes into a visible state.
Cloud type is determined by its height, shape, and behavior. They are classified according to the height of their bases as low, middle, or high clouds, as well as clouds with vertical development.
- Cloud classification. Match the Number to the description CLOUD CLASSIFICATION DESCRIPTION 1. Cumulus 2. Stratus 3. Cirrus 4. Castellanus 5. Lenticularus 6. Nimbus 7. Fracto 8. Alto
A - —heaped or piled clouds B —formed in layers C —ringlets, fi brous clouds, also high level clouds above 20,000 feet D - —common base with separate vertical development, castle-like E - —lens shaped, formed over mountains in strong winds F - —rain-bearing clouds G —ragged or broken H - —meaning high, also middle level clouds existing at 5,000 to 20,000 feet
