Weather MSL Practice Question Answers
A) Explain the composition of air and identify their percentages.
Air is composed mainly of Nitrogen (78%) and Oxygen (21%). The remaining 1% of air is made of trace gases
such as carbon dioxide and argon. Air also contains water vapor, but it fluctuates so much that it is not included
when discussing air. That’s why we talk about the percentage of gases in dry air
B) Construct the layers of the atmosphere. Within each layer include the differences in temperature, pressure, how
the molecules are arranged, and one example of what can be found in that layer.
Lowest layer – troposphere – This layer is warm enough
to sustain life. It contains most of the mass of the
atmosphere and has the greatest pressure. Humans live
in this layer of the atmosphere.
2nd layer – stratosphere – This layer is cold near the
bottom but gets warm above the ozone layer. The ozone
layer is found in the middle of this layer and blocks UV
radiation.
3rd layer – Mesosphere – This layer is the coldest part of
the atmosphere and is where meteoroid burn up
4th layer – Thermosphere – This is the outer most layer of the atmosphere and is very hot. It is divided into two main
parts – the ionosphere and the exosphere. The ionosphere is where the aurora borealis is found and also where radio
waves bounce back from the charged particles called ions. They are also reflecting light which causes the aurora.
C) Compare the differences in air pressure, density and oxygen molecules if you were standing at the top of a
mountain and then at the bottom of the mountain.
In the atmosphere, the molecules’ density decreases as the altitude increases. In other words, as you go up, the
molecules get more spread out. The pressure does the same. When altitude increases, pressure decreases
because the molecules are not as tightly packed together. When molecules have more room, there is less
pressure. The oxygen percentage in the air never changes; no matter where you are there is always 21%
oxygen. The reason that it seems like there is less oxygen at mountain tops is because of density and pressure.
The molecules of oxygen are more spread out and you do not get as many molecules in each breath you take.
D) Explain how the cycling of water (water vapor) in and out of the atmosphere can affect weather patterns on
Earth.
Water evaporates into the atmosphere and becomes water vapor. We measure this water vapor content and
call it humidity. When the air reaches the dew point, water in the atmosphere will condense and form clouds.
Depending on the type of cloud that is formed, we can expect different types of weather. When these clouds
become too heavy to hold the water any longer, it will fall to the Earth’s surface as some form of precipitation.
The type of precipitation depends on the cloud type and air temperature. This cycling of water can lead to
floods in some areas of the World and drought in other areas depending on how the clouds and weather
systems move across the globe.
E) Explain the influence convection, global winds, and jet stream has on weather and climatic conditions.
 Convection currents create wind in areas where there are differences in temperature. This wind can
change the temperature of an area and push clouds and fronts. These currents also create local winds in
areas like the beach and along the banks of larger lakes.
 Global winds blow over large areas of the globe and are always present. They move weather around the
globe. The global wind over North Carolina blows from west to east and is one of the reasons that
weather systems move from west to east in our state.
 Jet streams circle the globe and blow from west to east. They are also responsible for pushing weather
systems around the globe. They are the reason that weather moves mostly from the mountains to the
coast in North Carolina.
F) Compare the movement of a cold and warm air mass and describe the kind of weather associated with each.
 Cold air mass – has more density than a warm air mass and is moved by the jet streams and global
winds. Maritime polar air masses bring cool temperatures and damp weather. Continental polar air
masses bring cool, dry weather.
 Warm air mass – has less density than a cold air mass and is moved by the jet streams and global winds.
Maritime tropical air masses bring warm, moist weather. Continental tropical air masses bring warm,
dry weather.
G) Compare the movement of the four different fronts; explain why they move the way they do and describe the
kind of weather associated with each.
 Warm front – A fast moving warm air mass overtakes a slow moving cold air mass. The warm air mass
pushes the cold, slow moving air mass out of the way. This can cause extended periods of raining or
cloudy weather. Warm, humid weather usually follows a warm front.
 Cold front – A fast moving cold air mass overtakes a slower moving warm air mass. The cold air mass
pushes under the warm air mass because cold air has a higher density than warm air. This front can
cause abrupt changes in weather, particularly thunderstorms. After the front, the weather will normally
be clear and cooler.
 Stationary front – A cold and warm air mass meet but neither can move the other because they are both
about equal in size and strength. This can cause extended periods of precipitation and possible flooding.
 Occluded front – A warm air mass is caught between 2 cooler air masses and cut off from the ground.
This is because cold air is denser than warm air. Clouds and precipitation can be expected with this type
of front.
H) Describe the differences between a low and high pressure system.
 Low pressure system – This system forms around centers of low pressure and are represented
on weather maps by an L. Warm air rises and spins counterclockwise around the center.
Storms and precipitation are associated with areas of low pressure as the warm air rises &
condenses to form clouds & precipitation.
 High pressure systems – These systems are formed around centers of high pressure and are
represented on weather maps by an H. Cold air sinks and spins clockwise around the center.
Dry weather and clear skies are associated with areas of high pressure as the cooler air falls &
becomes warmer causing a drop in relative humidity.
I)
Describe the causes and properties of thunderstorms, hurricanes, and tornadoes.
 Thunderstorms – These storms only occur in cumulonimbus clouds and are most common along a cold
front. They typically form on hot, humid afternoons during the spring and summer months. They are
fast moving storms that are often accompanied by heavy precipitation, frequent thunder and visible
lightning.
 Hurricanes - Tropical cyclone (low pressure) that typically measures 300-500 miles across with winds
from 70-200 mph. They are guided or directed by the Trade winds and can only form over water that is
at least 80ºF. They typically form during the months of late July to early October in the Atlantic Ocean.
 Tornadoes - Tornadoes can form in any situation that produces severe weather. They typically form
during the Spring & Summer under the same conditions as those of a thunderstorm. They occur most
often in the area of the US called Tornado Alley as well as in the state of Florida. Tornados form when
warm, moist air flows in at the bottom of a cumulonimbus cloud & rapidly moves upward generating a
low pressure area inside the cloud. The warm air begins to rotate due to winds within the cloud blowing
in different directions: The result is the cloud begins to spin like a top. As part of the cloud descends to
touch the ground, a tornado or funnel cloud is generated with winds up to 340 mph.
J)
Compare the three main types of clouds describing their shape, type of weather associated with it and elevation.
 Cirrus
o Shape – Thin, wispy clouds that are made of ice crystals
o Types of weather – Cirrus clouds indicate fair weather in the immediate future. However, they
can also be an indication of a change in weather patterns within the next 24 hours (most likely a
change of pressure fronts).
o Elevation – These are high clouds that form at 16,000 - 43,000 feet
 Stratus
o Shape – Solid clouds that seem to blanket the sky. They are normally dull and grey in color
o Type of weather – They will often they bring drizzle, rain, or light snow.
o Elevation –These are low clouds that form below 6,500 feet
 Cumulus
o Shape - Cumulus clouds are your stereotypical white "cotton ball" clouds.
o Type of weather – When the cloud looks like low clumps floating across the sky, there will be fair
weather. However, you need to keep an eye on these clouds because any vertical growth can
indicate the start of a large storm.
o Elevation – These clouds tend to have a base that hangs really low (5,000 feet) and a top that
climbs really high (over 50,000 feet).
K) Describe how and why a weather map, satellite, and radar would be used to predict weather.
 Weather map – Scientists use weather maps to track weather patterns. They use symbols to represent
different weather factors and events. They use the knowledge of these patterns to predict how the
systems will move across the area.
 Satellite – Weather satellites help scientists collect weather data from all around the state, the country,
and the globe. They use this data on the weather maps to track how systems are moving. This
information can help them to predict how the weather will move and what people can expect in the
next few days.
 Radar – used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail, etc).
Modern weather radars are capable of detecting the motion of rain droplets in addition to the intensity
of the precipitation. Both types of data can be analyzed to determine the structure of storms and their
potential to cause severe weather.
L) Provide an explanation for why there is a hole in the ozone layer. Support your answer with details.
Scientists have determined that a hole is occurring in the Ozone layer, the main cause for this is a
group of gasses called Chlorofluorocarbons (CFCs). These CFCs react with the Ozone molecules and
prevent them from reforming, breaking the cycle of new ozone being created. Many nations have
agreed to stop using substance that contain CFCs. Scientists believe that if this continues over a long
period of time, the ozone layer will gradually recover.
M) Cite evidence for the most common causes (at least 3) of air pollution and propose a practical solution
for one of the causes.
1. Automobiles – New cars can be developed with cleaner emissions to help reduce the
pollution. Public transportation and car pooling will help to reduce the number of
automobiles on the road. Giving people incentives for using public transportation may be
helpful in large cities and help to reduce traffic problems
2. Power Plants – Regulating the emissions and giving incentives for lower emissions and/or
giving penalties for having a high rate of emission.
3. Factories - Regulating the emissions and giving incentives for lower emissions and/or giving
penalties for having a high rate of emission.
a.)
Analyze the map by describing the kind of weather
North Carolina is experiencing and explain how you know this.
NC is located near a high pressure system to the North and has
a pressure reading of 1020. There is also a cold front to the
South and East. Because we know that weather systems
normally move from West to East, we would predict that NC
would have nice, clear weather. That is because high pressure
systems are associated with dry, clear weather.
b.) Analyze the map above by predicting what the weather will be like in North Carolina in two days and explain
how you know this.
Because weather in the US moves from West to East, we need to look to the Mid-West to have an idea of the
weather that we can expect. In the Mid-West, there is a stationary front and a Low pressure system. Low
pressure systems are normally associated with precipitation, storms, and other types of bad weather. If the
stationary front does not move, we may keep our dry, clear weather in NC. If the cold air mass becomes
stronger, it will turn into a cold front and can bring precipitation, potential for storms, and cooler temperatures.