climatology Flashcards
defintion of weather
state of atmosphere at any given time
definition of climate
long term state of atmosphere
what is the main source of energy for the atmopshere
solar radiation (from sun)
what is a blackbody
- object that absorbs all radiation that strikes it
- emits radiation at a maximum rate
- eg sun
what does stefan boltzmann law calculate for
energy emitted
what does wiens law calculate for
maximum wavelength
how does the troposhpere contain 80% of the air in the atmosphere
because air/gas is compactable
what is earths axial tilt
23.5 degrees
where in the world is there an energy surplus and what occurs there
equator, atmopshere has to redistribute energy using circulation systems
what is albedo
reflectivity
what happens to shortwave radiation
- reflected at top of atmosphere
- reflected, absorbed, or scattered by clouds/water vapour
- transmitted to surface then either absorbed or reflected
what happens to longwave radiation
- earths surface emits longwave radition
- some escapes through atmosphere, leading to cooled earth
- some is absorbed by clouds
- clouds then emit longwave in all directions
- downward movement warms earth, while upward movement cools earth
why are there seasons
- earths revolution around sun
- earths rotation on axis
what is latent heat
energy needed to change phase
- usually associated with water phase change (eg evaporation, condensation etc)
what is dew point temperature
temperature at which air needs to cool to allow condensation to occur
what happens to air in a stable atmosphere
vertical motion is suppressed
what happens to air in an unstable atmosphere
vertical motion is enhanced
what density is warm air
low density
what density is cool air
high density
what does low density mean
warm air
air rises/more buoyant
what does high density mean
cold air
air descends/less buoyant
what happens to rising air
cools by expansion
what happens to falling air
warms by compression
what is the dry adiabaitc lapse rate
the rate at which dry air cools by expansion or heats by compression
what is the moist adiabatic lapse rate
added heat offsets rate of cooling as air rises
what are the 3 main factors that affect wind
- pressure gradient force (pgf)
- coriolis effect
- friction
what is the pressure gradient force
air moves from high to low pressure
what is the coriolis effect
- force used to explain deflection of air as it moves across the surface of earth
- earth rotation produces effect
- deflects air to left in southern hemisphere
what is geostrophic wind
theoretical concept approximating observed wind using pressure graident force and coriolis effect
- wind tries moving from high to low, but corioilis effect brings it back
what impact does friction have on wind
friction near surface disturbs balance between pressure gradient and coriolis forces
- caused by air moving over land surface
what is agradient airflow
lowering wind speed from friction weakens the coriolis effect
what direction does air flow in a high pressure zone/anti-cyclone
- anti-clockwise
- out from high pressure zone
what direction does air flow in a low pressure zone/cyclone
- clockwise
- into low pressure zone - causing uplift and cloud
what is an airmass
large body of air whose physical properties are uniform horizontally
what happens to airmasses during summer
southward shift
- nz recieves more tropical maritime
what happens to airmasses during winter
northward shift
- south island of nz recieves more polar maritime
- tropical maritime shifts further north so doesn’t affect
what happens in a cyclone
low pressure zone -> convergence of air -> uplift -> cloud development
what happens in an anti-cyclone
high pressure zone -> divergence of air -> descending
what is frontogenesis
when 2 contrasting airmasses collide
what is a warm front
occurs when an advancing airmass replaces cold airmass
- slow moving
what is a cold front
represents boundary of cold airmass advancing towards warm air mass
- forced to rise quickly
what is an occluded front
- cold front moves faster than warm front
- as it catches up, warm air mass is wedged and lifted up
what is a stationary front
occurs when neither warm or cold front dominates
- remains stationary
what happens to stable air when blocked
has to flow around obstacle
what happens to unstable air when blocked
air able to pass over obstacle
- forms lee waves
what is the foehn effect
- northwesterly wind
- results in precicptation on windward side of mountain range and a drying effect on leeward side
- eg southern alps/west coast
what is the land-sea breeze circulation system
during day
- sun is shining - warms land surface faster than ocean surface
- leads to breeze onshore
during night
- no sun shining - ocean surface warmer than land surface
- leads to offshore wind
what are the two energy balance equations
Q* = K* + L*
(Q* = net allwave radiation, K* = net shortwave radiation, L* = net longwave radiation)
Q* = K(intake) - K(output) + L(intake) - L(output)
what is the energy balance equation for heat flux density
Q* = Q(G) + Q(H) + Q(E)
(Q(G) = ground/conductive heat, Q(H) = sensible heat, Q(E) = latent heat)
what happens to the surface during night (energy balance)
- no sunlight = no shortwave
- recieve longwave from atmosphere, lose from surface
- net defecit of energy = surface cools
- sensible heat - atmosphere warmer than surface, heat governed to surface
- latent heat - governed to surface to compensate for defecit of radiation
- ground/conductive heat - soil warmer than surface, heat governed to surface
what happens to the surface during the day (energy balance)
- incoming solar radiation (some reflected)
- recieve longwave from atmopshere, lose from surface
- net surplus of energy = surface warms
- sensible heat - surface heats lower atmosphere
- latent heat - energy available to evaporate water at surface
- ground/conductive heat - surface warmer than soil, heat goverened to soil
is the albedo of snow or ice higher and what does this mean
snow is higher
once glacier loses snow in summer, glacier absorbs more energy and melts as it is less reflective
what is the greenhouse effect
- absorption of longwave radiation by atmopshere results in warming of earths surface and lower atmosphere
what would the surface temperature be if there was no atmosphere
-18deg celcius
what is the enhanced greenhouse effect
if extra greenhouse gases are added to atmosphere from humans, they will absorb more longwave radiation and therefore lead to extra warming of the earth
what is an el nino southern oscillation (enso) event
- fluctuations in intensity of walker circulation are characterised by southern oscilalltion index (soi)
- soi derived from pressure difference between tahiti and darwin
- soi index leads to either el nino or la nina events
what happens when the soi is high/positive
la nina event
- normal walker circulation
what happens when the soi is low/negative
el nino event
- weaker walker circulation
what happens in nz during a la nina event
- low pressure zone to northwest of nz
- leads to northwesterly/northeasterly flow
what happens in nz during an el nino event
- migration of warm water
- replace low pressure zone with high to northwest of nz
- low zone to south
- southwesterly flow
- colder
- more precipiation on west coast
what is the projected temperature by the end of the century
global surface temperature likely to exceed increase of 1.5deg
- could be as large as 4.8deg
what is the projected sea level by the end of the century
global mean sea level likely to rise between 0.4-0.8m
