Atmospheric Mechanics 3.2 Flashcards
Explain Pressure Gradient.
Rate of Pressure Change in a Direction perpendicular to the Isobars(horizontal Distance).
Explain Gradient Winds
Found above 2000 ft AGL.
Result of PGF and Coriolis Force.
Flow Perpendicular to the Pressure Gradient Force(PGF) and Flows parallel to the Isobars.
Explain Buys Ballot’s Law for Isobars in Northern Hemisphere.
If the Wind is at your back, the area of lower pressure will be to your Left.
Low will be slightly forward or directly left because the winds flow across the Isobars.
Explain Surface Wind Direction in Respect to Gradient Winds in a pressure system in the Northern Hemisphere
Found below 2000ft AGL.
Move Clockwise around Highs and Counter around Lows
Blow across Isobars at 45 angle and moves air out of High Pressure and into Low Pressure.
Describe the Jet Stream.
Narrow band of Strong Winds min 50kts Vert. Or Horizontally.
- Winds Average 100-150kts but reach 250kts.
- 1000-3000Mi - Length & 100-400Mi - Width & 3k-7kFT in Depth
- *Found at 30,000 Ft MSL flows West to East.
Describe Sea Breezes.
Onshore Wind, blowing from the Sea - 15-20Kts
During the Day, Press. Over Warm Land becomes Lower than Colder Water. Cool Air(higher Pressure) over the water moves toward the Lower pressure, replacing the warm air over the land that moved upward.
Describe Land Breezes.
At Night, Air Movement from Land to Sea.
Sea Breeze is stronger than Land Breeze.
Press. Over Warm Water becomes Lower than Colder Land. Cool Air(higher Pressure) over the Land moves toward the Lower pressure, replacing the warm air over the Water that moved upward.
Describe Mountain Winds.
At night, air contact with the mountain slope is called by outgoing terrestrial radiation and becomes more dense, high dense air flows downhill, fro the top of the Mtn.
Describe Valley Winds.
Daytime, Mountain slopes are heated by the Sun’s radiation, and in turn, heat the adjacent air through Conduction. As air rises further away from slope cools and settles downward towards the valley floor, the Downward motion force the warmer air near the ground up the mountain and since it is flowing from the valley.
Define Saturation.
Air contains the Maximum amount of water vapor for a given Temperature.
Define Dew Point Temperature.
The temperature at which Saturation Occurs.
Define Dew Point Depression.
Difference between the Air Temperature and the Dew Point Temperature. Or “Dew Point Spread”
*Dew point will always be the lower value.
Define Relative Humidity.
Amount of Water Vapor in the Air.
Describe the Relationship between Air Temperature and Dew Point Temperature with respect to Saturation.
The higher the Temperature the more Water Vapor the air can hold.
*higher Dew Point = Greater chances of clouds , fog, Precipitation.
Describe 3 Characteristics of Precipitation.
- *Showers: Sudden Beg-End, Abrupt change in Intensity’s Cumuliform Clouds.
- *Continuous: Steady, Intensities Gradual change, Stratiform Clouds (STrat=STeady)
- *Intermittent: Stop and restarts at least once an hour. Intermittent precipitation may be showery or steady and be either Clouds.
Describe the types of Precipitation.
- *Drizzle: Small Droplets, Float in ATM.
- *Rain: Larger Droplets, Fall to the Ground
- *Frozen.
Describe the 4 Principal Cloud Groups.
- *Low Clouds- SFC-6500 AGL, STratus=STeady precipitation. (Sheet like) Cumulous = Puffy= Showery.
- *Middle Clouds- 6500-20000AGL, ALTO=Light, AltoSTratus
- *High Clouds- >20000AGL; Ice Crystals=Cirro= Zero precipitation
- *Special-Vertical Development-CB Cumulonimbus=Thunderstorm “up build. //. NimboSTratus = STeady Precipitation “down build”
Describe the Weather Conditions Associated with Various Clouds.
STratus = STeady Precipitation
Cumulus = Showery Precipitation
Alto = Light
Cumulonimbus “CB” = Thunderstorm(up Build)
NimboSTratus = STeady Precipitation (Down Build)
Describe the types of Atmospheric Stability.
- *Stable - colder than the surrounding air after being lifted
- *Neutrally Stable - Same Temp. Of the surrounding air after being lifted; remains at the same place until acted upon
- *Unstable - warmer than the surrounding air after being lifted; continues to rise after lifting force is removed due only to parcel’s warmer Temp.
Describe the 4 methods of Lifting.
**FOCT** Frontal - Cold Front only Orographic - Mtn Side Convergence - 2 Air masses pushing on each other Thermal - Radiated
Describe the Flight conditions Associated with Stable Atmosphere.
FATVIPWC
F Fronts - Warm. V Visibility - Poor. W Winds - Steady
A Airmass - Warm. I Icing - Rime. C Clouds - STratus
T Turbulence - Smooth. P Precipitation - Steady
Describe the Flight Conditions associated with an Unstable Atmosphere.
FATVIPWC
F Fronts - Cold. V Visibility - Good. W Winds - Gusty
A Airmass - Cold. I Icing - Clear. C Clouds - Cumulus
T Turbulence - Rough. P Precipitation - Showery
