赤潮水体红光波段反射光谱的模拟及形成机理

REFLECTANCE SPECTRA SIMULATION AND FORMATION MECHANISM IN THE RED BAND OF RED TIDE WATERS

赤潮水体红光波段反射光谱中"荧光峰"的红移现象一直备受研究者的广泛关注。本文基于前向辐射传输模型,通过2011年7月9日在大连湾海域实测的赤潮水体吸收系数和后向散射系数模拟了弹性散射作用下的反射光谱,发现在未考虑叶绿素荧光的情况下,红光波段仍存在显著的反射峰,且随叶绿素浓度的增加,反射峰出现红移现象;加入叶绿素荧光后,模拟光谱红光波段反射峰的位置与高度出现不同程度的改变,与实测光谱的更接近;对比模拟光谱与实测光谱可确定,红光波段的反射峰由吸收、后向散射以及叶绿素荧光共同控制,而文献中通常提到的"荧光峰"红移实由浮游藻类红光波段的强吸收作用导致,与叶绿素荧光无关,因此反射峰红移的说法更为合理。

Red-shift of fluorescence peak appears in red band of red tide waters, which has drawn wide attention of researchers. Based on measurement data in the Dalian Bay taken when red tide occurred on July 9, 2011, we simulated remote sensing reflectance spectra using total absorption coefficient, backscattering coefficient, and chlorophyll fluorescence in forward radiation transmission model. The results show a significant reflection peak in red band regardless of chlorophyll fluorescence, and the peak has the red-shift due to the increase of chlorophyll concentration. By adding chlorophyll fluorescence, simulated spectrum reflection peak position and height presented a certain degree of change in red band, and the consistency of the measured spectrum was enhanced. Comparing simulated spectrum with the measured, it can be determined that reflection peak is jointly controlled by absorption, scattering, and chlorophyll fluorescence in red band. In addition, ＂fluorescence red shift＂ as referred previously in literature is caused by phytoplankton strong absorption and nothing to do with chlorophyll fluorescence. Therefore, the term of ＂reflection peak red-shift＂ is more accurate and scientific.