Meteorology Unit 6

Energy Exchange in the Atmosphere ________- the state of the atmosphere at a given time and place. ____________- the study of the entire atmosphere including its weather. Atmospheric variables- temperature, wind, humidity, pressure, and atmospheric transparency Weather Meteorology

A. Energy Transfer in the Atmosphere _____________-the transfer of energy by movements of liquids and gases (fluids) -movements are caused by differences in densities in the fluids. -heat is carried by ____________________ (______________) Convection convection currents convection cell Water becomes colder, more dense, and sinks Water becomes warmer, less dense, and rises

2. _______________- transferring heat by touching an object i. e 2. _______________- transferring heat by touching an object i.e. pan on stove, air on radiator, air on earth’s surface 3. ________- the transfer of electromagnetic energy through space. -heat emanating from a body as wavelengths of energy conduction radiation

B. Heat Balance Energy enters and leaves Earth by radiation. ___________-incoming solar radiation Energy that Reaches the Atmosphere 30% reflected back into space 70% absorbed - 19% absorbed by water vapor, clouds, ozone, and dust - 51% absorbed by earth’s surface - 21% of energy is radiated back by surface -30% of energy is transferred to atmosphere by conduction and convection insolation

The Greenhouse Effect Short wavelengths of energy from the sun pass through the gases of the atmosphere but the longer wavelength radiation given off by the surface is reflected back to the surface The is increasing the greenhouse gases burning of fossil fuels

Greenhouse Gases Carbon Dioxide Methane Water Vapor

Electromagnetic Spectrum p. 14 in the Reference Tables

Greenhouse Effect long wave, infrared radiation is released from surface

C. Factors Affecting Atmospheric Variables Temperature-measure of the energy of molecules a. Latitude- higher latitude -lower temperatures b. Altitude- higher altitude -lower temperatures c. Closeness to large bodies of water - less fluctuation in temperature of nearby land areas *Due to specific heat capacity- water has a high specific heat, meaning it heats up and cools down more slowly than land.

a. temperature –the higher it is, the more moisture the air can hold 2. moisture- liquid (water droplets), solid ice and snow), gas (water vapor) a. temperature –the higher it is, the more moisture the air can hold b. capacity – the amount of water vapor the air can hold c. saturated – the air contains all the water vapor it can at that temperature d. dewpoint temperature –temperature at which condensation occurs e. absolute humidity – the amount of water vapor actually present in the air f. relative humidity – a comparison between the amount of moisture in the air and the amount the air can hold. -if the air is “half full” of water, the relative humidity is 50%

When is Relative Humidity 100%? When is Relative Humidity highest? When is Relative Humidity lowest? Notice when the high and low temperatures are for the day. Why?

Sling Psychrometer -________________- instrument used to find dewpoint. -two thermometers (one “wet”, one “dry”); as water evaporates from the wet thermometer, the temperature drops. The drier the air, the more it evaporates, and the more it drops. Psychrometer

3. Pressure Air Pressure- the force, or weight, of the air pushing down on a unit surface area -also called ______________________or ____________________. ___________- the greater it is, the higher the pressure. ______________- the greater it is, the less the density and pressure. atmospheric pressure barometric pressure density temperature

________________- instrument used to measure atmospheric pressure Aneroid Barometer Barometer ________________- instrument used to measure atmospheric pressure ________- lines on weather maps joining places with equal air pressure Isobars Mercury Barometer

As air temperature increases, air pressure decreases. Inverse Relationship

c. moisture- the more moisture in the air, the the atmospheric pressure. d. altitude- as altitude increases, the density and pressure of the air lower decrease

D. Air Movement winds _______- large horizontal movements of air near the Earth’s surface _________- local horizontal movements of air _________- vertical air movements Pressure gradient- the rate of change in pressure between two locations. Steep pressure gradient- isobars are and winds are Gentle pressure gradient- isobars are and winds are breezes currents close together strong far apart light

Land and Sea Breezes -occur because land and faster than water -sea breeze- onshore breeze -land breeze- offshore breeze heats up cools off Land and Sea Breeze Animation NOAA Website for Diagrams Air always moves from high to low pressure

Convection Cells -occur because gravity pulls cool, dense air toward the Earth’s surface, forcing warmer, less dense air to rise. -zones of - high pressure regions where air descends and spreads out (dry). -zones of - low pressure regions where air comes together and rises (wet) L H divergence convergence

Planetary Winds -If the earth did not rotate, air would at the equator and at the poles, creating a large convection cell. -Since the earth does rotate, winds are modified by the Coriolis Effect. They are deflected to the in the Northern Hemisphere and to the in the Southern Hemisphere (causes wind belts and jet streams). rise sink right left

Major Wind Belts North and South Poles- Polar Highs 60°N to 90°N, 60°S to 90°S- Polar Easterlies 30°N to 60°N, 30°S to 60°S- Prevailing Westerlies 30°S and 30°N- Horse Latitudes 0° to 30°N- Northeast Trades 0° to 30°S - Southeast Trades Equator- Doldrums and Intertropical Convergence Zone (ITCZ)

Prevailing Westerlies Subpolar High Polar Easterlies Northeast Trades Horse Latitudes Doldrums Southeast Trades Polar Easterlies Prevailing Westerlies Subpolar High

Jet Streams Bands of swiftly moving winds Move in an west to east direction Found near the top of the troposphere Thousands of kilometers long Hundreds of kilometers wide One kilometer from top to bottom Our weather is affected by a polar jet stream, which is stronger than the tropical jet stream

Reference Tables p. 14

E. Clouds and Precipitation Condensation- process by which gaseous water vapor changes to -must condense onto a -occurs when the air is Condensation nuclei- particles in the air such as that water condenses on Deposition- when water vapor changes directly into a solid (ice or snow). -temperature must be below ______- condensation of water onto the ground ______-deposition of water onto the ground liquid surface saturated dust or salt zero °C dew frost

Clouds- collections of tiny water droplets or ice crystals suspended in the atmopshere -Air rises vertically, expands, and cools. If it cools to the dewpoint temperature, clouds form. ________________-occurs when mountains act as barriers to the flow of air, forcing it to rise to get to the other side ____________- occurs when warm, lighter air rises over cool air orographic lifting frontal wedging

Cloud Types _______________- low rain clouds _______________-thunderclouds ___________- fair weather (heap) clouds ___________- fair weather (high, wispy) clouds ____- cloud resting on the Earth’s surface nimbostratus cumulonimbus cumulus cirrus fog

Precipitation- the falling of liquid or solid water from clouds _______- large falling drops of water _______- fine falling drops of water _______- rain that freezes as it forms _______- falling ice crystals _______- when water droplets freeze and start to fall they collect water and are forced upward, freeze again, fall, collect water, and are forced upward, etc. Seeding- placing into the atmosphere where there is some available water vapor rain drizzle sleet snow hail condensation nuclei

F. Weather Maps Station Models

Isobars- isolines connecting points of equal Isotherms- isolines connecting points of equal Pressure gradient- high (steep) where isobars are ; this produces strong winds _______- the boundary between two different air masses -moving in the direction of the triangles or half-circles pressure temperature close together front

Weather Map of the United States Cold, Dry Air L H Warm, Moist Air

Air Masses Air mass- huge body of air in the troposphere having similar -characteristics depend upon their geographic region of origin (source region). __________(m)- air masses that develop over water (moist) __________(c)- air masses that develop over land (dry) _________(P)- air masses that develop over higher latitudes (cool) _________(T)- air masses that develop over lower latitudes (warm) characteristics maritime continental polar tropical

Air flows from west to east across the United States. Jet Stream- narrow, fast moving current of air that flows just below the tropopause Air flows from west to east across the United States.

cyclone (low)- low-pressure air-mass with the winds moving counter clockwise toward its center -often produce rain ____________(high)- high pressure air-mass with winds moving in a clockwise direction away from its center -cool, clear weather anticyclone

Fronts -the boundary (interface) between two air masses -usually (meaning they have big differences between temperature and moisture) -often produce -the half-circles and triangles point in the direction the air-masses and front are moving. unstable clouds, strong winds, precipitation, temperature and pressure changes

__________- occur when warm air meets and rises over cold air on the ground -long gentle slopes (1000km) -cause extended periods of precipitation warm fronts mT cP

2. __________- occur when cold air meets and pushes out warmer air -short, steep slopes -move faster than warm fronts -cumulonimbus clouds- violent thunderstorms -precipitation falls for a very short period of time -abrupt weather change, winds shift from southerly to northerly cold fronts

Cold Front Cumulonimbus mT cPcP

3. ________________- occur when a faster moving cold front overtakes a slower moving warm front and lifts the warmer air between the two fronts off the ground Occluded fronts

stationary front 4. ______________- occurs when a warm air-mass and a cold air-mass are side-by-side, with neither air mass moving. -gentle slope, weather similar to that of a warm front

Mid-latitude Cyclones -Begins when cold air pushes down from the north, changing a stationary front into a pair of warm and cold fronts moving around a low pressure center. -As the low moves eastward, the cold front the slower-moving warm front, producing an overtakes occluded front

Cyclone Animation

AC takes 12-24 hours D- 3-4 days

Warm front would approach and bring 2. Then you would have Cyclones are “driven” by the heat energy released by condensation (latent heat), causing the low pressure to become even lower, thereby strengthening the winds. In summer, cyclones move about 800 km a day, while in winter they move about 1,100 km a day. A mid-latitude cyclone may cover as much as one-half of the entire continental United States at one time. Warm front would approach and bring 2. Then you would have 3. The cold front would arrive with long, steady rainfall warm temperatures, high humidity thunderstorms

2 3 1 1 2 3 City 3 -Temperature increasing -Pressure decreasing City 1 -Long-lasting, light precipitation City 1 -Temperature decreasing -Pressure increasing -Short, heavy precipitation -Thunderstorms 2 3 1 1 2 3 City 2 -Warm temperature -Pressure steady -Humid, but no precipitation

Predictions Decreasing air pressure- Increasing air pressure- Precipitation, higher humidity, winds, building cloud cover Clear skies, dry air, lower humidity, calm