Investigating Weather – 17min

Weather Weather is the condition of Earth’s atmosphere at a particular time and place. Short-term: Hours and days Localized: Town, Region or State Sunny Rain showers Snow Tornadoes Hurricanes

Causes of Weather The movement or transfer of thermal energy, heat, in Earth’s atmosphere that influences: Temperature Air Pressure Wind Humidity

Temperature The measure of the average kinetic energy of the molecules that make up a substance. Faster the moving molecules = more kinetic energy = higher temperature Slower the moving molecules = less kinetic energy = lower temperature

Temperature Air molecules have mass and occupy space, volume = density. Colder air: Particle Speed = slower molecule speed Volume = lower volume Density = increased density Cold air sinks! Warmer air: Particle Speed = faster molecule speed Volume = increased volume Density = decreased density. Hot air rises! Convection

Temperature Temperature can be affected by several factors: Earth’s rotation Earth’s tilt and revolution Latitude Altitude Cloud Thickness Surface Color and Texture Proximity to Water

Factors Affecting Temperature Earth’s rotation Earth rotates, spins, once in 24 hours. Half of earth is facing the sun - Day Warmer temperatures - energy received by solar radiation. Half of earth is facing away from the sun - Night Cooler temperatures Night Day

Factors Affecting Temperature Earth’s tilt and Revolution Earth’s axis is tilted at 23.5 off perpendicular. Earth revolves, orbits, once around the sun in 365 days (1 year) Causes different amounts of sunlight to be absorbed or scattered during different seasons.

Factors Affecting Temperature 3. Latitude The distance North or South of the equator affects the amount of solar radiation an area receives – insolation. Equator receives direct sunlight year-round. Temperatures are consistently. Poles receive varying amounts of sunlight due to the tilt of Earth’s axis and revolution around the sun. Very cold winters (Northern Hemisphere), Warm/hot summers

Factors Affecting Temperature 4. Altitude The height into the atmosphere, away from sea level (0 m) Temperature decreases 3F every 1000 ft (333 m) in elevation

Why is it colder the higher up you go if hot air rises? Density of the air molecules decrease with elevation, more spread out, therefore causing heat to be lost. As the air cools, molecules compact and sink to where they encounter heat absorbed by solar radiation at the ground, Temperatures increase and rise again – convection currents!

Factors Affecting Temperature How much solar radiation is reflected back into space – Albedo

Albedo Effect 5. Clouds 6. Surface Color 7. Surface Texture Thicker clouds, 70-95% Thin clouds, 30-50% 6. Surface Color Lighter colors Snow - 80-95% Darker colors Asphalt – 5-10% 7. Surface Texture Rougher Forests - 10-20% Smoother Grass – 25-30%

Solar Radiation Reflection What are two ways humans could help reduce the amount of solar radiation being absorbed? Use lighter roofing materials instead of dark Stop blacktopping roads, use brick, stone or concrete instead

Temperature Maps Maps that show areas of similar temperature – Isotherms Can use color to identify areas of similar temperature Can use lines to connect areas of similar temperature.

Air Pressure Air pressure – the result of the weight of a column of air pushing down on an area. Pulled down by the force of gravity. Air pressure always moves from areas of high to areas of low: The closer to Earth’s surface the higher the air pressure. Sea level = greatest air pressure The farther away from Earth’s surface, altitude or elevation, the lower the air pressure. On top of a mountain = lowest air pressure.

Air Pressure What does air pressure indicate: Low air pressure – BAD weather Warmer air Faster moving particles – high energy Less dense Carries lots of moisture High air pressure - GOOD weather Cooler air Slower moving particles – less energy More dense Carries little moisture

Measuring Air Pressure Mercury Barometer Mercury adjusts to the amount of pressure pushing down on it. As air pressure increases, the mercury in the tube rises/high. Sunny and Clear As air pressure decreases, the mercury in the tube falls/low. Cloudy and Rainy

Measuring Air Pressure 2. Aneroid Barometer Aneroid = “without liquid” When air pressure increases, the walls push in, higher readings Fair to Dry conditions When air pressure decreases, the walls bulge out, lower readings Stormy and Rainy Measured in units called millibars (mb) Low High

Charting Air Pressure Isobars – similar air pressure recordings connected by a solid line. Low Pressure: Cloudy and rainy High Pressure: Sunny and Clear Close Lines: Windy Farther Apart Isobars: Calm Air Pressures move from regions of High to regions of Low L Isobars H

Low High 4 Each isobar differs from the next isobar by ______ millibars. The lowest air pressure reading on the map is _____ millibars. What weather conditions would they most likely be experiencing? The highest air pressure reading on the map is ______ millibars. What pressure range is New York City located in? 992 Stormy 1016 Change 1004-1008

Where Does Weather Occur? Weather takes place in the atmosphere. The layer of gases that surround planet Earth. Importance of the Atmosphere: Make conditions on Earth suitable for living things. Contains oxygen (O)and other gases. Keeps Earth warm enough for liquid water to exist. Protects organisms from radiation from the sun and meteoroids.

Composition of the Atmosphere Argon & Carbon Dioxide – 1% Made up of a mixture of gases: Nitrogen – 78% The most abundant gas Oxygen – 21% Argon - .93% Carbon Dioxide - .036% Oxygen – 21% Nitrogen – 78%

Layers of the Atmosphere The atmosphere is divided into 4 main layers based on temperature and air pressure changes. Troposphere Stratosphere Mesosphere Thermosphere

The Troposphere Closest to Earth’s surface. 0-16 km above sea level Earth’s weather occurs here! 0-16 km above sea level Contains almost all the mass of the atmosphere As altitude increases, temperature decreases 1 km increase = 6.5C cooling. At -60C it levels off.

The Stratosphere Extends from 16-50km above the earth’s surface Increases in temperature as altitude increases due to the ozone layer. Protective layer that absorbs the sun’s energy and converts it to heat.

The Mesosphere As altitude increases, temperature decreases. The coldest layer at -90C 50-80km above the Earth‘s surface. Protective layer where most meteoroids burn up.

The Thermosphere Extends from 80km to infinity – has no outer limit. Divided into two different sections: Ionosphere aurora borealis Exosphere satellites orbit Earth. The hottest layer at 1800C due to heat coming in.

Aurora Borealis A natural light display caused by the collision of energetic charged particles with atoms in the high altitude atmosphere