chapter 13

Air mass

A large body of air that has a uniform temperature, humidity, and pressure. They form when a large high pressure system lingers over an area fro a few days. When a high-pressure system comes in contact with Earth's surface it soon takes on the characteristics below it. Air masses are classified by their temperature and moisture.

Blizzard

A violent winter storm that is characterized by freezing temperatures, strong winds, and blowing snow. The snow during a blizzard is swirling around, so it reduces visibility. The freezing temperatures can cause hypothermia to humans if they are not properly clothed.

Tornado

A violent, whirling column of air that makes contact with the ground. A tornado is considered severe weather. Tornado alley is in central U.S. and ranges rom Nebraska to Texas. the cold wind that blows south from Canada collides with the warm moist air moving North from the Gulf of Mexico. This is ideal condition for tornadoes and thunderstorms.

Hurricane

An intense tropical storm with winds exceeding 119 km/h. Hurricanes are the most destructive storms on Earth. Thy have a circular shape with intense swirling winds. Hurricanes form over worm tropical water during the late summer. These massive storms can cause areal flooding and damage houses. When a hurricane reaches land the rain and wind intensify. Hurricanes are called typhoons in Asia and tropical cyclones in Australia.

Cumulonimbus Clouds

Are tall and vertical clouds that can reach up to 10 km in height. They are verticle with a flat top in shape. Associated with thunderstorm, snow, hail, tornadoes, and lighnting conditions.

Occluded Fronts

Cold air moves faster than warm fronts. When they catch up with each other a blocked front forms. The cold air pushes the warm air up and the cold air sinks to the surface. These fronts usually bring precipitation.

Tropical maritime air masses

Form over top of the Western Atlantic Ocean, the Pacific Ocean and the Gulf of Mexico. During the summer time these air masses contain hot and humid air. In the summer they bring warm temperatures and humidity, while in winter they bring heavy snowfalls.

Rain Gauge

Is a device used by meterologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time. The depth that is being measured by this device is usually measured in (mm).

High-pressure system

Is a large body of circulating air with high pressure at it's center and lower pressure outside of the system. The air in the system moves rom the center out due to air moving from areas of high pressure to areas of low pressure. High pressure systems are often associated with good, fair weather.

Low-pressure system

Is a large body of circulating air with low pressure at its center and high pressure outside of the system. The warm air from the system rises, condenses and form clouds causing precipitation. How pressure system,s are often associated with rainy, wet weather.

Cumulus Cloud

Is a type of the three main clouds and are fluffy, heaped, or piled up clouds. That reach altitudes of 2,000 to 6,000 meters.Form when warm air rises through evaporation and as is rises in the atmosphere the cooling air reaches the dew point and the tiny water droplets form clouds. Are associated with fair weather.

Psychrometer

Is an instrument used in measuring the relative humidity. This device gives out a percent. For example air with a relative humidity of 100 percent cannot contain any more moisture and dew or rain will form.

Stratus Cloud

Is one of the main three clouds and are flat, white, and layered clouds. They reach altitudes up to 2,000 meters. Formed when warm air rises through evaporation and as is rises in the atmosphere the cooling air reaches the dew point and the tiny water droplets form clouds. Are associated with wet conditions and weather.

Water cycle

Is the series of natural processes by which water continually moves among oceans, land, and the atmosphere. Precipitaion, condensation, runoff, and evaporation are phase changes in it.

Cold Front

It forms when a cold air mass moves towards warmer air mass. Cold air pushes underneath warm air. Warm air rises and cools. Showers and storms usually form with cold fronts. When a cold front passes through there is gust winds, temperatures decreases and severe storms.

Warm Front

It forms when less dense warm air moves toward colder, denser air. Water vapor in warm air condenses and forms clouds. Clouds often follow a warm front with steady showers or snow. The rain can occur for several days. warm fronts bring warm temperatures, and causes the wind to change direction.

Front

It is a boundary between two air masses. Drastic weather changes often occurs at fronts as air masses collide. Changes in temperature, humidity, cloud types, wind, and precipitation are common at fronts. Different types of front are cold, warm, stationary, and, occluded fronts.

Lake Effect Snow

Lake-effect snow forms when cold air passes over the warmer waters of a lake. Water holds on to heat more than air. and as a result, cold air passes over much warmer water. Causing some lake water to evaporate into the air and warm it. The warmer and wetter air rises and cools .Then the cooler and moist air forms clouds. The air moves away from the lake and over the land. Once it moves over the land, it dumps all that moisture on the ground. If it's cold enough, that moisture then would become snow.

Stationary Front

Sometimes a front will stall for days at a time. With cold air on one side and warm on the other. When the boundary stalls it is called a stationary front. These fronts are associated with cloudy skies and light rain.

Humidity

The amount of water vapor in the air. When humidity is high there e is more water vapor in the air. Days that have high humidity skin feels sticky and it slowly evaporates from skin. Humidity is measured in grams per cubic meter of air. (g/m3)

Relative humidity

The amount of water vapor preset in the air compared to the maximum amount of water vapor that could be in the air. the temperature determines amount of water vapor in the air. Warmer air contains more water vapor that cool air. It is measured by using a psychrometer given in percents.

weather

The atmospheric conditions, along with short-term changes, in a certain place at a certain time.

Air pressure

The force that column of air applies on the air or surface below. Air pressure is denser on Earth's surface and less dens at the top of the mountain. This is due to gravity pulling the sir molecules down to Earth's surface. Barometric pressure refers to air pressure. Air pressure is measure with a barometer and measured in millibars.

Dew point

The temperature at which air is saturated and condensation can occur. When the temperature decreases the sir can't hold as much water vapor. Measured in g/m3. Dew point is the point where clouds form due to the air not being able to hole anymore water.

Tropical continental air masses

These air masses form on tropics over dry and desert like land. These air masses contain hot and humid air. They usually are formed during the summer months. They result in clear skies and high temperatures.

Polar continental air masses

These air masses form over Canada. They bring fast moving air. . This air mass brings cold temperatures in both the wintertime and the summertime.

Arctic air masses

They form over top of Siberia and the Artic land. These air masses contain bitterly cold air. During winter the air temperature can reach a low of negative four degrees Celsius (-4).

Polar maritime air masses

They form over top of the North Atlantic Ocean and the Pacific Ocean. These air masses bring cold and humid air, and these air masses bring cloudy and rainy weather to Earth's surface.

Precipitation

Water in a liquid or solid state that falls from the sky. Examples would be rain. snow, sleet, or hail. It is measured in inches.

Cirrus Cloud

is a type of the three main clouds and they are wispy clouds. They reach altitudes above 6,000 meters. Form when warm air rises through evaporation and as is rises in the atmosphere the cooling air reaches the dew point and the tiny water droplets form clouds. Have fair weather and if they build up over time that means a warm front is on the way.