Soil Properties soil texture and classes heat capacity, conductivity and thermal diffusivity moisture conductivity

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Lecture 33 Lecture on Soil Physics, part 1

• Soil Properties

– soil texture and classes

– heat capacity, conductivity and thermal diffusivity

– moisture conductivity

it

d diff

i

– porosity and diffusion

• Theory, Heat Transfer

– Heat transfer, Fourier’s equation

Ob

ti

• Observations

– Temperature profiles

• Daily patterns, Phase lags and Amplitudes of soil temperature • Seasonal Patterns

• Seasonal Patterns

• Soil Heat Flux

– Daily patterns

Seasonal Patterns

ESPM 129 Biometeorology

– Seasonal Patterns

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Ode to Soil Ode to Soil

“Darkle, darkle, little grain, I wonder how you entertain A thousand creatures microscopic. Grains like you from pole to tropic

Support land life upon this planet I marvel at you, crumb of granite! “ I marvel at you, crumb of granite!

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Soil Profile

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Soil Components

• Clay

Clay

– < 0.002 mm

– Crystal lattices, Si, Al, O, OH

Crystal lattices, Si, Al, O, OH

• Silt

– 0.05 to 0.002 mm

0.05 to 0.002 mm

• Sand

– 2 to 0 05 mm

2 to 0.05 mm

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Soil Texture Triangleg

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Porosity, P, is a function of the volumes of air, v_a, water, v_w and solid, v_s

P



v

a



v

w y, , , _a, , _w , _s

P

v

_a

v

_w

v

_s





P

 

1 

b

It is also a function of the soil bulk density, _b

P

s

1 

Mass of soil per unit volume



_b

m

s s



s

v

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Soil Physical Properties

Soil type Bulk density, kg m-3 Porosity, percent

Peat 0.65-1.1 60-80

Ideal soil 1310 50-60

Clay 1220 45-55

Silt 1280 40-50

Medium to coarse sand 1530 35-40

Uniform sand 1650 30-40

Fi t di d 1850 30 35

Fine to medium sand 1850 30-35

Gravel 1870 30-40

ESPM 129 Biometeorology After Tyndall et al.. 1999

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Soil Moisture

w

m

v

w s w w s s b l









 



Mass ratio, Mass of water to mass of solid Mass ratio, Mass of water to mass of solid

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Volumetric water content







v



v

w

w t b w

Note: We need to know the Bulk Density!!!

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Fourier Soil Heat Budget Equation:

Time rate of Change in Soil Temperature Is a function of the Flux Divergences Time rate of Change in Soil Temperature Is a function of the Flux Divergences

of Soil Heat Flux, G



_s

C

_s

T

t

G

z



 



t

z



T

G



k



G

k

z



_s, soil density

C_s, specific heat of soil k, thermal conductivity

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Fourier Heat Transfer Eq



_s

C

_s



T

 



(

k



T

)



T



2

T



_s

C

_s

t

z



(



)







T

t

T

z



2 ₂

k

Thermal Diffusivity







k

C

s s ESPM 129 Biometeorology

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Soil Heat Capacity is a Weighted function of the Mineral Organic and Water components



_s

C

_s



 

_m _m

C

_m



 

_o _o

C

_o



 

_w _w

C

_w

C

2400000



b

4180000



Approximation of Campbell

C

_s



b



2 65

4180000



_

.

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Soil Heat Capacity K -1 3000000 3500000 clay aci ty , J kg -1 K 2000000 2500000 clay sand loam silt clay litter C p, he at cap a 1000000 1500000

Soil Moisture content

0.0 0.1 0.2 0.3 0.4

C

0 500000

Soil Moisture content

Which Material is the Best and Worst Store of Heat?

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t i l D it (M 3₎ _S _{ifi H} _{t (J} 1 _Th _l

Soil Thermal Properties

material Density (Mg m-3₎ _{Specific Heat (J g}-1

K-1₎ Thermal conductivity (W m -1 _K-1₎ Soil minerals 2.65 0.87 2.5 Granite 2.64 0.82 3.0 Quartz 2.66 0.80 8.8 Organic matterg 1.30 1.92 0.25 Water 1.00 4.18 0.56 Ice 0 92 2 1 2 22 Ice 0.92 2.1 2.22 air 0.0011875 1.01 0.024

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Thermal Conductivity is a function of soil texture and moisture 1.50 clay y ( W m -1 K -1 ) 1.00 1.25 clay sand loam silt clay litter C onducti vi ty 0.50 0.75 Therm al C 0.00 0.25

volumetric water content

0.0 0.1 0.2 0.3 0.4 0.5 0.6

0.00

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Soil Temperature Profiles ponderosa pine 0 1 0.0 e pt h ( m ) -0.3 -0.2 -0.1 d e 0 6 -0.5 -0.4 1 am 9 am 12 pm 430 pm Soil Temperature (oC) 5 10 15 20 25 30 35 40 -0.7 -0.6

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T z t

(

)

 

T

A

( ) exp(

0 

z D

/

) sin( (



t



t

)



z D

/

)

Temperate Deciduous Forest D180 1997

T z t

( , )

 

T

A

( ) exp(

0 z D

/

) sin( (



t

₀

)

z D

/

)

D180, 1997 ture ( C ) 22 23 24 2 cm 4 cm 8 cm 16 cm 32 cm S o il T e mpe ra t 20 21 Time (hours) 0 4 8 12 16 20 24 19 Damping Depth D 2  Damping Depth

 is angular frequency (radians per second)  is period of fluctuation

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Summer, Dry CA Grassland

Day 204, 2001, Vaira Grassland

40 re 30 35 _{2 cm} 4 cm 8 cm 16 cm o il Temperat u r 25 30 16 cm 32 cm S o 15 20 Time (hours) 0 5 10 15 20 10

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Temperate Deciduous Forest D80, 1997, dormant 20 2 cm (C ) 16 18 4 cm 8 cm 16 cm 32 cm o il T e mper atu re 12 14 S o 10 12 Time (hours) 0 4 8 12 16 20 24 8 ESPM 129 Biometeorology

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Less Ideal, Heterogeneous Site

young ponderosa pine

45 rature 30 35 40 2 cm 4 cm 8 cm 16 cm 32 cm So il Tem pe r 20 25 0 500 1000 1500 2000 5 10 15 Time 0 500 1000 1500 2000

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 

L



NM

O

QP

2 2 1 1 2 2 z z A A ln( / ESPM 129 Biometeorology

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1 K -1 ) 2.5 3.0 Vaira grassland, 2002 Verhoef method 2 to 16 cm Amplitude Method a l dif fu s iv ity ( W m -1 0 1.5 2.0  

L



NM

O

QP

2 2 1 1 2 2 z z A A ln( / ther m a 0.0 0.5 1.0

volumetric soil moisture @ 10 cm (cm3 cm-3)

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Annual Course in Soil Temperature

20

30 Air temperature, daily average Soil temperature, daily average

T emperat ure 10 20 T 10 0 Day 0 50 100 150 200 250 300 350 -10 ESPM 129 Biometeorology

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Mean Soil Temperature Scales with Mean Air Temperature FLUXNET Database ) 14 16 18 b[0] 0.6243257655 b[1] 0.9216133206 r ² 0.9342107631 oi l: an nual ( C ) 8 10 12 Ts o 4 6 8 Tair:annual (C) 2 4 6 8 10 12 14 16 18 2

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150 Wheat 100 125 d (W m -2) 50 75 G m o delle d 0 25 -50 -25 Time (hours) 0 400 800 1200 1600 2000 2400 -75 ESPM 129 Biometeorology

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D id F 30 Deciduous Forest W m -2 ) 20 25 ensity , G ( W 15 20 H eat Fl ux D 5 10 So il 0 5 0 400 800 1200 1600 2000 2400 -5

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30

Temperate Deciduous Forest

-2 ) 20 30 s ity , G (W m -10 a t Flux D e n s -10 0 S o il H e -20 -10 D 0 50 100 150 200 250 300 350 -30 ESPM 129 Biometeorology Day