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OU GEOG 1114 - Continuation of Pressure and Atmospheric Motion
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GEOG 1114 1st Edition Lecture 11Outline of Last Lecture -Characteristics of Pressure -Agents of Atmospheric Motion -Patterns/Speed of Surface Winds-General circulation of the Atmosphere Outline of Current Lecture -Continuation of Pressure and Atmospheric motion - Atmospheric Moisture -Transfer of Water to the Atmosphere -Measuring moisture in the Atmosphere Current Lecture Seven Surface Components of the General Circulation ModelSubtropical Highs Persistent zones of high-pressure 30-degree latitude in both hemispheres Trade Winds- Diverge from subtropical highs -Exist between 25 degrees N and 25 degrees S latitude-Easterly winds: southeasterly in Southern Hemisphere, northeasterly in Northern Hemisphere -Most reliable windsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-“Winds of Commerce -Heavily laden with Moisture -Do not produce rain unless forced to rise-If they rise they produce tremendous precipitation and storm conditions Hadley Cell -Convection cell -Vertical movement of wind from low at the equator to subtropical high -Trade complete the cell Intertropical Convergence Zone (ITZ): Semi permanent band of low pressure. Rising air: Region of convergence of the trade winds-Low pressure Belt near the equator -Constant rising motion and storminess in this region-Position seasonally shifts (more over land than water)-Doldrums *You get a polar front where easterlies and westerlies meet. Westerlies- (coming out of the west)-Wind system of the midlatitudes -Form on pole ward sides of subtropical highs -Two cores of high winds aloft Polar Front Jet StreamSubtropical Jet StreamRosby Waves path takes N/S direction- take a dip then it becomes a Rosby wave –brings cold air downPolar Highs- High pressure cells that develop over the poles build up very cold temperatures produce a thermal high Polar EasterliesSubpolar Lows -Low-pressure area between polar high and westerlies-Air masses conflict between warm westerlies and cold polar easterlies -Rising motion and precipitation -Contains polar frontModifications of the General Atmospheric Model:Latitudinal Shift with Seasons-Seven general circulation components shift seasonally -Components shift during Northern Hemisphere summer-Components shift southward during Southern Hemisphere summer Monsoons Seasonal wind shift-Winds onshore during summer-Winds offshore during winter-Develop due to shifts in the position of the ITCZ Local Winds (Continentally)Atmospheric MoistureHydrologic Cycle:1. Water enters atmosphere through evaporation of water from oceans and evapotranspiration from continents2. Transported as water vapor through the atmosphere by prevailing winds where it condenses into clouds 3. Then, when energy and moisture conditions are tight it falls to the earth surface by precipitation4.Overland stream flow from continents completes this cycle Transfer of water to the AtmosphereEvaporation1. Transformation of water from a liquid to a gas.2. Rates of Evaporation are a function of:-Amount of water already in atmosphere -Air temperature warm masses hold more moisture because as air temperatures rise, the heightened molecular activity of warmer air fosters higher vaporization -Water temperatures warmer water has more agitated molecular activity and heightens waters ability to vaporize -Winds: stirs up saturated zone, dispersing water vapor, allowing for more evaporation to take place - Cloudiness: decreased rate; absorb EMR required for evaporation 3. Limits to Evaporation: Vapor PressureThe pressure exerted by water vapor in the airWhen there are enough water vapor molecules in air to exert max vapor pressure at any given temp, the air is saturated.Evapotranspiration: The transformation of water from a liquid to a gas by the combined processes of:1. Evaporation of water from the continents soil 2. Transpiration of water form plant leaves The Process: Plants absorb water form the soil through their rootsPhotosynthesis CO2 + H2O » Carbohydrates + O2-Excess water taken in is released or transpired through plant leaves -Rates higher during sunlight hours Measuring Moisture in the Atmosphere-The moisture held in the atmosphere in the form of water vapor is referred to as humidity and measured in the following ways:Absolute Humidity: Amount of water vapor in a given volume of airExpressed in grams of vapor per cubic meter of air As volume of air changes so does humidity Affected by temperature: warm air capable of higher absolute humidity Direct indication of potential precipitation Specific Humidity: Mass of water vapor in a given mass of air Expressed in grams of vapor per kilogram of air Changes only as quantity of water vapor changes; not affected by volumeUseful in studying air masses Relative Humidity: Ratio between the water vapor in the air and the amount the air could hold if it were saturated.Expressed as a percentage Relative humidity = water vapor/capacity Example: if a parcel of air at 40 degrees C has a relative humidity of 50% it has 50% of the moisture it could hold if it were saturated A change in temperature will bring about a change in relative humidity Dew Point: The temperature at which saturation occurs (100% humidity) and condensation begins.Sensible Temperature: Temperature sensed by a person’s body-The temperature at which saturation occurs (100 humidity) and condensation begins - Varies with the moisture content of air -High Dew point indicate high moisture content in the


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OU GEOG 1114 - Continuation of Pressure and Atmospheric Motion

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