Weather and Climate Ch5

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1. hydrologic cycle
movement of water between Earth and the atmosphere
2. evaporation
the process whereby molecules break free of the liquid volume (opposite of condensation)
3. condensation
the process whereby water vapor molecules randomly collide with the water surface and bond with adjacent molecules. (opposite of evaporation)
4. saturation
saturation is the equilibrium resulting from the constant gains and losses of evaporation and condensation.
5. sublimation
the change of phase between ice and water vapor, without passing through the liquid phase (opposite of deposition)
6. deposition
the change of phase between water vapor and ice, without passing through the liquid phase (opposite of sublimation)
7. Humidity
the amount of water vapor in the air
8. vapor pressure
part of the total atmospheric pressure due to water vapor
9. saturation vapor pressure
Because there is a maximum amount of water vapor that can exist, there is a corresponding maximum amount of vapor pressure that can exist called saturation vapor pressure.
10. absolute humidity
the density of water vapor, expressed as the number of grams of water vapor contained in a cubic meter of air.
11. specific humidity
an index for representing atmospheric moisture
12. saturation specific humidity
Because there is a maximum amount of water vapor that can exist at a particular temperature, there is a corresponding maximum specific humidity.
13. mixing ratio
the measure of the mass of water vapor relative to the mass of the other gases of the atmosphere
14. saturation mixing ratio
the maximum possible mixing ratio
15. relative humidity (RH)
The amount of water vapor in the air to the maximum possible at the current temperature.
16. dew point temperature (dew point)
the temperature at which saturation occurs.
17. frost point
when the temperature at which saturation occurs is below 0 degrees C (32 degrees F), we refer to it as the frost point (as opposed to the dew point)
18. precipitation fog
a type of fog that develops when falling raindrops evaporate enough water vapor into the air to saturate it.
19. steam fog
fog that forms when cold air moves over a warmer water surface
20. homogeneous nucleation
[seldom if ever happens because heterogeneous nucleation happens instead] droplets form by the chance collision and bonding of water vapor molecules under supersaturated conditions.
21. hygroscopic
water-attracting
22. heterogeneous nucleation
[often happens] the formation of water droplets onto hygroscopic partices (condensation nuclei/certain aerosols)... these particles then dissolve into the water to form a solution.
23. condensation nuclei
the hygroscopic particles (certain water-attracting aerosols) on which water droplets form during the process of heterogeneous nucleation.
24. haze
aerosols in the atmosphere that are capable of attracting water at relative humidities below 90% and forming extremely small droplets... we observe these droplets as haze.
25. supercooled water
water having a temperature below the melting point of ice yet still existing in a liquid form (when saturation occurs between 0 degrees C and -4 degrees C the surplus water vapor condenses to form supercooled water)
26. ice nuclei
(rare in the atmosphere) just as the formation of liquid droplets require condensation nuclei, the formation of ice chrystals at temperatures near 0 degrees C require ice nuclei
27. sling psychrometer
measures humidity (simple and most widely used), consists of a pair of thermometers.
28. wet bulb/dry bulb thermometers
mounted to a pivoting device, are circulated through the air, measures humidity.
29. wet bulb depression
the difference between wet bulb and dry bulb temperatures depending on the moisture content of the air.
30. aspirated psychometers
use fans to circulate air around the psychometer (as opposed to being circulated)
31. hair hygrometer
human hair, expands and contracts on response to relative humidity.
32. hygrothermograph
continuous measure of humidity
33. heat index (apparent temperature)
expresses the effect of high humidity and high temperatures
34. diabatic process
(one of 2 air temperature changes) a process in which energy is added to or removed from a system [as opposed adiabatic process]
(one of 2 air temperature changes) a process in which temperature changes but no heat is added or removed from a substance [as opposed to diabatic process]
36. second law of thermodynamics
dictates that energy moves from regions of higher to lower temperatures.
37. dry adiabatic lapse rate (DALR)
the rate at which a rising parcel of unsaturated air cools
38. lifting condensation level (LCL)
the altitude at which condensation or deposition occurs when a parcel of air rises high enough to be cooled, lowering its temperature to the dew or frost point.
39. saturated adiabatic lapse rate (SALR)
the rate at which saturated air cools (saturated air cools at a slower rate than unsaturated air)
40. environmental lapse rate (ELR)
the vertical change in temperature through still air
41. Dew
liquid condensation on a surface
42. frost
ice chrystals on a surface (much like dew, only at temperatures below 0 degrees C)
43. frozen dew
dew forms at slightly above 0 degrees C, the lower temperatures come in a freeze that dew. (different from frost)