Meteorology - Earth Science

Meteorology - Earth Science

1. Pressure

   • Barometric Pressure
     • mb, in. of mercury
     • barometer
     • weight of the overlaying atmosphere pushing down on a unit of area
     • isobars
       • form circular patterns showing large masses of air
   • Factors that Affect Pressure
     • > Temp = farther apart molecules = < pressure
     • >altitude = air < dense, = < pressure
     • MOISTURE: Humidity > = > H20, lighter than O2/N2, = < pressure
       • water vapor enters atmosphere via evaporation, sublimation, and transpiration
         • Factors that Affect Rate of Evaporation
           • Temp >, R.O.E. >
           • Humidity >, R.O.E. <
           • Wind >, R.O.E. >
           • Sur. Area >, R.O.E >
       • Saturation
         • rate of evaporation = rate of condensation
         • when air holds as much water vapor as possible at given temp
         • Dew Point
           • Temp the air must be cooled to to reach saturation
           • Affected by amount of WV in air, NOT R.H.
           • sling psychrometer
           • When air temp + dew point are =, air is saturated, and condensation occurs
           • decreases w/altitude
           • As water vapor increases, dew point temp increases
       • Humidity
         • As temp >, the amount of water vapor that can be hold >.
         • Absolute Humidity: Amount (mass) of water vapor in air
         • Relative Humdity (RH): Amount of W.V. in air compared to how much can be held.
         • Sling Psychrometer
           • dry bulb = air temp
           • Wet bulb depends on R.O.E., thus depends on dryness of air
   • Pressure systems
     • High pressure
       • anticyclone
       • winds blow clockwise and away from center
       • sinking air
       • cool, dry weather
     • Low Pressure
       • cyclone
       • winds blow counterclockwise and towards center
       • rising air
     • As pressure gradient >, wind speed >

2. Clouds

   • In order to form:
     • moisture in air
     • cooling temperature (due to rising air)
     • condensation nuclei (aerosols, dust particles)
   • Formation:
     • I. warm air rises
     • II. Rising air expands
     • III. Expanding air cools to the dew point temp
     • IV. At dew point temp, condensation occurs and clouds form
     • Adiabatic Cooling
       • Cooling of air due to expansion, rising air expands and cools
       • Forms clouds in low pressure
     • Adiabatic Warming
       • Warming of air due to compression, sinking of air compresses and warms
       • No clouds form in high pressure systems

3. Air Masses

   • Large body of air in troposphere with similar characteristics of temp, moisture, and press
     • Tropical: form @ tropics, high temps
     • Polar: form @ high latitudes, low temps
     • Arctic = VERY cold
     • Continental: form @ land, dry
     • Maritime: form @ water, wet
   • Source Region = where air mass forms
     • take on characteristics of surfaces over which they form

4. Fronts

   • Cold
     • cold air mass moves into region of warm air
       • Cold air = dense, stays near surface
         • forces less dense warm air to rise above it
           • Thus, clouds form at leading edge
       • Precip occurs along frontal boundary at surface
         • narrow band of heavy rain/thunderstorms
   • Warm
     • warm air mass moves into region of cold air
       • warm, less dense air is forced to rise over the top
       • Precip occurs before frontal boundary at surface
       • Wide band of steady, all day shower
   • Stationary
     • 2 different air masses not moving relative to one another
       • steady, heavy rain
       • precip occurs in a wide band along the front at the surface
   • Occluded
     • cold air mass moves into and takes over a region of warm air
       • steady, all day rains followed by heavy rain/thunderstorms
       • precip occurs in a wide band before and along the front
   • Always associated with low pressure systems
     • counterclockwise circulation of air in L press draw warm, moist air up from lower latitude and colder, dry air down from high latitudes

5. Rain

   • occurs when air rises, expands, cools adiabatically to dew point temp, condenses to form clouds, ff droplets get heavy enough to fall
   • Areas of Rain
     • Windward Wide of Mountain/Orographic Effect
       • Windward side is cool, wet
       • air rises as it is forced over mountain
       • Leeward side is cool and dry
         • Rain shadow - very dry region on leeward side of mountain due to sinking air
     • Equatorial Regions
       • Warm air rises due to convection
       • Recieve most direct insolation, so air is heated and rises
     • Low Pressure Systems
       • Surface air converges and rises at center of L. press systems
     • Fronts
       • Warm, less dense air rises over colder, more dense air
     • Areas with little rain
       • where air is sinking, compresses, warms (adiabatically)

6. Storms

   • Thunderstorms
     • Form from uplifting warm air associated with cold front
     • located in inland regions
     • produce heavy rains, hail, winds, thunder/lighting
   • Tornadoes
     • rapidly rotating low press. funnel associated with strong thunderstorms and cold fronts in spring
     • Very narrow: 100 ft - 1 mile in dm
     • Last for few minutes to an hour
   • Hurricanes
     • Form as low pressure centers over warm tropical waters in late summer/early fall
     • gain energy from condensation of moisture evaporated over warm ocean water
     • Warm rising air produces a very strong low pressure system
     • Lose strength as they move over land
     • Flooding along coast - storm surge-causes most damage
     • Minimum winds = 74 mph
   • Lake Effect Snow
     • prevailing winds move across the rel. warm Great Lakes, pick up moisture, which is uplifted over Tug Hill, where it snows dues to orographic effect
   • Storm Tracks
     • Prevailing Westerlies - winds over US
       • blow W -> East
     • Tropical storms that affect US develop West of Africa
       • trade winds carry them to US South east