CLIMATE REGIONS Flashcards
What is the driving force for global circulation?
Uneven thermal distribution due to the difference in heating at the equator vs. the poles.
What local variations affect the general global circulation?
sea currents, land masses, water vapour
Draw the general global circulation
Met book pg 256.
Draw a cross section of the global circulation (Tarbuck & Lutgens model)
Pg 258, to include;
Equator
Tropical/Hadley cell
Sub trop high
Sub trop jetstream
Mid-lat cell
Polar-frontal jet
Polar front
Polar cell
Pole
Latitudes, High & Low pressures identified
What is the walker cell?
A semi-permanent high pressure system in the eastern pacific off the coast of Peru. Formed & maintained by the Humbolt current that flows from the southern oceans.
How does a STRONG Peruvian current affect the Walker Cell?
“La Nina”
Colder and stronger than usual Peruvian current drops SFC temps & therefore increases pressure. H system increases in size
How does a WEAK Peruvian current affect the Walker Cell?
“El Nino”
Peruvian current fails at the surface & is replaced by warmer sea temps. SFC pressure therefore lower & the H “shrinks” as a result.
How is the ITCZ formed?
Formed by the clash of SE trade winds from the SH, with NE trade winds on the northern side of the equator.
“collision” results ascent over a vast area and therefore TSRAGS/heavy rain.
How is the SPCZ formed?
Forms when mid latitude westerlies clash with northerly outflow from the walker cell.
Results in frequent thundery SH.
SPCZ is the birthplace of TC in the south pacific and iss largely controlled by the size of the Walker Cell
How does El nino affect the SPCZ
SPCZ migrates further east, results in a stronger SW flow over NZ and therefore cooler temps & higher rainfall in the south Is. Other regions will be drier.
El Nino shifts TCs east towards the Cook Is & Tahiti
How does La Nina affect the SPCZ
Larger Walker cell pushes SPCZ towards NZ.
Warmer temps & increase in rainfall in the north island can be expected.
During La Nina summers, North NZ experiences more cyclones than usual.
What affects the location of the equatorial trough
Located on AVERAGE at the equator.
Drifts with the zone of maximum heating
How does the general circulation change during NZ summer?
Major convergence zones & sub tropic anticyclones move further south.
Zone of westerlies and polar Lows also move south, taking the cold with them,
Wx patterns are slower moving, with occasional injection of warm & moist air from the tropics.
How does the general circulation change during NZ winter?
Anticyclone centre moves further north, polar lows “travel” over and impact the south Island more frequently. frontal systems associated with these lows affect all of NZ
Autumn & Spring seasons in NZ?
Autumn more closely resembles Summer weather patterns & Spring resembles Winter.
These are usually the seasons of strongest wind (due to the thermal contrast between mT and cT being the greatest).
