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I HM Flashcards

1
Q
  • Role of water
  • Is water a resource?
A
  • Water has formed the earth, determined the evolution, our physiology, our cultures and our religions.
  • Yes, limitation in spatial and temporal availability turn water into a resource
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2
Q

Temperature development in Germany

Describe graph

A

Between 1900 and 2014 the average temperature has increased from about 8.5 degrees to 10 degrees in Germany

Highest slope since the 1970s..

Yearly temperatures are chaningly/repeatedly higher and lower than the average (fluctuate) –> Its about the increase of the average…

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3
Q

Observed change of average surface temperature between 1901-2012

  • Affected regions
  • Unaffected regions
A

Trend on land between 0.2 and 2.5 degrees

Highest warming in vast parts of central Asia, North-West Africa, Brasil and Canada

Europe not a lot of 2.5 degree-cells

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4
Q

Oberserved change in precipitaation over land

1901-2010 (Period A) vs. 1951-2010 (Period B)

  • Comparison
  • Problems
A

Change in both directions

Period B displayes more and more intensive changes across the world than Period A
–> Change more drastic in the recent decade

For period B: Sometimes in countries some areas increase, while others decrease (Australia, China).. –> Governments have to react to both extremes (droughts, floods)

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5
Q

Role of snow for water management

  • Negative impact
A
  • Snow Drought
  • Snow Water Equivalent Percentage going down in California
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6
Q

Percentage change of mean annual streamflow
(for a global mean temperature rise of 2°C)
(2.7 °C above pre-industrial)

  • Modelling approach
  • Stand-out regions
A

Percentage change of mean annual streamflow

5 GCMs (General Circulation Models)

11 GHMs (Global Hydrological Models)

–> 55 GHM-GCM combinations

High decrease in Southern Iberical Half Island, Western Cape, Chile, Marocco, Middle East

High increase in Northern Russia, Northern Canada, India

(for a global mean temperature rise of 2°C)

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7
Q

Current vulnerabilities of freshwater resources

(read)

A
  • Land subsidence and land slides (Mexico)
  • Damage to riparian ecosystems due to flood protection along Elbe River
  • Area of a african lake declining
  • Precipitation decrease + irrigation –> River running dry
  • Aqueous ecosystems affected by decreasing streamflow and increased salinity (Australia)

–> Water stress level is quantifiable! (–> Water stress indicator (WSI): Between 0 and 1 (1 = overexploited)

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8
Q

Great weather and flood catastrophes over the last fourty years

  • characteristics of graph
  • explanation
A

Huge spike since the 90s

BUT not only due to climate change!
Stichwort: “Attribution”! Can the trend be attributed to climate change only? No: People own more (economic progress; no. of people increased –> moving to riskyier areas; data acquisition methods changed/improved/became more effective

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9
Q

Future climate change impacts on freshwater

–> Threat to sustainable development of affected regions

(read)

A
  • Decreasing groundwater recharge
  • Electricity production potential decreases
  • Thickness of small island freshwater lenses decine by factor 2.5 due to 10 cm sea level rise
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10
Q

Water & Sanitation Facts

  • Freshwater-injustice
  • Daily water usage
  • River basins
A
  1. 1 bn without clean drinking water
  2. 6 bn with lack of adequate sanitation
  3. 6 mio/a die from waterborne diseases

per capita use:

Dubai: 500 l/p/d

NA: 300 l/p/d

Germany: 120 l/p/d

Sub-Saharan Africa: 10-20 l/p/d

UN: Minimum: including basic hygiene needs and basic food hygiene: 20 l/p/d

260 river basins are shared by various countries –> inadequate legal and institutional arrangements

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11
Q

Global Water footprint by sector

  • Regionen Beispiele
A

Agriculture: 85%

Industry: 10%

Domestic: 5%

Deutschland und Länder drum rum: –> Industriy Sector –> Majority

Africa; S.Am; S.E.A : Fast nur Agriculture

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12
Q

Key issues with water management

A
  • Water quantity and distribution
  • Water quality
  • Waterborne diseases
  • Population pressure
  • Climate Change
  • Access to basic sanitation, drinking water

Summary:

–> too little, too much, too dirty

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13
Q

What are the main components of the hydrological cycle?

  • Source
A

Fluxes (103 km3/y):

1.1 Precipitation over ocean: 400

1.2 Precipitation over land: 110 (10:1 Rain:Snow)

2.0 Net water vapor flux transport: 50

  • *3.1** Total terrestrial evapotranspiration/transpiration: 60
  • *3.2**Total ocean Evaporation: 450

4.0 Rivers: 45

Storage (103 km3):

5.0 Sea: 1.4 mio

6.0 Glaciers and snow: 25,000

7.0 Gw: 24,000

8.0 Permafrost: 300

9.0 Lake: 175

10.1; 10.2 Soil moisture; Wetland: Each: 17

11.1: 11.2 Water vapor over sea/land: 10; 3

12.0 River: 2

Source: Oki und Kanae 2006

Ocean to and Water vapor transport: 40

Atmosphere contribution: 12.7

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14
Q

Water in the climate system

3 points

A
  • Water vapor in the atmosphere is the most important greenhouse gas
  • Clouds and ice sheets can cool the earth by reflecting sunlight
  • Water vapor and ocean currents distribute heat over the planet
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15
Q

Hydrology

Definition

A
  • Science of water
  • Study of water in all its three forms
  • on/in/over earth
  • distribution, circulation, behaviour, chemical/physical properties
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16
Q

Water distribution

-surface percentages

A
  • 70% earth coverage
  • 3% is fresh water (mostly glaciers, polar regions)
  • only 0.6% of ground/surface water on earth is suitable for human use
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17
Q

Water distribution II

  • Percentages Ocean–> ARFW
A

Oceans: 70%

Glaciers & Icecaps: 1.73%

Total Fresh Water: 0.77%

Available & Renewable Fresh Water: 0.0008%

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18
Q

Water distribution III

  • Areas
A

Total Water: 1.36 x 1018 m3

Oceans: 97.2%

Fresh Water: 2.8%

Von den 2.8% Fresh Water (3.8 x 1016 m3):

78% Locked in polar ice, soil, rock, water vapor

22% Surface + Ground water

(0.01 % can be used economically)

Von den 22% Surface + Ground water (8.4 x 1015 m3):

Inaccessible: 99.4 %

Accessible: 0.6 %

Accessible water: 5 x 1013 m3

(um den Faktor 27,000 kleiner)

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19
Q

Fresh water resources

(%)

5x

A

Solid (glaciers, polar, sea ice) 75%

Ground Water 20%

Lakes 0.3%

Rivers 0.01%

Gaseous / atmosphere 0.04%

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20
Q

Turnover rate hydrological cycle

2 examples

A

Ocean Water

0.04% is part of hydrological cycle (turnover rate: 2500 years)

Atmosphere:

9.1 days

Retention time: Between (10,000 years = Deep ground water, permafrost & evaporated rainfall: sec-min)

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21
Q

Hydrological Cycle:

  • 3 characteristics
A
  • Cycling from water from the ocean to the land and back again (storage and flux of water)
  • Ocean, atmosphere, land
  • Through: Vapor, cloud water, snow, sea ice, glaciers, ice shields
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22
Q

What is driving the cycle?

Processes & factors

A

Driving force: Radiant Energy from Sun –> Heating causes evaporation = Transfer from liquid to gaseous state –> atmospheric vapor transport

  • Condensation of water vapor –> Precipitation
  • Closure of cycle though run-off

(Precipitation/ Run-off: Gravity (driving force))

Big amounts of Water stored in ocean

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23
Q

Global hydrological cycle

  • pro Jahr
  • fluxes
  • asize of areas
A

1 mm = 1 l / m2 !!

In 103 km3 / a

LAND
Precipitation: 110
Evaporation: 70

OCEAN
Precipitation: 400
Evaporation: 400

River flow: 40
Atmospheric Vapor Transport: 40

Areas

LAND: 150 * 106 km2 (30%)
OCEAN: 350 * 106 km2 (70%)

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24
Q

Hydrological Balance Equation

(short term balance on land areas)

A

Precipitation =
Evapotranspiration(ET) + Runoff/Streamflow Q + Change in storage (soil, snow, ice)

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25
Q

Implications Hydrological Cycle

(Read)

A
  • Provides continuous supply of fresh water
  • More than half of the rainfall over land lost as evaporation
  • Runoff: Diverted for human uses; lost to the oceans
  • “Climate conditioning system”
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26
Q

Main mode of energy transport in the atmosphere

A

Latent heat

Sunlight evaporates water from ocean/other surfaces –> energy is stored in form of latent hear in water vapor

–> energy loss by condensation

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27
Q

Global Energy Balance

  • Incoming vs. Outgoing
  • Einheit
A

in W/m2

Incoming solar radiation: 340

Outgoing Longwave Radiation: 235

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28
Q

Terrestrial radiation

  • Important parameter
  • Units
A

Important Parameter To (surface temperature)

Unit: Daily radiation: (kW/m2 day)

Mean annual global radiation (W/m2)

(Watt)

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29
Q

Water balances with different time scopes

A
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30
Q
A
  • P over oceans is 3.5 x greater than on land
  • E over oceans is 6 x greater than on land
  • Annual renewed fresh water volume amounts only
    ~ 40 000 km
  • On average 64 % of P on land is lost by E
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31
Q

Hemispheric water balances

A

Globe total:

NH %

P = 100
E = 90
R =10

SH %

P = 100
E = 110
R = -10

Bei nur Land Area Betrachung ungefähr beide bei zwei Drittel zu ein Drittel E/R

Bei nur Ocean Area Betrachtung beide ungefähr so wie SH oben, SH etwas ausgeprägter

in 103 km3

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32
Q

Hemispheric Water Balance II

  • Conclusion
A
  • Almost no differences in precipitation
  • NH provides 46.1 %, SH 53.9 % of E
  • SH has surplus of E which is transported as water vapor to the NH
  • NH gains water which is transported by ocean currents to the SH
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33
Q

Water balance Germany

A

850 mm Precipitation

500 mm ET

Rest 50/50 Run-off / GW

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34
Q

Water demand and scarcity

demand and

scarcity

A

Not stressed: > 1700 m3 / person-y

Stressed: < 500 m3 / person-y

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35
Q

Average Water Demand pP pY

A
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36
Q

Difference virtual water and water footprint

A
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37
Q

Downward terrestrial radiation (“back radiation”) Ea

A
  • E is partly absorbed by atmosphere (absorption bands of greenhouse gases)
  • reemitted to all directions
  • downward part Ea
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38
Q

Outgoing longwave radiation Eeff

A
  • difference between terrestrial E and back radiation Ea
  • Eeff = E - Ea
  • under clear sky Ea ~ 75% of E
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39
Q

Coupling water and energy balance

A

Surface water balance:

P = (ET) + R

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40
Q

Where can we find the most positive and most negative radiation balance values globally (at the upper surface of the atmosphere)?

A

Most positive: Equator

Most negative: The two pols

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41
Q

General circulation of the atmosphere

A

Ferrel cell (between 30 -60

between the two co-rotating Hadley and Polar Cells

Anti-Clockwise (NH)

Die instabile Ferrel-Zelle – Westwinddrift

Zwischen den beiden gleichläufigen Systemen Hadley- und Polarzelle jeder Halbkugel passt je ein drittes gegenläufiges, nicht unähnlich dem Ineinandergreifen von Zahnrädern. Dort wird in Bodennähe Luft polwärts verlagert, woraus unter Einwirkung der Jetstreams westliche Winde entstehen. Die Zone heißt daher auch Westwindzone oder Westwinddrift der gemäßigten Breiten. Sie ist die instabilste, weil auf rund 60° bis 70° geographischer Breite die feuchtwarmen Westwinde auf kalte polare Ostwinde treffen: die Polarfront bildet sich. Die Ferrel-Zelle (nach William Ferrel) ist die Zelle größter (Sonnen-)Energieunterschiede (und damit verbunden auch Temperaturunterschiede). In ihr befinden sich ca. 38 % des gesamten Energieunterschieds zwischen Innerentropen und den Polen. Die äquatorseitige Grenze liegt bei rund 35° Breite.

Part of the air rising at 60° latitude diverges at high altitude toward the poles and creates the polar cell. The rest moves toward the equator where it collides at 30° latitude with the high-level air of the Hadley cell. There it subsides and strengthens the high pressure ridges beneath. A large part of the energy that drives the Ferrel cell is provided by the polar and Hadley cells circulating on either side and that drag the Ferrel cell with it.[5] The Ferrel cell, theorized by William Ferrel (1817–1891), is therefore a secondary circulation feature, whose existence depends upon the Hadley and polar cells on either side of it. It might be thought of as an eddy created by the Hadley and polar cells. The Ferrel cell is weak, and the air flow and temperatures within it are variable. For this reason, the mid-latitudes are sometimes known as the “zone of mixing.” At high altitudes, the Ferrel cell overrides the Hadley and Polar cells. The air of the Ferrel cell that descends at 30° latitude returns poleward at the ground level, and as it does so it deviates toward the east. In the upper atmosphere of the Ferrel cell, the air moving toward the equator deviates toward the west. Both of those deviations, as in the case of the Hadley and polar cells, are driven by conservation of angular momentum. As a result, just as the easterly Trade Winds are found below the Hadley cell, the Westerlies are found beneath the Ferrel cell. The forces driving the flow in the Ferrel cell are weak, and so the weather in that zone is variable. Thus, strong high-pressure areas which divert the prevailing westerlies, such as a Siberian high, can override the Ferrel cell, making it discontinuous.

While the Hadley and polar cells are truly closed loops, the Ferrel cell is not, and the telling point is in the Westerlies, which are more formally known as “the Prevailing Westerlies.” The easterly Trade Winds and the polar easterlies have nothing over which to prevail, as their parent circulation cells are strong enough and face few obstacles either in the form of massive terrain features or high pressure zones. The weaker Westerlies of the Ferrel cell, however, can be disrupted. The local passage of a cold front may change that in a matter of minutes, and frequently does. As a result, at the surface, winds can vary abruptly in direction. But the winds above the surface, where they are less disrupted by terrain, are essentially westerly. A low pressure zone at 60° latitude that moves toward the equator, or a high pressure zone at 30° latitude that moves poleward, will accelerate the Westerlies of the Ferrel cell. A strong high, moving polewards may bring westerly winds for days.

The Ferrel cell is driven by the Hadley and Polar cells. It has neither a strong source of heat nor a strong sink to drive convection. As a result, the weather within the Ferrel cell is highly variable and is influenced by changes to the Hadley and Polar cells. The base of the Ferrel cell is characterized by the movement of air masses, and the location of those air masses is influenced in part by the location of the jet stream, even though it flows near the tropopause. Overall, the movement of surface air is from the 30th latitude to the 60th. However, the upper flow of the Ferrel cell is weak and not well defined.

In contrast to the Hadley and Polar systems, the Ferrel system provides an example of a thermally indirect circulation. The Ferrel system acts as a heat pump with a coefficient of performance of 12.1, consuming kinetic energy at an approximate rate of 275 terawatts

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42
Q

Different pressure systems

A
  1. Thermal pressure systems (Ferrel)
  2. Dynamic pressure systems
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43
Q

Thermal pressure systems (Ferrel)

A
  • seasonal change
  • summer: air over continents more heated than over oceans
  • drop of pressure from ocean to land
  • near-surface thermal low over continents
  • winter: stong cooling of continents (negative radiation balance)
  • near-surface cold continental high
  • large land-sea-breeze-system –> thermally caused (e.g. monsoon)
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44
Q

Dynamic pressure systems

A
  • driver: differences in the energy balance

–> energy surplus in the tropics, energy deficit at higher latitudes

  • Coriolis effect / force
  • no direct meridional compensating flow possible
  • deflection by Coriolis: NH to right, SH to left

–> formation of permanent H and L

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45
Q

Pressure systems

A

low: rising air masses, condensation, formation of clouds. precipitation, cyclonic rotation, air masses “sucked in”

high: sinking air masses, droplets evaporate, no clouds, no precipitation, anti-cyclonic rotation, air masses “flow out”

Coriolis “force”: deflects air masses to the right (N) or left (S-Hemisohere)

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46
Q

Potential evaporation

A

max. evaporation possible

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47
Q

Actual evaporation

A

Real evaporation

(over a free water surface actual can equal potential evaporation)

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48
Q

transpiration

A

Evaporation of water from stomata openings in leaves of plants

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49
Q

Evapotranspiration

A

Evapotranspiration = Evaporation + Interception + Transpiration

Forest: 10E, 30I, 60T
Grassland: 25E, 25I, 50T
Farmland: 45 E, 15I, 40T
Soil: 100E

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50
Q

humid

arid

A

P > E

P < E

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51
Q

Evapotranspiration

Characteristics

A

Evapotranspiration [mm] decreases with height

  • Isolines of evapotranspiration
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52
Q

Do we have enough freshwater on earth?

A

Yes, but:

sometimes there are quality issues: –> chemicals, pathogens

sometimes there are spacial distribution issues: freshwater resources in Norway per person versus freshwater resources in Saudi Arabia per person

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53
Q

Feeding the world

A

Findings from the table:
- Industrial countries consume more meat than vegetables (total in l/d: IC: 3600, DC: 2050)

  • Meat diet is more water intensive than vegetable diet
    (difference in l/d: IC: 1300, DC: 300)

-

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54
Q

Megacities

A
  • Especially in Asia, Central-West Africa, East Coast of S.Am., Europe neglectable
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55
Q

Access to clean drinking water

Access to safe santitation

A

Whole subsaharan africa a problem.. Even Congo..

Same same for subsaharan africa. In addition, India, South-East Asia

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56
Q

Horton

A

Inflitration, run off

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57
Q

Thornthwaite and Penman

A

Climatic aspects, evapotrans.

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58
Q

Global latent heat flux

A

Evapotranspiration

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59
Q

Mean annual cloud amount

A

NH!

Equator!

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60
Q
A
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61
Q

Albedo

  • Definition

.- Characteristics

  • some numbers
A
  • measure for reflectance or optical brightness of a surface
  • scale from zero (corresponding to a black body that absorbs all incident radiation) to one (corresponding to a white body that reflects all incident radiation)

snow: up to 0.8-0.9
clouds: 0.6-0.9
desert: 0.3
forest: 0.05

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62
Q
A
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63
Q

Intertropical Convergence Zone

A
  • (ITCZ)
  • a region of equatorial lows
  • area encircling Earth near the Equator, where the northeast and southeast trade winds converge
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64
Q

Global Windsystems

A

see pic

65
Q

Land-Sea-Breeze

A

see pic

66
Q

Tropospheric Circulation

One cell vs. three cells

A

see pic

67
Q

Continental Water Balances

A

E / P as indicator:

Between Australia: 0.94 and Antarctica: 0.17

(Africa 0.84)

–> R / P: Australia: 0.06 usw.

More rain in Africa, more evaporation.

  • Volumes are highest in Asia
  • Africa characterized by high E and relative low R
  • Africa, Europe, Australia: –> Runoff around 30%
  • Europe, Americas: –> Runoff around 50%
  • Highest precipitation in S-America (tropical forests, Andes)
68
Q

Cohesion

A

Property of water:

Molecues tend to stick to one another

Water is attracted to other water

Surface tension = cohesion forces

69
Q

Water Scarcity Index

A

Rws = (W - S) / Q

W: annual withdrawal by all sectors

S: water use from desalinated water

Q: annual RFWR

–> High water stress: Rws > 0.4

70
Q

Adhesion

A

Property of water:

Molecules tend to stick to objects

Water is attracted to other materials

Capillary action = adhesion forces

71
Q

Unique characteristic of water

A

in its solid phase it is less dense than in its liquid phase

72
Q

Density of water

A

Highest at 4 degrees

73
Q

Stomata

A

is a pore, found in the epidermis of leaves

74
Q

Specific heat

A

amount of energy required to change the temperature of a substance (by 1 °C)

Water has high specific heat –> can absorb large amounts of heat energy before it gets hot

–> releases heat energy slowly

75
Q

Conduction

A

Water good with heat conduction

–> Water is perfect for heating due to its high specific heat and capability of conduction

76
Q

Phase Change Diagram

A

see pic

77
Q

Triple point

A

when ice, water and vapor can coexxist (around 0 degrees)

78
Q

Supercooled water

A

Hail

79
Q

Specific humidity

A

q

[g / kg]

atio of the mass of water vapor (in a sample of moist air) to the total mass of the sample

80
Q

absolute humidity

A

Vd

[g / m3]

vapor densitiy

mass of water vapor per unit volume of air

81
Q

relative humidity

A

RH [%]

= ( e / E) * 100

ratio between actual (e) and saturation (es, esat, E) vapor pressure at a given temperature

82
Q

Saturation vapor pressure E

A
  • E is the maximum of vapor in the atmosphere without condensation
  • E depends on the temperature, not air pressure
  • Eabove water is higher than above ice
83
Q

Measures of the extent of atmospheric saturation and temperatures used when measuring the vapor pressure of moist air

A

see pic

84
Q

Precipitation formation

A

Preconditions:

  • water vapor saturated air (moist air must be cooled to its dew point = Kondensationspunkt)
  • phase transition (–> presence of condensation nuclei)
  • growth of water droplets
85
Q

Cooling mechanisms

A
  1. Adiabatic cooling
    - also orographic lifting by mountain range or convection (rising air, decrease in pressure –> decrease in temperature)
  2. Frontal systems
    - mixing of two air masses with different temperature; warm moist air rises
  3. Contact cooling
    - moist air flows over cool surface -> fog
  4. Radiative cooling
    - at night: surface cooling by negative radiation balance -> dew, frost, cooling of air and build up of radiative fog
86
Q

Condensation Nuclei

A
  • air temperature below dew point
  • water vapor content bigger than max. cap of atmosphere
  • surplus of water vapor is condensed around small airborne particles (condensation nuclei)
87
Q

Two main types of condensation nuclei

A
  • hygroscopic particals having affinity for water vapor (mainly ocean salt particles)
  • non-hygroscopic particle: attracting condensation after some degree of super saturation, depending on size
88
Q

Growth of water droplets

A

clouds are formed –> growth depends on hygroscopic and surface tension forces, humidity of air…

89
Q

Theories how cloud droplets grow to become raindrops

A
  • Bergeron- Findeisen process
  • Growth by collision
  • Growth by accretion
90
Q

Ice-crystal (Bergeron) process

A

T < 0°C

mixed cloud (droplets & ice particles)

water vapor deposits on the ice particles

air becomes unsaturated with respect to water, droplets evaporate

crystals grow at the expense of droplets

91
Q

Growth by collision

A

T > 0°C

no ice

larger droplets fall faster than smaller ones

they collide and coalesce –> grow

maritime clouds –> T high, water vapor amount: high

92
Q

Growth by accretion

A

mix of droplets and ice particles

snow/hail is formed as droplets fuse on to ice particles

takes place in same type of cloud that favors the Bergeron process –> except large amout of liquid water is necessary for collision

93
Q

Cloud seeding

A

fake nuclei (dry ice)

94
Q

Classification of clouds

A

High clouds (10km): Cirrus (ice crystals)

Middle clouds (5km): Alto- (water droplets or ice crystals)
(Altocumulus, Altostratus)
Low clouds (2 km): Mainly with waterdroplets
(Cumulus, Cumulonimbus, Nimbostratus)

(Cirrocumulus, Cirrostratus)

95
Q

Precipitation types

(5 Stück)

A
  • Orographic rainfall
  • Convective precipitation
  • Cyclonic precipitation
  • Monsoon (ITCZ intertropical convergence zone)
  • Waves in the Easterlies
96
Q

Convective precipitation

A

Maritime air mass over land

air is heated –> rise by convection

  • deep cumulus clouds are formed
  • many parts of tropics –> strong rainfall
97
Q

Frontal zone

A

Boundary between two air masses

98
Q

Cumulus

A

Sunny intervals, possibly showers

99
Q

Cumulusnimbus

A

Bursts of heavy rain, Possible Thunder

100
Q

Altostratus

A

Sunny intervals, increasing cloud

101
Q

Altocumulus

A

Sunny, warm and humid

102
Q

Nimbostratus

A

Dull with more continuous moderate rain

103
Q

Altostratus

A

Cloudy with light rain and drizzle

104
Q

Cirrostratus

A

Bright, some watery sunshine

105
Q

Waves in the easterlies

A

Divergence and Convergence

106
Q

Waves in the easterlies

A
  • Small disturbance in the trade winds 5- 25 ° N / S
  • Heavy rainfall possible
  • Low pressure may deepen to form hurricanes, cyclones
107
Q

Monsoon

A
  • Weather pattern of seasonal nature
  • changes in atmospheric pressure –> movements of the ITC
108
Q

ET

Small scale variability

A

ET variability can be as high as 20% in a field

Issues to measure surface temperature

109
Q

Approaches to determine the evapotranspiration

A

Micrometeorological approaches

eddy covariance
energy balance

physiological approaches

sap flow
dendrometer

hydrological approaches

evaporation balance
soil water measurement

lysimeter

remote sensing

determination of the NDVI (normalized differnece vegetation index)

models

statistical approaches (Haude, Dalton)
simple physical approaches (Penman - Monteith)
110
Q

Measurement of potential evaporation

A

Wildsche Waage (Wild evaporimeter scale)

Piche Evaporimeter

111
Q

Actual evaporation

A

Weighable Lysimeter

112
Q

Portable porometer

A

Controls the water loss from plant leaves

113
Q

Measure soil moisture

A

Tensiometer

114
Q

Evapotranspiration from natural surfaces

A

single plant –> small lysimeter (weight of potted plant)

plant community –> Big Lysimeter

Water surface –> Evaporation tanks

Soil area –> Water content

Natural canopy –> Micrometeorological approaches

Landscape –> Water balance

Continent, globe –> Water balance

115
Q

Haude approach

A

determine potential evapotranspiration

with:

air temperature

vapour pressure (e)

additional factor for season and crop

116
Q

Penman approach

A

simple physical -empirical approach to determine potential evaporation

includes wind function

radiotaion balance

saturaltion vapour pressure deficit

117
Q

Penman - Monteith approach

A

includes the effect that plants can regulate their transpiration by stromata closure or opening

canopy resistance (stomata resistance introduced)

–> method is practical for calculating the actual evapotranspiration

118
Q

Temperature correcetion

A

In the Penman - Monteith approach the surface temperature is assumed as the air temperature

–> Measure surface temperature –> apply correction

–> Evapotranspiration can reach 20% in a field

119
Q

Calculation Lysimeter

A

Given:

Surfce area of lysimeter

lysimeter mass before and afterwards

Precipitation durch measurement interval

Meassured infiltrated water

Measured surface runoff

–> Actual evaporation (evapotranspiration) during time t

120
Q

Over several years: Mean of actual/real evaporation in watershed

A

Water balance equation

Many years –> Storage is neglectable –> ETR can be calculated with Precipitaation and Runoff

121
Q

Energy balance approach

A

Bowen ratio

sensible heat flux / latent heat flux

122
Q

Lysimeter equation

A

Precipitation = Evapotranspiration + delta soil water + percolation

p (precipitation) : Measured with rain gauge aside

Delta soil water: Measured either by weighing or separated soil moisture measurements

123
Q

Dendrometer

A

Graph shows beginnig and end of growth periods… Rainfall… Dry periods

124
Q

Sap flow

A

Measures temperature in “Sapwood” part of tree

125
Q

Groundwater

Shallow ground water

Water table

A

Water beneath the surface in the saturated zone (saturated kommt unter unsaturated)

Groundwater greatly affected by evapotranspiration and interaction with surface water

Water table: Surface of saturation

126
Q

Watershed

A

unit of land on which all water that falls collects by gravity and runs out via a common outlet

127
Q

Distribution of run off and variability

Factors affecting the total volume of run off

Factors affecting the distribution run off in time

A

Climatic factors (precipitation vs. evapotranspiration)

Catchment factors:

total area

slope

soil

rock type

Meteorological factors (rainfall intensity)

Catchment factors

Human factors (hydraulic structures, agricultural techniques, urbanization)

128
Q

Variations of run off

A
  • Spacial variability
  • Seasonal variability (regime of the river)
129
Q

Forests

A

Streamflow moderators

130
Q

IWRM

A

Moves water as a resource and a habitat more into the centre of policy making

131
Q

Distrometer

A

Laser beam –> Raindrops

–> fall velocity can be derived

Problems:

Wind speed

Masking effect

Margin fallers

Technical problems

Birds, pollen, insects, spider webs

132
Q

IPCC

A

Terminology: Virtually certain to Exceptionaly unlikely

133
Q

Natural greenhouse effect

A

water vapor:

greenhouse effect 62%

Co2: 22%

03: 7%

134
Q

Global Carbon Cylce

A

More fossil fuel burning –> more decomposition over the ocean –> ocean gets more acid

135
Q

How can we tell that additional CO2 in the atmosphere is not from natural sources?

A

Co2 in oceans also increasing, pH lowering

Different isotopic signature of fossil fuel buring

Falling levels of O2 in the atmosphere

Amount of CO2 emitted known

136
Q

Positive feedback through GHG-emissions

example

A

see pic

137
Q

What causes the sea level to change?

A

As the ocean warms up, the water expands (bigger effect than additional water)

Melting of glaciers, ice caps

138
Q

Detection vs. Attribution

A

Detection:

Is change statistically significantly different from what can be explained by internal variability?

Attriution:

unlikely to be due entirely to internal variability

139
Q

Optical Rain Gauge

A

Precipitation Measurement

counting drops through laser iode

140
Q

Tipping bucket rain gauge

A

Precipitation measurement

funnel –> channels precipitation into container –> after enough water is collected –> dumped –> electrical signal sent

Not that accurate –> tends to underestimate the amount of rainfall

141
Q

Problems with rain gauges

A

Doesnt work well with snow

Would need electricity to melt snow

–> weighing bucket gauge?

142
Q

Isohydal method

A

Estimating mean precipitation accross an area by drawing lines of equal precipitation / topographic lines

143
Q

Hyposomotric method

A

For regions were orographic precipitaion is important

144
Q

Class A Pan

A

potential evaporation

cylinder with a diamerter of 120 cm. Daily evaporation is measured

pan is filled up to exactly 5 cm.. After 2 hours the amount needed to refill the pan is measured

145
Q

Lysimeter

A

Measures the amount of water that infiltrated into the soil

Soil is weighted, perculation is considered and then compared to the actual perculation

transpiration can be calculated

good for farm crops, difficult for forests

ONLY INSTRUMENT THAT MEASURES ACTUAL EVAPOTRANSPIRATION

146
Q

Tensiometer

A

Measures soil moisture

burry in soil

handpump –> partial vacuum

Water added to the soil –> Vacuum inside the tube pulls moisture from the soil and decreases

147
Q

Psychometer

A

evaporation

(wet and dry bulb thermometer)

  • measures the water vapor in air
  • like hygrometer: dry bulb measures temperature and wet bulb measures temperature: difference –> relative humidity
148
Q

Hygrometer

A

measuring the water vapor in the atmosphere

149
Q

Porometer

A

An instrument for measuring the area of stromatal openings of a leaf by amoutn of gas passing through (–> control of the water loss of a plant)

150
Q

Piche evaporimeter

A

evaporation

graduated tube, closed at one end, filled with destilled water. covered with piece of filter paper.

Amount of evaporation –> change in level of meniscus of water

151
Q

Wildsche Wage

A

Evaporation

a bowl filled with water… measurement can be directly read from scale

152
Q

Disdrometer

A

precipitation

counts the drops falling though a laser beam

measures the size, no of drops, diameter

–> reports the no. of drops with a specific diameter and their velocity

153
Q

Dendrometer

A

For the estimation of circumference of a tree stem and the size of a tree

–> diameter variance of a tree indicates water stress

154
Q

Gutter for precipitation (stemflow)

A

Disadvantage: Water loss through evaporation, leaves/dirt blocking system

155
Q

Heat ratio method (sap flow)

A

Measures ratio of increase in temperature following the release of a pulse of heat downstream (blue) and upstream (blue) from heater (red)

–> direction of water flux can be calculated

156
Q

Anemometer

A

Measures the wind speed

157
Q

Ultrasonic wind measure - Eddy covariance method

A

measures wind speed and direction

158
Q

Gauge station

A

To see the height of e.g. a river

Convert into discharge, also measuring velocity of the river

Water level at gauge station

159
Q
A

Side Folder (3 decks)

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