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Meteorology

Meteorology. (3) Water, The Water Cycle, Humidity, Air Pressure and Clouds.

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Meteorology

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  1. Meteorology (3) Water, The Water Cycle, Humidity, Air Pressure and Clouds

  2. The 3 states of matter are solid, liquid, and gas. When water changes from one phase to another, heat energy is either absorbed or released. The heat energy that is absorbed or released is called latentheat. The process of sublimation occurs if a solid (ice) changes directly into a gas (water vapor) [“dry ice” which is carbon dioxide gas frozen into a block]. Deposition occurs if a gas changes directly into a solid [snow and frost]. Changing forms of Water

  3. The continuous movement of water between the atmosphere, land and the oceans. Processes include: • Evaporation (change from liquid water to water vapor) • Transpiration (the process by which plants release water vapor into the atmosphere) • Evapotranspiration (the total loss of water from an area – includes evaporation from soil and transpiration from organisms) • Condensation (change from water vapor to liquid water): clouds, dew, frost and fog. • Precipitation (any form of water that falls to Earth’s surface from the clouds): rain, snow, sleet, hail. • *Infiltration (when water soaks into the ground) The Water Cycle

  4. The amount of water vapor in the air is called humidity. Humidity is controlled by temperature. The higher the temperature, the more water vapor the air can hold. When the air contains as much water vapor as it can hold, we say the air is saturated. The dew point is the temperature to which the air must be cooled to reach saturation. If the air is saturated, and the temperature drops, the air cannot hold the water vapor so condensation occurs. Humidity is expressed as percent (%). Relative humidity is a measure of how close the air is to reaching dew point. Relative humidity is expressed as a ratio and can be calculated. Humidity

  5. We measure humidity with a variety of instruments including a psychrometer and a hair hygrometer. To calculate how much humidity is in the air you need to take two temperature readings. The first is called a dry bulb reading. This is just a measure of the air temperature. The second temperature is taken by placing a wet cloth on the bulb of the thermometer. You then need to fan the thermometer for one minute. This is called the wet bulb reading. You subtract the two temperatures and use your reference table to find the relative humidity of the air.

  6. Atmospheric pressure results from the air molecules being compressed and held to the Earth’s surface by gravity. This pressure is exerted equally in all directions. The pull of gravity on the atmosphere is strongest when it is closest to the earth. This means that 99% of the atmosphere is within 32 kilometers of the earth’s surface. This also means that the farther away you are from the Earth’s surface, the less atmospheric pressure there is. • As altitude increases, atmospheric pressure decreases. (ALT , P ) Atmospheric Pressure

  7. Temperaturealso affects atmospheric pressure. When air is warmer, the molecules move faster and as a result they move farther apart. This means that there are less molecules in a certain area so the atmospheric pressure decreases. • As temperature increases atmospheric pressure decreases. ( T , P ) • Meteorologists measure atmospheric pressure with 3 units: atmospheres (atm), millimeters or inches, or millibars (mB). Atmospheric pressure is measured with an instrument called a barometer.

  8. Mercury Barometer

  9. Clouds are collections of small water droplets or ice crystals that fall slowly through the air. In order for a cloud to form, a condensation nuclei, or small solid surface, must be available. As the warm air rises, the temperature drops and the dew point is reached. At this point, the water vapor will condense onto any condensation nuclei in the air. The height at which the air has cooled enough to form clouds is called the condensationlevel. Air can be forced upward by mountains or by a front. Clouds

  10. Fog is a stratus cloud on the ground. Fog can form when the air near the earths surface becomes cooled to below the dew point. This is called radiation fog. You typically see this type of fog in valleys and low places. Here in Virginia Beach, we often get advection fog. This occurs when warm air from the ocean moves across the cooler land. The air is cooled to below the dew point and fog develops.

  11. Nimbo-, -nimbus = RAIN (Latin = rain-bearing) • Cumu-, cumulo-, -cumulous = PUFFY (a heap) • Alto- = MIDDLE • Cirro-, -cirrus = HIGH (a hair) • Strat-, strato-, -stratus = FLAT (a layer) Prefixes/Suffixes for Naming Clouds

  12. Clouds are classified by SHAPE and ALTITUDE • Cloud Site • Weather WizKids Typical Examples of the 10 Main Cloud Types

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