Optical Measurements

(LiCor) & KD Values

Briana Rice

CHM 576

Fall 2009

OutlineMeasurementsMeasurements

KKDD Values Values

SignificanceSignificanceEffectsEffects

Depth vs. PAR IrradianceDepth vs. PAR Irradiance

KKDD vs. Turbidity vs. Turbidity

KKDD vs. DOC vs. DOC

Measurements

LiCor sensor used for measurementsLiCor sensor used for measurements

Scalar collector- measuring light Scalar collector- measuring light from any directionfrom any direction

Blocked upward irradiance to Blocked upward irradiance to measure in airmeasure in air

Measure irradiance at various Measure irradiance at various depthsdepths

KD Values

Diffuse attenuation coefficient in mDiffuse attenuation coefficient in m-1-1

Determined by inherent optical Determined by inherent optical properties, but are strictly properties of properties, but are strictly properties of the radiation fieldthe radiation field

Light attenuation is exponential with Light attenuation is exponential with depthdepth

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KD =1

z2 − z1

lnEd z1( )Ed z2( )

KD Value Effects

Larger KLarger KDD value, light attenuated so does not reach as far value, light attenuated so does not reach as far

Varies with different water bodiesVaries with different water bodies

Scattering overcomes difference in beam angle (sunlight), Scattering overcomes difference in beam angle (sunlight), so Kso KDD can be used to compare one water body to another can be used to compare one water body to another

Varies with different water typesVaries with different water types

KKDD increases with increasing turbidity increases with increasing turbidity

KKD D increases with increasing DOC concentrationincreases with increasing DOC concentration

Calculated KD Values (units m-

1) Station

Cruise 1

LCFRP Sept ‘08

Cruise 2

LCFRP Oct ‘08

M18 1.36 1.07 1.55 0.82

M23 1.37 1.01 1.43 1.34

M35 2.05 1.91 1.79 2.27

M42 2.15 2.48 1.95 2.56

M54 2.11 2.07 2.40 3.10

M61 2.59 3.03 2.46 3.68

HB 2.60 4.02 2.46 3.79

ln (E0/Ez) vs. Depth (m)

Cruise 1 (Station M42): Depth Plot for KD

Cruise 2 (Station M42): Depth Plot for KD

Cruise 1: KD Values vs.

Turbidity

Cruise 2: KD Values vs.

Turbidity

KD vs. DOC Concentration

KD vs. DOC Concentration