《厦门大学学报（自然科学版）》

浮游植物类群遥感是海色遥感的热点问题,关乎全球变化生态响应研究及有害藻华的辨识.针对目前广泛应用的浮游植物类群遥感全球算法PHYSAT,应用台湾海峡夏季表层浮游植物光合色素与SeaWiFS同步卫星遥感数据,探讨其区域适用性.结果显示两种主要类群(硅藻(Diatom)和聚球藻(Synechococcus))的遥感光谱异常(Ra)分布交错,且同一类群的Ra在不同航次、不同站位之间也存在差异,用PHYSAT算法阈值标准均不能得到有效识别.在建立归一化离水辐射率nLwref(λ,Chla)台湾海峡区域查找表的基础上,重新生成硅藻和聚球藻的Ra,不同类群的Ra依旧混杂.这可能与建立PHYSAT算法的标准海域和台湾海峡水体光学组分差异及台湾海峡的水体光学组分时空差异,尤其是颗粒后向散射系数bbp的变动有关.采用K-means和FCM(Fuzzy c-means)方法对443 nm归一化的Ra进行聚类,准确率超过70%.该结果说明在类似台湾海峡的区域水体,浮游植物类群的遥感分辨可能需要更多考虑光谱谱形上的差异,而非如PHYSAT算法进行量值范围区分.

PHYSAT,one of the widely-accepted methods to detect multiple phytoplankton groups from space,was tested for its applicability in the Taiwan Strait(TWS)with 27 match-ups of in situ photosynthetic pigments collected during three cruises in summer and SeaWiFS daily data.Reflectance anomalies(Ra)spectra of the two dominant phytoplankton groups(Diatom and Synechococcus)in the TWS were completely mixed.Significant temporal and spatial variabilities in Ra distribution were also observed among samples of a specific phytoplankton group.The phytoplankton group in the TWS was not identified successfully using Ra with PHYSAT threshold and additional spectral criteria,even Ra based on the regional lookup table of nLwref(λ,Chla)for the TWS,which may be due to different bio-optical characteristics in waters,especially particulate backscattering coefficients(bbp).Clustering methods,K-means and FCM(Fuzzy c-means),were applied with Ra normalized at 443 nm.More than 70% of the samples were successfully identified.It seems that the remote sensing of phytoplankton groups may pay more attention to the difference in Ra spectra shape rather than in the magnitude by PHYSAT method in regional areas such as the TWS.

引言
1 材料与方法
2 结果与分析
3 讨论
4 结论

图1 2004—2006年夏季航次的台湾海峡浮游植物色素采样站位<br/>Fig.1 Phytoplankton pigment sampling stations in the Taiwan Strait during summer cruises in 2004-2006

图1 2004—2006年夏季航次的台湾海峡浮游植物色素采样站位
Fig.1 Phytoplankton pigment sampling stations in the Taiwan Strait during summer cruises in 2004-2006

图2 台湾海峡四大浮游植物类群的Ra分布<br/>Fig.2 Ra distribution of four phytoplankton groups in the Taiwan Strait

图2 台湾海峡四大浮游植物类群的Ra分布
Fig.2 Ra distribution of four phytoplankton groups in the Taiwan Strait

表1 浮游植物类群PHYSAT算法的判别标准[11]<br/>Tab.1 Ra criteria for plankton groups in the PHYSAT method[11]

表1 浮游植物类群PHYSAT算法的判别标准[11]
Tab.1 Ra criteria for plankton groups in the PHYSAT method[11]

图3 台湾海峡四大浮游植物类群在2004年(a),2005年(b),2006年(c)夏季航次的Ra分布<br/>Fig.3 Ra distribution of the four phytoplankton groups in the Taiwan Strait during summer cruises in 2004(a),2005(b)and 2006(c)

图3 台湾海峡四大浮游植物类群在2004年(a),2005年(b),2006年(c)夏季航次的Ra分布
Fig.3 Ra distribution of the four phytoplankton groups in the Taiwan Strait during summer cruises in 2004(a),2005(b)and 2006(c)

图4 台湾海峡MODIS-Aqua 4 km 8 d平均bbp(443)<br/>Fig.4 MODIS-Aqua 4 km 8 d rage bbp(443)in the Taiwan Strait

图4 台湾海峡MODIS-Aqua 4 km 8 d平均bbp(443)
Fig.4 MODIS-Aqua 4 km 8 d rage bbp(443)in the Taiwan Strait

图5 基于nLwref(λ,Chla)区域查找表的台湾海峡2004—2006年夏季航次的硅藻和聚球藻Ra分布<br/>Fig.5 Ra distribution of Diatom and Synechococcus in the Taiwan Straitbased on the regional lookup table of nLwref(λ,Chla)during summer cruises in 2004-2006

图5 基于nLwref(λ,Chla)区域查找表的台湾海峡2004—2006年夏季航次的硅藻和聚球藻Ra分布
Fig.5 Ra distribution of Diatom and Synechococcus in the Taiwan Straitbased on the regional lookup table of nLwref(λ,Chla)during summer cruises in 2004-2006

图6 443 nm归一化的硅藻和聚球藻Ra分布<br/>Fig.6 Ra distribution of Diatom and Synechococcous normalized at 443 nm

图6 443 nm归一化的硅藻和聚球藻Ra分布
Fig.6 Ra distribution of Diatom and Synechococcous normalized at 443 nm

表2 K-means和FCM聚类结果<br/>Tab.2 Clustering results by K-means and FCM

表2 K-means和FCM聚类结果
Tab.2 Clustering results by K-means and FCM

图7 443 nm归一化Ra作为输入的硅藻和聚球藻K-means和FCM聚类结果<br/>Fig.7 K-means and FCM clustering results for Diatom and Synechococcous,using Ra normalized at 443 nm as input

图7 443 nm归一化Ra作为输入的硅藻和聚球藻K-means和FCM聚类结果
Fig.7 K-means and FCM clustering results for Diatom and Synechococcous,using Ra normalized at 443 nm as input

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引言

1 材料与方法

2 结果与分析

3 讨论

4 结论

学报简介

备注

引言

1 材料与方法

2 结果与分析

3 讨 论

4 结 论

学报简介

3 讨论

4 结论