chaper 4 w and c - Chapter 4 -The concentration of...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 4 -The concentration of invisible gas water vapor is normally less than a few percent of all the atmospheric molecules -It transforms into cloud droplets and ice crystals -humidity -the amount of water vapor in the air -more water vapor in the hot dry air in the Sahara Desert than in cold wet air in New England Circulation of Water in the Atmosphere -In the atmosphere there is an unending circulation of water -70% of the earth’s surface is water -the sun’s energy transforms enormous quantities of liquid water into water vapor in a process called evaporation -winds then transport the moist air to other regions where the water vapor changes back into a liquid forming clouds in a process called condensation -under certain conditions the liquid or solid cloud particles may grow in size and fall to the surface as precipitation -rain snow or hail -if the precipitation falls on a continent a great deal of the water returns to the ocean in a complex journey -This cycle of moving and transforming water molecules from liquid to vapor and back to liquid again is called the hydrologic water cycle -In the simplistic form of this cycle water molecules travel from ocean to atmosphere to land and then back to the ocean -A portion of falling rain evaporates back into the air before it reaches the ground -Some is interrupted by vegetation where it evaporates or drips to the ground long after a storm has ended -Once on the surface a portion of the water soaks into the ground by percolating downward through small openings in the soil and rock, forming groundwater that can be tapped by wells. -what doesn’t soak in collects in puddles of standing water or runs off into streams and rivers which find their way back to the ocean -even the underground water moves slowly and eventually surfaces, only to evaporate or be carried seaward by rivers -over land a considerable amount of vapor is added to the atmosphere through evaporation from the soil, lakes, and streams -even the plants give up moisture by a process called transpiration -hydrologic cycle is exceedingly efficient in circulating water in the atmosphere Evaporation, condensation, and saturation -the temperature of the water is a measure of the average speed of its molecules -at the surface, molecules with enough speed and traveling in the right direction would occasionally break away from the liquid surface and enter into the air above -molecules changing from the liquid state into the vapor state are evaporating -while some water molecules are leaving the liquid, others are returning. -those returning are condensing as they are changing from a vapor state to a liquid state -when the total number of molecules escaping from the liquid (evaporating) is balanced to the number returning (condensing) the air is said to be saturated with water vapor -the temperature of the water influences evaporation -warm water will evaporate more readily than cool water -when heated, the water molecules will speed up -at higher temperatures a greater fraction of the molecules have sufficient speed to break through the surface tension
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/10/2008 for the course ATM OCN 100 taught by Professor Martin during the Fall '08 term at University of Wisconsin Colleges Online.

Page1 / 8

chaper 4 w and c - Chapter 4 -The concentration of...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online