Fig. 1. Investigated waters and sample point distributions. (a) Taihu Lake; (b) Poyang Lake; (c) Pearl River Estuary; (d) Daya Bay
Fig. 2. Quasi-synchronization sample point distribution of remote sensing data from VIIRS satellite
Fig. 3. (a) Influence of Secchi disk depth on remote sensing reflection spectra of waters; (b) SD_H
Fig. 4. Relationship between Secchi disk depth and SD_H
Fig. 5. Relationship between measured and calculated Secchi disk depth
Fig. 6. Comparison of Secchi disk depth remote sensing evaluation models. (a) Single-band model; (b) band ratio model; (c) three-band model; (d) QAA and SD_H model
Fig. 7. (a) Comparison of measured and satellite-derived remote sensing reflectance ratio
Rrs
; (b) comparison of remote sensing reflectance spectrum and satellite remote sensing image reflectance spectrum measured at quasi-synchronous sampling points; (c) comparison of satellite remote sensing image and measured SD_H
Fig. 8. Spatial distributions of Secchi disk depth in Pearl River Estuary, Daya Bay, Taihu Lake, and Poyang Lake. (a) Satellite data evaluation results in Pearl River Estuary and Daya Bay (white represents cloud-shaded water, where the transparency is set to zero); (b) field monitoring data in Pearl River Estuary and Daya Bay; (c) satellite data evaluation result in Taihu Lake; (d) satellite data evaluation result in Poyang Lake
Fig. 9. Correlation among Secchi disk depth of investigated waters,
cTSS
,
cChla
and
aCDOM
(440). (a) Pearl River Estuary; (b) Daya Bay; (c) Taihu Lake; (d) Poyang Lake
Fig. 10. Correlation among Secchi disk depth of all sampling points, (a)
cTSS
, (b)
cChla
and (c)
aCDOM
(440)
Fig. 11. Comparison of Secchi disk depth products between VIIRS and MODIS Aqua observations on 2014-01-03 in Pearl River Estuary. (a) VIIRS; (b) MODIS
Type | Model | Algorithm |
---|
Empirical model | Single-band model | DSD
=
a+bRrs
(678) | Band-ratio model | DSD
=
a+b
[
Rrs
(488)/
Rrs
(555)] | Three-band model | DSD
=
a+bRrs
(678)+
c
[
Rrs
(488)/
Rrs
(555)] | Quasi-analytical model | QAA-based model | DSD=
ln
|
|
Table 1. Transparency remote sensing evaluation models
Step | Property | Expression |
---|
1 | rrs | rrs
=
Rrs
/(0.52+1.7
Rrs
) | 2 | u
(
λ
)
= | u
(
λ
)
=
,
g0
=0.089,
g1
=0.125 | 3 | a
(555) | a
(555)=
aw
(555)
+
,
χ=
lg
| 4 | bbp
(555) | bbp
(555)=
-bbw
(555) | 5 | η | η
=2
.
0
| 6 | bbp
(
λ
) | bbp
(
λ
)=
bbp
(555)
| 7 | a
(
λ
) | a
(
λ
)=
| 8 | kd
(
λ
) | kd
(
λ
)=(1
+m0θs
)
a
(
λ
)
+m1
{1
-m2
exp[
-m3a
(
λ
)]}
bb
(
λ
),
m0
=0.005,
m1
=4.26,
m2
=0.52,
m3
=10.8,
γ
=0.265 | 9 | SD | SD
=
ln
|
|
Table 2. Calculation procedure of transparency remote sensing evaluation model based on QAA
Investigated area | Sampling date | Waters | Site No. |
/m |
/(mg·L
-1
) |
/(μg·L
-1
) | aCDOM
(440) /m
-1 |
---|
Taihu Lake | 2011-05-01—2011-05-08 | Taihu Lake
(2011-05) | 51 | 0.25±0.11 | 48.31±37.16 | 23.17±64.93 | 1.41±1.04 | Poyang Lake | 2011-08-08—2011-08-10 | Poyang Lake
(2011-08) | 38 | 0.22±0.12 | 108.97±100.63 | 6.53±7.54 | 1.67±0.94 | Pearl River
Estuary | 2014-05-11—2014-05-13 | Pearl River
Estuary(2014-05) | 23 | 0.84±0.44 | 25.45±18.53 | 2.01±1.20 | 0.55±0.27 | Daya Bay | 2014-05-15—2014-05-18 | Daya Bay
(2014-05) | 27 | 2.41±1.28 | 21.97±5.58 | 4.92±1.55 | 0.26±0.18 |
|
Table 3. Sampling information and ecological parameter statistics of waters in Taihu Lake, Poyang Lake, Pearl River Estuary, and Daya Bay
VIIRS | MODIS |
---|
Band | Central
wavelength /nm | Wavelength
range /nm | Spatial
resolution /m | Band
No. | Central
wavelength /nm | Wavelength
range /nm | Spatial
resolution/m | M1 | 412 | 20 | 750 | 8 | 412 | 15 | 1000 | M2 | 445 | 18 | 750 | 9 | 443 | 10 | 1000 | M3 | 488 | 20 | 750 | 10 | 488 | 10 | 1000 | 3 | 469 | 20 | 500 | M4 | 555 | 20 | 750 | 12 | 551 | 10 | 1000 | 4 | 555 | 20 | 500 | I1 | 645 | 50 | 375 | 1 | 645 | 50 | 250 | M5 | 672 | 20 | 750 | 13 | 667 | 10 | 1000 | M6 | 751 | 15 | 750 | 15 | 748 | 10 | 1000 | M7 | 865 | 39 | 750 | 16 | 870 | 15 | 1000 | I2 | 865 | 39 | 375 | 2 | 859 | 36 | 250 |
|
Table 4. Comparison of water color band settings of VIIRS and MODIS