Underwater optical environment in the coastal waters of British Columbia, Canada
Abstract
Introduction
Materials and methods
Study area
Data collection
Modelling
HydroLight radiative transfer modelling
411 nm | 530 nm | 650 nm | 675 nm | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
April | July | April | July | April | July | April | July | |||||||||
r 2 | Slope | r 2 | Slope | r 2 | Slope | r 2 | Slope | r 2 | Slope | r 2 | Slope | r 2 | Slope | r 2 | Slope | |
Ed (0−,λ) | 0.79 | 1.41 | 0.91 | 1.17 | 0.72 | 1.27 | 0.92 | 1.06 | 0.90 | 1.40 | 0.90 | 1.05 | 0.90 | 1.42 | 0.89 | 1.03 |
Lu (0−,λ) | 0.76 | 1.32 | 0.81 | 1.25 | 0.71 | 1.35 | 0.81 | 1.19 | 0.92 | 1.24 | 0.96 | 1.74 | 0.85 | 1.20 | 0.96 | 1.72 |
K Ed(0−,λ) | 0.79 | 0.78 | 0.74 | 0.84 | 0.85 | 0.64 | 0.79 | 0.61 | 0.72 | 0.40 | 0.79 | 0.43 | 0.64 | 0.36 | 0.69 | 0.35 |
Rr (0−,λ) | 0.46 | 0.40 | 0.36 | 0.27 | 0.81 | 0.99 | 0.90 | 0.71 | 0.90 | 0.90 | 0.88 | 0.88 | 0.60 | 0.84 | 0.71 | 0.73 |
Note: Ed (z,λ), spectral downwelling plane irradiance; Lu (z,λ), spectral upwelling radiance; K Ed(z,λ) downwelling irradiance attenuation coefficient; Rr (z,λ), underwater radiance reflectance; 0–, in the water.
Results and discussion
Hydrographic data and water optical constituents
Optical dynamics
Scalar irradiance and the average cosine
Optical water mass | 411 nm | 530 nm | 650 nm | 675 nm | |||||
---|---|---|---|---|---|---|---|---|---|
April | July | April | July | April | July | April | July | ||
(z,λ) | OM1 | 0.77 ± 0.03 | 0.67 ± 0.05 | 0.61 ± 0.03 | 0.52 ± 0.06 | 0.62 ± 0.05 | 0.55 ± 0.09 | 0.66 ± 0.05 | 0.57 ± 0.10 |
OM2 | 0.81 ± 0.04 | 0.82 ± 0.03 | 0.71 ± 0.06 | 0.74 ± 0.05 | 0.78 ± 0.05 | 0.80 ± 0.05 | 0.73 ± 0.07 | 0.75 ± 0.07 | |
OM3 | 0.85 ± 0.02 | 0.90 ± 0.02 | 0.76 ± 0.04 | 0.78 ± 0.04 | 0.84 ± 0.03 | 0.85 ± 0.03 | 0.64 ± 0.14 | 0.63 ± 0.16 | |
Ed (0−,λ) (× 102) (W·m−2·nm−1) | OM1 | 0.91 ± 1.83 | 2.19 ± 3.27 | 8.55 ± 8.00 | 14.57 ± 11.30 | 7.00 ± 6.10 | 10.24 ± 8.13 | 5.26 ± 5.52 | 8.28 ± 7.56 |
OM2 | 1.96 ± 3.51 | 3.44 ± 8.51 | 17.76 ± 14.04 | 19.18 ± 23.15 | 6.75 ± 8.25 | 8.23 ± 13.96 | 3.70 ± 5.38 | 5.75 ± 11.49 | |
OM3 | 0.67 ± 2.16 | 0.02 ± 0.04 | 7.04 ± 6.30 | 4.40 ± 3.82 | 1.44 ± 3.04 | 0.21 ± 0.32 | 0.85 ± 2.45 | 0.06 ± 0.10 | |
Lu (0−,λ) (× 102) (W·m−2·sr−1·nm−1) | OM1 | 0.002 ± 0.005 | 0.015 ± 0.024 | 0.078 ± 0.082 | 0.25 ± 0.26 | 0.058 ± 0.066 | 0.17 ± 0.23 | 0.037 ± 0.048 | 0.13 ± 0.18 |
OM2 | 0.003 ± 0.005 | 0.005 ± 0.011 | 0.074 ± 0.078 | 0.059 ± 0.070 | 0.013 ± 0.0.22 | 0.013 ± 0.025 | 0.016 ± 0.020 | 0.015 ± 0.024 | |
OM3 | 0.001 ± 0.002 | 3.53 × 10−5 ± 5.99 × 10−5 | 0.023 ± 0.026 | 0.010 ± 0.007 | 0.001 ± 0.003 | 2.19 × 10−4 ± 2.49 × 10−4 | 0.003 ± 0.005 | 6.54 × 10−4 ± 6.26 × 10−4 | |
K Ed(0−,λ) (m−1) | OM1 | 2.28 ± 0.52 | 2.01 ± 0.67 | 0.69 ± 0.14 | 0.84 ± 0.35 | 0.68 ± 0.06 | 0.87 ± 0.22 | 0.87 ± 0.06 | 1.01 ± 0.19 |
OM2 | 0.75 ± 0.22 | 0.73 ± 0.27 | 0.26 ± 0.08 | 0.26 ± 0.10 | 0.52 ± 0.07 | 0.49 ± 0.06 | 0.69 ± 0.13 | 0.61 ± 0.09 | |
OM3 | 0.48 ± 0.09 | 0.43 ± 0.10 | 0.15 ± 0.03 | 0.15 ± 0.03 | 0.42 ± 0.02 | 0.42 ± 0.02 | 0.48 ± 0.11 | 0.45 ± 0.10 | |
Rr (0−,λ) (× 103) (sr−1) | OM1 | 2.00 ± 0.51 | 6.00 ± 2.00 | 8.00 ± 2.00 | 17.00 ± 7.00 | 7.00 ± 3.00 | 15.00 ± 10.00 | 6.00 ± 2.00 | 13.00 ± 8.00 |
OM2 | 1.58 ± 0.58 | 1.70 ± 0.60 | 4.00 ± 1.95 | 4.00 ± 3.00 | 1.53 ± 0.83 | 1.78 ± 1.78 | 9.00 ± 10.00 | 8.00 ± 9.00 | |
OM3 | 1.40 ± 0.29 | 1.45 ± 0.42 | 3.00 ± 1.00 | 2.00 ± 1.44 | 1.60 ± 1.15 | 1.83 ± 1.66 | 28.00 ± 27.00 | 29.00 ± 28.00 | |
bb′(z,λ) (m−1) | OM1 | 0.041 ± 0.015 | 0.091 ± 0.050 | 0.038 ± 0.015 | 0.088 ± 0.052 | 0.036 ± 0.014 | 0.083 ± 0.052 | 0.035 ± 0.015 | 0.082 ± 0.053 |
OM2 | 0.007 ± 0.005 | 0.008 ± 0.006 | 0.008 ± 0.005 | 0.007 ± 0.006 | 0.007 ± 0.005 | 0.007 ± 0.006 | 0.006 ± 0.005 | 0.006 ± 0.005 | |
OM3 | 0.002 ± 0.001 | 0.002 ± 0.002 | 0.003 ± 0.002 | 0.002 ± 0.001 | 0.002 ± 0.002 | 0.002 ± 0.001 | 0.002 ± 0.001 | 0.002 ± 0.001 | |
bb′(z,λ)/bp′(z,λ) | OM1 | 0.010 ± 0.003 | 0.014 ± 0.006 | 0.010 ± 0.003 | 0.014 ± 0.007 | 0.010 ± 0.003 | 0.014 ± 0.007 | 0.010 ± 0.003 | 0.014 ± 0.007 |
OM2 | 0.009 ± 0.005 | 0.012 ± 0.006 | 0.009 ± 0.005 | 0.012 ± 0.007 | 0.009 ± 0.005 | 0.012 ± 0.007 | 0.009 ± 0.005 | 0.012 ± 0.007 | |
OM3 | 0.008 ± 0.004 | 0.011 ± 0.007 | 0.008 ± 0.004 | 0.011 ± 0.007 | 0.008 ± 0.004 | 0.011 ± 0.007 | 0.008 ± 0.004 | 0.011 ± 0.007 | |
nEo (0−,λ) | OM1 | 0.016 ± 0.031 | 0.029 ± 0.047 | 0.154 ± 0.141 | 0.216 ± 0.180 | 0.159 ± 0.141 | 0.152 ± 0.130 | 0.113 ± 0.121 | 0.117 ± 0.114 |
OM2 | 0.021 ± 0.036 | 0.031 ± 0.064 | 0.172 ± 0.111 | 0.152 ± 0.137 | 0.071 ± 0.076 | 0.079 ± 0.110 | 0.039 ± 0.051 | 0.055 ± 0.091 | |
OM3 | 0.014 ± 0.042 | 0.000 ± 0.001 | 0.120 ± 0.106 | 0.036 ± 0.022 | 0.029 ± 0.062 | 0.002 ± 0.003 | 0.018 ± 0.049 | 0.001 ± 0.001 |
Note: (z,λ), average cosine of downwelling irradiance; Ed (z,λ), spectral downwelling plane irradiance; Lu (z,λ), spectral upwelling radiance; K Ed(z,λ) downwelling irradiance attenuation coefficient; Rr (z,λ), underwater radiance reflectance; bb′(z,λ), particulate backscattering; bp′(z,λ) particulate scattering; nEo (z,λ), normalized scalar irradiance; 0–, in the water.
Month | Station | Modelled K Eo(z,PAR) (mean) (m−1) | Modelled K Ed(0−,PAR) (mean) (m−1) |
---|---|---|---|
April | S1-1 | 0.361 | 0.356 |
S1 | 0.288 | 0.288 | |
S2-1 | 0.169 | 0.169 | |
S2-2 | 0.240 | 0.245 | |
S2-3 | 0.998 | 0.963 | |
S3 | 0.181 | 0.182 | |
S3-1 | 0.260 | 0.256 | |
S3-2 | 0.658 | 0.653 | |
S4-1 | 0.221 | 0.220 | |
S4-2 | 0.337 | 0.338 | |
S4-3 | 0.478 | 0.491 | |
July | S1-1 | 0.306 | 0.308 |
S1-2 | 0.254 | 0.253 | |
S1 | 0.232 | 0.232 | |
S2-1 | 0.286 | 0.291 | |
S2-2 | 0.400 | 0.400 | |
S2-3 | 1.957 | 1.900 | |
S3 | 0.358 | 0.333 | |
S3-1 | 0.563 | 0.565 | |
S3-2 | 0.648 | 0.618 | |
S3-3 | 0.393 | 0.388 | |
S4-1 | 0.211 | 0.213 | |
S4-2 | 0.412 | 0.415 | |
S4-3 | 0.473 | 0.475 | |
S5 | 0.381 | 0.387 | |
S5-1 | 0.264 | 0.268 | |
S5-2 | 0.442 | 0.441 | |
S6 | 0.255 | 0.257 | |
S6-1 | 0.237 | 0.237 | |
S6-2 | 0.283 | 0.279 |
Note: K Eo(z,PAR), scalar irradiance attenuation coefficient; K Ed(0−,PAR), downwelling irradiance attenuation coefficient; PAR, photosynthetically available radiation, 0–, in the water.
Conclusions
List of abbreviations
- AOP
- apparent optical property
- CDOM
- chromophoric dissolved organic matter
- chl a
- chlorophyll a
- FF
- Fournier-Forand
- HPLC
- high-performance liquid chromatography
- IOP
- inherent optical property
- Minispec OCR
- miniature hyperspectral ocean colour radiometer
- MSV
- Marine Science Vessel
- OM
- optical water mass
- PAR
- photosynthetically available radiation
- SoG
- Strait of Georgia
- SD
- standard deviation
Fundamental quantities and other symbols
- 0+
- above water
- 0−
- in the water column
- B wd
- wavelength-dependence of the backscattering coefficient
- p
- probability value
- r 2
- coefficient of determination
- λ
- wavelength (nm)
- z
- depth (m)
- Z 1%
- depth of 1% irradiance (m)
- Z eu
- depth of the euphotic zone (m)
Radiometric quantities
- Lu
- upwelling radiance (W·m−2·sr−1)
- Lw
- water-leaving radiance (W·m−2·sr−1)
- Ed
- in-water downwelling irradiance (W·m−2)
- Es
- above-water downwelling irradiance (W·m−2)
- Eu
- above-water downwelling irradiance (W·m−2)
- Eo
- scalar irradiance (W·m−2)
- nEo
- modelled normalized scalar irradiance (W·m−2)
Inherent optical properties
- a t′
- scattering-corrected absorption coefficient (m−1)
- a c′
- scattering-corrected CDOM absorption coefficient (m−1)
- b t′
- total scattering coefficient without water scattering coefficient (m−1)
- b p′
- particulate scattering coefficient without water scattering coefficient (m−1)
- b b′
- modelled particulate backscattering coefficient (m−1)
- c t′
- measured total beam attenuation coefficient without water beam attenuation coefficient (m−1)
Apparent optical properties
- Rr
- radiance reflectance (sr−1)
- K Ed
- downwelling irradiance attenuation coefficient (m−1)
- K Eo
- scalar irradiance attenuation coefficient (m−1)
- average cosine
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