Chapter 4 Atmospheric Humidity Flashcards
what is a molecule?
a group of 2+ atoms held together by mutually shared electrons
what are covalent bonds?
bond between two hydrogen (H) and one oxygen (O) atoms, strong bonds
what is a dipolar molecule?
one side is + charge, one side is - charge
what is a hydrogen bond?
the attraction between individual H2O molecules, strong:
-high water surface tension
-high solubility of chemical compounds in water
-unusual thermal properties of water
-unusual density of water
how would you describe the speed of the Ice and Water Vapor phases?
ice is the coolest/slowest phase
water vapor is the warmest/fastest phase
what is humidity?
the amount of water vapor in the air
what is evaporation?
-liquid→gas
-↑evaporation=↑ H2O vapor in atmosphere
-requires heat
what is condensation?
-gas→liquid
-↑condensation=↓ H2O vapor in atmosphere
-releases heat
-occurs on condensation nuclei
molecules move fast in warm air and can’t stick to condensation nuclei, move slower in cold air (near clouds) and turn from liquid to gas
what is saturation?
an equilibrium condition in which for each molecule that evaporates, one condenses
-air is holding all the water vapor that it can
-clouds=saturated
-the higher the temperature, the more water vapor air can hold
what factors can affect evaporation rates?
-wind increases evaporation
-warmer water increases evaporation
what is absolute humidity?
mass of water vapor/volume of air (g/m3)
-“water vapor density”
-doesn’t work if change in altitude, not commonly used
what is specific humidity?
mass of water vapor/total mass of air (g/kg)
what is mixing ratio?
mass of water vapor/mass of dry air (g/kg)
Saturation mixing ratio: the mixing ratio of a saturated air parcel (changes with temp)
what is vapor pressure?
atmospheric pressure exerted by water vapor
-more water molecules=higher vapor pressure
saturation vapor pressure: max potential vapor pressure
-vapor pressure and saturation vapor pressure equal each other when air is saturated
what is relative humidity?
vapor pressure/saturation vapor pressure x100%
-if water vapor is constant, as T↑ RH↓, as T↓ RH↑
-when air is saturated RH=100%
