IMS 9 - Atmospheric Circulation

Atmospheric Circulation

Atmospheric Structure

·         90km above earth surface

·         78.08% N₂; 20.95% O₂

·         Trace elements 0.93% Ar; 0.036% CO₂

Troposphere

·         Lowest major layer

·         Frm earth surface till stratosphere base

·         Temp reduce with height

·         Earth weather occurrences

Stratosphere

·         10 – 47km altitudes

·         Temp slowly rise; sunlight absorption by ozone

·         Cloud free, weather stops at tropopause

Air Movement

·         High press to low press

·         Non-spinning Earth

Atmospheric Circulation

·         Heated air @ equator expand & less dense; rise to high colder latitudes, vapour rise & cool till rain

·         Low press region form below

Coriolis Effect

·         By French Engineer Gaspard Gustave de Coriolis

·         Caused by Earth rotation & decreasing velocity as latitude rise

·         Influence all moving objects, esp large distance

·         Change only the direction; x speed

·         Deflection right in N Hemisphere; left in S Hemisphere

·         0 effect @ Equator; High effect/deflection @ high latitude; maximum lvl @ poles

Boundaries

Doldrums

·         Boundary between trade winds; lack wind

·         ITCZ (Intertropical Convergence Zone)

Horse Latitude

·         High press; clear, dry, fair condition

Polar Front

·         High precipitation; cloudy condition

 

Northern Indian Ocean

·         Have seasonal pattern (monsoon)

Winter

·         Asian air cool rapidly, high press

·         Air blown mainland to ocean

·         Northeast monsoon (Nov – March)

Summer

·         Asian air warms faster > ocean; low press

·         Air blown ocean to continent

·         Southwest monsoon (May – Oct)

Malaysia Monsoon

·         Heating land & sea

·         Summer – Land heats rapidly (SW Monsoon)

·         Winter – Land cools rapidly (NE Monsoon)

span>High temp, sal & press; high sound speed

·         High speed till 200m; minimum speed till 1000m

Sound Fixing & Ranging (SOFAR)

·         Sound channeling through thermocline due to temp & press difference

·         Sound wave refract towards minimum sound speed

·         Up-down bending low-freq sound waves allow distant travel w/o energy lost

·         SOFAR / Velocity Minima channel between 600-1200m below surface (except high latitude)

·         Hydrophone @ right depth – record distant whale calls, earthquakes, man-made noise

Shadow Zone

·         Thin, high-sound velocity layer

·         Depth 80m deflects sound