lec 12

Question 1

how much of the atmos is water

Answer 1

0-4%. its highly variable due to its low retention time
this percent encompasses both vapour, clouds and free molecules

Question 2

what are the different categories of humidity?

Answer 2

vapor pressure
abs humidity
mixing ratio
relative humidity

Question 3

what is total atoms pressure?

Answer 3

the weight of all gas molecules pushing down (from all layers)

Question 4

partial pressure

Answer 4

what fraction of total presure is imparted by a specific compound. we can calc but not measure directly

Question 5

what is humidity and how is it measured

Answer 5

the measurement of water vapor in the air. measured via a hygrometer. is uses a substance with a known ‘reaction’ to the amount of vapor in an air parcel (it will expand or contract)

Question 6

what happens when water vapour is added to a system

Answer 6

generally will result in the expansion of the substance in the hygrometer

Question 7

what is saturation

Answer 7

the condition where an air parcel obtains the max amount of water at a certain temp

Question 8

evaporation dynamics at temps

Answer 8

at warmer temps = more water will evap
at cooler temps more water will condense

Question 9

how does saturation vapor pressure change with temp (over water)

Answer 9

warmer air has the capacity to hold more water than cold water

Question 10

what is super cooling

Answer 10

at very low temps condensation can occur without water solidifying. this is why we can observe saturation at temps below 0.

Question 11

how does saturation vapor pressure change with temp (over ice)

Answer 11

it will follow the same trend as over water (higher capacity at warmer temps), though overall saturation will be LOWER as fewer water molecules are able to effectively escape via sublimation.

Question 12

sublimation

Answer 12

the transition from a solid to a gas without passing through a liquid medium

Question 13

what controls net evap rate

Answer 13

vapor pressure deficit dictated by region (is there space for vapor)
the availability of water governed by transpiration
turbulence (mixing of air via convection or mechanical mixing)
total energy available to promote phase change

Question 14

what is the equaition for total energy?

Answer 14

Q*= QH + QE + QG
QH= sensible heat
QE= latents heat
QG= ground conduction

total energy= (Kincoming-Koutgoing)+(Lincoming-Loutgoing)

Question 15

what is evap

Answer 15

water moles turning into water vapour at the surface of a water body (any temp)

Question 16

what is boiling

Answer 16

evaporation occuring through an entire volume of valter at a specific temp (100)

Question 17

what is the boiling point temp

Answer 17

when the saturation vapor pressure is equal to the atmospheric pressure
at lower pressure the boiling point decreases

Question 18

what is absolute humidity?

Answer 18

it is that mass of water vapor contained in a volume of air
measure in kg/m^3

Question 19

vapour pressure

Answer 19

the partial pressure exerted by vapor in the atmos

Question 20

humidity mixing ratio

Answer 20

the mass of vapour to the mass of dry air
g/kg

Question 21

max humidity

Answer 21

the maximum mount of water vapour an air parcel can hold at a given temp

Question 22

specific humidity

Answer 22

the mass of vapor in an air parcel at a given time, commonly less than the capacity.
g of vapor/kg of dry air

Question 23

relative humidity

Answer 23

the ratio of specific over the max hum, measuring how close an air parcel is to saturation.

Question 24

how does relative humidity change

Answer 24

1) when the vapor pressure changes
2) when the temperature of the air parcel changes

at lower temps the max capacity is lower (particles become closer together and less room as available for vapor) and vice versa. this way the specific hum is commonly higher at night, even with the same amount fo water present

more vapor in the air at the same temp means more of the open space in the parcel is occupied. this will increase the ratio, moving it closer to sat

Question 25

dew temp

Answer 25

the temperature where a parcel of air will become saturated. this involves the specific hum or measured vapor pressure.

Question 26

what is meant by a high dew point

Answer 26

it means there is a greater amount of moisture in the air, TF the air will need to cool substantially for saturation to occur. with the high amount of vapour, heat is retained better (water is a GHG).

Question 27

vapor pressure deficit

Answer 27

the diff between the saturation vapor pressure and the measure vapor pressure

Question 28

dew point depression

Answer 28

the difference between the air temp and the dew point temp

Question 29

how is realtive humidity measured?

Answer 29

psychometry.

Question 30

what is psychometry

Answer 30

a device that uses a wet and dry bulb to measure relative humidity. In unsaturated air, after spinning it in the air the wet bulb will have become dry. in saturated air the wet bulb will remain wet. Dew to the evap of the moisture there will be a difference in temp between the wet and dry blub. this difference quantifies the RH

Question 31

how does humidity impact temp

Answer 31

vapor is a GHG. areas with a high RH will retain outgoing radiation much more efficiently than areas with a low humidity.
that’s is why a humid region of 30 deg feels warmer than a dry region of 30 deg. in humid situations, the body is unable to remove sweat via evap.

Question 32

how does low humidity impact dew point?

Answer 32

low humidity regions often experience warmer dew points in respect to their environment. This often leads to low cloud formation