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weather – the condition of the outside air or atmosphere at a particular time and place. climate - the average weather conditions over a very long period of time o The climate of a region will also determine the type of plants that grow there and the types of animals that live there. cloud – a mass of tiny water droplets or ice crystals in the air o water vapor must lose heat energy before clouds can form Types of Clouds 1. cirrus clouds - thin wispy clouds that form high in the sky o form when wind is strong o if they get bigger and thicker, it's an indication of a change in weather 2. stratus clouds - flat, horizontal clouds that form in layers. o form when a large mass of air is gently lifted into the atmosphere. o usually form at low altitudes and cover large areas of the sky. o tend to block out sunlight. o Fog is a stratus cloud that forms near Earth's surface. o might bring light mist or drizzle 3. cumulus clouds - fluffy, white clouds that look like pieces of cotton balls with flat bottoms o form as warm air rises and are usually a sign of fair weather. 4. cumulonimbus clouds o can cause lightning, thunder, hail, strong rains, strong winds, and tornadoes o have a dark base; towers in the sky o can be found from near the ground to up to 75,000 feet ****Clouds that bring precipitation usually start with nimbo or end with nimbus High Clouds - form above 18,000 feet cirrus cirrocumulus cirrostratus Middle Clouds - form between 6,500 feet to 18,000 feet altocumulus altostratus Low Clouds - form below 6,500 feet stratus stratocumulus nimbostratus cumulus Weather Instruments rain gauge – measures the amount of rain wind vane – shows wind direction – where the wind is coming from anemometer – measures wind speed barometer – measures air pressure hygrometer – measures the amount of water vapor in the air – the humidity AIR PRESSURE – the weight of the atmosphere pressing at a certain place Air pressure can also tell us about what kind of weather we might have. Changes in air pressure mean that the weather is about to change o HIGH PRESSURE = fair weather o LOW PRESSURE = rainy or stormy weather Air pressure has the greatest effect on wind speed. Air pressure changes depending on the altitude. o HIGHER ALTITUDE = Decreased air pressure o LOWER ALTITUDE = Increased air pressure (This is why your ears "pop" when you are riding in an airplane or driving high into the mountains) air mass - a large body of air that has the same temperature and level of humidity throughout front - the area in which two air masses meet cold front - forms when a cold air mass moves under a warm air mass and causes the warm air mass to rise. o brings heavy rains, thunderstorms, and sometimes snow o temperature drops when cold front passes over an area warm front - forms when a warm air mass meets a cold air mass and slowly rises over it o brings rainy, drizzly weather conditions o after a warm front passes over an area, the temperature rises occluded front - forms when a warm air mass is caught between two cold air masses. o brings cool temperatures and lots of rain and snow stationary front - occurs when a warm air mass and a cold air mass meet, but neither front has enough energy to push against the other o brings many days of overcast, rainy weather Earth’s Three Climate Zones tropical zone – found near the equator; areas in this zone get the most energy from the sun so they tend to be warm to hot all year temperate zone – found between the polar and tropical zones; these areas tend to have seasons with very different temperatures polar zone – found at the Earth’s North and South Poles; areas in this zone get the least energy from the sun, so they tend to be cool to cold all year. Types of Air Masses Moisture content is noted by the first letter. m = maritime = wet c = continental = dry Temperature is noted by the second letter P = polar = cool T = tropical = warm Maritime Tropical - mT o Warm and humid o Originates closer to the Tropics over water Maritime Polar - mP o Cold and damp o Originates in the Poles over water Continental Tropical - cT o Warm and dry o Originates closer to the Tropics over land Continental Polar - cP o Cold and dry o Originates closer to the Poles over land Global Winds current – a flow of air or water in a certain direction the uneven heating of the earth’s surfaces causes wind. as the warm air at the equator rises, large areas of low air pressure form there at the poles, the air is cold so it sinks. Areas of high pressure form there wind blows from areas of higher pressure toward areas of lower pressure jet stream – an air current in the upper atmosphere that flows from west to east o fast flowing river of air o winds can range from 120-250 mph o can be thousands of miles long, a couple of hundred miles across and a few miles deep. o responsible for transporting highs and lows o affects precipitation and temperatures o marks boundaries between massive air masses o air to the south of the jet stream is warm. o air to the north of the jet stream is cold. Coriolis Effect Makes moving objects appear to curve toward the right in the northern hemisphere and toward the left in the southern hemisphere. prevailing westerlies winds that blow from the west to the east and move toward the poles and are between 30 and 60 degrees latitude responsible for many of the weather movements across the United States and Canada. called prevailing westerlies because they’re named from the direction where they form polar easterlies Form when the atmosphere over the poles cools. This cool air then sinks and spreads over the surface. As the air flows away from the poles, it is turned to the west by the Coriolis effect. Because these winds begin in the east, they are called easterlies trade winds air movements toward the equator. warm, steady breezes that blow almost continuously. Coriolis Effect makes the trade winds appear to be curving to the west, whether they are traveling to the equator from the south or north. doldrums a region of the ocean near the equator where there is little or no wind Breezes sea breeze – the movement of air caused by cool air over the ocean moving toward the land o occurs during the day o land temperature near the beach is rising more rapidly than the ocean temperature land breeze – the movement of air created by cool air over land moving toward the ocean o occurs at night o land quickly loses heat at night; water retains heat so the air over water is warmer, less dense and begins to rise Ocean Currents Warm currents from tropical areas carry warm water near the coastlines of cooler areas. The warm water helps keep land near the coastlines warm Cold water currents from the poles travel toward the equator. The cold water brings cooler temperatures to some coastlines in those areas Gulf Stream – a warm ocean current in the Atlantic Ocean flows northeast along the eastern coast of the US moves warm waters out across the Atlantic Ocean, then towards the north keeps weather along the eastern coast mild by warming the air and land there during the cooler months Radiation from the sun warms the waters of the Gulf Stream. Then the water warms the air above it – warms coastal land over which it moves El Nino – an unusual warming of the surface water in the eastern Pacific Ocean near the equator usually brings more rain and higher temperatures causes rising surface temperatures of the Pacific Ocean, drought in the western US and flooding on the Pacific coast of South America. La Nina – an unusual cooling of the surface water in the eastern Pacific Ocean near the equator