BRNC Met CH1-3 Flashcards
What is an inversion layer
An inversion is a layer in which temperature increases with height
What is an isothermal layer
An isothermal layer is a layer in which temperature remains the same with height
The source of the earths heat is the sun. What type of radiation does it emit?
Short wave radiation
How much of the suns radiation enters the earths atmosphere
45%, the rest is either reflected (by clouds or the earths surface), scattered (by particles in the atmosphere) or absorbed (by earths surface)
How is the atmosphere heated
From below, by conduction, convection and absorption of long wave radiation
What factors influence global surface temperature variation
- Time of day
- effect of cloud cover on surface temp
- effect of wind on surface temp
- Seasons
- Latitude
- Nature of the surface
What is the temperature variation between land and sea
The temperature variation between day and night over the open sea is only about 1 degree C, whilst over the land it is often 15 degrees C.
This is due to;
•Specific heat, transparency, reflection, convection
Is the solar energy that reaches the earths surface at the poles, greater or less than that at the equator?
Less, which is why there is such a large temperature difference between the 2 regions
What is the underlying cause of global air movement in the atmosphere?
The temp difference between the poles and equator
In equatorial regions what happens to the heated air?
It becomes less dense, rises, and creates a low pressure zone at the surface called the Inter Tropical Convergence Zone (ITCZ).
The air cannot rise indefinitely, and so spills over in the upper troposphere and diverges to the poles
What happens to the cooled air in polar regions?
It becomes more dense and sinks, creating an area of high pressure called the Polar High
At the surface the air then diverges away from this high pressure region (our cold northerlies), while at altitude air converges to replace the subsided air
What are the Polar Easterlies
The name given to the resultant winds that are always easterly due to the coriolis effect being greatest at the polar regions in both the northern and Southern Hemisphere
What are the Westerlies (roaring forties)
The resultant winds that flow westerly in temperate latitudes in the Southern And northern hemisphere.
*next band from the polar easterlies
In low latitudes where the coriolis effect is least, what directions are the winds
Northern hemisphere = Winds coming from NE (NE Trade winds)
Southern Hemisphere = Winds coming from SE ( SE trade winds)
What is the axis of low pressure around the equatorial regions called
Inter Tropical convergence zone (ITCZ).
It is the zone in which 2 equatorial airflows (north east & south East trade winds) from northern & Southern Hemispheres converge
What happens when the NE & SE trade winds converge in the ITCZ?
As both winds are unstable, when they converge the air may be forced to rise to the Tropopause (at equator hgt =55,000ft) which results in heavy and possibly thundery showers
What are the sub-tropical high pressure belts
They are the belts located between the trade winds and westerlies in both hemispheres.
This area of subsidence or sinking air is where large semi-permanent anticyclones occur over the oceans.
There is little cloud or precipitation, large land areas at these latitudes are where the major arid areas of the world are (Sahara, kalahari, Australian deserts)
What is a polar front
It is the bands between the polar easterlies and westerlies (roaring forties) in both hemispheres. Where air with a polar origin meets air with a tropical origin, in temperate latitudes
What is a jet stream
It is a strong, narrow stream of air concentrated at or near the tropopause.
There are 2 separate jet streams
•Polar jet
•Subtropical jet
The 2 jet streams are rarely continuous, speed and position vary day to days. Wind speeds are generally greater than 100knots and are marked on upper air charts when speeds exceed 50 knots
What weather would you find in a;
1- High pressure zone
2- Low pressure zone
1- fine weather
2- poor weather
What is pressure gradient force
The amount of change of pressure over a given distance
What is geostrophic wind
As air starts to move under the influence of Pressure Gradient Force, it is soon acted upon by the Coriolis forces that acts at right angles to the direction of motion (of the air).
Eventually an equilibrium will be reached, when the two forces balance each other out. The resulting flow of air moves along the isobars, aka geostrophic wind.
In what direction does air circulate in the northern hemisphere (in low / high pressure flows)
Air circulates in a clockwise direction around a high pressure isobar (anticyclone) and anti-clockwise for a low pressure isobar (depression) “”remember L for left and low””
What is Buys Ballot law
Buys Ballot law states that if you stand with your back to the wind in the northern hemisphere, low pressure will always be to your left.
The converse is true in the Southern Hemisphere.
However within 5 degrees of the equator, Coriolis force is negligible and buys ballot laws does not apply.
