Water in the Atmosphere 18 CHAPTER Water in the Atmosphere EXIT CHAPTER 18.1 Humidity and Condensation 18.2 Clouds 18.3 Precipitation CHAPTER OUTLINE

18.1 Humidity and Condensation CHAPTER Water in the Atmosphere CHAPTER HOME 18.1 Humidity and Condensation VOCABULARY Water exists in the atmosphere as a solid, a liquid, and a gas. water vapor condensation DEPOSITION (Heat released) FREEZING CONDENSATION MELTING EVAPORATION LIQUID WATER (clouds, rain, dew) ICE (snow, hail, frost) WATER VAPOR (invisible) SUBLIMATION (Heat absorbed) Heat released Heat absorbed specific humidity saturated relative humidity dew point condensation nuclei Evaporating water absorbs heat from the surroundings, which become cooler. Condensing water releases heat to the surroundings. SECTION OUTLINE

18.1 Humidity and Condensation CHAPTER Water in the Atmosphere CHAPTER HOME 18.1 Humidity and Condensation VOCABULARY Humidity is the measure of water vapor in the air. Warmer air can contain more water vapor, while cooler air can contain less. water vapor condensation specific humidity saturated Fog and clouds form when air is cooled to its dew point and water in the air condenses on condensation nuclei. Dew or frost forms if air cools to the dew point upon contact with cold ground and the water vapor condenses directly on the ground. relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere water vapor CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor condensation water vapor specific humidity An invisible gas formed when water reaches 100°C or above and evaporates. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere condensation CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor condensation condensation specific humidity The change from water vapor to liquid water. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere specific humidity CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor condensation specific humidity specific humidity The amount of water vapor in the air at a given time and place; expressed as the number of grams of water vapor per kilogram of air. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere saturated CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor water vapor condensation saturated specific humidity The condition in which the air is holding as much water vapor as possible at a given temperature and pressure. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere relative humidity CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor condensation relative humidity specific humidity A comparison of the actual amount of water vapor in the air with the maximum amount of water vapor that can be present in air at a given temperature and pressure. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere dew point CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor water vapor condensation dew point specific humidity The temperature at which saturation occurs and condensation begins; a measure of the amount of water vapor in the air. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 Water in the Atmosphere condensation nuclei CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY water vapor condensation condensation nuclei specific humidity Microscopic particles on which water vapor condenses to form cloud droplets. saturated relative humidity dew point condensation nuclei SECTION OUTLINE

18 18.2 Clouds Water in the Atmosphere CHAPTER Water in the Atmosphere CHAPTER HOME 18.2 Clouds VOCABULARY Clouds are classified by their height above ground and their shape. The main types of clouds are stratus (layered, low clouds), cumulus (fluffy clouds with flat bases), and cirrus (high, feathery ice clouds). stratus cumulus cirrus condensation level dry-adiabatic lapse rate Cirrus Stratus Cumulus Cumulonimbus moist-adiabatic lapse rate Cumuliform clouds are formed by rising air, and stratiform clouds form in horizontal layers. SECTION OUTLINE

18 18.2 Clouds Water in the Atmosphere CHAPTER Water in the Atmosphere CHAPTER HOME 18.2 Clouds VOCABULARY Rising air cools at the dry-adiabatic lapse rate with no condensation, and at the moist-adiabatic lapse rate with condensation. stratus cumulus cirrus condensation level Heat released through condensation within a cloud can cause air within the cloud to rise to great heights. dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE click here to enlarge

18 Water in the Atmosphere stratus CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY stratus cumulus stratus cirrus Clouds that form in low, horizontal layers. condensation level dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE

18 Water in the Atmosphere cumulus CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY stratus cumulus cumulus cirrus Thick, fluffy clouds with flat bases, formed by vertically rising air currents. condensation level dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE

18 Water in the Atmosphere cirrus CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY stratus cumulus cirrus cirrus High-altitude clouds that are thin, feathery tufts of ice crystals. condensation level dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE

18 Water in the Atmosphere condensation level CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY stratus stratus cumulus condensation level cirrus The altitude at which water vapor begins to condense. condensation level dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE

dry-adiabatic lapse rate 18 CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY stratus cumulus dry-adiabatic lapse rate cirrus The rate at which unsaturated air cools as it rises, about 10°C for every kilometer. condensation level dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE

moist-adiabatic lapse rate 18 CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY stratus cumulus moist-adiabatic lapse rate cirrus The rate at which saturated air cools as it rises; varies from about 5°C per kilometer to about 9°C per kilometer. condensation level dry-adiabatic lapse rate moist-adiabatic lapse rate SECTION OUTLINE

18 18.3 Precipitation Water in the Atmosphere CHAPTER Water in the Atmosphere CHAPTER HOME 18.3 Precipitation VOCABULARY Water droplets in clouds grow by colliding with each other. precipitation sleet Growth of a Raindrop freezing rain hail Ice crystals grow from collisions and by using water vapor that evaporated from super-cooled drops. The forms of precipitation include drizzle, rain, sleet, snow, freezing rain, and hail. SECTION OUTLINE

18 18.3 Precipitation Water in the Atmosphere CHAPTER Water in the Atmosphere CHAPTER HOME 18.3 Precipitation VOCABULARY Precipitation’s type depends on the conditions as it forms and falls. Precipitation falls in regions where moist air tends to rise, producing condensation. precipitation sleet freezing rain Less than 25 25 to 50 100 to 250 50 to 100 More than 250 Mean Annual Precipitation (cm) hail Cold air sinks near the North Pole. This area is dry. Cold air sinks near the South Pole. This area is dry. Air near the equator rises. Equatorial areas are usually wet. The windward side of the Andes Mountains are wet. The leeward side of the Andes Mountains are dry. SECTION OUTLINE

18 Water in the Atmosphere precipitation CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY precipitation sleet precipitation freezing rain Any form of water that falls from a cloud to Earth’s surface, such as rain, snow, sleet, and hail. hail SECTION OUTLINE

18 Water in the Atmosphere sleet CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY precipitation precipitation sleet sleet freezing rain Clear ice particles formed when raindrops freeze before they reach the ground. hail SECTION OUTLINE

18 Water in the Atmosphere freezing rain CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY precipitation sleet freezing rain freezing rain Supercooled raindrops that freeze instantly when they hit a solid surface. hail SECTION OUTLINE

18 Water in the Atmosphere hail CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY precipitation sleet hail freezing rain Small, nearly spherical pieces of ice made up of concentric layers formed by the successive freezing of layers of water. hail SECTION OUTLINE

I. Humidity and Condensation 18 CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY I. Humidity and Condensation water vapor A. Characteristics of Water condensation B. Humidity specific humidity 1. Relative Humidity saturated 2. Measuring Humidity relative humidity C. Condensation dew point 1. Cooling and Condensation condensation nuclei 2. Formation of Dew and Frost 3. Formation of Fog KEY IDEA SUMMARY

18 Water in the Atmosphere II. Clouds A. Types of Clouds CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY II. Clouds stratus A. Types of Clouds cumulus B. Cloud Formation cirrus 1. Dry- and Moist-Adiabatic Lapse Rate condensation level 2. Cumulonimbus Clouds dry-adiabatic lapse rate 3. Layer Clouds moist-adiabatic lapse rate 4. Predicting the Lifting Condensation Level KEY IDEA SUMMARY

18 Water in the Atmosphere III. Precipitation CHAPTER Water in the Atmosphere CHAPTER HOME VOCABULARY III. Precipitation precipitation A. How Precipitation Forms sleet 1. Growth of Water Droplets freezing rain 2. Growth of Ice Crystals hail 3. Kinds of Precipitation B. Measuring Precipitation C. Where Does Precipitation Occur? D. Weather Modification KEY IDEA SUMMARY

Cumulonimbus Cloud Formation EXIT 32°C 24°C 16°C 8°C 0°C –8°C –15°C –20°C –25°C –30°C –35°C 0 km 1 km 2 km 3 km 4 km 5 km 6 km 7 km 8 km 9 km 10 km STABLE AIR UNSTABLE AIR 35°C 25°C 20°C 15°C 9°C 2°C –5°C –13°C –21°C Dry-adiabatic lapse rate: 10°C/km Moist-adiabatic lapse rate: 5°C/km Moist-adiabatic lapse rate: 9°C/km 3. When the temperature and density inside the cloud are the same as the temperature and density outside the could, the air spreads to the side. 2. Although the air cools as it rises, it stays warmer and less dense than the air outside the cloud, so it continues to rise. 1. Warm air rises and water vapor condenses to begin forming clouds.

18 Water in the Atmosphere CHAPTER Water in the Atmosphere CHAPTER HOME This is the end of the chapter presentation of lecture notes. Click the CHAPTER HOME button or exit the presentation.