Chapter 8

Gradient wind

in curved flow, there is a centripental acceleration directed inward towards the center of rotation and an apparent force called the centrifugal force directed outward

sea breeze during the day

uneven heating of the coastline during the day In areas of high P, higher P over land than over sea due to thermal expansion on shore, higher P over sea, horizontal movement of air Temperature contrast leads to P gradient force net force

Balance of forces and geostrophic wind

wherever the spacing of the isobars or height contours is wide, reduce the wind speed and strength of PGF; wherever it is narrow (isobars are close to each other), increase the wind speed, stronger PGF

subgeostrophic

Around a low (troph), the centrifugal force pulls the air in the same direction as the COR, and it is the sum of both forces that balance the PGF. Wind speed and COR are weaker. COR is proportional to wind speed. Slower than geostrophic wind.

supergeostrophic

Conditions around high pressure areas (ridge); the centrifugal force points in the same direction as the PGF. Air under goes rapid acceleration and the Coriolis force dominates the pressure gradient force. Faster than geostrophic wind.

wind speed and latitude

Influence the magnitude of the Coriolis force

Geostrophic flow

PGF balanced by Cor force

at high altitudes

The geostrophic wind concept is most like the real atmospheric winds

P gradient force

The initial force that generates wind

Upper air winds

are generally faster than surface winds

geostrophic wind

flows along lines of P, parallel to the h of the P contours, a balance b/w PGF and Cor, no acceleration

Land Breeze at night

higher P over land off shore, lower P over sea on shore, cooling of air, clouds over sea

The Coriolis effect occurs because of this characteristic of the earth

its rotation

steep pressure gradient

produces strong winds

When geostrophic conditions exist in the atmosphere...

the net force on the moving air is zero