10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld Chapter 7 Water and Atmospheric Moisture I Water on Earth a Comes from the mantle and core geysers b 70 75 of the Earth is water i Southern Hemisphere is the water hemisphere ii Northern Hemisphere is the land hemisphere c Where we find water i Ocean Salt Water 97 28 Pacific Ocean holds the most ii Fresh Water 2 78 1 Surface 77 78 Ice and Glaciers 99 357 a b Lakes 0 33 c Atmosphere 0 03 out of all of the water on the planet only 0 001 is in the atmosphere even though that is the major way that energy and heat is transferred on Earth d Rivers and Streams 0 003 2 Sub Surface 22 22 a Groundwater 11 02 b Deep Groundwater 11 02 c Soil Moisture 0 18 II Unique Properties of Water a Polar Oxygen is electronegative so it makes the hydrogen end of the water molecule slightly positive while the oxygen side is slightly negative enables water to be the universal solvent b H bonds between molecules of water enable the liquid state of water to occur naturally and bring about adhesion water sticks to itself thus capillary action and surface tension c Three states of H2O Each time you move to a new phase there is an absorption or releasing of energy i Solid less dense than liquid water expands when freezes forms a hexagonal crystal ii Liquid connected by H bonds non compressible fluid takes on the shape of its d Phase Changes Each time you move to a new phase there is an absorption or releasing structure container iii Gas water vapor of energy 10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld III Humidity a Humidity the water vapor content of air b Measures of Humidity i Absolute Humidity mass of water vapor per volume of air 1 Hard to apply to atmosphere because the volume is not constant 2 Same mass of water vapor double the water volume half the absolute humidity ii Relative Humidity RH Actual Water Vapor X 100 Water Vapor Capacity at temperature 1 Changes with temperature even if the amount of water vapor doesn t change so not the best measurement but it does show how close the air is to saturation At room temperature it takes more calories to evaporate in nature things rarely occur at 100 C As air warms it is less dense so there is more space to pack water molecules 10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld 2 Maximum water holding capacity depends on temperature 3 Humidity Patterns of Relative Humidity a At the coldest points of the day there is the highest relative humidity while at the hottest points of the day there is the lowest relative humidity assuming that moisture level is constant throughout the day 10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld b This trend occurs all year long but there is overall seasonal variability coldest part of the year has the highest relative humidity and the warmest part of the year has the lowest relative humidity c Relative Humidity also varies with latitude highest relative humidity is in Antarctica because it is the coldest however relative humidity is almost as high in the tropics because lots of moisture Oceans and precipitation High Pressure Zones create dips in relative humidity because hot dry areas iii Specific Humidity mass of water vapor per total mass of air Not affected by changes in temperature or pressure 1 Latitudinal Variability 10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld c Saturation i Liquid water will evaporate into the atmosphere until it reaches saturation 1 Saturation is when the air contains the maximum amount of water vapor possible ii When the rate of evaporation the rate of condensation equilibrium is reached which is saturation and RH 100 iii Temperature at which air is saturated is called the dew point temperature happens in the morning IV Atmospheric Stability a Water vapor is in the atmosphere as clouds and fog b Stability is the tendency of an air parcel to remain in place and to NOT RISE in the atmosphere i Air Parcel is a body of air with homogeneous temperature and humidity characteristics low density air parcel will expand because less pressure as you move upward while a high density air parcel will be compressed because there is an increase in pressure as it sinks c Parcel is stable if it resists upward movement and or sinks back to its starting point Parcel is unstable if it rises and continues to rise freely on its own i To determine you need to know the temperature of the air parcel and of the surrounding air d Lapse Rates i Adiabatic warming or cooling rate of an air parcel assuming that temperature change occurs without a loss or gain of energy from the environment it is an internal process based on pressure ii Two rates at which air parcels can warm cool 1 Dry Adiabatic Lapse Rate DAR 10 C 1000m applies to ANY unsaturated air RH 100 2 Moist Adiabatic Lapse Rate MAR 6 C 1000m applies to ONLY saturated air RH 100 4 less than the DAR because saturated air can t hold any more moisture so condensation happens which gives off heat so cools off less 10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld iii Adiabatic Cooling unsaturated iv Adiabatic Heating unsaturated 10 9 15 10 12 15 10 14 15 and 10 16 15 Dr Frauenfeld 1 Temperature of the Parcel Tparcel always use either DAR or MAR 2 Temperature of surrounding environment Tenv always varies will be provided v Adiabatic Heating Cooling summary 1 Dry unsaturated Parcel a Rises and cools 10 C 1000 m b Sinks and warms 10 C 1000 m 2 Moist saturated Parcel a Rises and cools 6 C 1000 m b Sinks and warms 10 C 1000 m e Stability Guidelines i Need to Know ii iii Environmental Lapse Rate ELR If Tparcel Tenv 1 Parcel is cooler denser 2 Parcel does not rise 3 Means a stable atmosphere If Tparcel Tenv 1 Parcel is warmer less dense 2 Parcel rises and cools adiabatically 3 Means an unstable atmosphere f Three Scenarios i First Scenario If ELR 5 C 1000 m and the starting temperature of an unsaturated air parcel is 25 C then when the parcels moves up 1000 m the Tparcel 15 C Tenv 20 C Tparcel Tenv therefore the atmosphere is stable clear skies and stagnant air conditions If ELR MAR then the atmosphere will ALWAYS be stable ii Second Scenario If ELR 12 C 1000 m and the starting temperature of an unsaturated air parcel is 25 C then when the parcel moves up 1000m the Tparcel 15 C Tenv 13 C Tparcel Tenv therefore the atmosphere is unstable condensation formation of clouds and possible precipitation 10 …