Name __________________________________ Period ____
Humid Continental Climates
A huge body of air that has similar temperature, humidity and air pressure at any
given height is called an air mass. Air masses bring constantly changing weather to
humid continental climates. Air masses can form over land or over water and are
either warm or cold. Four major types of air masses influence the weather in North
America. They are: maritime polar, continental polar, maritime tropical and
continental tropical. Polar (cold) air masses form north of 50˚ north latitude and
south of 50˚ south latitude. Tropical (warm) air masses form in the tropics.
Continental air masses form over land and are dry while maritime air masses form
over oceans and are humid (moist).
Directions: Complete the chart by using the following: warm, cold, moist, dry
TYPE OF AIR MASS
TEMPERATURE OF AIR
HUMIDITY OF AIR
Maritime tropical
Continental tropical
Maritime polar
Continental polar
KEY
(m) maritime
- forms over water; wet
(c) continental
- forms over land; dry
(P) polar
- forms over polar regions; cold
(T) tropical
- develops over the Tropics; warm
1. Which air masses form over Canada?
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2. What kind of weather do they bring?
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3. Which air masses form over the Gulf of Mexico? ______________________________________
4. What kind of weather do they bring? __________________________________________________
5. What kind of weather would you expect from a maritime polar air mass?
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6. Flying by airplane from New York to Los Angeles takes 5 hrs and 45 min. It takes
5 hrs and 15 min to fly from Los Angeles to New York. Why do you think there
would there be a 30 minute difference? ________________________________________________
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Prevailing Winds
Weather patterns depend on the movement of these huge air masses by
prevailing winds. In the continental United States, the air masses are commonly
moved by the prevailing westerlies and jet steams.
Prevailing westerlies are the major wind belts over the United States that
generally push air masses from west to east. Jet streams, which are contained
within the prevailing westerlies, are bands of high-speed winds about 6 miles above
Earth’s surface. As jet streams generally blow from west to east, air masses are
carried along their tracks.
CALCULATING: When planes fly from west to east across the United States, they fly
with the jet stream, and therefore can fly faster. The opposite happens when planes
fly from east to west. To calculate the rate at which planes fly, divide the distance
traveled by the time it takes.
Rate = Distance
Time
or
MPH = Miles
Hrs
If a plane flies from Denver, Colorado, to New York City, a distance of about 1632
miles, it takes about 3 hrs and 30 min. The return flight takes about 4 hrs.
7. Calculate the rates of air travel, in miles/hrs, in each direction.
a. Denver to New York:
b. New York to Denver:
8. How much extra speed does the jet stream add to the west-to-east flight?
Source Region
Source region is the location from which an air mass originates. An example of a
source region would be the icy continental portions of Canada in the winter. As a
giant mass of air moves over this source region, the air will acquire the
characteristics of the underlying surface. In this case, the air will be dry (continental)
and mild to cold (polar).
As an air mass stays over a region, it will acquire the properties of that land or
ocean region. When air masses move from their source region, they tend to be
modified (changed) by the land or water that they pass over.
9. How might a continental polar air mass be modified as it passes over the Great
Lakes? Why? ______________________________________________________________________________
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10. How would you predict a maritime tropical air mass might be modified as it
travels from the Gulf of Mexico? Why? __________________________________________________
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Directions:
a. Read the national weather forecast below.
b. Based on the weather forecast, draw circles on the map showing where the
six underlined areas are located (Ex: northwest U.S.).
c. Based on the weather experienced in those areas, fill in the circles with the type of
air mass that would cause that area’s weather (use the labels below).
mP = maritime polar
mT = maritime tropical
cP = continental polar
cT = continental tropical
National Weather Forecast
The northeast and northwest United States will experience cool, humid weather
today, while the northern middle of the country will be cool and dry. The southern
part of the country will be hot, with storms and humidity in the southeast and
southwest. Dry weather will prevail over the central region.
11. Weather in North America tends to move from west to east. Based on your
weather map, write a three day weather forecast for the northeastern part of the
United States (New Jersey).
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