Lab 4

Lab 4

Orographic Lifting, Apparent Temperature, Satellite Imagery, Radar Imagery, Surface Patterns of Pressure and Wind, Constant Pressure Surfaces

On labs and stuff…

Please read/answer the whole problem. Use units. Come to my office hours/ask me anything Review for midterm: 10/1 7:30-8:30

Orographic Lifting● Orographic - of or related to mountains; associated or induced by

the presence of mountains● Orographic Lifting - lifting of air by terrain● Clouds form when air rises● Clouds disperse when air sinks

Orographic Lifting

erh.noaa.gov

Apparent Temperature● What the temperature “feels like” to the average person if the

effect of moisture content of the air is taken into account● AKA “Heat Index,” AccuWeather’s “RealFeel”● Apparent Temperature = Air Temperature + (Vapor Pressure -16)● Find the Apparent Temperature:

○ T = 80°F, Td = 70°F○ Equilibrium Vapor Pressure at 70°F is 25mb○ Ta = 80 + (25-16) = 89°F

Satellite Imagery - Visible● Uses visible radiation from the sun back-scattered off objects on

the earth● Meteorologists are able to distinguish between different cloud

types because of differences in albedo● Thick clouds (i.e. Cumulonimbus) have higher albedo than thin,

wispy clouds (Cirrus)● Since it uses radiation from the sun, it’s only useful with daylight

Satellite Imagery - Visible

Satellite Imagery - Infrared● Uses infrared radiation emitted by the earth and objects near the

surface (i.e. clouds)● Distinguish between high and low clouds based on temperature

and the amount of radiation the cloud emits● Useful day and night since objects always emit radiation

Satellite Imagery - Infrared

Satellite Imagery - Water Vapor● Water vapor is the dominant emitter of infrared radiation around

6.7 microns● Satellites are calibrated to measure this radiation so we can get a

sense of water vapor in the atmosphere● BUT...a radiometer attuned to radiation at wavelengths near 6.7

microns can only detect water vapor residing in the upper or middle regions of the troposphere

Satellite Imagery - Water Vapor

Radar Imagery● RAdio Detection And Ranging● Ground-based remote-sensing instruments● First successfully used in World War II● Radar works by transmitting pulses of radio waves from an

antenna. The pulse is reflected off a “target,” such as a rain shower, and returns to the radar’s receiver giving us the size and distance of the target

Radar Imagery

Radar Imagery - Complication Height of radar beam increases with distance from radar Sometimes overshoots shallow clouds/precipitation

Surface Patterns of Pressure and Wind● 3 Forces that Control the Wind

○ Pressure Gradient Force (PGF)○ Coriolis Force○ Friction

Pressure Gradient Force (PGF)● The wind is caused by differences in air pressure● Pressure Gradient Force - force that sets the air in motion in a

determined effort to erase the pressure gradient

“THE WIND WILL BLOWFROM HIGH TO LOW”

-Mr. Anderson

Coriolis Force/Coriolis Effect● The force that deflects objects moving along the surface of the

earth to the right in the northern hemisphere and to the left in the southern hemisphere

● Caused by the rotation of the earth● CCW rotation around lows● CW rotation around highs

Friction● The Earth’s surface is not smooth (mountains, hills, trees,

buildings, etc.)● Acts to slow wind speeds and reduce the effect of coriolis

Lake Erie Wx

Correcting to Sea Level Pressure● Air pressure decreases with increasing altitude● What city has a higher surface pressure: Miami, FL or Denver,

CO?● We correct to sea-level pressure because it removes the effect of

elevation

Constant Pressure Surfaces (Heights)● Surfaces (height) at which pressure is constant● The same pressure does not occur at the same height

everywhere, so these surfaces are not flat

Heights and Temperature

Lab 4● 4.14(a,b)● 4.15(c)● 5.4(a,b,c)● 5.10(a,b)● 5.18● 6.2(a,b)● 6.7(a,b)● 6.9(a,c,d)● 7.9(a,b)