GEO 211 1st Edition Lecture 12 Outline of Last Lecture I Atmospheric Humidity A the hydrologic cycle a circulation mechanisms B Unique phases of water a ice to liquid b liquid to water vapor c water vapor to liquid d liquid to ice e ice to water vapor f water vapor to ice Outline of Current Lecture II Measuring Humidity A 3 types of humidity 1 Absolute humidity A H 2 Specific humidity S H and mixing ratio M R 3 Relative humidity R H B Absolute humidity C Specific humidity D Relative Humidity E Humidity instruments hygrometers 1 Hair hygrometer 2 Sling hygrometer measures R H and dew point Current Lecture II Measuring Humidity A 3 types of humidity 1 absolute humidity A H 2 specific humidity S H and mixing ratio M R These 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 3 relative humidity R H B Absolute humidity Mass of water vapor in a given volume of air mass volume Expressed as grams of water vapor per cubic meter of air g m 3 When volume increases absolute humidity decreases Not commonly used Absolute humidity mass of water vapor Volume of air C Specific humidity Mass of water vapor in a given mass of all the air including water vapor Specific humidity mass of water vapor Total mass of air weight over weight Mixing ratio mass of water vapor to a given mass of dry air excluding water vapor Mixing ratio mass of water vapor Mass of dry air Specific humidity and mixing ratio are both expressed as mass over mass o Grams of water vapor per kilogram of air g kg o S H and M R does not change when volume changes Fig 4 8 page 94 D Relative Humidity Ratio of actual amount of water vapor in the air compared to amount required for saturation Expressed as a percentage Relative humidity actual amount content X 100 water vapor capacity OR Relative humidity actual vapor pressure X 100 saturation vapor pressure Relative humidity changes two ways 1 by evaporation transpiration 2 by temperature changes in the air E Humidity instruments hygrometers 1 Hair hygrometer 2 Sling hygrometer measures R H and dew point Dew point temperature to which air has to be cooled to absorb When R H is 100 air is saturated Air is at its maximum capacity to absorb water vapor
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