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GEOG 445/645

Climatology

Water Balance, Soil

Hydrology,


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GEOG 445/645: Climatology Axel Kleidon

•Assignment ! due

•Assignment " #anded out on Tuesday•W#at a$out your term pro%ect&

Annoucements


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'n t#e climatic mean, (uxes in and out o) t#e "

$oxes $alance*

Water Balance

Ocean Land

Atmosphere

6!"4 ## 6"

$

$

all (uxes in ++!

m"

-

yr


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Water $alance )or t#e atmosp#ere*

change in precipitable water

= evapotranspiration - precipitation

- divergence of moisture

transport

in t#e climatic mean* no net accumulation

Atmospheric Water Balance

IN

OUT

CHANGE

IN

OUT

div

v ⋅ q( )= − P − E ( )

dPW

dt = E − P − div

rv ⋅ q( )


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%ean &recipitation .mm-d/


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%ean E'aporation .mm-d/


7/35GEOG 445/645: Climatology Axel Kleidon

Climatological %ean &(E )mm/day*



Water Balance



Water Balance

#ttp*--0001nodc1noaa1go2-3eneral-456C7cdrom1#tml



atmosphere:

7 .P - E/* remo2al o) moisture, sin8 )oratm1 moisture

.9di2ergence o) moisture transport:/

7 net release o) latent #eat

ocean:

7 .P - E/* )res#0ater (ux .; ri2er $asindisc#arge/

7 a



Land +ur,ace -ydrology



.he +oil matri

o2erall soil moisture as*

7 moist air space

7 0ater #eld $y ad#esi2e )orces

7 0ater #eld $y capillary )orces7 ground 0ater


=arc#er, P#ysiological Plant Ecology



6i



Matric Potential

descri$es t#e a$ility o)t#e soil to #old moisture.i1e1 #o0 muc# 0or8 isrequired to release0ater/

Field capacity descri$est#e amount o) moisture#eld a)ter 0etting

Permanent Wilting Point

descri$es moisturecontent at 0#ic# plantsare una$le to extractmoisture



Permanent Wilting Point .PWP/

?ield Capacity .?C/

Sand=oam

2olumetric moisture content

9 @ a t r i c P o t e n t i a l :

. @ P a /



Plant Available Water

(PAWis t#e di


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-o0 deep is thesoil1



2eep 3oots in Amaonia

Nepstad et al. (1994) Nature

SE Amazonia

top 30 cm: 69% of biomass

top 2 m: 98% of biomass

18 m: rooting depth

“deep roots”



2eep 3oots and E'apotranspiration

M J J A S O N D J F

20

0

Preci-pitation(mm)

Leaf Area(%)

0

PlantAvailableSoil Water

(mm)

200

0

200

400

0

0 - 2m

2 - 8m

preent-!a"climate mo!el

#!eep root$

!r" eaon

Nepstad et al. (1994)


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-180 -120 -60 0 60 120 180

-90

-60

-30

0

30

60

90

0 100 200 300 400 500Soil Moisture Depletion (mm)

after Kleidon and Heimann (1998) Predicted PAW6


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Simulated e


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Simulated e


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Simulated e


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+oil -ydrology

•soil texture determines t#e a$ility o) soil to#old moisture

•coarser texture 7D less a$ility to retainmoisture

•ner texture 7D 0ater #eld more tig#tly $ysoil matrix

•climatologically rele2ant dept# is set $y t#edept# o) t#e rooting >one

•soil moisture capacity acts as a $u


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.ranspiration


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GEOG 445/645: Climatology Axel Kleidon#ttp*--0001$at#1ac1u8-ceos-plants+1#tml


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=ea) cross7section*

.ranspiration

Conducti2ity H



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E


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Estimating E'aporation 3ates

!ow to estimate evaporation from sparse data"

sur)ace energy $alance .land/*E G +-= .S 7 SH 7 3/

Penman equation .)or saturated sur)ace/*

7 Bo0en ratio

7 Saturated sur)ace*

7 yields*

7 re0rite energy $alance* B =1


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&enman Euation

Estimating e2aporation )rom a saturated

sur)ace*

0it#*

also pro2ides estimate )or potential evaporation E = E air

=


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9Buc8et: @odel* Concept

7 actual evapotranspiration as t#e minimum o)atmosp#eric demand .or potential e2aporation/ andsoil moisture supply

- soil moisture storage and seasonality in

precipitation*

limit o) no storage* e2apotranspirationmirrors precipitation

7 o2erall 0ater $udget .0it# sucent storage/*

potential evapotranspiration (PE# $ precipitation (P

=$ arid, E# is 0ater limited

potential evapotranspiration (PE# % precipitation (P

GD #umid, E# is radiation limited

Annual Balance 7ariations


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Budy8o .+IJ/* atio ET-P as a )unction o)

A6-P



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+easonal 7ariations


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+ummary

7water budgets& land, atmosp#ere, ocean, sin8s

.con2ergence/ and sources .di2ergence/ o)atmosp#eric moisture transport7land surface hydrology * land sur)ace (uxes, soil#ydrology .eld capacity, permanent 0iltingpoint, plant a2aila$le 0ater/, role o) roots andclimatic e