GEO 211 1st Edition Lecture 12 Outline of Last Lecture I. Atmospheric Humidity A. the hydrologic cyclea. circulation mechanismsB. Unique phases of watera. ice to liquid b. liquid to water vapor c. water vapor to liquidd. liquid to icee. ice to water vaporf. water vapor to iceOutline of Current Lecture II. Measuring HumidityA. 3 types of humidity1. Absolute humidity (A.H.)2. Specific humidity (S.H.) and mixing ratio (M.R.)3. Relative humidity (R.H.)B. Absolute humidityC. Specific humidityD. Relative Humidity E. Humidity instruments: hygrometers1. Hair hygrometer2. Sling hygrometer (measures R.H. and dew point)Current LectureII. Measuring HumidityA. 3 types of humidity1. 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 vaporVolume of airC. Specific humidity- Mass of water vapor in a given mass of all the air (including water vapor)- Specific humidity= mass of water vaporTotal 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 masso 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/transpiration2. by temperature changes in the airE. Humidity instruments: hygrometers1. Hair hygrometer2. 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
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