General Flashcards
How are clouds formed?
Saturated air caused by moisture accumulation or temperature reduction condenses water vapour around condensation nuclei of small suspended particles or aerosols
What radius is needed for a particle to be a condensation nucleus?
Radius >1micron
Why are mountaintops cold when so close to the sun
Tropospheric heat is irradiated from land below, with rising parcels expanding as they reach lower pressures. This requires energy consumption in heat form. Also, there are fewer GHG molecules to radiate heat back to you
What is air pressure?
Air pressure is closely approximated by the hydrostatic pressure caused by the weight of air above a point, but also depends on the amount life on the air
How do pressure & density change with height?
Both decrease with height
What are isobars?
Imaginary lines on a map denoting points of equal atmospheric pressure
How do high & low pressure affect circulation?
High pressure: air moves clockwise (downwards) from a bird’s eye view
Low pressure: air moves anti-clockwise (upwards)
What is wind?
The movement of air from areas of high to low pressure
What is a cyclone?
A system of winds rotating inwards due to low pressure
What is the Coriolis Effect?
The deflection of the paths of objects not connected to the ground due to the Earth’s rotation & the difference in distance around the Earth at the Equator & the Poles. The Equator moves faster than the Poles, so NH air deflects to the right
What is geostrophic wind & where is it found?
Wind that moves parallel to isobars; found in higher layers of the atmosphere
What effect does surface friction cause in the lower atmosphere?
Turbulence
Where do Hadley, Polar, & Ferrel cells occur?
Hadley: points of highest insolation (near Equator)
Polar: high latitudes
Ferrel: between cells
What drives Hadley, Polar, & Ferrel Cells
Hadley: Contrast in insolation
Polar: Cold air at Poles
Ferrel: surrounding Cells
How does the atmosphere change away from the ITCZ?
It ‘shrinks’
What are jet streams & where do they form?
Narrow bands of strong winds moving west to east; form along upper boundaries of large warm & cold air masses at the Tropopause
How do jet streams form?
Pressure falls faster in colder air, so that higher pressured warm air pushes towards cold air to create geostrophic winds flowing around the planet, ranging between 50-300mph
Where is the northern polar jet stream & why is it relevant?
Altitudes of 8-11km; it causes major influences on UK weather
What waves cause long-term positioning of jet streams?
Rossby waves: planetary waves occurring naturally in rotating fluids
How did volcanic debris from Mount Pinatubo spread to cover ~42% of the world in 60 days?
Ash was caught in Hadley cells, moving upwards & northwards. Ash that reached the stratosphere mixed into stratospheric winds & jet streams
What factors shaped the Earth’s atmosphere
Extra-terrestrial bodies, surface water, magnetic field, gravity, ice volume, rock weathering, plate tectonics, topography, volcanoes, & life
What allows the atmosphere to remain on the planet?
The magnetic field prevents stripping of the atmosphere by solar wind & Earth’s strong gravity holds onto the atmosphere
Describe the greenhouse effect
Short wavelength radiation from the sun is partially absorbed into the Earth’s surface (2/3), whereas 1/3 is reflected into space. Earth radiates equivalent energy into space at longer wavelength, which is absorbed into the atmosphere & trapped to reradiate heat to the Earth
What is the Snowball Earth Hypothesis?
The idea that during some icehouse climates the Earth’s surface becomes nearly entirely frozen
