lecture 6 - winds and global circulation Flashcards
Wind is caused by
differences in atmospheric pressure (pressure gradient) from place to place with air moving from high to low pressure (pressure gradient force).
Pressure conditions are shown on a map using isobars —lines connecting places of equal pressure
Coriolis effect causes
air currents to appear to follow gently curving paths as they blow across the Earth’s surface (deflection is to the right in the northern hemisphere and to the left in the southern hemisphere).
Hadley cells
Since the surface and atmosphere is heated more intensely at the equator a zone of surface low pressure forms what is known as the equatorial trough.
The heated air rises at the equator, which creates two large- scale convection loops (in each hemisphere) called Hadley cells (where air rises over the equator and is drawn toward the poles).
subtropical high-pressure belts
At about lat. 30° in each hemisphere, the Hadley cell circulation descends, creating high pressure belts called subtropical high-pressure belts.
Winds at the subtropical high-pressure centres spiral outward and move toward the equator (strong northeast and southeast trade winds) and also toward the midlatitudes.
These winds move toward the equatorial trough where the air converges and rises at the intertropical convergence zone (ITCZ).
polar front
When colder polar air meets the warmer subtropical air, it creates a conflict zone, termed as the polar front
Subtropical High Pressure Belts
Southern Hemisphere
three large high-pressure cells that persist year round over the oceans (fourth, weaker high- pressure cell forms over Australia in July, as the continent cools during the southern hemisphere winter).
Subtropical High Pressure Belts: northern hemisphere
- two large high-pressure cells occur over the subtropical oceans — the Hawaiian High in the Pacific and the Azores High (commonly referred to as the Azores-Bermuda High) in the Atlantic.
