| A | B |
|---|
| El Nino Southern Oscillation | Reversal of normal water flow in the Pacific; occurs every 3-8 years; underlying cause unknown |
| surface tension | water molecules hold together |
| capillary action | upward movement of water through soil and plants |
| maximum humidity | Max amount of water vapor a body of air can hold; warmer air holds more water vapor |
| specific humidity | Measurable amount of water vapor in a mass of air (grams water vapor/kg air) |
| relative humidity | Ratio of specific to maximum humidity; how close air is saturated; RH (%) = (SH/MH) x 100 |
| saturation | air with max amt of water vapor is saturated; can hold no more |
| dew point temperature | not really a temperature; IS a measure of moisture content; when air temp trie to decrease below the dew point, surplus water vapor is removed from the air by condensation |
| Evapotranspiration | combination of evaporation and transpiration; depends on net radiation (higher in sunshine), air temp (higher in warm temps), and RH (higher in lower humidity |
| adiabatic processes | rising air expands due to reduced pressure, thus rising air cools; falling air compresses due to greater pressure, thus, falling air warms |
| condensation level | the height at which the relative humidity (RH) of an air parcel will reach 100% when it is cooled by dry adiabatic lifting |
| condensation nuclei | a small particle (as of dust) upon which water vapor condenses in the atmosphere |
| freezing rain | rain that freezes on impact with ground |
| hail | ice crystals that are repeatedly drawn up into a violent thunderstorm, growing each time |
| sleet | rain that freezes before hitting ground |
| snow | ice crystals that do not melt before they hit ground |
| clouds | visible masses of suspended, minute water droplets or ice crystals |
| fog | forms when surface air is saturated |
| radiation fog | cool or cold air is trapped at the surface; temperature inversion, in deep valleys or over snowy/ice surfaces |
| advection fog | warm air flows over a cooler surface-air cools to saturation |
| sea fog | cool marine air contacts colder ocean water; California coast |
| rainshadow | a region having little rainfall because it is sheltered from prevailing rain-bearing winds by a range of hills |
| windward | facing the wind or on the side facing the wind; in front of the mountain |
| leeward | on or toward the side sheltered from the wind or toward which the wind is blowing; in back of the mountain |
| Environmental lapse rate | decrease in temperature that generally occurs with respect to altitude in the troposphere; 6.4 C per kilometer or 3.5 degree F per 1000 ft |
| Dry Adiabatic Lapse Rate | Rate at which an unsaturated body of air cools while lifting or warms while descending; 5.5 deg. F per 1000 ft |
| Wet Adiabatic Lapse Rate | Rate at which a saturated body of air cools as it lifts; 2.7 deg F per 1000 ft. |
| Stable Atmosphere (Air) | Upper troposphere warmer; Low ELR; 2.7 degrees F/1000 ft; hinders strong convection; wet adiabatic lapse rate |
| Unstable Atmosphere | Cold upper troposphere; easy to get precip to storage; High ELR (>5.5 degrees F/1000 ft; Drives strong convection; worst case: tornado, hail, thunderstorm |
| mP air mass | maritime Polar; moist (humid) and cold; Washington/Oregon |
| cP air mass | continental Polar; dry and cold; |
| cT air mass | continental Tropical; dry and warm |
| mT air mass | maritime Tropical; more humidity and precipitation and warm |
