Water in the Atmosphere Hydrological(Water) Cycle Hydrological Cycle vocabulary Evaporation: the process of converting a liquid to a gas Transpiration: process where plants absorb water through the roots and then give off water vapor through pores in their leaves Precipitation: any form of water that falls from a cloud to Earth’s surface(rain, snow, sleet, hail, glaze) Evapotranspiration: the rapid cycling of water vapor into the atmosphere by evaporation from Earth’s surface or by transpiration from plant leaves Hydrological Cycle vocabulary Sublimation: conversion of a solid directly to a gas without passing through the liquid state Infiltration: movement of surface water into rock or soil through cracks and pores Percolation: the movement and filtering of fluids through porous materials. H2O exists in atmosphere in all three states of matter… Solid: snow hail ice Liquid: rain and cloud droplets Gas: invisible H2O vapor H2O may change from one state to another: Melting: • from solid ice to liquid H2O Freezing: • liquid H2O to solid ice Evaporation: • from liquid H2O to H2O vapor Condensation: from H2O vapor to liquid H2O Sublimation: change from solid to H2O vapor Example: Dry ice Deposition: process of water vapor turning directly into a solid Frost on a window pane Phase Changes : Turn to page 505 and copy figure 2 into your notes. Quick Check: Use the chart you drew to assist you. 1. Is energy lost or gained when a gas changes into a solid? 2. What is the above process called? 3. Name the process that occurs when ice cream absorbs 334 joules of energy? 4. Give an example of sublimation. Atmospheric Moisture • Invisible in the form of water vapor gas (only what we can’t see) • Where does it come from? Insolation(energy from the sun) -- heats water *changing it into a gaseous state Warm air can hold much more water than cold air Water vapor enters the atmosphere from the evaporation of water from oceans, lakes, marshes and glaciers • Humidity: water vapor in the air • Described as a. Specific humidity b.relative humidity Relative Humidity (The measure we encounter daily) Measure of the amount of water vapor present in air relative to the maximum amount that the air can contain at a given temperature (%) – e.g. if relative humidity is 50%, then it contains 1/2 the amount of water vapor it could hold at a given temperature Relative humidity decreases as temperature increases Temp. Increase, ability to hold water increases Then RH Decreases Relative Humidity and Temperature Figure 4.7, p. 125 Relative humidity=specific humidity X 100 capacity (saturated) Psychrometer: instruments used to measure relative humidity • Works on principle that evaporation causes cooling • 2 thermometers…wetbulb and dry-bulb • Readings show how dry the air is Dew point: the temperature at which air is saturated with water vapor • Dew, clouds, and fog forms • If dew point is below freezing, frost will form Dew Point Temperature • As air is cooled it eventually becomes saturated (100% relative humidity) • the temperature of saturation is called the dew point temperature • If cooling continues, condensation begins and dew forms Clouds: simply high fogs, mist, or haze • Form when air above surface cools below dew point • Shape depends on air movement that forms it: -horizontal air movement = layers -vertical air movement = piles • Temperature above freezing – clouds drop water • Temperature below freezing – clouds drop snow crystals Three main cloud types: CIRRUS: - thin, feathery, made of ice crystals - form at high altitudes - seen when weather is fair, but can mean rain or snow STRATUS • Low sheets or layers; gray and smooth • Block out the sun • Associated with rain and drizzle CUMULUS • Piled in thick, puffy masses • Formed by vertically rising air currents • Usually mean fair weather Other cloud types: Cirrostratus Stratocumulus Cirrocumulus Altocumulus Nimbostratus Cumulonimbus: large cloud that produce LIGHTNING, THUNDER, HEAVY SHOWERS = Thunderstorms Precipitation: • Water that falls from the atmosphere to the earth • Occurs when cloud droplets grow into drops heavy enough to fall to Earth FORMS OF PRECIPITATION • Drizzle: fine drops, very close together, fall slowly ….less than 0.5mm diameter • Rain drops: larger, farther apart, fall faster… 0.5mm to 5mm diameter • Snow: falls in clumps of six-sided crystals • Sleet: pellets of ice tha fall to the ground when raindrops fall through freezing air • Hail: forms in cumulonimbus clouds- irregular balls or lumps made of layers of ice Acid precipitation: acid drops that fall to the ground - contain nitrate and sulfate particles that come from burning fuels, volcanoes and cars Rain gauge: instrument used to measure the amount of rainfall • Cloud seeding: method to cause an increase in precipitation Condensation nuclei: suspended particles that provide the necessary surfaces for cloud forming condensation.