Wind, Climate, Clouds, Air masses, and Blizzard Earth Science

Weather Instruments Anemometer is an instrument used to measure wind speed Barometer is an instrument used to measure air pressure Wind Vane is an instrument used to measure wind direction Doppler Radar is an instrument used to measure cloud cover Psychrometer is an instrument used to measure relative humidity Thermometer is an instrument used to measure temperature

Clouds __Cirrus_______Wispy, feathery clouds made mostly of ice crystals that form at high levels, above about 6 kilometers. ___Cumulus_____Clouds that form less than 2 km above the ground and look like fluffy, rounded piles of cotton. _Stratus_______ Clouds that form in flat layers.

Atmosphere Troposphere is where all of Earth’s weather occurs. Stratosphere is where the ozone layer is. Mesosphere is where most meteoroids burn up. Thermosphere is divided into two layers. Ionosphere is where the aurora borealis occurs, and radio waves are reflected back to Earth. Exosphere is where satellites orbit, and is the furthest layer away from Earth.

Wind __Wind_________ the horizontal movement of air from an area of high pressure to an area of lower pressure. _Local Wind____ are winds that blow over short distances. _Land Breeze___ is the flow of air from land to a body of water. _Sea Breeze____ is the flow of air from a body of water to land.

Wind continued _Coriolis Effect is the way Earth’s rotation makes winds curve. _Global Winds__ are winds that blow steady from specific directions over long distances. _Latitude______ is the parallel distance from the equator measured in degrees.

Climate and Weather _Weather_______ is the state of the atmosphere at a particular place and time described in terms of temperature, air pressure, clouds, wind, and precipitation. _Climate_______ is the long term average of weather. It is observed over periods of many years, decades, and centuries. The two most important factors in describing the climate of an area are _Temperature___ and _Precipitation_.

Climate and Weather continued Average yearly temperature varies with latitude. The larger the latitude the _cooler________ the temperature usually is. The prevailing wind of the United States is __westerlies___. The main factors that influence temperature are: _altitude_____, __latitude_____ , distance from large bodies of water, and ocean currents.

Air Masses Continental- “dry” land Maritime- “humid” water Tropical- “warm” air Polar- “cold” air 4 types of Air Masses Continental Polar and Continental Tropical Maritime Polar and Maritime Tropical

MID-LATITUDE LOW PRESSURE SYSTEMS ARCTIC MARITIME from Arctic Ocean Cold, humid. POLAR CONTINENTAL from E.Europe Cold, dry in winter Warm, dry in summer. POLAR MARITIME from Greenland Cool, humid. POLAR FRONT this shifts polewards in summer and equatorwards in winter, hence British seasonal contrasts. POLAR MARITIME RETURN Coolish, very humid. TROPICAL MARITIME from Atlantic near tropic Warm, humid TROPICAL CONTINENTAL From N.Africa Hot, dry

A FRONT is the boundary betwen two air masses A FRONT is the boundary betwen two air masses. A depression has two, a warm (the front of the warm air) and a cold. WARM FRONTS 1 TROPICAL MARITIME AIR The warm front is angled gently due to ground level friction which slows the air at low level as the whole system moves eastwards. POLAR MARITIME AIR The warm tropical maritime air moves up and over the cold air mass. The amount of precipitation depends on the humidity and temperature of the warm air mass, and the particles available. Usually causes it to rain for days

COLD FRONTS POLAR MARITIME TROPICAL MARITIME The cold front is steeper, also due to ground level friction slowing the lower air, so uplift is more rapid than along the warm front. Causes storms that last for hours. This causes cumulo-nimbus clouds and possible thunderstorms rather than thick stratus cloud. Eventually, the two fronts meet, forcing the warm air off the ground. This is an OCCLUDED FRONT (occlusion), and happens to all depressions as they ‘fill’. The whole system takes about 24 hours to pass.

Stationary front- can turn into a warm front after stalled for days Stationary fronts occur when cold and warm air masses meet, but neither air mass can move the other. Where the warm and cold air meet, water vapor in the warm air condenses into rain, snow, fog, or clouds. If a stationary front stays over an area, it may bring many days of clouds and precipitation. 

Occluded Front Occluded fronts occur when a warm air mass is caught between two cooler air masses. The denser cool air masses moves underneath the less denser warm air mass, and push the warm air upwards. The two cooler air masses can mix when they meet in the middle. The warm air mass then becomes cut off from the ground, so the temperature near the ground becomes cooler. As the warm air cools and its water vapor condenses, the weather might turn cloudy and rain or snow may fall.

Blizzard of 77