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Transcript of Weather
Weather Tools and Weather Terms
Clouds are made up of millions and millions of small water drops or tiny pieces of ice.
Clouds give us clues about how the weather may change.
An anemometer measures how fast the wind is blowing
A thermometer measures air temperature. It's measured in degrees Celsius and Fahrenheit (U.S.).
A wind vane or wind sock shows which direction the wind is blowing. It points to the direction the wind is coming from
Barometers are important for measuring air pressure. Air pressure can help you predict good or bad weather.
A rain gauge measures how much rain or snow has fallen
Cumulus or cumulo- (prefix) means heap. These clouds look big and puffy like balls of cotton, usually in middle-altitude.
These are "fair-weather" clouds,but when these clouds start piling up and turn dark, they can bring a storm.
Stratus means stretched out or sheet-like. These clouds make the whole sky look dark and gray because they cover the sky and block the sun;this is called overcast.
They are low, gray clouds that usually bring rain or snow
Cirrus or cirro- (prefix) means curl. These clouds are very high up in the sky.
They are made of ice crystals and look wispy or feathery and hold only a little bit of water.
We see these clouds when the weather is sunny.
Meteorologists are scientists who use special tools to measure, predict, and study weather conditions
The conditions of the atmosphere at a particular time and place.
Nimbo (prefix) and nimbus (suffix) added to a cloud name, means a rain cloud (ex. nimbostratus, a low, gray rain cloud, or cumulonimbus, a thunder cloud)
Alto (prefix) meaning "middle altitude" (for example, altostratus)
The Beaufort scale relates common observations to wind speeds
Weather satellites- orbit Earth's surface to make images of clouds and storms in order to track their movement.
Radar-stands for RAdio Detecting and Ranging, sends out radio signals that are reflected from objects such as clouds and rain. The reflections are turned into images (ex Doppler Radar). Ground level radar usually identifies precipitation in different colors to show different amounts.
Weather stations- measures weather conditions such as temperature, atmospheric pressure, wind direction and speed, amount of cloud cover, and precipitation. The National Weather Service uses data to make weather maps.
A station model shows how data from a weather station may appear on a weather map.
A psychrometer measures relative humidity.
Air Masses and Fronts
Air Mass- a large body of air that has similar temperature and moisture throughout.
North American Air Masses:
maritime-forms over water;wet
continental- forms over land;dry
polar-forms over the polar regions;cold
tropical-develops over the Tropics,warm
Front- the boundary that forms when two different air masses meet (due to differences between temperature and humidity).
Cold Front: A cold more dense air mass meets and displaces a less dense-dense warm air mass, pushing it up.
Cold fronts move fast, produce thunderstorms,heavy rain,or snow. Cooler weather follows because the warm air is pushed away.
Warm Front: A warm air mass meets and over-rides a cold air mass. The warm air less dense air moves over and gradually replaces the denser cold air.
Warm fronts generally bring drizzly precipitation; after the front passes,weather conditions are clear and warm.
Occluded Front:a faster-moving cold air mass overtakes a slower-moving warm air mass and forces the warm air mass up.
An occluded front has cool temperatures and large amounts of precipitation.
Stationary Front: A cold air mass meets a warm air mass and little horizontal movement occurs.
A stationary front has similar weather to that of a warm front,drizzly precipitation and then clear and warm.
humidity-the amount of water vapor or moisture in the air.
relative humidity-the amount of moisture the air contains compared to the maximum amount it can hold at a particular temperature; expressed in percentages.
Suppose 1 m3 of air at a certain temperature can hold 24g of water vapor. However, the air actually contains 18g of water vapor.
---------------- X 100 =relative humidity 75%
High pressure situations are generally associated with fair, sunny weather. As high pressure is an area of sinking air, and air tends to dry out as it sinks, leaving sunny skies.
Low pressure areas are generally cloudy/rainy areas -- where strong areas of low pressure bring our stormiest weather. That's because it's an area of rising air, and as air rises, it condenses into clouds and rain.
Air moves from higher pressure to lower pressure, so if you have a high and a low nearby, it can be windy as air rushes between the two.
Circulation of Ocean Currents
The oceans of the earth transfer heat from one location to another via massive ocean currents. These currents are like rivers flowing across the vastness of Earth, bringing warm waters from the equator up towards higher latitudes, and cooler water down towards the equator.
Global Wind Patterns
The Coriolis Effect
The rotation of the Earth causes an interesting phenomena on free moving objects on the Earth.
Objects in the Northern Hemisphere are deflected to the right, while objects in the Southern Hemisphere are deflected to the left.
"Rivers" of wind high above in the atmosphere. They typically run from west to east. Each hemisphere has two primary jet streams — a polar and a subtropical.
A wind blowing steadily toward the equator from the northeast in the northern hemisphere or the southeast in the southern hemisphere, especially at sea.
The Gulf Stream:
A strong, fast moving, warm ocean current that originates in the Gulf of Mexico and flows into the Atlantic Ocean.
It keeps sea surface temperatures warm, causing the areas around it to be warm. (such as Florida & Southeastern United States)
It has the greatest impact on Europe's climate, because it warms the North Atlantic Current.