LANDSCAPE ECOLOGY
SREM 3011
LECTURE 14
Dr Brendan Mackey
Department of Geography
The Australian National University
Radiation Modelling
Amount of radiation critical for plants and animals:
(1) Affects photosynthesis?primary productivity
(2) Thermal regime?air and soil temperature
(3) Controls evaporation rate?soil moisture
- Evaporation liquid water?water vapour requires energy
ground? atmosphere
- Energy comes from solar radiation
Hence,people record aspect as an index of how
exposed/sheltered a site is,as shaded sites are
cooler and moister
Components and
parameters of the
SRAD solar radiation
model
Only those parameters
relevant to incoming
short-wave radiation
are shown
NB SRAD calculates radiation
using a DEM
But,amount of radiation received at a location is
a function of:
(1) Aspect
(2) Slope
(3) Horizon shading
(4) Time of year
(5) Latitude angle of sun in the sky
ie,In winter,sun is to the north and
low in horizon
Tasmania
S-E Aust
Tropic of
Capricorn
Equator
Tropic of
Cancer
0
-180
July
Jan
March Sept
Cairns,
Radiation is measured by Met,bureau using
radiometers on flat ground
Therefore,interpolation surface contains no samples
of radiation on an inclined surface
Alternative is to model radiation using a deter-
ministic,process-simulation model -,cloudy”
requires user to provide estimates of about 10
parameters to calibrate model to prevailing
atmospheric and terrain conditions
calculates radiation on an inclined surface
Stations with measured mean monthly solar radiation
+ Type 1 stations; * Type 3 stations,Hatched area denotes Hunter Valley region.
Estimating monthly mean values of daily total solar radiation for Australia
Units,MJ/m2/day
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
N
E
S
N
As
pe
ct
No
rth
-e
as
t Q
ld
Ja
n
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
As
pe
ct
N
or
th
-e
as
t Q
ld
Ju
ly
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
As
pe
ct
So
uth
-e
as
t A
us
t J
an
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
As
pe
ct
So
uth
-e
as
t A
us
t J
uly
Slope and aspect can combine to drastically alter
the prevailing meso climate conditions producing
micro,localized climatic conditions
Cannot be modelled just from met,data alone
Many?disjunct? biological distribution patterns are
a function of this localized modification of the
radiation
NB Ratio sometimes > 1.0
Modelling radiation regime superior to using?aspect?
- closer index of actual process
- provides a more?transportable? correlate
- integrates a number of environmental variables into
a measure of the primary environmental regimes
Increasing scale at which moisture and radiation
regimes are spatially modelled:
Precipitation / Evaporation
P:E / Catchment hydrology
P:E / Catchment hydrology
+ Soil attributes
(Large scale)
(Small scale)
Radiation Regime
Extra-terrestrial
Radiation
Atmospheric
Attenuation
Slope,Aspect,
Horizon-shading
Canopy Cover
(Large scale)
(Small scale)
MESO
TOPO
MICRO/
STAND/
CANOPY
SREM 3011
LECTURE 14
Dr Brendan Mackey
Department of Geography
The Australian National University
Radiation Modelling
Amount of radiation critical for plants and animals:
(1) Affects photosynthesis?primary productivity
(2) Thermal regime?air and soil temperature
(3) Controls evaporation rate?soil moisture
- Evaporation liquid water?water vapour requires energy
ground? atmosphere
- Energy comes from solar radiation
Hence,people record aspect as an index of how
exposed/sheltered a site is,as shaded sites are
cooler and moister
Components and
parameters of the
SRAD solar radiation
model
Only those parameters
relevant to incoming
short-wave radiation
are shown
NB SRAD calculates radiation
using a DEM
But,amount of radiation received at a location is
a function of:
(1) Aspect
(2) Slope
(3) Horizon shading
(4) Time of year
(5) Latitude angle of sun in the sky
ie,In winter,sun is to the north and
low in horizon
Tasmania
S-E Aust
Tropic of
Capricorn
Equator
Tropic of
Cancer
0
-180
July
Jan
March Sept
Cairns,
Radiation is measured by Met,bureau using
radiometers on flat ground
Therefore,interpolation surface contains no samples
of radiation on an inclined surface
Alternative is to model radiation using a deter-
ministic,process-simulation model -,cloudy”
requires user to provide estimates of about 10
parameters to calibrate model to prevailing
atmospheric and terrain conditions
calculates radiation on an inclined surface
Stations with measured mean monthly solar radiation
+ Type 1 stations; * Type 3 stations,Hatched area denotes Hunter Valley region.
Estimating monthly mean values of daily total solar radiation for Australia
Units,MJ/m2/day
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
N
E
S
N
As
pe
ct
No
rth
-e
as
t Q
ld
Ja
n
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
As
pe
ct
N
or
th
-e
as
t Q
ld
Ju
ly
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
As
pe
ct
So
uth
-e
as
t A
us
t J
an
0 5 10 15 20 25 30 35 40 45 50 55 60
Slope
As
pe
ct
So
uth
-e
as
t A
us
t J
uly
Slope and aspect can combine to drastically alter
the prevailing meso climate conditions producing
micro,localized climatic conditions
Cannot be modelled just from met,data alone
Many?disjunct? biological distribution patterns are
a function of this localized modification of the
radiation
NB Ratio sometimes > 1.0
Modelling radiation regime superior to using?aspect?
- closer index of actual process
- provides a more?transportable? correlate
- integrates a number of environmental variables into
a measure of the primary environmental regimes
Increasing scale at which moisture and radiation
regimes are spatially modelled:
Precipitation / Evaporation
P:E / Catchment hydrology
P:E / Catchment hydrology
+ Soil attributes
(Large scale)
(Small scale)
Radiation Regime
Extra-terrestrial
Radiation
Atmospheric
Attenuation
Slope,Aspect,
Horizon-shading
Canopy Cover
(Large scale)
(Small scale)
MESO
TOPO
MICRO/
STAND/
CANOPY
