Chapter Four - Test Two Flashcards
Movement of Water Vapor through the Atmosphere
What cycle?
The Hydrologic Cycle (Fig 4.2)
The Hydrologic Cycle (Fig 4.2)
- Annually 3.80 x 105 km3 of water evaporates/precipitates
- Enough to cover the entire globe with roughly 1 meter of rain
- ____ times more water is carried by the atmosphere over North America than by all the rivers on the continent!
Six
Water’s Changes of States
Water (H2O) is unique in that it is the only substance that can exists in all three phases (states) in the atmosphere
Keep in mind that the substance isn’t changing, only the distance between the molecules and the way in which they interact
Ice, Liquid Water and Water Vapor (Fig 4.3)
Solid (Ice):
the molecules, lacking Kinetic Energy, are locked into a six-sided (hexagonal) crystal lattice, unable to move.
Liquid (Water):
the molecules, having more Kinetic Energy, are now able to slide by one another, but are still in constant contact.
Gas (Water vapor):
the molecules now have enough Kinetic Energy to break all bonds and move about freely as individual molecules.
Whenever water changes state, it either releases or consumes energy
A process called Latent Heat Transfer (Fig. 4.3)
Going from a high energy state to a low energy state ____ energy
releases
-thereby: Warming the atmosphere.
gas→→→____→→→liquid→→→____→→→solid
gas→→→→→→→→→→→____→→→→→→→→→→solid
Condensation; Freezing; Deposition
Going from a low energy state to a high energy state ____ energy
consumes
- thereby: cooling the atmosphere.
There are numerous ways to express the water vapor content of the atmosphere (Fig. 4.6), which as seen earlier comprises between ___% and ____% of its volume;
0.1; 4
Four ways to express the water vapor content of the atmosphere:
- Mixing Ration (MR) [g/kg]
- Relative Humidity (RH) [%]
- Dewpoint Temperature (T d) [F, C]
- Wetbulb Temperature (T w) [F, C]
Mixing Ratio (MR)
The ratio of mass of water vapor in a unit mass of dry air, expressed as:
Grams of water vapor (g) / 1 kilogram of dry air (1 kg or g 1kg -1)
- Values range from:
20 g/kg in tropical regions
While the Mixing Ratio tells us how much water vapor is ____ ____ ____, its also important to know how much water vapor could be in the air, or stated differently, how much is water vapor is necessary to saturate the air
in the air
The amt. of water vapor necessary to saturate 1 kg of air is called the:
Saturation Mixing Ratio (MRs)
Saturation Mixing Ratio (MRs)
This amount is solely dependent upon the air’s temperature, therefore, if you know the air’s T, you know its MRs. This association is provide in both Fig 4.9 and Table 4.1
- Rule of thumb: for every 10ºC increase in T, the amount of water vapor needed to saturate the air (MRs) roughly doubles
The _____ of the air’s actual water-vapor content (MR) compared with the amount of water vapor required for saturation (MRs) which as we just saw depends on the T
ratio
Relative Humidity [RH] MR subscript =
= Water vapor content / Water vapor Capacity
= (MR / MRs) X 100%
Ex: Given: T = 25ºC; MR = 10g/kg
From Table. 4.1 We know that MRs = 20.0 g/kg
Therefore RH = 0.50 X 100% =- 50%
The RH is the most familiar and widely used measure by the public,however its also the most misunderstood, because:
RH tells us how close the air is to being saturated, not how much water vapor is in the air!
When the RH reaches 100%,(i.e. when MR = MRs) the air is ____.
saturated
RH is based on the air’s ____ content, as well its ____
water vapor; temperature
