1. 1
Advanced Soil and Water
Engineering #6
Masahiro Tasumi
Dept. Forest & Env. Sci.
Class schedule
No. Date Contents
1 4/11 Course outline for Advanced Soil and Water Engineering
2 4/18 Physical characteristics of soil I
3 4/25 Physical characteristics of soil II (NO CLASS)
4 5/9 Physical characteristics of soil III
5 5/16 Physical characteristics of soil IV
6 5/23 Micrometeorology I
7 5/30 Micrometeorology II
8 6/6 Micrometeorology III
9 6/13 Micrometeorology IV
10 6/20 Soil water and Evapotranspiration I
11 6/27 Soil water and Evapotranspiration II
12 7/4 Soil water and Evapotranspiration III
13 7/11 Soil and water engineering in operation I
14 7/18 Soil and water engineering in operation II
15 7/25 Discussions
Today’s Topic
Micrometeorology for
Soil and Water
-Micrometeorology I＆II
Soil and water conservation engineering
Theory
Experience
Science
Engineering
A Good
Engineer
Practical
Operational
Fundamental
Universal
Academic
2. 2
Material provided by Prof. Uchijima
Energy flow from Solar Earth Human Activities Energy and material cycle in the ecosystem
Material provided by Prof. Uchijima
Very small and
ignorable
in terms of Energy
Balance
Key for
irrigation &
crop water requirement Assume that you teach “surface radiation and heat
balance” to undergraduate students, using power-
point, in 15-30 minutes. Please make a power-point
file with explanatory, because not the presentation but
the file is evaluated. Please do this homework by your
own. Assignment due date is indicated in class.
You may want to teach the each energy component of
the following equations, and the balance.
The purpose of the assignment is to promote your
understanding of the concept of energy balance.
Homework Assignment 2
outinsn LLR1R
GEHR n
3. 3
Solar Radiation,
Rs
Solar Radiation
reflected, Rs
Incoming Longwave
Radiation, Lin
Outgoing Longwave
Radiation, Lout
Land Surface
Lin reflected,
(1- )Lin
outinBBsn LLR1R
Surface Radiation Balance
Rn = Net Radiation
Fundamental Theory for
Surface Radiation Balance
Heat transfer process:
Three fundamental mechanisms of
Heat transfer =
Conduction, Convection, Radiation
Refer to:
http://www.wisc-online.com/objects/heattransfer/
http://en.wikipedia.org/wiki/Heat_transfer
Fundamental Theory for
Surface Radiation Balance
Radiation fundamentals:
Stefan-Boltzmann Equation
4
sBB TL
where LBB is total broad-band radiation from an object (W/m2), ε is
surface emissivity of the object, σ is the Stefan-Boltzmann constant
5.67•10-8 W/m2/K4, and Ts is surface temperature of the object (K).
Stefan-Boltzmann Equation says;
Every object discharges energy as radiation, from the
surface. And the intensity of the energy depends on
emissivity and temperature to the 4th power. (i.e. a hot
object discharges a tremendous amount of energy)
Fundamental Theory for
Surface Radiation Balance
Radiation fundamentals:
Planck’s Equation
where Bλ is radiation flux (W/m2) for wavelength λ (μm), ελ is surface
emissivity of the object for wavelength λ, T is surface temperature of
the object (K).
Planck’s Equation says;
Surface temperature controls not only the intensity of
radiation energy but also the wavelength (= characteristics)
of radiation.
x ελ
4. 4
Fundamental Theory for
Surface Radiation Balance
Radiation fundamentals:
Planck’s Equation
Planck wanted to quantitatively measure “temperature”
by “color”.
2500-3900℃
3900-5300℃3900-5300℃ 5300-6000℃6000-7500℃
10000-29000℃7000-10000℃
世界天文年2009日本委員会 「ガリレオ君と仲間たち」より
Example of Planck’s equation
Calculation results of Planck’s
equation
Human eyes can
see 0.38-0.77um
5780K (Sun) 300K (desk)
Wavelength
is different!
Intensity is
different!
0.5 9.7
Human’s eyes are optimized to “see” the
radiation energy from the Sun.
Solar Radiation,
Rs
Solar Radiation
reflected, Rs
Incoming Longwave
Radiation, Lin
Outgoing Longwave
Radiation, Lout
Land Surface
Lin reflected,
(1- )Lin
outinBBsn LLR1R
Return to Surface Radiation Balance
Rn = Net Radiation
5. 5
Surface Heat Balance
Rn = Net Radiation
Ground Heat
Flux, G
Sensible Heat
Flux, H
Land Surface
Latent Heat Flux,
lE
Net Radiation, Rn
GEHR n
Net radiation energy is
“immediately” converted
to heat at surface, and be
used for three purposes.
Surface Heat Balance
Ground heat flux, G
GEHRn
z
T
G s
s
Land Surface
G
T = Ts
z = z0
T = T-1
z = z-1
Thermal conductivity = s
G is positive (= downward) in daytime and negative (upward)
in nighttime, approximated as nearly zero in 24-hour average.
Surface Heat Balance
Ground heat flux, G
GEHRn
1972 Potato Field, Kimberly ID
10:00 - 12:00 am Clear-sky dates only
Data provided by Dr. James L. Wright, USDA/ARS
0.00
0.10
0.20
0.30
0.40
0.00 2.00 4.00 6.00
LAI
G/Rn
y = 0.226e-0.45x
-0.0293
R2
= 0.678
1972 Potato Field, Kimberly ID
10:00 - 12:00 am Clear-sky dates only
Data provided by Dr. James L. Wright, USDA/ARS
0.00
0.10
0.20
0.30
0.40
0.00 2.00 4.00 6.00
LAI
G/Rn
y = 0.226e-0.45x
-0.0293
R2
= 0.678
Surface Heat Balance
Sensible heat, H
GEHRn
ah
pair
r
dTCρ
=H
Land Surface
z = d + z1
zero plane displacement (d)
, T = T1
z = d
z = d + z2 , T = T2
Resistance, rah
H
dT = T1 - T2
6. 6
Surface Heat Balance
Latent heat, lE
GEHRn
( )
av
21
air
r
q-q
ρ=E
Surface Heat Balance
Resistance
ku
z
z
ln
r
*
)z(h)z(h
1
2
ah
12
Land Surface
z = d + z1
zero plane displacement (d)
, T = T1
z = d
z = d + z2 , T = T2
Resistance, rah
H
dT = T1 - T2
)z(m
om
z
*
z
z
ln
ku
u
Resistance depends on;
- Wind speed (u)
- Surface condition (zom)
- Air stability status (Ψ)
Resistances for;
momentum, heat and
vapor transports
Surface Heat Balance
Wind speed
Wind speed has logarithmic
relationship to the height.
Datum is “d (zero-plane
displacement)” plus zom
(surface roughness length)
0
10
0 2.5
d
zom
Wind Speed
Height
