Heating the Atmosphere

Electromagnetic Waves The sun is the ultimate source of energy that creates our weather. You know that the sun emits light and heat as well as the ultraviolet rays that cause a sunburn.

Electromagnetic Waves These forms of energy are only a part of a larger array of energy called the electromagnetic spectrum. All radiation, whether X-rays, radio waves or infrared waves, travel through the vacuum of space at 300,000 kilometers per second.

Only 7% of the light energy received by the earth is visible light.

Electromagnetic waves are classified by their wavelengths; the distance from the crest of one wave to the crest of the next wave.

Heat transfer Three mechanisms of energy transfer as heat are —Conduction —Convection —Radiation All three processes happen simultaneously in our atmosphere. These mechanisms work to transfer energy between Earth’s surface (both land and water) and the atmosphere.

Heat transfer Conduction – the movement of heat from molecule to molecule; through molecular activity Heat flows from the higher temperature matter to the lower temperature matter Metals are good conductors of heat; air is a poor conductor of heat.

Heat transfer Because air is a poor conductor, conduction is important only between Earth’s surface and air directly in contact with the surface. For our atmosphere, conduction is the least important mechanism of heat transfer.

Heat transfer Convection – the movement of heat by circulation within a substance Much of the heat transfer that occurs in the atmosphere is convection Convection takes place in fluids where the molecules can move freely. The atmosphere behaves like a fluid

Heat transfer example of convection: a pot of boiling water

Heat transfer Radiation – the release and transfer of energy in wavelengths of heat and light through space. Solar Energy reaches the Earth from the sun by radiation There are actually 4 laws that govern radiation….

1: All objects, at any temperature, emit radiant energy 1: All objects, at any temperature, emit radiant energy. Not only hot objects like the sun, but colder objects like the Earth (including it’s polar ice caps) continuously emit energy.

2. Hotter objects radiate more total energy “per unit area” than colder objects do.

3. The hottest radiating bodies produce the shortest wavelengths of maximum radiation The sun, at 6000C, radiates at .5 micrometers.

When radiation strikes an object, there are usually three different results. 1. Some energy is absorbed by the object. When radiant energy is absorbed, it is converted to heat and causes a temperature increase. Like what??

When radiation strikes an object, there are usually three different results 2. Substances such as water and air are transparent to certain wavelengths of radiation. These substances transmit the radiant energy. In other words – Radiation goes THROUGH the object

When radiation strikes an object, there are usually three different results 3. Some radiation may bounce off the object without being absorbed or transmitted. Thus being scattered

This scattering is why the sky is blue…

… and the sunsets are often red (what do you think is the meaning of “Red sky at night, sailors’ delight; red sky in the morning, sailors’ take warning”

Heat Budget of the Atmosphere

When it reaches the Earth, some is reflected back to space by clouds, some is absorbed by the atmosphere, and some is absorbed at the Earth's surface. Since the Earth is much cooler than the Sun, its radiating energy is much weaker (long wavelength) infrared energy.

Heat energy from the earth can be trapped by clouds leading to higher temperatures as compared to nights with clear skies. The air is not allowed to cool as much with cloudy skies. Under partly cloudy skies, some heat is allowed to escape and some remains trapped. Clear skies allow for the most heat to escape & cooling to take place.

About 50% of solar energy reaches the surface and is absorbed. Most of THIS energy is reradiated. The atmosphere absorbs the longer wavelengths Larger molecules, like water vapor and CO2, absorb the energy This energy is transformed into molecular motion – rise in temperature

Simplified diagram of the heating of the atmosphere

Albedo (Al-bee-dough) The percent of radiation returning from a surface compared to that which strikes it When an object reflects most of the light that hits it, it looks bright and it has a high albedo. When an object absorbs most of the light that hits it, it looks dark. Dark objects have low albedos.

Clouds’ albedo is near 60% Snow’s albedo is up to 95 percent Water’s albedo is (on average) about 10% Average albedo for earth and clouds is about 30%

Conditions of the Air Temperature – amount of hotness or coldness relative to something else Thermometer – an instrument that measures relative hotness or coldness Dew Point temperature – The temperature at which air becomes saturated Isotherm – a line connecting places with equal temperature on a weather map Temperature scales: 1°C = 1.8°F or 1°F = 5/9 ° C

Celsius to Fahrenheit and Fahrenheit to Celsius Formula °C  x  9/5 + 32 = °F (°F  -  32)  x  5/9 = °C

For Example Convert 37°C to Fahrenheit. 37°C x 9/5 + 32 = 98.6°F OR 5  Convert 98.6°F to Celsius. (98.6°F  -  32)  x  5/9 = 37°C (98.6°F - 32) x 5 = 37°C  9

Conditions of the Air (cont.) Air pressure - the downward pressure exerted by the weight of the overlying atmosphere or the “weight” of the atmosphere per unit AREA. Barometer – an instrument used to measure air pressure Measured in inches of mercury in a column Or millibars (metric conversion) Average air pressure at sea level is 1013 millibars

What do you notice about the relationship between air pressure and volume?

What do you notice about the relationship between air pressure and temperature?

What do you notice about the relationship between volume and temperature?

Pressure depicted on a weather map Isobars – lines con-necting points of equal pressure

Isobars on the ‘vertical’

Note: the density of molecules close to the surface

Measurement of the Atmosphere The condition(s) of the atmosphere is measured by the radiosonde

A radiosonde is a small instrument package tethered to a weather balloon. take a vertical profile of the atmosphere as the balloon ascends to altitudes up to 115,000 feet. the data is relayed by radio transmitter to a computer at the surface

Launch of a weather balloon off an aircraft carrier

photo shows the weather balloon bursting at 99,712 feet http://www.brothers-brick.com/2008/08/06/mindstorms-nxt-fans-launch-lego-into-space-via-weather-balloon/

Synoptic Map Station models – group of symbols depicting weather conditions Isobar – line of equal pressure a. show locations of High or Low pressures b. close lines mean strong winds c. lines far apart mean gentle winds

Station Model how meteorologists can put a lot of information in a small area

Water in the atmosphere Water Vapor Humidity – the amount of water vapor in the air Relative humidity – the actual amount of water vapor in the air compared to the greatest amount the air can hold

Water in the atmosphere Water Vapor Saturated – to be completely filled with water vapor Psychrometer – an instrument to measure relative humidity Hygrometer – an instrument used to measure the air’s humidity

Precipitation water or ice that condenses in the air and falls to the ground as: Rain- liquid water that falls to the ground Snow - ice crystal flakes; water vapor in the atmosphere that froze into ice crystals and falls to the ground in the form of flakes Sleet -partially melted grains of ice Hail - pellets made of layers of ice and snow Freezing rain – rain that freezes into ice as it hits the ground

Weather Advisories Weather WATCH – predictions about approaching severe weather Weather WARNING – specific severe weather conditions have been actually observed by a person or verified by a computer

http://www. sleepingdogstudios. com/Network/Earth%20Science/ES_17 http://www.sleepingdogstudios.com/Network/Earth%20Science/ES_17.2_files/frame.htm