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Understanding Weather. Weather and Water Cycle. Weather – condition of the atmosphere (mixture of gases) at a certain time and place Mainly affected by amount of water in the air. Humidity. As water evaporates from lakes, oceans, and plants it becomes water vapor.
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Weather and Water Cycle • Weather – condition of the atmosphere (mixture of gases) at a certain time and place • Mainly affected by amount of water in the air
Humidity • As water evaporates from lakes, oceans, and plants it becomes water vapor. • Humidity – amount of water vapor in air • When temp increases so does amount of air’s ability to hold water vapor
Relative Humidity • Amount of water vapor in the air compared with the maximum amount of water vapor that the air can hold at a certain temperature • Given as a percentage • When air is able to hold all of the water it can at a given temp., it is called saturated (100% relative humidity)
Dew Point • Dew point is the temperature at which a gas condenses (changing state) into a liquid. • At dew point, air is saturated
Clouds • A collection of small water droplets or ice crystals suspended in air, which forms when the air is cooled and condensation occurs • Clouds are classified by form and altitude
Types of Clouds • Cumulous – fair weather • Stratus – layered, block out sun • Cirrus – thin, feathery • Nimbus – produce precipitation • Cumulonimbus = thunderstorms • Nimbostratus = light to heavy rain
Precipitation Types include: • Rain – most common… interesting fact: before a water drop can fall as rain, it must become about 100x its original size • Sleet – rain fallws through layer of freezing air • Snow – when water vapor changes directly to a solid when temps are super cold • Hail – updrafts of raindrops freeze, water recoats it, updraft, repeat….
Air Mass • Large body of air where temperature and moisture content are constant throughout • Maritime (Wet) • Continental (Dry) • Polar (Cold) • Tropical (Warm)
Front • Air masses have different densities • they don’t mix • Warm air rises etc. • When two air masses meet it is called a Front • Types include: Cold, Warm, Occluded, Stationary
Cold Front • Where cold air moves under warm air (Less Dense) and pushes warm air up • Move quickly • Bring Thunderstorms, Heavy rain, and snow • Usually cool weather follows
Warm Front • Where warm air moves over cold, denser air • Warm air gradually replaces cold air • Bring drizzly rain and are followed by clear and warm weather
Thunderstorms • Small intense weather systems that produce: • Strong winds • Heavy rain • Lightening • Thunder
Lightening and Thunder • Lightning - electric discharge that occurs between a positively charged area and a negatively charged area • Can happen between two clouds, Earth and a cloud, or even between two parts of the same cloud. • When lightening strikes, energy is released. • This energy is transferred to air and causes the air to expand rapidly sending out sound waves… Thunder is result
Tornado • Only occur in 1% of all thunderstorms • Tornado – small, spinning column of air that has high wind speeds and low central pressure • Starts out as a funnel cloud that pokes through the bottom of a cumulonimbus cloud • Becomes tornado when it makes contact with ground
Hurricane • Large rotating tropical weather system that has wind speeds of at least 120km/h • Most powerful storms • Synonym – typhoon or cyclones • Mostly occur between 5 and 20 latitudes
