A FIRST LOOK AT THE MODIS 8-DAY PSN DATA FOR 2001 MODIS Science Team Mtg 19 December 2001 Steven W....
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Transcript of A FIRST LOOK AT THE MODIS 8-DAY PSN DATA FOR 2001 MODIS Science Team Mtg 19 December 2001 Steven W....
A FIRST LOOK AT THE MODIS 8-DAY PSN A FIRST LOOK AT THE MODIS 8-DAY PSN DATA FOR 2001DATA FOR 2001
MODIS Science Team Mtg19 December 2001
Steven W. RunningNTSG, Univ. of Montana
MODIS PhotosynthesisMODIS Photosynthesis
GPP = Radiation
UseEfficiency
AbsorbedPhotosynthetically
ActiveRadiation
x
The Monteith equation….The Monteith equation….
APAR
(FPAR) (0.45Rnet )
0
20
40
60
80
100
120
0 5 10 15 20 25 30
Daily APAR (MJ m-2 day-1)
GP
P (
gC
m
-2 d
ay
-1)
Grass
Forest
Wheat
Photosynthesis Under Optimum Conditions
Epsilon is the slope of theline described by
GPP = APAR
MODIS PhotosynthesisMODIS Photosynthesis
Radiation Use EfficiencyRadiation Use Efficiency
= max [mtmin ][mvpd ]
MaximumRadiation Use Efficiency
under ideal conditionsfor each biome
Vapor Pressure DeficitCoefficient
Temperature Coefficient for each biome
The coefficients are calculated from daily minimum and maximum air temperature which are therefore necessary inputs to the model
0.0
0.2
0.4
0.6
0.8
1.0
1.2
-10 -5 0 5 10 15 20 25 30
Daily Minimum Temperature
mtm
in
Grassland Biome
Tmin_max & Tmin_minare Tabulated by biome
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
700 1200 1700 2200 2700 3200 3700 4200
Vapor Pressure Deficit (Pa )
mv
pd
All Biomes
Tmin_maxTmin_max
Tmin_minTmin_min
VPD Tmin
VPD & Tmin CoefficientsVPD & Tmin Coefficients
maxTm in, VPD fPAR, Rnet GPP
LAI SLA
fine rootm ass
allom etry
leaf m ass
Q10, Tavg MR
-
Daily"NPP"
=
MRindex
MOD-17Daily "NPP"
Photosynthesis
Maintenance Respiration
does not include growth respiration orlive wood maintenance respiration costs
leafm ass
D aily O utputs
ESTIMATION OF DAILY NPP IN MOD17 ALGORITHM
MODIS 8-day PSN Winter 2001
MODIS 8-DAY PSN SUMMER 2001
MODIS 8-day LAI Product
LAI of center pixel
Park Falls forest site17MAY2001 – 16OCT2001
Park Falls forest site17MAY2001 – 16OCT2001
The variability in LAI around the flux tower is shown by the scatter of blue (3x3 km) and green (5x5 km) dots.
The variability in LAI around the flux tower is shown by the scatter of blue (3x3 km) and green (5x5 km) dots.
Park Falls5x5 km
Land Cover
around towerDavis et al.
Land Cover around towerDavis et al.
LAI field data Co-KrigedAug 2000
Gower et al.
LAI field data Co-KrigedAug 2000
Gower et al.
MODIS Cutouts: fPAR for Park Falls
All pixels in5x5 cutoutGreen=rejectedBlue=accepted
Acceptedpixels
Day of Year
0 50 100 150 200 250 300 350
Ma
xim
um
Ca
no
py P
ho
tosyn
the
sis
a
nd
Eco
syste
m R
esp
ira
tio
n
( m
ol m-2
s-1)
-40
-30
-20
-10
0
10
Tallgrass Prairie in OklahomaWinter wheat in OklahomaGrassland in California
Photosynthesis
Respiration
FLUXNET GRASSLAND SITES
Day of Year
0 50 100 150 200 250 300 350
Ma
xim
um
ca
no
py p
ho
tosyn
the
sis
a
nd
Eco
syste
m R
esp
ira
tio
n
(
mo
l m-2
s-1)
-40
-30
-20
-10
0
10Respiration
Photosynthesis
Scots pine forest in FinlandMixed deciduous forest in TennesseeAspen forest in Canada
FLUXNET FOREST SITES
SUMMARY
3 Sources of variability of MODIS PSN
1. Radiometric – MODIS FPAR and LAI2. Meteorological – DAO IPAR and Temps3. Ecological – MOD 17 representation of plant physiology
Each require a different mode of validation