Evaluation of the Influence of Aquatic Plants and Lake Bottom on the Remote-Sensing Reflectance of Optically Shallow Waters

Figures & data

Fig. 1 Location of Lake Taihu, the study area. The ODW and OSW sites are shown on the map.

Fig. 2 Total absorption spectra a(λ) (left) and total backscattering coefficients b_b(λ) (right) at all available sites in Lake Taihu.

Table 1. Selected sites and their corresponding chl a concentrations.

Site No.	3	4	63	70	80	85	87	97	100
chl a (mg m^−3)	108.90	27.21	8.97	31.24	80.05	43.56	15.91	47.82	97.39

Fig. 3 (a) Comparison of the standard deviation of the measured and simulated R_rs(λ) and (b) spectra shape for the two sites.

Fig. 4 Comparison of the peak magnitudes between the simulated R_rs(λ) and measured R_rs(λ) (left: first peak around 560 nm; right: second peak around 700 nm). The triangles indicate the simulated values; the dashed-dotted lines show y = x, and the solid lines show the actual relationship between the simulated and measured values.

Fig. 5 Comparison of the peak positions between the simulated R_rs(λ) and measured R_rs(λ) (left: first peak around 560 nm; right: second peak around 700 nm). The triangles indicate the simulated values; the dashed-dotted lines show y = x, and the solid lines show the actual relationship between the simulated and measured values.

Table 2. Detailed description of the simulated and measured R_rs(λ) at the nine selected sites.

Sites	3	4	63	70	80	85	87	97	100
Measured Rrs(λ)
Peak_550 value (Sr^−1)	0.029	0.033	0.035	0.033	0.016	0.022	0.031	0.028	0.038
Peak_550 position (nm)	554	564	569	579	557	574	571	565	558
Peak_700 value (Sr^−1)	0.026	0.025	0.021	0.027	0.010	0.018	0.026	0.018	0.034
Peak_700 position (nm)	704	698	693	703	697	699	696	696	705
Simulated Rrs(λ)
Peak_550 value (Sr^−1)	0.031	0.033	0.034	0.034	0.014	0.022	0.031	0.027	0.033
Peak_550 position (nm)	561	577	570	580	563	578	576	569	565
Peak_700 value (Sr^−1)	0.026	0.025	0.023	0.027	0.010	0.017	0.027	0.018	0.028
Peak_700 position (nm)	707	697	695	701	700	700	698	700	703

Fig. 6 (a) R_rs spectra measured at several typical sites with (a) different water depths (1.4, 1.5, 1.7, and 1.9 m) and (b) different SDD transparency (SDD = 0.7, 0.9, 1.375, and 1.75 m).

Fig. 7 (a) R_rs spectra measured at three typical sites with different aquatic plant heights under the water surface (0.6, 1.0, and 1.5 m from the surface to the aquatic plant top). (b) R_rs spectra measured at three typical sites with different percentages of aquatic plant cover on the water surface (15%, 60%, and 80% cover).

Fig. 8 Measured R_rs spectra (left) and simulated R_rs spectra (right) in the OSWs of Lake Taihu.

Fig. 9 Comparison of the simulated and measured R_rs (upper left) at sites No. 39 and No. 45 (two typical sites with different aquatic plant leaf cover floating on the surface) and the contribution rate estimate at the two sites from 400 to 750 nm (upper right) and magnified in the range of 400 to 700 nm (bottom right).

Fig. 10 Comparison of the simulated and measured R_rs (left) at sites No. 42 and No. 43 (two typical sites with different heights of submerged plants) and the contribution rate estimate at the two sites from 400 to 750 nm.