The Earth System Recap Flashcards
What does the climate system refer to?
An interactive system consisting of the atmosphere, hydrosphere, cryosphere, the land surface and the biosphere.
What is the most unstable and rapidly changing part of the climate system?
The atmosphere
Atmospheric processes have a direct impact on human activities…
Agriculture, water resources, extreme weather events.
Humans have interacted with atmospheric processes by…
Changing land cover, burning fossil fuels and adding important trace gases.
Seasonal differences in climate across the globe are caused by…
The spherical shape of the Earth- large N-S temperature differences.
Tilt of the Earth’s axis of rotation (23.5o)
What are the seasons called?
September 23 (Autumnal Equinox) June 22 (Summer Solstice) March 21 (Vernal Equinox) December 22 (Winter Solstice)
Wind systems- annual and seasonal variations are caused by…
Inequalities in the distribution of solar radiation over the Earth’s surface.
The Earth’s rotation.
Energy surplus at the equator and deficit at the poles leads to…
Heat transfers.
What is convection?
The dominant process for transferring heat upwards from the Earth’s surface.
What is adiabatic motion?
Temperature changes occur with vertical motions in the atmosphere
Why is the atmosphere continually turning?
Mass balance dictates that as some air masses rise some must also fall.
Where does atmospheric overturning occur?
In the troposhere
Over long timescales the complete Earth–atmosphere system is in thermal equilibrium
Heat energy is transferred from the tropics to poles by the north–south circulations in the atmosphere and oceans
What is the dry adiabatic lapse rate?
Rate of temperature fall with height in a rising parcel of air (9.8oC per km)
What is the saturated adiabatic lapse rate?
Lapse rate in the presence of condensation
What is the coriolis effect?
- Air should move 90° to isobars but is deflected by the
force of the Earths’ rotation - Observations show air flow is almost parallel to the
isobars (except very near to the surface and at the
equator)
What are geostrophic winds?
- Deflected winds >1km above the surface
- Speed is proportional to pressure gradient and strength
of coriolis effect - Airflow is anticlockwise around low pressure in the N
hemisphere and the converse for the S hemisphere
3-cell atmospheric circulation model in each hemisphere (controlled by a pressure
gradient force)
Hadley cell
Ferrel cell
Polar cell
What are jet streams?
Fast-moving bands of air embedded in Rossby waves caused by sharp temperature differences (speeds up to 140 kms-1)
What is the Subtropical westerly jet stream?
Poleward boundary of the tropical Hadley cell
Just below tropopause
In winter it divides around the Tibetan Plateau
What is the polar front jet stream?
Associated with the warm and cold fronts of temperate-latitude depressions
Considerable day-to-day variation
What are Rossby waves?
Middle-latitude the atmosphere is highly disturbed (Ferrel cell is largely schematic)
Surface air circulation- irregularly shaped,
eastward-drifting, cyclonic and anticyclonic systems
Higher atmosphere – smooth wave-shaped patterns
Why are Rossby waves important?
They strongly influence the formation and subsequent
evolution of surface weather features
Where do middle-latitude frontal depressions form?
Grow rapidly just downwind of upper troughs of
Rossby waves
Where do anticyclones form?
Just downwind of upper ridges
Rossby waves
Differences between the hemispheres
Southern temperate-latitudes
Rossby waves could arise anywhere in the middle latitudes due to ocean cover
Rossby waves
Differences between the hemispheres
Northern temperate-latitudes
Preferred locations, because influenced by thermal properties of land and sea and the location of key mountain ranges (Rockies and Himalayas)
Summary
- Energy surplus at the equator and deficit at the poles leads to heat transfers.
- The large-scale circulation of the atmosphere is organised into cells.
- Jet streams form at the boundaries of the cells and play a major role in storm development.
- Jet streams form into standing waves that affect the positions of major air masses.
