Lecture 14: Chapter 7, Water and Atmospheric Moisture The Heat Properties of WaterFor water to change from one state to another (solid, liquid, or vapor), heat energy must be absorbed or liberated (released). A change from one state to another is called a phase change.To cause this, the amount of heat energy must be sufficient to affect the hydrogen bonds between molecules. The exchange between physical states of water provides more than 30% of the energy that powers the general circulation of the atmosphere, so, as shall be seen, it is an important part of weather and climate. The phase changes are:Melting: change from ice (solid) to water (liquid)Freezing: change from water (liquid) to ice (solid). Ice forms crystals, no two of which are alike.Condensation: change from vapor (gas) to water (liquid)Evaporation: change from water (liquid) to vapor (gas)Sublimation: direct change from ice (solid) to vapor (gas) or direct change from vapor to ice. Matching:1. Melting D2. Freezing C3. Condensation A4. Evaporation E5. Sublimation BA. change from vapor (gas) to water (liquid)B. direct change from ice (solid) to vapor (gas) or direct change from vapor (gas) to ice (solid).C. change from water (liquid) to ice (solid). D. change from ice (solid) to water (liquid)E. change from water (liquid) to vapor (gas)Energy involved in moving from one phase to another.To change from one phase to another, heat energy has be absorbed or released.Turn water to ice (freezing): lose 80 calories (that is, lose/release heat)Turn ice to water (melting): gain 80 calories (that is, gain heat)Turn water at 100 degrees to gas (vaporization/evaporation): gain 540 calories; to turn water at 0 degreesto gas: gain 640 calories (that is, gain heat)Turn gas to water (condensation): lose 540 calories (that is, lose/release heat)Turn ice to gas (sublimation): gain 720 calories (that is, gain heat).So heat energy is absorbed when?A. MeltingB. FreezingC. CondensationD. Evaporation Heat energy is released when?A. Melting B. FreezingC. CondensationD. EvaporationHumidity Humidity refers to water vapor in the airThe amount of water vapor air can hold depends mainly upon the temperature of the air. The warmer the air, the more water vapor it can hold. The cooler the air, the less it can hold.Relative humidity: the amount of water vapor that is in the air compared to the maximum amount of water the air is able to hold at a given temperature. Specific humidity: the actual mass of water vapor in the air at any specified temperature. Saturation: 100% humidity. The air is holding all the water vapor it possibly can at that given temperature. Any more water vapor added to the air – or any cooling of the air – will result in some of the water vapor condensing out. Dew Point: The _temperature at which a mass of air becomes saturated and condensation occurs forming water dropletsDaily patterns of relative humidity: Relative humidity is highest at dawn, when air temperatures are lowest. This is why we so often have morning dew. Relative humidity is lowest in the late afternoon when air temperatures are highest.Seasonal Patterns of relative humidity: Relative humidity is generally higher in the winter because the colder air cannot hold as much moisture.This is why warm tropical air over the ocean can hold so much water vapor, igniting the thunderstorms of the ITCZ. It also explains why cold air is “dry”. Cold air near the poles does not produce a lot of precipitation (it contains too little water vapor, even though it is near the dew-point temperature).Matching:1. Relative humidity D2. Specific humidity A3. Dew point B4. Saturation CA. The actual mass of water vapor in the air at any specified temperature.B. The temperature at which a mass of air becomes saturated and condensation occurs forming water droplets.C. 100% humidity. The air is holding all the water vapor it possibly can at that given temperature.D. The amount of water vapor that is in the air compared to the maximum amount of water the air isable to hold at a given temperature.Clouds and FogClouds Clouds are fundamental indicators of overall conditions, including stability and moisture content.They form as air becomes saturated with water. A cloud is a grouping of tiny moisture droplets and ice crystals that are suspended in air, great enough in volume and concentration to be visible.When pilots encounter turbulence what do they do? Slow down, change altitude, and avoid the redareas on the radar screensCloud formation process: Initially, clouds are a great mass of moisture droplets, each invisible without magnification. Moisture droplets are extremely small: it takes a million or more to form an average raindrop. As an air parcel rises it may cool to the dew-point temperature and 100% relative humidity. As it lifts and cools further, condensation of water vapor into water occurs and clouds formCondensation requires cloud-condensation nuclei: microscopic particles that are always present in the atmosphere.Dust, soot, ash from volcanoes and forest fires, sea salts, and particles from burned fuel typically provide the nuclei.The air over cities contains high quantities of nuclei. The air over oceans has sea salts from ocean sprays. Which are TRUE about clouds?A. They form out of thin air; condensation nuclei are not neededB. Clouds are made up of water vapor that has not yet condensedC. Clouds are made up of water droplets and ice crystalsD. Dust, soot, ash from volcanoes and forest fires, sea salts, and particles from burned fuel are all condensation nucleiiCloud Classification Altitude and shape are key to cloud classification.Basic shapes:Stratiform: flat and layered.Cumuliform: puffy and globularCirriform: wispy, high, and made of ice crystalsAltitude: Low Clouds Stratus: low gray clouds that are stratiform (flat and layered)Stratocumulus: low, soft gray globular clouds Nimbostratus: gray, dark, low clouds with drizzling rainAltitude: Middle Level clouds Altostratus: mid-altitude clouds that are thin to thick, with the sun’s outline just visibleAltocumulus: mid-altitude clouds that look like cotton balls or rippling waves , often arranged in lines. Altitude: High Clouds Cirrus clouds: high, wispy clouds with a feathery look that are often made up of ice crystalsCirrostratus: high altitude clouds that are like a veil_Cirrocumulus: high altitude clouds that are dappledVertically Developed:Cumulus: puffy