Tropical Met

Question 1

State the latitude limits of the tropics

Answer 1

Between the Tropic of Capricorn 23.5°S (southern hemisphere)
•Tropic of Cancer 23.5°N (northern hemisphere

Question 2

Describe the Hadley cell

Answer 2

A large-scale atmospheric convection cell in which air rises at the equator and sinks at medium latitudes

•Sinks at around 30°N/S

•Responsible for the trade winds in the Tropics and control low-latitude weather patterns

Question 3

Describe what’s meant by horse latitudes

Answer 3

Located between 30-40º in both hemispheres.

Light winds, little rain due to anticyclones that form here.

Question 4

Describe what’s meant by doldrums

Answer 4

Exists with the intertropical convergence zone
•Between 5°N/S
•Trade winds converge resulting in light winds
•Frequent heavy thunderstorms due to convection caused by sun and moist air

Question 5

Describe the equatorial trough and inter-tropical convergence zone (ITCZ)

Answer 5

The trough is centered on the thermal equator, its a Near continuous belt of low pressure around the low latitudes and which has a very high dew point therefore large amounts of moisture in the air

•Contains the doldrums, ITCZ and part of the trade winds

ITCZ - narrow band of convection Cb’s surrounding the glove resulting from the convergence of the NE trade winds from the northern hemisphere with the SE trades from the Southern Hemisphere.

Question 6

State the seasonal location of the equatorial trough and ITCZ

Answer 6

Both move with the sun into the warmer hemisphere

•Causes the trade winds to change from SE to SW when crossing over the equator in northern hemisphere summer

•NE trade winds become NW in southern hemisphere summer

•Smaller movements over the ocean than land

Question 7

State the typical low-mid level weather in active and inactive ITCZ

Answer 7

If trade winds meet head on theres a strong convergence, e.g NE wind converging with SW trade wind.

Weaker/inactive ITCZ caused by winds meeting at similar angles . E.g ene meeting ese wind

Question 8

State the typical low and mid-level weather In an active and inactive ITCZ

Answer 8

Active = extensive Cu, TCu, Cb and thunderstorms with heavy showers, icing and strong up/downdraughts

•Inactive = Low level fair weather cumulus, light winds

Question 9

Explain the origin and common location of the South Pacific convergence zone

Answer 9

Most active in Southern Hemisphere summer.

Caused by semi-stationary high in eastern pacific and anticyclones originating/travelling east from Australia/NZ.

NE wind meets SE wind creating zone of intense cloudiness between Papa New Guinea and French Polynesia.

Question 10

Describe weather associated with the SPCZ

Answer 10

Summer = convective thunderstorms and tropical disturbances

Winter = weaker convective thunderstorms or fair weather Cu

Question 11

Regards to trade winds describe the mechanism that drive the trade winds.

Answer 11

Pressure differential between the anti-cyclones at 30º and depressions at the equator.

As it moves from high to low, Coriolis force deflects the wind left in SH and right in NH but ultimately caused by the sun and aid in heat distribution.

Question 12

Describe the latitudinal and vertical limits of the trade winds

Answer 12

Between 30ºN and 30ºS

8000ft amsl

Question 13

Regards to trade wind describe seasonal location and direction

Answer 13

Follow the sun.

Moves north in NZ winter and south in summer.

Southern H = SE in NZ summer, SW in winter
Northern H = NW in NZ summer, NE in winter

Question 14

Regards to trade wind, describe associated weather

Answer 14

Weather associated with high pressure systems closer to 30° latitude

•The closer to the equator the trade winds get, the more unstable the weather and clouds become

•Wind strength = 10-20kts occasionally 30kts

•Trade winds stronger in winter than summer

Question 15

Regard to trade winds, winds and weather usually experience above the trade winds

Answer 15

Above trade wind inversion at closer to 30° = good visibility, dry air and clear skies

•Closer to the equator moisture content and instability increase creating TCu and Cb cloud at altitude

•Above the trade winds = light westerlies

Question 16

Describe the topographical influences on the trade winds

Answer 16

•Land heats up and cools down faster than the ocean which Increases instability in summer on coasts exposed to SE trade wind and increases cloud development

•Steeper terrain will also cause orographic rising

•In winter stability is increased reversing the effects

Question 17

Define monsoon

Answer 17

Derived from Arabic word mausim
•Means season and can be ‘wet’ or ‘dry’
•Caused by continental highs and lows creating giant land breezes or sea breezes

Question 18

Describe the mechanisms involved with regard to wet monsoons

Answer 18

Occurs when land is heated up in spring/summer. Creates intense instability causing air to rise.

Replacement air from oceans travel inland and create large thunderstorms, heavy precipitation and squalls.

Mountain barriers increase the development as they push the air up.

Question 19

State the seasons during which Australian monsoon occur

Answer 19

Occurs between November and April, peaks in February
•Summer

•Occurs when moist NW trade wind blows onto northern Australia, inter tropical convergence zone causing Coriolis force to deflect it the other way when it crosses over the equator

•In winter the dry monsoon blows from the SE trade wind bringing dry weather

Question 20

Describe the requirements for the formation and development of tropical cyclones

Answer 20

Sea temperature must be 26.5ºC or higher.

Associated with low pressure area known as equatorial trough.

Between 5-20ºC latitude due to Coriolis force being to weak Above 5 and 20º latitude due to coriolis force being too weak above 5º

Must develop over ocean due to moisture requirement

Little to no vertical windshear

Must be high-level divergence just below the tropopause and requires a warm core created by release of latent heat. Warm core creates the upper level high pressure zone.

A cyclone eye to reduce pressure below 1000hPa through adiabatic warming

Question 21

,

Question 22

Describe the weather conditions associated with tropical cyclones

Answer 22

Air pressures as low as 950 hPa
•Hurricane forces winds of 64kts or greater are sustained
•Torrential rain, thunderstorms and violent squalls
•Can last up to 2 weeks and travel west

Question 23

Explain El Niño events

Answer 23

•Caused by the collapse of the Walker Cell

Occurs when pressure increases in the west near Darwin and decreases in the east near Tahiti, meaning Trade winds can reverse in direction and it can enhance westerlies in mid-latitudes

Question 24

Explain factors causing La Niña events

Answer 24

Caused by the Walker Cell and Humboldt current
•Occurs when pressure decreases in the west near Darwin and increases in the east near Tahiti
•Trade winds enhanced
•Westerlies in mid-latitudes reduced or even reversed into easterlies

Question 25

Describe how El Niño and La Niña events influence the weather in New Zealand

Answer 25

El Nino causes more rain on the west coast and dryer conditions on the east coast

•La Nina causes more rain on the east coast and dryer conditions on the west coast

•Higher chance of ex-tropical cyclones in summer months with La Nina