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Weather Instruments. Measure wind direction with a wind vanewind vane A wind vane is a tool for measuring wind direction. Knowing the direction of the

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Weather Instruments

Weather Instruments1Measure wind direction with a wind vaneA wind vane is a tool for measuring wind direction. Knowing the direction of the wind helps meteorologists determine in which direction a storm or weather system will travel.2Determine air pressure with a barometer. To measure air pressure, weather forecasters use a barometer. When the air pressure is rising, good weather is on the way. When air pressure is falling, the weather will get stormier.

3Calculate wind speed with an anemometer. Meteorologists use anemometers to measure wind speed in one area. With this data, they can determine how quickly a storm, or weather system, will travel to other areas.

Use a rain gauge to measure how much rain falls in a given period of time.Measure temperature with a thermometer.4Wind- A windsock is a tube designed to indicate wind direction and relative wind speed.***Remember wind direction is the opposite of the direction in which the windsock is pointing5A contrail, also known as a condensation trail, is a cirrus-like trail of condensed vapor (often resembling the tail of a kite) that is produced by jet aircraft flying at high altitudes.

6Contrails are produced at altitudes high enough for water droplets to freeze in a matter of seconds before they evaporate. Temperatures at such altitudes are typically below -38 degrees Celsius.7Contrails are clouds formed when water vapor condenses and freezes around small particles that exist in aircraft exhaust8A contrail forms because one of the components of jet engine exhaust is water. Jet fuel is made of carbon and hydrogen When jet fuel burns with oxygen, most of the exhaust consists of CO2 (carbon dioxide) and H2O (water). The water is generally an invisible vapor.

9When you exhale, your breath contains a great deal of invisible water vapor as well. You may have noticed that on certain days in the winter, your breath will form a cloud of condensation when you exhale. 10In the summer, however, you don't see your breath. Cold air can hold a lot less moisture than warm air, so in the winter, when the moisture in your breath hits the cold air, the moisture condenses into a visible cloud.11The same thing happens when a jet engine "exhales." If the temperature, winds and humidity in the upper atmosphere are right, long, white contrails form when the moisture in the exhaust condenses.

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14What are clouds?15

16CirrusCirrus clouds are thin, wispy clouds blown by high winds into long streamers. They are considered "high clouds" forming above 6000 m (20,000 ft). Cirrus clouds usually move across the sky from west to east. They generally mean fair to pleasant weather.

17Cirrus Clouds

18Stratus CloudsStratus clouds are uniform grayish clouds that often cover the entire sky. They resemble fog that does not reach the ground. Usually no precipitation falls from stratus clouds, but sometimes they may drizzle. When a thick fog "lifts," the resulting clouds are low stratus.These clouds form below 6,000 feet from the ground

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20CumulusCumulus clouds are puffy clouds that sometimes look like pieces of floating cotton. The base of each cloud is often flat and may be only 1000 m (330 ft) above the ground. The top of the cloud has rounded towers. When the top of the cumulus resembles the head of a cauliflower, it is called a towering cumulus. These clouds grow upward, and they can develop into a giant cumulonimbus, which is a thunderstorm cloud.

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