Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Weather Chapter 24 Air Masses • Differences in air pressure are caused by unequal heating of Earth’s surface. • Heated equatorial air rises & creates a low-pressure belt. • Cold air near the poles sinks & creates a high-pressure centers. • Differences in air pressure creates the wind patterns How does air move? • Moves from areas of high pressure to low pressure. • Worldwide movement of surface air from poles toward equator. • Temperature & pressure differences give us the wind belts. Formation of Air Masses • Air mass = large body of air throughout which temperature & moisture content are similar. • Air masses over frozen polar regions are cold & dry; air masses formed over tropical regions are warm & moist. Types of Air Masses • • • • • • 4 TYPES: MARITIME (WET) CONTINENTAL (DRY) POLAR (COLD) TROPICAL (WARM) Can be different combinations, example maritime polar - mP North American Air Masses Fronts • When 2 unlike air masses meet, density differences usually keep the air masses separate. • Cool air mass is dense; doesn’t mix with less-dense air of a warm air mass. • A boundary --- known as a front --forms between the air masses. Types of Fronts • Cold fronts = the front edge of a moving mass of cold air that pushes beneath a warmer air mass Warm Front • Front edge of advancing warm air mass that replaces colder air with warmer air Stationary & Occluded Fronts • Stationary = a front of air masses that moves either very slowly or not at all. • Occluded = forms when a cold air mass overtakes a warm air mass & lifts the warm air mass off the ground & over another air mass. Symbols Used for Fronts Weather Instruments • Weather observations are based on a variety of measurements including: atmospheric pressure, humidity, temperature, wind speed, & precipitation. Instruments Used to Measure LowerAtmospheric conditions Thermometer = measures & indicates temperature Barometers = measures atmospheric pressure Wind vane = used to determine direction of wind Anemometer = used to measure wind speed Instruments Used to Measure UpperAtmospheric Conditions • Radiosonde = package of instruments carried by a balloons to measure temp, dew point, & wind velocity • Radar = a system that uses reflected radio waves to determine velocity & location of objects • Weather satellites • Computers Forecasting Weather • Data that is collected by weather stations are transferred onto weather maps. • Station model = a pattern of meteorological symbols that represents the weather at a particular observing station & that is recorded on a weather map. Weather Symbols Plotting Temperature, Pressure, Fronts & Precipitation • Lines that connect points of equal atmospheric pressure are called isobars. • Closely spaced isobars indicate a rapid change in pressure & high winds • Isobars that form closed circles indicate centers of high or low air pressure. (Marked with an H or L). Isobars