Technote BEAM Lakes Project
Realisation of the bio-optical model for Finnish Lakes in the Hydrolight Code
s. code module ACRIMER_lake_fin1_20070705.for
This module is called by hydrolight for each run to produce a new water leaving radiance reflectance spectrum within a loop.
Random numbers are used to select the concentration within a defined range on the logarithmic scale.
The ranges are:
log_agelb_an = log(0.5) !log begin/end of absorption /scattering at 443 nm lake Finland log_agelb_en = log(15.0) log_bpart_an = log(0.10*0.951) ! in TSM concentration units lake Finland log_bpart_en = log(20.0*0.951) ! in TSM concentration units lake Finland log_apig_an = log(0.5) ! in chlorophyll concentration units, later converted into absorption log_apig_en = log(50.0) ! in chlorophyll concentration units log_bwit_an = log(0.001) ! scattering of white particles log_bwit_en = log(0.01)
The wavelength exponents for yellow substance absorption (== fulvic acid), bleached particle absorption (== humic acids) and scattering of particles and white particles are:
mean_ex_agelb = 0.02 ! spectral exponent gelbstoff fulvic acid (Carder et al.)
mean_ex_apart = 0.01 ! spectral exponent particle absorption lake Finland and humic acid (Carder et al)
mean_ex_bpart = 0.705 ! spectral exponent particle scattering lake Finland
ex_bwit= 0.8 !spectral exponent for mean white scatterer
c..spectral exponent modification using std and random normal distribution
c
ex_agelb=mean_ex_agelb+gasdev(idumrand)*std_agelb
ex_apart=mean_ex_apart+gasdev(idumrand)*std_apart
ex_bpart=mean_ex_bpart+gasdev(idumrand)*std_bpart
c..draw random concentration for this case
conc_agelb=exp(log_agelb_an+ran1(idumrand)
1 *(log_agelb_en-log_agelb_an))
conc_bpart=exp(log_bpart_an+ran1(idumrand)
1 *(log_bpart_en-log_bpart_an))
conc_apig =exp(log_apig_an +ran1(idumrand)
1 *(log_apig_en -log_apig_an))
conc_apart=conc_bpart/0.951*0.078*(1.1-ran1(idumrand)*0.2) ! conc_apart calculated in aborption unit for 443 nm for Finland lake
c....compute conc of white scattering material
conc_bwit=exp(log_bwit_an+ran1(idumrand)! scattering of white particles
1 *(log_bwit_en-log_bwit_an))
c calculate IOPs for each component for all spectral bands
c
do ilam=1,nlam
agelb(ilam)=exp(-ex_agelb*(lam(ilam)-442))
apart(ilam)=exp(-ex_apart*(lam(ilam)-442))
bpart(ilam)=(lam(ilam)/442)**(-ex_bpart)
apig(ilam)=(pig_a(ilam)*conc_apig**(-pig_b(ilam)))*conc_apig
asub(ilam)=apig(ilam)+conc_agelb*agelb(ilam)
1 +conc_apart*apart(ilam)
bwit(ilam)=(lam(ilam)/442)**(-ex_bwit)! white scatterer
bsub(ilam)=conc_bpart*bpart(ilam)+conc_bwit*bwit(ilam)
enddo
The optical constants are:
Pigment properties:
data piglam/412.0, 442.0,490.0,510.0,555.0,560.0,620.0,664.0, 1 670.0,708.0,753.0,778.0,865.0/ data pig_a/0.0354,0.04,0.022,0.0153,0.0078,0.0075,0.0091, 1 0.0141,0.0176,0.0019,0.000024,0.00001,0.000001/ data pig_b/0.1397,0.1496,0.0944,0.0576,0.0472,0.045, 1 0.0729,0.1134,0.126,0.003,0.0,0.0,0.0/
Wavelengths (MERIS and SeaWiFS):
data lam/4.123e+002,4.423e+002,4.897e+002,5.096e+002,5.550e+002, 1 5.595e+002,6.194e+002,6.643e+002,6.700e+002,7.081e+002, 2 7.530e+002,7.782e+002,8.646e+002/ Absorption of pure water: data awat/4.597e-003,6.884e-003,1.492e-002,3.250e-002, 1 5.960e-002,6.167e-002,2.746e-001,4.263e-001,4.390e-001, 2 8.147e-001,2.298e+000,2.710e+000,4.605e+000/
pure water scattering:
c..compute scattering of pure water do ilam=1,nlam bwat(ilam)=0.00288*(lam(ilam)/500.0)**(-4.32) enddo
Roland Doerffer 12.Oct. 2007