The Atmosphere

Air Pressure and Altitude The higher you climb in altitude air pressure decreases. The greatest air pressure is at sea level

How air pressure is measured A Barometer measures air pressure applied to the earth’s surface High pressure ( clear skies, sunny weather ) causes the barometer to rise. Low pressure causes the barometer to lower.

Layers of the Atmosphere All of the earth’s weather occurs in the Troposphere. The ozone layer is located in the Stratosphere

Clouds

Cloud Classification The four main cloud types you need to focus on are the following Cirrus Cumulus Nimbostratus Cumulonimbus

Cirrus Clouds These are high altitude clouds often called mares tails. They often are the first clouds that are visible when a LOW front is approaching

Cirrus

Cumulus These are “puffy” white clouds which are seen on sunny days. They are caused by convectional heating during the day. They often disappear in the early evening once the sun starts to go down. ( it cools off)

Fair weather Cumulus

Cumulus

Cumulonimbus NIMBUS = Rain Cumulonimbus= puffy white rain clouds. When there is extreme day time heating or a fast approaching Front, we will often see HUGE vertical clouds with anvil shaped tops

Cumulonimbus

When a fast approaching cold front(high pressure system) approaches a warm front (low pressure) the warm air is forced up causing the vertical cumulonimbus clouds. Rain/snow/hail will be localized

Cumulonimbus clouds cause localized rain, snow, hail

Hail stones

A low front is approaching a high front – it is going to rain! After several days of sunny weather you may notice a change in the cloud cover over several hours that will indicate the weather may be changing. You will first notice high altitude cirrus clouds

Mid altitude clouds soon appear As the low ( warm ) front approaches even closer, the clouds will drop to mid altitude and thicken up These are called Altostratus ( layered )

Nimbostratus – low lying, steady rainfall These clouds are the last to arrive. The low front is now right on top of you and we experience light, steady rain – often for days and days…….

Alto_____ Alto means mid or middle. These cloud are mid altitude and can be altostratus, altocumulus These indicate that the warm front is getting closer and the weather is going to get worst.

Altocumulus

Orographic Clouds When MARCCSAP occurs and warm moist air is forced over mountain ranges clouds will form on the windward side of the mountain

Lightening When two (2) front approach each other you may experience strong winds, thunder and lightening.