Geography 111 Lecture 8 Notes 8-24
Geography 111 Lecture 8 Notes 8-24 GEOG 1111
Popular in Intro to Physical Geography
Popular in Geography
This 6 page Class Notes was uploaded by Bridget Notetaker on Monday August 29, 2016. The Class Notes belongs to GEOG 1111 at University of Georgia taught by Hopkins in Fall 2016. Since its upload, it has received 56 views. For similar materials see Intro to Physical Geography in Geography at University of Georgia.
Reviews for Geography 111 Lecture 8 Notes 8-24
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 08/29/16
Geography 1111 Lecture 8 Notes Air Pressure and Wind: o Air Pressure is measured as the force of the air pushing down on a surface In meteorology it is measured by the height of a column of mercury and expressed in units of millibars (mb) or inches of Hg It will vary both spatially and temporally, with the average sea-level barometric pressure being 1013 mb When displayed on a map, lines of equal barometric pressure are called isobars o A high or “heavy” pressure cell is represented by: Refer to photo below with H o A low or “light” pressure cell is represented by: Refer to photo below with L Pressure Gradient Force (PGF): is the difference in barometric (air) pressure between two points o If this difference is horizontal across the Earth’s surface, this will initiate the horizontal movement of air or the process of advection, commonly called WIND o Air pressure and the PGF determine wind direction and wind strength or speed o A steep pressure gradient, a strong PGF, will yield stronger (faster) winds o A gentle pressure gradient, a weak PGF, will yield weaker (faster) winds Winds: will flow (blow) from an area of HIGHER pressure toward an area of LOWER pressure o These differences in pressure are set-up by differences in temperature created by differential heating o A portion of the Earth’s surface which receives more solar radiation will absorb more energy and heat-up This will in turn heat-up the air above it and this warmed air will rise As the air rises, it exerts less force/pressure on the surface and an area of Low barometric pressure is formed o Conversely, colder air from higher in the Troposphere will sink, exerting more force/pressure on the surface This forms an area of High barometric pressure Also, as that sinking air reaches the surface it will spread out away from the center of High pressure flow toward an area of Low pressure Energy imbalance temperature Pressure wind difference difference o Winds generated by a PGF would flow in relatively straight paths, but do not because of various other forces also acting on them Coriolis Force: is the apparent deflection in movement of an object (wind, ocean currents, planes, etc.) from a straight path due to the Earth’s rotation o What causes this? Earth is a sphere, rotates on its axis and the whole Earth’s surface does not spin at the same velocity. Also, objects that move independent of the Earth’s rotation will be affected by its rotation With your back to the wind (or other object), deflection is: To the right of the original path in the Northern Hemisphere To the left of the original path in the Southern Hemisphere o Characteristics of Coriolis Force (CF): It is strongest at the poles & zero at the equator An objects speed will alter the amount of deflection with a higher speed yielding greater deflection CF alters the direction, but NOT the speed of an object Types of Wind: o Geostrophic winds (or upper-level winds): are those that flow 1 - 2 kms above the surface. They are formed, like all winds, by Pressure Gradient Force and affected by Coriolis Force o This yields a net effect such that when shown on a map, geostrophic winds flow parallel to the isobars o Two main patterns of flow thus emerge, Zonal and Meridional Zonal flow: pattern which exhibits a more “flattened” air flow with a primarily E-W orientation Meridional flow: more curved flow pattern with distinct curves, ridges and troughs, showing a more N-S orientation o Jet Stream: is a geostrophic wind pattern of particular interest and importance It is a meandering “river” of air 100-300 miles wide, 3,000-7,000' deep at an attitude between 25,000'- 35,000' above sea level It has average wind speeds between 50 and 110 mph, but can reach 190 mph They are highly turbulent and their speeds and location will vary considerably o Two of interest are the Polar Jet Stream and the Subtropical Jet Stream o Rossby Waves: are essentially a subset of the Polar Jet Stream stretching from one trough to another, their wavelengths on the order of thousands of kilometers in length Often a series of Rossby Waves circle the planet, forming meridional pattern of ridges and troughs. o Surface winds: are those which flow below 1-2 kms altitude and thus are in contact with the Earth’s surface, unlike geostrophic winds They are formed, like all winds, by Pressure Gradient Force and affected by Coriolis Force, but unlike geostrophic winds are also affected by Friction Force with the ground o This yields a net effect such that when shown on a map, surface winds flow across the isobars o The effect of all these forces on wind patterns in relation to a High and Low pressure cell will thus be different Low pressure cells: have Cyclonic or counterclockwise flow/circulation in the NH (clockwise flow in the SH) High pressure cells: have Anticyclonic or clockwise flow/circulation in the NH (counterclockwise flow in the SH) o So remember all the aspects of how winds flow in relation to a High cell versus a Low cell: In a High Cell: winds sink and diverge (flow away) from it in a clockwise circulation (NH) In a Low Cell: winds rise and converge toward it in a counterclockwise circulation (NH) Wind Measurements: o Direction is measured by compass directions, north, south, east, west, NE, SW, etc. Winds: always named for the direction they are coming from o Speed is recorded by an anemometer in mph or kph or knots Calm = <1mph Moderate wind = 13-18 mph Gale = 39-46 mph Hurricane = >73 mph o Winds can viewed at 3 or 4 different scales: 1. Macroscale: Planetary: 1000 - 40,000 km Westerlies Synoptic: 100 – 5,000 km Hurricanes 2. Mesoscale: 1 - 100 km Thunderstorms 3. Microscale: <1 km Tornadoes & Dust Devils Types of Local Winds: o Land/Sea Breezes: often form along ocean coastal areas because of differential heating between the land and water surface, which forms a PGF between the two areas o A Sea Breeze: one which flows from the sea toward the land forms when an area of lower pressure forms over the land and an area of higher pressure forms over the water o A Land Breezes: one which flows from the land toward the sea and forms when an area of lower pressure forms over the water and an area of higher pressure forms over the land o Valley/Mountain Breezes: often form in mountainous regions when warm air flows up the mountain during the day and cool air flows down the mountain at night This pattern occurs on the same side of the mountain o Chinook wind: a warm, dry wind coming off (down) a mountain that started on the opposite side of the mountain o Known as the Santa Ana winds in Southern California o Katabatic wind: is a flow of dense cold air downslope under the influence of gravity in areas of large continental ice sheets such as Greenland and Antarctica Global Patterns; Pressure and Wind: o Air Pressure: Low Pressure Belts or Cells: areas of uplift and convergence at the surface and often produce unstable, severe weather Ex: Intertropical Convergence Zone (ITCZ), Subpolar Lows (SPL) High Pressure Belts or Cells: areas of subsidence and divergence at the surface and often produce stable, nice weather Ex: Subtropical High (STH), Polar High (PH) o Winds: Are dictated by; Pressure Gradient Force, Coriolis Force and Friction On a global scale a simplified 3-cell model can be identified, but the interaction of these cells and overall weather processes create a more complex system of winds For the Test: o Know the major pressure belts/cells: ITCZ STH SPL PHP Know whether the air is rising or sinking, converging or diverging for each of these o Know the major wind patterns: Northeast and Southeast Trade Winds Westerlies Easterlies Know at what latitudes they will be found and which direction they flow
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'