Pressure and Winds. General Circulation of the Atmosphere Geog 210 - Physical Geography Geog 311 - Climatology. Global balance – local imbalances.
General Circulation of the Atmosphere
Geog 210 - Physical Geography
Geog 311 - Climatology
Source: Columbia University
The imbalance of radiative budget between the tropics and higher latitudes is the main cause that drives weather and climate! The ultimate energy source is, of course, the sun.
Global weather phenomena as observed by NOAA’s geostationary satellite GOES-12 on Oct 7, 2003.
Pressure unevenness is the main cause of winds. This unevenness causes a pressure gradient from areas of high pressure areas of low pressure. The pressure gradient force causes winds to blow.
When we observe the movement of an air parcel on earth, we find that the moment the air parcel starts to move, it will be subject to this force immediately. N
The deflection of the movement is such that the parcel will be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Thus, the wind patterns are rotating in opposite sense near high and low pressure centers in Northern and Southern Hemispheres, as shown in the figure to the right.Coriolis Force
The basis for average air flow around the earth can be examined using a non-rotating, non-tilted, ocean covered earth.
Heating is more intense at the equator, which triggers Hadley cells to redistribute rising heat from the tropical low to the polar highs.
The wind system on the earth surfaceThe earth is rotating, and rotation makes the wind system a bit more complicated than implied by the 3-cell structure.
The semi-permanent Pacific high blocks moist maritime winds and rain from the California coast, while the Bermuda high pushes moist tropical air and humidity over the eastern states.
During winter months, the Pacific high migrates southward and allows for maritime winds with moisture and rains to reach California.
On the east coast, precipitation is rather even throughout the year, and moisture is always from the Gulf of Mexico and the tropical Atlantic.
Land-sea temperature differences trigger ridges and troughs in the isobaric surface.
Thermal wind is the most fundamental and significant dynamical balance controlling thelarge-scale circulation of the atmosphere and ocean. It is a consequence of hydrostatic and geostrophic balance, and relates horizontal buoyancy gradients to changes in the horizontal wind with height.
“What goes up must come down,
spinning wheel got to go ‘round.”
Blood, Sweat and Tears
Surface maps chart pressure contours, highs and lows, and wind direction.
Winds blow clockwise around highs, called anticyclones.
500 mb maps reveal patterns that on average are 5600 m above the surface, where westerly winds rise and fall across ridges and troughs.
World Climates (Ritter)Please go to the website below and look at the climagraphs for locations all over the world. Study the controlling factors.