DO 1000 ITER=1,2
Adapted from Goudriann (1977) with permission, page #148,
downward radiance
KM=0.0
DELTA=0.1
SUMDEV=100.0
DO 580 K=1,ITKM
581 SUMDEV1=SUMDEV
SUMDEV=0.0
MAXDEV=0.0
DO 550 J=1,IDPTH
DEV=EXP(-KM*(J-1)*LS(J))-PAR(J) ‘equation 1 this
paper”
MAXDEV=AMAX1(ABS(DEV),MAXDEV)
550 SUMDEV=SUMDEV+DEV*DEV
IF(SUMDEV.GT.SUMDEV1) GO TO 582
KM=KM+DELTA
GO TO 581
582 DELTA=-0.1*DELTA
580 CONTINUE
LAD is KM corrected to site (NF) sun zenith (ZANGLE [in
degrees]), XPI=PI/180°
LAD=KM*COS(ZANGLE(NF)*XPI)
Adapted differential form of equation 15 in AccuPAR Refer-
ence Guide (Decagon Devices Inc 2014). FB is the direct over
total downwelling irradiance fraction. From AccuPAR output,
or if not available, FB can be calculated from above-canopy
PAR recordings. A is the canopy PAR absorption (equation 3
this paper). PARDEL and PARMN are the difference and aver-
age PAR for each sequential depth interval.
Note: On first pass, ITER=1, the optimized KM based on
LS=0.2 is used. On the second pass, ITER=2, KM based on
LS=(LAI increments) is converted to LAD and LAD substi-
tuted for KM in the loop below.
DO 700 J=IDPTH-1
LAI=((1.0-1.0/(2.0*KM))*FB(NF)-1.0)*PARDEL/
PARMN ‘equation 4 this paper’
LAI=LAI/(A*(1.0-0.47*FB(NF)))
700 LS(J)=LAI
1000 CONTINUE
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PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
