Do Now 1. What Factors influence air temperature? 2. What factors influence air pressure? 3. How does air move in and around a low pressure system? 4. What happens to air as it rises?

Dew Point and Relative Humidity

Dew Point The temperature at which the air can no longer hold all of its water vapor, and some of the water vapor must condense into liquid water. The dew point is always lower than or equal to the air temperature.

If the air temperature cools to the dew point, or if the dew point rises to equal the air temperature, then dew, fog or clouds begin to form. If the dew point temperature equals the air temperature, the relative humidity is 100%. Relative Humidity is a comparison of the actual amount of water in the atmosphere to the amount of moisture it can hold.

As air temperature increases the air’s ability to hold moisture increases. In order for a cloud to form there must be condensation nuclei present and the air must be saturated(100% relative humidity). 2c&safe=active 2c&safe=active

Rising Moist Air = Cloud As air rises it expands and cools.

Why do we sweat? Evaporation is a cooling process. When the air is dry(low relative humidity) evaporation happens quickly When the air is moist(high relative humidity) evaporation happens slowly

Dry Bulb 22°C Wet Bulb 16°C

Dry Bulb 22°C Wet Bulb 16°C

Dry Bulb 4°C Wet Bulb -1°C

Dry Bulb 4°C Wet Bulb -1°C

Dry Bulb 4°C Wet Bulb -1°C

Dry Bulb 4°C Wet Bulb -1°C

Forms of Precipitation Rain Snow Sleet Freezing Rain Hail Condensation- Dew, Frost, Clouds

Condensation = Clouds

Fog

Wet Snow

Freezing Rain

Mechanisms That Cause Precipitation Fronts Lows Convection Within An Airmass Geographic Barriers

Earth’s Surface is Heated. Warm Air Rises and expands causing it to cool.

Mechanisms That Cause Precipitation Fronts Lows Convection Within An Airmass Geographic Barriers KUMtT0v0&safe=active KUMtT0v0&safe=active

Air Masses Air masses are described by their place of origin. Where an air mass originates determines the properties of the air mass. Air masses are described by temperature and moisture content.

Fronts Cold Front Warm Front Occluded Front Stationary Front

Cold Front A continental polar airmass moves into a maritime tropical airmass. The denser continental polar air mass moves under the maritime tropical airmass forcing it to rise. As the maritime tropical air rises it cools allowing clouds and precipitation to form.

cP mT Cold Front X Earth’s Surface

Where is the zone of precipitation? What types of clouds form along a cold front?

Warm Front A maritme tropical airmass moves into a continental polar airmass. The less dense maritme tropical airmass rides up and over the continental polar airmass. As the maritime tropical air rises it cools allowing clouds and precipitation to form.

mT cP Warm Front X Earth’s Surface

Occluded Front An occluded front forms is association with a low pressure system when a maritime tropical air mass gets caught between two continental polar air masses. The less dense maritime tropical air mass is forced to rise between the two continental polar air masses. As the maritime tropical air rises it cools allowing clouds and precipitation to form.

cP mT Occluded Front Earth’s Surface X

Rotation is faster for the cold front

Stationary Front A stationary front forms when two airmasses meet and do not move for a period of time. This type of front is a temporary condition, eventually one the airmasses starts to move. Low pressure systems can form along a stationary front.

Mechanisms That Cause Precipitation Fronts Lows Convection Within An Airmass Geographic Barriers

Mechanisms That Cause Precipitation Fronts Lows Convection Within An Airmass Geographic Barriers

Northern Hemisphere Southern Hemisphere Tornado Video

Tropical Weather Systems Tropical weather systems form over warm equatorial ocean water. These systems gain their energy and moisture from warm ocean water.

Tropical weather systems grow due to convection. A tropical weather system starts off as an area of thunderstorms over warm ocean water.

As a tropical weather system grows it may develop a cyclonic (counterclockwise) twist due to the coriolis effect. As the air pressure drops in a hurricane the wind speed increases.

Steps in the Formation of a Hurricane Tropical Wave Tropical Depression Tropical Storm Hurricane

Saffir-Simpson Scale Category mph Category mph Category mph Category mph Category 5 - greater than 155 mph

Atlantic Hurricanes Hurricanes in the Atlantic Ocean tend to move from the east to west due to the Trade Winds. Some begin as tropical waves that come from west Africa

Hurricane Watch vs Warning Hurricane Warning- the hurricane may reach an area in 36 hours Hurricane Warning - the hurricane will reach an area within 24 hours

Effects on Coastal Areas Storm Surge Flooding Erosion Heavy Rain Tornadoes

Typhoons and Cyclones Typhoons are hurricanes that occur in the western Pacific Ocean. Cyclones are hurricanes that occur in the Indian Ocean.

Typhoon Bart

Andrew