ITService-G107PhysicalGeography

1、G107 Physical GeographyDraft draft draft draft draffffffffffffttttSection II Power Point Slides1Draft Prepared by Isiorho May 29, 2001Winds and Global CirculationWind is air in motionResults from difference in pressure between two areasPressure is force acting on an areaStandard Pressure Standard ba

2、rometric pressure (SBP) is pressure at mean sea levelPressure Scales (numbers at mean sea level)Inches of mercury (29.92 in)Centimeters (76 cm)Millibars 91013 mb) 2Draft Prepared by Isiorho May 29, 2001WindsPressure Gradient Force mass movement of airHigh temp results in low pressure & low temp resu

3、lts in high pressurePressure gradient, Friction, Gravity and Coriolis effect affect wind speed and directionCoriolis effect is due to earths rotation & it is the deflection of wind to the right in the northern hemisphere or to the left in the southern hemisphere (imagine yourself going in the same d

4、irection as the wind) 3Draft Prepared by Isiorho May 29, 2001Circular Moving AirCyclone is the circular moving air mass around a low pressure centerAnticyclone is a circular moving air around a high pressure centerNote the pattern of cyclone/anticyclone in both the northern and southern hemispheres4

5、Draft Prepared by Isiorho May 29, 2001Circular Moving AirNote the pattern of cyclone/anticyclone in both the northern and southern hemispheres5Draft Prepared by Isiorho May 29, 2001Circular Moving AirNote the convergent and divergent winds6Draft Prepared by Isiorho May 29, 2001Circular moving air in

6、 Ft. WaynePhotos my Burnet7Draft Prepared by Isiorho May 29, 2001Tornado Pictures from Ft. Wayne8Draft Prepared by Isiorho May 29, 2001Global Air PatternLow and High pressure areas of the world (linked to solar radiation/temperature)Pressure zones include low equatorial zone and midlatitude high pre

7、ssure zoneThe NE Trades and SE Trades air moves toward the equator from the north and south respectivelyWhere the two trade winds collide, the area is called Intertropical Convergence Zone (ITCZ) and when they do not collide violently, the are is called Doldrum9Draft Prepared by Isiorho May 29, 2001

8、Global Air Pattern Contd.Global wind pattern10Draft Prepared by Isiorho May 29, 2001Local WindsLand & Sea breezesHeating of the land and seaMountain and Valley WindsDrainage winds (e.g. Chinook, Bora, Taku, Foehn, Mistral, & Santa Ana)Winds Aloft- winds at high altitudeGeostrophic winds (Jet stream

9、& Rosby waves)- winds flow parallel to isobars 11Draft Prepared by Isiorho May 29, 2001Ocean CurrentsCurrents- form when wind moves over water surface in a given direction. frictional forceOcean current could be warm or coldSome ocean currents areAlaska, Agulhas, Antartic circumpacific current, Beng

10、uela, Brazi, California, Canaries, Falkland, Guinea, Gulf Stream, Kuroshio (Japan), Labrador, North Atlantic drift, N. Equatorial, Oyashio (China), Pacific, Peru, S. Equatorial, and West Wind Drift.Circular moving ocean currents are called GYRES12Draft Prepared by Isiorho May 29, 2001Atmospheric Moi

11、sture and precipitationHumidity amount of water vapor in the airHumidity can be measured three different waysAbsolute Humiditymass of water vapor in a given volume of airSpecific humidity the mass of water vapor in a given mass of airRelative humidity ratio of water vapor present in the air compared

12、 to the amount of water vapor that will be present when the air is saturated at the given temperatureConcept of saturation point13Draft Prepared by Isiorho May 29, 2001When air becomes SaturatedAir can become saturated either with addition of water or cooling of the air.When air cools such that it b

13、ecomes saturated, the temperature at which it becomes saturated is called the DEW POINT.Cloud is the first physical evidence that the air is saturated14Draft Prepared by Isiorho May 29, 2001CloudsSeveral cloud types but they all begin as cirrus (high altitude clouds that are feather like), stratus (

14、form layers), or cumulus (cotton bulb-like or cauliflower like)Clouds are classified based on elevationsHigh 7.6 km e.g. Cirrus, cirrostratus, cirro cumulusIntermediate (middle) 2-7.6 km (stratus, stratocumulusLow 0.2 km.Cumulus, cumulonimbusNimbus or Nimbo are prefix or suffix in cloud terminology

15、that indicate precipitation15Draft Prepared by Isiorho May 29, 2001Clouds16Draft Prepared by Isiorho May 29, 2001Classification of Clouds17Draft Prepared by Isiorho May 29, 2001Precipitation formsDrizzleRainSnowHailSleet18Draft Prepared by Isiorho May 29, 2001Classification of PrecipitationOrographi

16、c- rain shadow effectBest found near the west coast effective side is east of the west coast mountainsConvectional PrecipitationCyclonic/Frontal SystemsConvergent19Draft Prepared by Isiorho May 29, 2001Weather systemsAir mass- covers large area with similar temperature, pressure and moistureAir Mass

17、 properties depend on a) source region and b) region over which the wind passesThe area over which an air mass forms is called the Source Region20Draft Prepared by Isiorho May 29, 2001Types of Air MassesClassified is based on latitudinal position and underlying surface (water or land)Artic (A) mA (m

18、aritime) & cA (continental)Antarctic (AA) mAA & cAAPolar (P) mP & cPTropical (T)mT & cPEquatorial (E) mE & cE21Draft Prepared by Isiorho May 29, 2001FrontsWhen air masses move, the leading edge is called a FRONTThere are four types of frontsWarmColdStationaryOccluded22Draft Prepared by Isiorho May 2

19、9, 2001Traveling CyclonesWave cyclone (midlatitude and Artic regions)Tropical (Hurricanes & Typhoons)Tornado (small storm related to sever convectional activity)Why do most storms occur in Spring and Summer?23Draft Prepared by Isiorho May 29, 2001Weather and ClimateWeather involves the every day wea

20、ther related activitiesElements of weather include temperature, cloud types, cloud cover, wind, wind direction, fog, precipitation, sunshine, etc.Climate is the average weather condition of a given locationTakes into account the extreme weather conditions also.24Draft Prepared by Isiorho May 29, 2001Physical components of climateRadiationSensible heatBarometric pressureWindsRelative and Specific HumidityDew PointCloud cover and typeFogPrecipitation type and intensityEvaporation and TranspirationCyclones