Lec 3 Flashcards
Global climate is caused by
The tilt of the Earth’s rotational axis and its spherical shape that make the angle of incidence of sunlight uneven at different latitudes
What gives rise to seasons
The difference in average insolation at different latitudes and hemispheres
Low temp is due to
Low solar radiation
Highly seasonal environment (winter and summer)
Winter-No incoming solar radiation above the arctic circle
Summer-24 hour daylight and high solar input
Which hemisphere do temps vary more
The Northern Hemisphere because it has less oceans to store heat
Factors that affect global distribution of solar radiation
Amount absorbed by the surface, depends mainly on what grows on the surface
Amount absorbed by air
Light reflected by clouds (higher in temperate regions due to dense clouds)
Reflection by the surface is highest at the poles (more in Antarctica than the Arctic due to more snow reflecting)
Amount of UV light reaching a surface varies with
Latitude
Surface orientation
Impact of Polar ozone on UV
Chemical ozone destruction occurs over both polar regions in local winter-spring
Antarctic: Almost complete removal of lower-stratospheric ozone
Arctic: Ozone lose is highly variable and limited (started in 2011)
CFC-Chloroflourcarbons
Breaks ozone apart, destroying ozone molocules
Climate depends on
Energy received from the sun which warms land and seas
Planetary energy balance
Loss of heat via long-wave radiation>energy input from solar radiation at northern latitudes
Radiation imbalances produces low temps and results in redistribution of heat from southern latitudes by air and ocean currents
Two subtypes of climate
Maritime
Continental
Maritime
Coastal areas with moderate stormy winters, high precipitations
Summer is cloudy and mild temp
Norway Iceland and western Alaska
Continental
Much lower precipitation, great contrast between summer and winter
General global circulation
Warm rising air at the equator radiates heat back into space and creates cells
Position of continents exert secondary effect on global pattern of
Precipitation
More rain in southern hemisphere because
More lake and oceans
North Atlantic Oscillation (NAO)
The anomalous difference between the polar low and subtropical high
NAO is the dominant mode of winter climate variability
NAO is a large scale seesaw in atmospheric mass between the subtropical high and the polar low
Index varies from year to year, but also exhibits tendency to remain in one phase for intervals lasting years
Positive NAO
Stronger than usual subtropical high pressure and a deeper than normal Icelandic low
Effect of positive NAO
Warm and wet winters in north Europe and dry winters in north Canada and Greenland
Negative NAO
A weak subtropical high and weak Icelandic low
Arctic Oscillation (AO)
Arctic oscillation is linked to the NAO and driven by similar pressure differences
AO effects are not restricted just to the Arctic, it also represents an important source of variability for the Northern Hemisphere as a whole
Are AO and NOAs correlated
Both have been largely positive since the end of the 1980s and have coincided with relatively warm conditions in the Arctic and net melting of the Arctic ice pack
Polar vortex
An area of low pressure located in the Arctic (almost always present)
When a polar vortex is strong
Cold air remains in the north
A weaker polar vortex means
A wavier jet stream and cold Arctic air moves south
