The Actual Exam Flashcards
Explain what is meant by sky radiation
Any scattered radiation (by clouds/aerosols) that reaches the earths surface
What is global solar radiation?
The sum of sky radiation and direct radiation reaching the Earths surface
How does the earths atmosphere warm?
Solar radiation reaches the surface causing the surface molecules to excite, causing the surface to increase in temperature. They then emit energy as terrestrial radiation (IR) which is what warms the atmosphere as CO2, water vapour & cloud droplets absorb. Can be described as a hot plate effect. As the surface emits energy it will cool, so needs a constant supply of solar radiation to allow the surface to warm
What factors determine an air mass?
Horizontal uniformity with vertical changes in temperature, temperature lapse rate and moisture being relatively the same.
…possibly stability
Describe the effect of cold advection on Australia
Cool air from Antartica moves to Australia.
Lowest levels warm and gain moisture.
ELR steepens creating instability and Cu/Sc buildup developing Cb build up near the coast.
Central Australia is still unstable but without cloud buildup.
Describe the effects of warm advection on Australasia
As warm moist air moves south it’s lower levels will cool and condense to form low level cloud/stratus and fog. The subsidence due stability reduces vertical mixing so upper layers will cool slower so may result in inversions.
As this air reaches NZ, it will be forced aloft due terrain which will create cloud, rain/drizzle and reduced vis. Will mainly affect Northland, BoP, Auckland, Malbrough Sounds & Nelson but May differ due moisture content, direction of flow and time of year.
Go do some practice questions on thermal winds
SERIOUSLY
What are the required conditions for radiation fog to develop?
Light winds, clear sky, high pressure, high RH
What are the conditions for advection fog to occur
Moist air move over already cool surface, light winds, inversion.
Helpful is stable atmosphere
Just know the following…
Beneath the Cb of a mature system, precipitation will evaporate and cool accelerating downdrafts
Describe how a orographic TS forms, it’s durations and when they are most likely
They form as moist unstable air is forced over high terrain. Seasons and time of day have no major impact on this type of thunderstorm, although thermally unstable air may be easier met on summer/autumn days. Unlike other thunderstorms which typically are short lived, orographic thunderstorms can last as long as moist unstable air is forced over terrain.
Describe how heat type TS form and their occurrence
Thermal TS require intense heating from below to encourage instability of warm moist air. Best occurs near large water sources to help Cb develop. In temperate climates will occur mainly in summer during the afternoon along coasts. In tropical climates it is a daily occurrence that can last past sunset throughout the year, it just along coasts
Describe what leads to convergence TS
…convergence.
Heat type TS technically fall into this category.
Low pressure systems or the ICTZ can also create convergence.
Basically any system that causes moist unstable air to converge and rise.
How do nocturnal equatorial TS form. When are where are the most likely?
They form +/-10* of the equator where the oceans are warm (30*c). As the sun sets, the water retains its temperature but the upper atmosphere cools which steepens the ELR (large ELR). At dawn the ELR is greatest and this is when the storms are most likely to occur, dying out by mid morning.
Describe how cold stream TS form? Can they occur NZ/AUS? How strong are they?
As cool air passes over a warm patch of water, it absorbs large amounts of water and its lower levels warm. The warming of the lower levels steepens the ELR (greater) allowing instability vertical mixing which can generate Cb.
Can occur in Aussie as polar air moves over in winter/spring or in NZ in summer/autumn.
