ATPL Tropical Met Flashcards
Explain what’s meant by equatorial trough (meteorological or thermal equator)
The meteorological equator is the annual mean latitude of the intertropical convergence zone (ITCZ)
•Meteorological equator located at 5°N
•The thermal equator is a different line joining all points of highest mean annual surface temperature
Explain the inter-tropical convergence zone (ITCZ)
Marks the place where trade winds from norther and Southern Hemispheres converge
Centered on the thermal equator
Explain what’s meant by South Pacific convergence zone (SPCZ)
Formed where the outflow from the walker cell clashes with the semi-permanent highs at 30° south
•Is the birth place for all south pacific tropical cyclones
State the region where maximum convergence and convention and maximum cloud development are
20ºN 15ºS
Max convergence = when ITCS moves away from equator by about 5º or more while remaining in the tropics. Causing the south east trade winds to go into the northern hemisphere deflecting them west cos of coriolis force making them clash into each other. North east trade winds become north west and clash with southeast trade winds.
Max convection = same as convergence and further enhanced over large continental land masses. Cos of increased surface heating ( due to higher specific heat of land).
Max cloud development = same as above.
Describe the following weather associated with active and inactive ICTZ
Active = thunderstorms and heavy showers of rain up to 600km (300nm) wide
•Most active in the afternoon during summer
•Inactive = some showers, light winds. 500km wide
•Least active over ocean in the winter
Describe icing in active and inactive ICTZ
Active = Moderate to severe icing above the freezing level, especially within the first 10,000 to 15,000ft above it
•Inactive = light to none
Describe turbulence in ICTZ
Active = moderate to severe due to Cb clouds
•Can’t fly under turbulence because cloud bases are 1,000ft
•Can’t fly over turbulence as clouds too high
•Inactive = light to none
Describe cloud related factors associated with ITCZ
Active = Wall of Cu, Cb, Tcu clouds going all the way up into the stratosphere.
•Large deviations required if wanting to go around an active ITCZ
•Inactive = Various oktas of cumulous
Describe the preferred location and characteristics of the South Pacific converge zone
Papa New Guinea to French Polynesia
Use diagrams to explain the following aspects of the trade winds in both hemispheres of the Pacific Ocean relating to anticyclonic subsidence and associated met conditions
Semi-permanent highs occur between 25° to 35° latitude in both hemispheres and travel eastward
•Clear skies, light winds that are deflected by the Coriolis force
•Causes trade winds to be NE in northern hemisphere and SE in southern hemisphere
Where are the approximate latitudinal and vertical limits of the trade winds
Between 30ºN and S
Vertical limit of 8000ft AMSL
Describe the seasonal changes in location and their effect on wind direction on trade winds
Follows the sun
•Moves north in NZ winter and south in summer
•Southern hemisphere = SE in NZ summer, SW in winter
•Northern hemisphere = NW in NZ summer, NE in winter
Describe the typical wind strengths, including variation from summer to winter regarding trade winds
Steady and persistent in strength
•Wind strength = 10-20kts occasionally 30kts
•Trade winds slightly stronger in winter than summer
•Winds above are generally light westerly
Explain the effect of the trade winds on the wx experienced in island groups and northern Australia on trade winds
Increased rain in summer on south east coasts of islands and Australia, drier on the west coasts or inland
•In winter trade wind strength is reduced due to land breeze
•Winter might still have some cloud on the SE coasts from the trade winds but overall much drier and stable
Outline how tropical convection can occur as individual convective cells or as organised clusters
Individual cells caused by turbulence in the friction layer creating long streets of cumulus aligning itself parallel to the trade winds
•Organised clusters are mesoscale convective areas. Caused by heating and instability through deep layers
Describe the factors involved in wet monsoons in terms of seasonal factors
The wet monsoon occurs in summer for either hemisphere
•Enhanced more over land than over sea due to specific heat differences
Describe the effect of large land masses and orographic obstructions on monsoons
The larger the land mass, the greater the difference in temperature between the land and the sea increasing the wet monsoon in summer
•Mountains and hills encourage rising of air so that the moist air reaches its dew point, increasing rainfall
Describe the location of major monsoon regions
Concentrated along the south Asia continent
•Moist air from Indian ocean causes monsoons in India, Pakistan, Myanmar etc
•Northern hemisphere monsoon from June to September
•Also the north Australian continent in summer
State where tropical cyclones, typhoons and hurricanes are in relation to oceans
Cyclones - South Pacific Ocean, Indian ocean (all Southern Hemisphere)
Typhoons - north west Pacific Ocean
Hurricanes - North Atlantic Ocean, north east Pacific Ocean
With regard to formation and development of tropical cyclones, describe the relationship with the equatorial trough and/or the SPCZ
A pre-existing disturbance at low levels provides a focal point for rotation of large masses of thunderstorms
•The wave disturbance is caused by convergence zones or quasi-stationary fronts
•These are most likely to occur in the equatorial trough or south pacific convergence zone
Describe the requirement for and supply of sensible and latent heat in regard to cyclones
Sensible heat is the increase in temperature of a body as more heat is added
•Latent heat is released as clouds form increasing instability and sensible heat
•This sensible heat is delivered to the center of the storm through radial flow
Describe the effect of upper-level divergence
Subsiding air in the storm eye should increase pressure
•Upper-level divergence removes air from the column at the top of the troposphere faster than it is entering the system at the surface
•This reduces surface pressure increasing convergence
Describe the characteristics of the cyclone e’ye
Light winds
•Subsiding air causes adiabatic warming which dissipates clouds
•Clear skies
•Where the lowest surface pressure exists
Describe the requirement for a warm core in regard to tropical cyclones
Instrumental as it encourages the development of an upper level high-pressure zone
•This creates more upper level divergence and therefore more low level convergence
