Weather

• the state of the atmosphere at a given time and place
• Usually includes cloud cover, rain or snow, sunshine, barometric pressure, moisture in the air, wind speed, and temperature

Meteorology

• Weather is studied by scientists called Meteorologists
• Meteorologists must understand how the atmosphere heats and cools, how clouds form, and even the composition of the atmosphere
• Direct observation of the atmosphere is one of the best techniques to study the weather
• Just looking at the sky and the clouds can tell you what the weather will be like within the next few hours
• Feeling the effects and speed of wind can also help you detect weather patterns. Ex - folklore says that winds from the east will always bring rain
• Take a look at the Beaufort Scale on Page 478.

Temperature

• Temp. cannot be felt as accurately, but most people claim to be able to feel its affects
• In winter, people feel colder when the wind is blowing
• This is caused by the wind evaporating moisture off your skin...causing a cooling of your skin surface
• Scientists have developed the Wind Chill Factor to explain this cold feeling
• See the chart on Page 479!!!
• If it is 20 deg. outside with a wind @ 35mph, you will feel as if it is -20 !
• Note: Non-living things are not affected by the wind chill factor

Composition of the Atmosphere

• Earth's lower atmosphere is a mixture of many gases called Air
• The two main gases in air are Nitrogen and Oxygen
• Helium, Hydrogen, Neon, and Carbon Dioxide are also found in minor amounts
• The lowest layer of air is mostly oxygen to about 1000km; Helium to about 2400km; and Hydrogen thins out to space
• Water vapor fills the air of the lower atmosphere because of the evaporation that takes place all over the world

The Ozone

• The problems with the ozone layer of earth has been a longtime issue
• Ozone thinning results from the release of gases called Chlorofluorocarbons or CFC's
• The gases contained are chlorine, fluorine, and carbon
• CFC's do not break down easily and rise to the ozone where they begin thinning the ozone when reacting to sunlight.
• CFC's are released into the atmosphere from man-made products like air conditioners, coolers, electronic cleaners, etc.

The Atmospheric Layers

• Scientists divide the atmosphere into four layers that are based on temperature changes
• Troposphere - lowest layer closest to earth and contains all of earth's weather
• Stratosphere - from about 10-18km up to 50km; contains clear and dry air and often jet airplanes fly in the stratosphere
• Mesosphere - from 50km to 80km above the surface; temps. get cooler in this layer
• Thermosphere - 80km to 500+km (space); temps. rise in this final layer of atmosphere
• Ionosphere - named for the group of thermosphere and mesosphere together; filled with ions and aids in allowing us to transmit radio source signals around the world; charged ions appear as Auroras!

• Changes in weather involve air movement, formation of clouds, and precipitation
• The energy needed to make these changes comes from the sun
• Heat energy enters and moves through the atmosphere in three different ways:

1. Radiation
2. Conduction
3. Convection

• Radiation - comes from the sun radiating its heat to earth
• Conduction - air that touches warm ground or ocean water gets heated
• Convection - water on the stove heated - water in the bottom of the pan heats by conduction, but the water on the surface of the pan heats because it is circulated (convection current) with the water from the bottom

• Ideally, just as much energy enters Earth as leaves Earth
• Earth would either heat up or cool down if a balance was not in effect
• Energy leaving or coming to Earth is by radiation only
• Incoming energy to Earth is called Insolation (Incoming Solar Radiation)
• We only get about 1 / 2-billionth of the sun's heat energy
• Suppose 100 units of solar energy reach us:

1. 30 are reflected back
2. 19 are absorbed by clouds and vapor
3. 51 are absorbed by the ground

• Energy is then reflected back to space through conduction of the ground transferring heat to the lower level of air, then convection carries the warm air up to the upper atmosphere into space

Greenhouse Effect

• Earth's surface radiates infrared waves which warm the atmosphere as they are trapped in by the water vapor and carbon dioxide in the air
• Just like a greenhouse, the atmosphere traps this heat close to Earth's surface, warming the air around us…this is called the Greenhouse Effect
• Because of burning of fossil fuels like coal, oil, and natural gas, we have added to the atmosphere's ability to block the heat loss
• This has caused us to see an increase in the Greenhouse Effect and greenhouse gases
• This is not actually a good thing as it is causing an increase in carbon dioxide and causing unusual melting patterns in glaciers, etc., increasing our water levels
• Increased rainfall could affect the way ecosystems function around the globe

Altitude and Temperature

• People often go to the mountains to cool from summer heat
• Temps do become cooler at about 1 deg C for every 160 meters - this is called the Normal Lapse Rate
• Rising air cools from expansion as air is densest near the surface, holding in heat
• Temperature can be cooler near the surface during a Temperature Inversion
• T.I. is caused by winds pushing warm air up into the high atmosphere, allowing cool air to sink to the surface

The Seasons

• Because Earth is round, the sun strikes the surface at angles from 0 to 90 deg.
• Places near the equator get sun rays at 90 deg all year long
• Other places receive rays at varying angles, causing their temps to be cool or warm depending on how the rays strike the surface
• Angle of strike varies with seasonal changes - closer the angle is to 90 deg - warmer the temperature
• Daily temperature range varies by weather conditions - averages about 10-20 deg between night and day
• Coolest time of day is usually just before dawn - warmest is late afternoon

Air Temperature

• Temperature is a measure of the energy of molecules
• The more energy, the hotter it feels
• Thermometers are the instruments that are designed to measure temperature
• Warmer temps cause molecules to expand and move apart - causing a rise in the fluid in the tube of the thermometer
• Colored alcohol or mercury are most common materials found in thermometers
• Bi-metal bars are used also - often brass and iron - found in household thermostats
• Temperature Scales

1. Celsius - 0 deg is freezing; 100 deg boils
2. Fahrenheit - 32 is freezing; 212 boils
3. 1 deg C = 1.8 deg F; 1 deg F = 5/9 deg C

• Isotherms are lines drawn on maps that connect places with the same temperature
• See the maps on Pages 492-493
• Isotherms shift their positions on the map as temperature change during seasonal changes
• Note: Usually will see the hottest and coldest places will be on land