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Part 4

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Week 16, 17, 18 and 19The Atmosphere

• Modules 3, 4, 7 and 8 in AP• The study of the Air and the Atmosphere and how we

measure them• Movement of the Atmosphere - Air Masses, Winds

and Storms• Weather Prediction

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• Next test: Week 19 T Jan 23/25 - covers the atmosphere and hydrosphere

• Week 20 A Jan 30 - I will be away - analysis exercise

• U of IL - Wx Course

• Lyndon State Course

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Prep Questions• Week 16

– (1) What role does the sun play in causing seasons and the weather?

– (2) What is the composition of the air?– (3) What is the role of each component?

• Week 17– (1) What are the 5 layers of the atmosphere?– (2) What is temperature?– (3) What is Ozone hole?

• Week 18 – (1) What factors influence the weather?– (2) What are the weather elements?

• Week 19– (1) What are the factors that cause precipitation?– (2) What are the differences and common characteristics

of a thunderstorm, tornado, hurricane and a nor'easter low pressure system?

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Current Weather ReviewCurrent Weather Review  

 http://hss-1.us/phys-sci/Weather-Information.htmRadar/Sat US Radar US Radar NWS

Goes Sat Page US Sat IRNRL Sat

US Sat VisNY VIS

Sfc Analysis NWSSurface Plots

Surface 12 Hour Fcst Surface 24 Hour Fcst Surface 36 Hour Fcst Surface 48 Hr Fcsts

Emergency CURRENT SVR Wx RADAR

National Weather Situation Page http://

www.VueTOO.com

Severe Weather Alert Link 

Your Local Forecast  

Local Fcsts Rome NY   43.23°N 75.46°W  Rome Griffiss Airfield

Lat: 43.23   Lon: -75.41   Elev: 504 ft Lat/Lon: 43.23°N 75.46°W   Elevation:482  

BGM Discussion 

Wx Maps NAM GFS 1. GFSx -Upper 2.GFSx-MRF- Precip

Long Range NWS Model

ECMWF CPC Datastreme

Climo SYR CLIMO CLIMO STAT CNY ALB CLIMO  

Other NASA Solar Science Solar-Sun Spot-Space-Wx

Sun & Moon Rise & Set Tables Moon Phases

Your Sky Start ChartsTides Maine NOAA Space Wx Forecast Central

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Factors that Influence the Weather

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Prep Questions• Week 16

– (1) What role does the sun play in causing seasons and the weather?

– (2) What is the composition of the air?– (3) What is the role of each component?

• Week 17– (1) What are the 5 layers of the atmosphere?– (2) What is temperature?– (3) What is Ozone hole?

• Week 18 – (1) What factors influence the weather?– (2) What are the weather elements?

• Week 19– (1) What are the factors that cause precipitation?– (2) What are the differences and common characteristics

of a thunderstorm, tornado, hurricane and a nor'easter low pressure system?

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Conditions (elements) of the atmosphere that need

to be measured.

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Wind

TemperatureHumidity & Precip

Clouds

Air Pressure

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* Five Methods of Heat Transfer

• Radiation - Transfer of energy by Electro-magnetic Radiation (Some form of Light)– Does not need a transfer medium

• Conduction - transfer by contact

• Convection - transfer by movement of mass

• Advection - horizontal component of convection

• Latent Heat

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Describe how vertical and latitudinal heat balance is

achieved.• Maintaining Vertical and Latitudinal Heat Balance•

• - Vertical - the ground must heat the air through a combination of conduction, convection and radiation

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• - Latitudinal - tropics must heat the poles primarily through advection (wind). The circulation of the atmosphere and oceans is driven by the atmosphere trying to maintain a latitudinal heat balance.

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Basic Elements of Weather: • Temperature. Avg KE of air - Thermometers .• Pressure Weight (fore of) of air per sqaure incn add paper .• Moisture. Humidity is the measure of the water vapor content in the air, combined

with the temperature, it causes many weather conditions. The amount of vapor in a given volume of air at a given time is called the absolute humidity. While relative humidity is the amount of water vapor that exists in a gaseous mixture of air and water, hot and cold weather are more comfortable when the relative humidity is low. Clouds are formed when water vapor condenses high above the ground. When cloud droplets grow larger and become too heavy to be held up by the air currents, they fall to the ground in a form of rain. If the raindrops fall through a layer of air which is below freezing, the drops freeze and fall in a form of snow.

• Precipitation is the primary mechanism for transporting water from the atmosphere to the surface of the earth. There are different forms of precipitations these include; dew and fog, it occurs when moisture in air just above the ground changes from vapor to liquid. Rain, snow, and hail occur as the result of the cooling of a mass of warm, moist air, cooling occurs when air rises. As it rises, the air expands, because atmospheric pressure is less at higher attitudes. Expansion in turn, causes the rising air to become cooler.

• Measuring Precipitation: Rain is measured in inches or millimeters in a rain gauge. Snow can be measured in two ways as snow, with an ordinary ruler; or as water, by being melted in a rain gauge. It normally takes about 10 inches of snow to produce 1 inch of water, but this figure can vary greatly. Sleet and hail must be melted first to be measured. Dew and fog ordinarily do not add enough water to the earth to be measured.

• Clouds: A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of the earth.

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Temperature versus Heat• Temperature is a measure of the average kinetic energy of the molecules in the substance. Heat is the

measure of the total energy of the molecules in a substance. There are three main temperature scales: • Fahrenheit - developed in the early 1700's by G. Daniel Fahrenheit• 0°F chosen as lowest temperature that a mixture of ice, water, and salt can reach.• 100°F chosen as close to the internal body temperature of a person (cow).

• Celsius - developed in the 18th Century (SI standard - used by most of world)– 0°C chosen as the melting point of ice.– 100°C chosen as boiling point of water (at sea-level pressure)

• Kelvin (Absolute) - Developed in the 18th Century – 0 K chosen as point where all molecular motion ceases (nothing can attain a temperature below this point).

This is referred to as absolute zero.– Very useful for many scientific calculations, since it begins at absolute zero, it has no negative numbers.

Note...the word "degrees" is NOT used with Kelvin.

• Conversion Between Scales– F = [(9/5)C] + 32– C = (5/9)(F - 32)– K = C + 273

• If you were able to measure the speed of the molecules in the air while you were traveling up through the troposphere, would the speed of the molecules increase, decrease, or stay the same as your altitude increased?

• The average speed of the molecules would decrease. Remember, temperature measures the average energy of molecules, which is directly related to their speed. Since temperature decreases with increasing altitude in the troposphere, the average energy of the molecules in the troposphere decreases, which means their speeds decrease as well.

•

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“What Will the Weather Be?” By Lynda DeWitt and Illustrated by Carolyn Croll

Weather Observation are taken in many ways….

Methods of measuring elements of the atmosphere

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Surface Weather Station

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Geostationary Satellites - 23,000 miles up

Polar Orbiting Satellites - 500 miles upPolar Orbiting Satellites - 500 miles up

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GeostationaryGeostationaryGOES (IR)GOES (IR)

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Polar Orbitor (Vis)Polar Orbitor (Vis)

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Weather RadarWeather Radar tells you tells you where the rain is, how hard where the rain is, how hard its falling, where it’s moving its falling, where it’s moving

to and how fast.to and how fast.

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Conventional RadarConventional Radar

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8 Controls of Temperature8 Controls of Temperature.•  Latitude is the Primary Control of Temperature

– This is because the amount of solar radiation received at any given point on the earth is a function of latitude. • Land – Water Distribution

– Areas with more land than water can change in temperature more quickly. Therefore, N. Hemisphere is more variable in temperature than S. Hemisphere, which has a higher percentage of water.

• Differential Heating of Land and Water– Difference in mobility – (water can move via ocean currents - land can’t move – at least quickly)– Difference in opaqueness– Difference in specific heat– Difference in evaporation rates

• Ocean Currents– East coast of continents has warm currents (Ex. Gulf Stream) – West coast of continents has cold currents (Ex. California Current)

• Altitude– Temperatures tend to be cooler and have a wider daily temperature range, the high you go.– Some of the change is due to the "Environmental lapse rate", but it can't explain all of the difference between a valley

temperature and a mountain temperature.– Daily temperature range generally increases with altitude (because atmosphere is less dense, and solar radiation is

more intense at higher altitudes).The amount of wind (mixing) is also controlled by altitude.

• Geographic Position– Windward vs. leeward coast – Mountains act as "rain shadow"

• Cloud Cover and Albedo– The effect of cloud cover on radiation received by the earth is the largest uncertainty in the "global warming" problem. – Clouds are good reflectors but poor absorbers.– During day, clouds lead to cooler temperatures.– At night, cloud cover results in warmer temperatures than if the sky were clear.– Snow absorbs less radiation than bare ground, and results in cooler temperatures. Dirty snow absorbs more

radiation than fresh snow.• Local Effects -

– Nature local effects such as a Land - sea breeze and human created local effects such as the urban Heat Island can significantly affect local temperatures.

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SeasonsBasic Earth /Sun Relationships

• The Earth's orbit around the Sun is not circular, but oval or elliptical – The elliptical orbit causes the Earth's distance from the Sun to

vary over a year. – This phenomenon is not responsible for the Earth’s seasons! – This variation in the distance from the Sun causes the amount of

solar radiation received by the Earth to annually vary by about 6%.

• On January 3, perihelion, the Earth is closest to the Sun 91,500,000 miles (147.3 million km).

• On July 4, aphelion, the Earth is farthest from the Sun 94,500,000 miles (152.1 million km).

• The average distance of the Earth from the Sun over a one-year period is about 93,000,000 miles (149.6 million km).

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Classification of Seasons• There are two ways to classify season, astronomical and meteorological. • Astronomical Seasons: divide year into 4 equal periods. Equinoxes occur when the

declination is zero (the sun directly over the Equator). Marks 12 hours of daylight everywhere on earth. March 20 or 21 - Vernal Equinox start of N. Hemisphere spring, (start of S. Hemisphere fall). September 22 or 23 - Autumnal Equinox, starts fall for N. Hemisphere, start of S. Hemisphere spring. Solstices occur when the sun is at its maximum declination (either North or South) of 23.5º. Marks longest or shortest "day" (daylight) of the year. June 21 or 22 - date of summer solstice for N. Hemisphere, winter solstice for S. Hemisphere. December 21 0r 22- date of winter solstice N. Hemisphere, summer for S. Hemisphere.

– Just remember spring starts ~March 21, then every 3 months there is a new season: June 21, Sep 21 and Dec 21. This is a good close approximation. Then think about which hemisphere is being discussed.

• Climatological Seasons are based upon "mean" or average weather conditions. Climatological seasons are defined by average weather conditions for a given region. So climatological seasons vary in length from location to location. For example, climatological winter ranges from about l 1/2 months in Miami, Florida to more than 4 months in Portland, Maine. Climatological summer extends more than 5 mo. in Florida, it only lasts 3 mo. in Maine. In mid-Atlantic region, there are 2 longer seasons (summer and winter; about 4 mo. each) and 2 shorter seasons (spring and fall; about 2 mo. each).