3.Evaporation Flashcards

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1
Q

Simplest form of evaporation is..

A

freewater evaporation

  • when water molecules are only in contact with other water molecules
  • ex: S Sask River
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2
Q

Evaporation from free water surfaces is promoted by:2

A

– External or meteorological factors

– Internal or lake factors

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3
Q

Evaporation from bare soil surfaces is promoted by :2

A

– External or meteorological factors

– Soil factors

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4
Q

Evaporation from vegetated surfaces is promoted by:3

A

– External or meteorological factors
– Soil factors
– Vegetation factor

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5
Q

3 External Factors promoting evap

3 Internap Factors Promoting Evap

A

• External factors
– Solar energy
– Humidity
– Diffusion and advection

• Internal factors – Salinity
– Water depth
– Surface area

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6
Q

.water vapour is constantly experiencing both upforce by _______ and downforce by _______
-how big they are relative to each other determines evaporation

A

vapourization

condensation

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7
Q

(Solar Radiation/Temperature) _______ is the best way to predict evaporation over time

A

Insolation

  • radiation gives you the amount of available energy
  • temperature does not drive evaporation
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8
Q

Why are the great lakes not as dependent on insolation for evaporation?

A

The great lakes store a lot of energy

-it means that they are not as dependent on incoming energy

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9
Q

Why do evaporation lines extend south over the cordillera?

A

lines of evaporation over cordillera bend south because of the mountains’ altitude
-higher altitude means lower evap

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10
Q

______ determines insolation which determines _____

A

latitude

evaporation

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11
Q

.water evaporates _____ in dry air

.water evaporates _____ into humid air

A

fastslow

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12
Q

Southern most points of canada experience about ___klyper year of insolation

A

40

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13
Q

Relative humidity has an _____ pattern to temperature

A

inverse

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14
Q

Evaporation from free water surfaces is affected by 3 external and 3 internal factors: be specific

A
  • External factors – Solar energy – Humidity – Diffusion and advection
  • Internal factors – Salinity – Water depth – Surface area
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15
Q

Dalton’s Law of Evaporation

A

E = f(u) (esat – eact)

E is the evaporation rate (cm day-1) f(u) is a function of the wind speed u esat is the saturated vapour pressure at the temperature of the water surface (mb) eact is the actual vapour pressure at the at thetemperature of the air (mb) u is the windspeed (km day-1) f(u) = 1.46 x 10-4 u

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16
Q

How does wind allow for more evaporation?

A

Advection takes place with wind
-it DISPERSES the humid air from the surface allowing for more evaporation
– Redistribution of large volumes of air
– Mixing of high humidity and low humidity air

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17
Q

diffusion

A

the movement of particles from an area of high concentration to an area of low concentration. For diffusion to work, the particles must be able to move around. This means that diffusion does not happen in solids – the particles in a solid can only vibrate and cannot move from place to place

– Redistribution at molecular level
– Random movement of molecules
– From high to low concentration – Can take place in still air

18
Q

How does the depth of a large water body compare to a small water body over a year?

A

Large water body:
Evaporation is at about 50mm and jumps to 125 over the winteras stored energy in used

Small water body evaporates about 125mm rate over the warmer months and then dops to 20mm over the winter as it has no stored energy to use

19
Q

.if we are looking at saline water, it is __% less evaporation because of salt vs fresh

A

3

20
Q

______ of water determines the amount of energy stored in a water body

A

volume

21
Q

Class A eVAPORATION pAN

A

has no vapour blanket and cannot store energy as it is too small in termsofvolume

– Pan receives energy through radiation and conduction through base and sides

22
Q

Vapour Blankets

A

Vapour blankets on large water bodies limits evaporation unless there is HIGH wind
-surface area determines whether vapour blankets can develop

23
Q

Pan Coeffecient

A
  • The ratio of the amount of evaporation from a large body of water to that measured in an evaporation pan
  • to relate pan evaporation to lake evaporation you must use the “pan coefficient”

Figure 7-6:

  • pan coefficient is less than average during rainy season (Feb,March,Apr)
  • pan coefficient is higher than average after the summer season as the lake gained and held energy over the summer and uses it when the temperature start to drop(sep,oct,nov,dec). The pan however, gets colder as it cannot store energy in such a small amount of water.
24
Q

The discharge is 4.2 l s-1 at 7:05 pm, and 9.6 l s-1 at 7:12 pm. The average discharge during this period is ____________ l s-1. In this period, there are __________ seconds. Every second, the volume of water flowing by is ______________ l. Over this entire period, the total volume of water flowing by is ______________ l.

A

6.9

420

6.9

2898

25
Q

Evaporation from bare soil surfaces

2 Major Factors and 2 minor factors

A
• Major factors 
– Moisture content – Capillary characteristics 
• Minor factors
 – Albedo 
– Seasonality of bare soil conditions
26
Q

Evaporation from bare soil surfaces

2 Major Factors and 2 minor factors

A
• Major factors 
– Moisture content – Capillary characteristics 
• Minor factors
 – Albedo 
– Seasonality of bare soil conditions

.Biggest difference between free water surface and soil surface is moisture supply and its replenishment

27
Q

3 phases of soil

A

Soil consists of 3 different phases(see picture of microscopic soil): a) solid particles,

b) Pore Space(water)(soil solution)
c) Gaseous (soil air)

28
Q

2 Important soil characteristics:

A

.particle size distribution: distribution of solid particles like clay, silt, and sand

.pore size distribution: distribution of small, medium, and large pores

29
Q

= < 2 microns

= >2 microns but <64 microns

= >64 microns but < 2mm

= >2mm

A

Clay= finer then 2 microns

Silt=64 microns is boundary between silt and sand

sand=

gravel=>2mm

30
Q

_____microns in a mm

A

1000

31
Q

Volumetric Soil Moisture content

Versus

Gravimetric Soil Moisture content

in terms of units

A

= m3 water/m3 soil or %

=kg water/kg dry soil or %

32
Q

What allows for more capillary rise..

A

.capillary rise is affected by space, the narrower the space the farther it can move

33
Q

Capillary Rise

A

the only thing that changes and effects change in the capillary rise equation is the radius of the space it is within

34
Q

bigger the pore size means the _____(faster/slower) the water will move

A

faster

35
Q

Deep ground water table=

Shallow Ground Water table=

In terms of capillary rise

A

Deep ground water table= means only specific(smaller) pore sizes can move water to surface
-evaporation would be low
Shallow ground water table= means all pore sizes can move water to surface
-evaporation would be high

36
Q

Evaporation from Vegetation

External factors:3

Soil Factors:1

Plant Factors:1

A

• External factors – Available energy
– Humidity
– Diffusion and advection
• Soil factors – Control flow of water to plant
• Plant factors
– Control transpiration of plant to atmosphere

37
Q

Describe a diagram of plant transpiration starting with water in the soil

A
  1. Water taken up by plant hairs
  2. Taken up and transported by XYLEM
  3. In the leaves water in held in the air spaces where transpiration occurs out of the STOMA
    - plant can control water levels by opening and closing STOMA
38
Q

Potential Evapotranspiration

A

Common Theme from the 2 definitions belowis that there is NO LACK OF WATER

– The water loss which will occur if at no time there is a deficiency of water in the soil for use of vegetation

– Evaporation from an extended surface of short green crop, actively growing, completely shading the ground, of uniform height, and not short of water

39
Q

Define Field Capacity and Wilting Point

A
  • Field capacity – Soil moisture content when soil has been drained by gravity (e.g. for 48 hours)
  • Wilting point – Moisture content at which vegetation can no longer extract water from the soil
40
Q

Albedo of

Water=

Snow(old and new)=

Deciduous Forest=

Coniferuous Forest=

A
  1. 05-0.15
  2. 30-0.90
  3. 15-0.20
  4. 05-0.15
    - absorves more then reflects so it would appear darker
41
Q

Lysimeter

A

is put underground at water table level and uses afloat to always know at what level the water table is

42
Q

Eddy Covariance Measurements

A

used o measure water vapour movement from and to atmosphere

-sonic waves