| GEO 125
Physical Geography
Global
Models: Atmospheric Pressure and Precipitation
Atmospheric pressure defined
Standard atmospheric pressure at mean-sea-level
- 29.93 inches of mercury
- 1013.25 millibars
Adjustment for atmospheric pressure with
altitude
Types of barometers
High versus low pressure
High pressure
- cool air
- descending air
- dry air
- stable air
- converging aloft
- diverging at the surface
- fair weather
- anticyclonic wind circulation
Low pressure
- warm air
- rising air
- moist air
- unstable air
- diverging aloft
- converging at the surface
- foul weather
- cyclonic wind circulation
Types of global pressure systems
- Thermal high pressure
- Thermal low pressure
- Dynamic high pressure
- Dynamic low pressure
Upper atmospheric circulation cells
- Hadley cell
- Ferrell cell
- Polar cell
Global pressure bands
- Equatorial low (thermal low pressure)
- Subtropical high pressure at 30 degrees north and south
longitudes (dynamic high pressure)
- Subpolar low pressure at 60 degrees north and south latitudes
(dynamic low pressure)
- Polar highs at north and south poles (thermal high pressure)
Global precipitation patterns
- Equatorial low - humid conditions
- Subtropical highs - arid conditions
- Subpolar lows - humid conditions
- Polar highs - arid conditions
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