Atmospheric Circulation & Water
Dan Walsh
Air Pressure
Collision of Air Molecules
15psi at sea level
Measuring Air Pressure
Barometer
Inches
Millibars
Mapping With Isolines
Wind
From Pressure Gradient
PGF (Pressure Gradient Force)
High PGF = High Wind
Low PGF = Low Wind
High & Low Pressure Systems
Air moves from High to Low
Coriolis Force
Deflection
R in NH
L in SH
Surface Winds
Spiral into Low
Spiral out of High
Wind Pattern Development
Global Patterns
Subtropical Highs
Trade Winds
Intertropical Convergence Zone (ITCZ)
The Westerlies
Polar Highs
Polar Easterlies
Subpolar Lows
Hadley Cell Circulation
Air Rises at Equator (ITCZ)
Descends at 20°-30° Latitude (STH)
Jet Streams
Rossby Waves
Global Atmospheric Circulation Model
Seasonal Variations in Latitude
All Shift N & S
Seasonal Pressure and Precipitation Patterns
Local Winds
Land-Sea Breezes
Mountain Valley Breezes
Katabatic Winds
Santa Ana Winds
Monsoonal Winds
Land-Sea Breezes
Variations in Heating/Rising Air
Mountain/Valley Breezes
Warm Air Rises in Day
Cool Air Sinks at Night
Mountain/Valley Breezes II
Warm Air Rises in Day
Cool Air Sinks at Night
Katabatic Winds
Descending Cool Air
Santa Ana Winds
High Pressure Over Great Basin
Descends
Warms
Dries
Concentrates in Passes
Monsoonal Winds
Shift N/S of ITCZ
Water
States of Water
Solid
Gas
Liquid
Water Phase Changes
Evaporation
Absorbs Energy
Latent Heat
Rate of Evaporation
Temperature & Humidity
Humidity
Absolute Humidity
Relative Humidity
Effects of Air Temp on Relative Humidity
Saturation/Condensation
100% Humidity – Dew Point
Condensation (releases Latent Heat)
Occurs with either adding H2O or Cooling Air
Cloud Formation
Water Droplets
Relative Humidity & Temperature
Lifting Air as Cooling Mechanism
Cools or Warms at Consistent Rate
Dry or Moist Adiabatic Rate
Cools/Warms at Dry Rate Below 100% Humidity
5.5°F/1000 feet
Cools at Moist (Saturated) Rate At 100%
3.3°F/1000 feet (varies)
Affected by Release of Latent Heat
Always Warms at Dry Rate (Descending Air)
Rising Air
LCL - Lifting Condensation Level
Orographic Lifting
Demonstrates Dry Adibatic & Moist Adibatic Rates at work
Windward, Leeward & Rain Shadow
Cloud Types
Classified by Height & Shape
Cirrus
Cirrostratus
Altocumulus
Altostratus
Stratus
Nimbostratus
Cumulus
Cumulonimbus
Fog (3 Types Shown)
Valley Fog
Type of Radiation Fog
Collects in Valleys
Tule Fog
Precipitation
Collision & Coalescence of Water Droplets in Cloud
…Back to ‘Lifting Air as Cooling Mechanism’
How does Air lift?
Convective Lifting
Orographic Lifting
Convergent Lifting
Frontal Lifting
Convective Lifting
Orographic Lifting
Convergent Lifting
Frontal Lifting