Air Masses

This side is really cold! This side is much warmer! What is the main difference between the left side and the right side of the blue line? This side is really cold! This side is much warmer!

Air Masses Air masses are responsible for our weather. The type of air mass our area is in will determine the type of weather we are having. An air mass is a huge body of air in the troposphere, up to 200 kilometers in diameter, having similar pressure, moisture, wind, and temperature characteristics throughout.

How did the air mass get these characteristics? Air that has stayed in an area for a period of time picks up the area’s characteristics. The area where the air mass came from is known as the source region.

Air masses around the world.

Air masses of the U.S.

What kind of air mass will it be? Air masses are named based on their moisture content (humidity) and temperature. Humid air mass. Dry air mass. What kind of air mass will it be? Hot air mass. cold air mass.

cA cA continental arctic- dry and really cold Originates in the arctic regions

cP cP continental polar- dry and cold Originates over Alaska and Canada

mP mP maritime polar- moist and cold Originates over the ocean in high altitudes.

mT mT maritime tropical- moist and warm Originates over the ocean in mid latitudes

cT cT continental tropical- dry and hot Originates over deserts in the mid and lower latitudes.

? ? ? cA mP mP ? cP What’s the air mass? ? cT ? ? mT mT

What rule should we follow when writing air mass symbols? 1st letter is lower case and for humidity 2nd letter is capital and for temperature

Air Mass source regions and typical paths they take.

Cyclones and Anticyclones Cyclones and anticyclones are weather systems that involve masses of air moving in a spiraling motion. Most types of cyclones and anticyclones are large features that move slowly across the Earth's surface, bringing changes in the weather as they move. The circulation of weather systems is determined by their pressure which in turn determines whether air ascends or descends. Air in low pressure will RISE resulting in clouds and poor weather. Air in high pressure will SINK resulting in no cloud formation and good weather.

What type of pressure is associated with cold or cooler air? When surface air pressure is highest in the center of an air mass it known as a high-pressure system or high. High pressure Away H Which way would the air blow – in towards the center or away from the center?

What type of pressure is associated with warm or warmer air? When surface air pressure is lowest in the center of an air mass it known as a low-pressure system or low. Low pressure Towards L Which way would the air blow – in towards the center or away from the center?

We know these winds do not travel in straight lines… Winds will Curve due to the Coriolis Effect

Why does it move away from the center? High Pressure anticyclones rotate clockwise and air moves away from the center. Why does it move away from the center? The highest pressure is in the center and air moves from high pressure to low pressure. Why is this air system associated with good weather? The air is sinking so clouds cannot form. H is for happy!

Low Pressure cyclones rotate counterclockwise and air moves towards the center. Why does it move towards the center? The lowest pressure is in the center and air moves from high pressure to low pressure. Why is this air system associated with poor weather? The air is rising so the air expands, cools to the dewpoint and condenses forming clouds. REC DC! L is for Lousy!

Cyclones and Anticyclones in action

CC = COUNTER-CLOCKWISE Tips for Remembering! HOC & LICC L = LOW I = IN CC = COUNTER-CLOCKWISE H= HIGH O = OUT C= CLOCKWISE

In high pressure air sinks Thumbs down Your fingers curl in the same direction as air moves in high pressure In low pressure air rises Thumbs up Your fingers curl in the same direction as air moves in low pressure.