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Unit 4 - Weather, Climate, and Biomes. What is Weather?. Definition: - the state or condition of the variables of the atmosphere at any given location for a short period of time - in fact, meteorology is the study of the weather. Where does Weather Occur?.
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What is Weather? • Definition: - the state or condition of the variables of the atmosphere at any given location for a short period of time - in fact, meteorology is the study of the weather
Where does Weather Occur? • Remember: Weather occurs in the layer of the atmosphere called the TROPOSHERE!!!
How do we Measure the Weather Variables? • Air Pressure: • Caused by the weight of the atmosphere, so air pressure is the greatest at Earth’s surface and decreases as you go higher in the atmosphere (think of diving deep in the ocean).
How do we Measure the Weather Variables? • Measuring air pressure: • Measured using a barometer • Barometers measure the effect of weight from the atmosphere
2 Factors that Affect Air Pressure 1. Temperature: Measured with a thermometer in degrees Celsius. Weather Shelter – where official temperature readings are taken
Factors that Affect Air Pressure • Temperature continued: • Cool air is more dense than warm air. • If air is warmed, it becomes less dense and air pressure decreases • If air is cooled, it becomes more dense and air pressure increases.
2 Factors that Affect Air Pressure • Altitude: • Air pressure decreases as you go up (when altitude increases). • This is due to the fact that there is less of the atmosphere above you pushing down. • This is why people who climb tall mountains carry oxygen tanks with them.
How Air Pressure Affects a Rising Balloon • http://www.classzone.com/books/earth_science/terc/content/visualizations/es1901/es1901page01.cfm?chapter_no=visualization
As the warm air rises, it becomes cooler and more dense Cool air is sinking – more dense Warm air is rising – less dense Cool air takes the place of the rising warm air-to fill space
What is Wind? WIND – • horizontal movement of air parallel to Earth’s surface
What Causes the Wind? • wind is created by the uneven heating of Earth’s surface • uneven heating causes differences in air pressure • wind will always blow from areas of high pressure to areas of lower pressure
Measuring the Wind Wind Measurement requires a size and direction to describe it Ex. 70 mi/hr SE wind - wind is named for the direction from which it came from Ex. A south wind (heading north but came from the south)
Measuring the Wind Wind continued… The speed of wind is measured using an anemometer - measured in mi/hr or knots (boats) The direction of the wind is determined using a weather vane
Wind Facts Wind continued… • Wind is responsible for creating waves in the ocean because energy from the wind is transferred to the water • Jet streams - areas of very fast winds in the upper atmosphere that separates warm air masses from cool air masses. • Affects where weather and storms flow.
Jet stream Facts • During World War II the Japanese used the air stream to fly balloons at 30,000 feet across the Pacific to the USA. • The jet stream is the reason why transatlantic flights are quicker going from America to Europe. • They can be as fast as 315mph.
Factors of Weather CLOUDS • Masses of water vapor combined with dust particles in the atmosphere • Takes about 1 million cloud droplets to make a single raindrop
How do Clouds Form? • Water evaporates from the surface of Earth into the atmosphere (liquid changes to a gas). • Water vapor molecules condense on dust particles (gas changes to a liquid). • When droplets become heavy enough, the water falls toward Earth as precipitation.
4 Basic Cloud Types • Cumulus - Look like a heap of cotton balls or whipped cream; summertime; typically no precipitation • Stratus - Clouds that look like a flat blanket in the sky; low rain clouds; cover whole sky
4 Basic Cloud Types 3) Cirrus - Look like curls of white hair; fair-weather cloud; whispy; look like airplane tracks 4) Cumulonimbus - cotton-like clouds that have built up in the middle or high part of the atmosphere; tall, deep, & dark; bring lightening, heavy rain, and severe weather
Precipitation PRECIPITATION- • falling of liquid or solid water from clouds toward the surface of Earth • to occur, ice crystals or water droplets in clouds must come together to become big enough so that they will fall under the influence of gravity
Precipitation Forms of precipitation include: rain drizzle snow sleet hail freezing rain - rain gauge: used to measure liquid precipitation; measured in inches or cm
Severe Weather Thunderstorms • Heavy rain & electricity (lightening) form from cumulonimbus clouds • Lightening is electricity that results from charges when water vapor molecules collide with each other • Lightening bolts are hot! (30,000-50,000°F) • This heats air around it so fast that the air expands sending out vibrations & shock waves we hear as sound (thunder)
Thunderstorms continued • At any time, over 2,000 thunderstorms are happening on Earth • Hail can come from T storms where water encounters below freezing temps
Severe Weather Tornados • Rapidly rotating extremely low pressure funnel that hangs down from thunderstorm clouds towards Earth’s surface • True tornados touch Earth’s surface • Narrow & at least 100 ft. wide • Can reach wind speeds of 350 mph
Tornados continued • Not clear how tornados are formed except formed when 2 air masses with huge temperature differences from thunderstorm clouds collide • Low air pressure vacuums up
Measuring Tornado Strength • Measured using the Fujita Scale. • From F0-F2 is moderate to significant – winds are 40-157 mph. Can tear off roofs of houses. • From F3-F4 is a devastating tornado 158 to 260 mph and can level houses and throw cars. • F5 is an incredible tornado 261-318 mph. Houses lifted off foundations, bark pulled off trees. • F6 is inconceivable – never been achieved
Tornado Videos • http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/tornadoes/tornado-montage.html
Severe Weather-Hurricanes Hurricanes • Large rotating, low-pressure storms • Develop late in summer, early fall in Atlantic Ocean between South America and Africa (where waters are very warm)
Severe Weather-Hurricanes • Evaporation of warm water • Condensation – releases energy for the storm • All low pressure systems rotate counterclockwise. (in the northern hemisphere)
Rating Hurricane Strengths • http://www.nhc.noaa.gov/aboutsshs.shtml
Other Forms of Severe Weather • Tsunami • Series of water waves caused by large body of water (ocean) that is rapidly displaced • Means harbor wave (in Japanese) • Caused by: earthquakes, volcano eruptions, underwater explosions (nuclear devices), etc.
Climates Define Climate: - long term weather pattern of an area including precipitation, temp, and wind - causes are solar radiation to an area - recall, the Earth has seasons because of the 23 ½ ° tilt which means the amount of solar radiation to hit the Earth varies depending upon the Earth’s location to the Sun
Types of Climate • Tropical climate - constant high temps and rain • Dry climates - 30% of Earth’s land area; hot temps, low precipitation, vegetation scarce; high solar radiation, few clouds • Mild climates - warm, muggy weather in summer and cool weather in winter
Types of Climate 4. Continental climates - area where tropical & polar air masses collide; rapid & violent changes in weather; summer & winter temps are extreme 5. Polar climates - coldest regions on Earth; constant cold; precipitation is low; cold air cannot hold as much moisture In these climates, there exist systems of animals and vegetation that thrive in that temperature range called BIOMES
