Estimation of chlorophyll-a concerntration using field spectral data.pdf

Environ Monit Assess (2009) 158:105–116 DOI 10.1007/s10661-008-0568-z Estimation of chlorophyll-a concentration using field spectral data: a case study in inland Case-II waters, North China JingPing Xu · Fang Li · Bai Zhang · KaiShan Song · ZongMing Wang · DianWei Liu · GuangXin Zhang Received: 9 May 2008 / Accepted: 11 September 2008 / Published online: 14 October 2008 ? Springer Science + Business Media B.V. 2008 Abstract In the remote sensing of chlorophyll-a (Chla) in inland Case-II waters, the assumption that the optical parameter of Chla specific ab- sorption coefficient a?ph remains constant usually restrains application of many models. In this paper, we presented a newly developed model[ R?1rs (λ1)? R?1rs (λ2) ] × Rrs(λ3)× a?ph?1(λ1) which was improved on a previous three-band model to isolate interferences from a?ph. In terms of the im- portance of water optical properties in the model development, spectral and absorption character- istics were analyzed for Shitoukoumen Reservoir and Songhua Lake in Northeast China, as typical examples of inland Case-II waters. Both waters showed overwhelming absorption sum of trip- ton and chromophoric dissolved organic matter (CDOM) owing to their relatively low Chla con- tents (1.53 to 19.35 μgl?1). According to the optical characteristics of waters studied, optimal positions for λ1, λ2 and λ3 were spectrally tuned J. Xu · F. Li (B) · B. Zhang · K. Song · Z. Wang · D. Liu · G. Zhang Department of RS and GIS, Northeast Institute of Geography and Agroecology, Chinese Academy of Science, 3195 Weishan Road, 130012, Changchun, China e-mail: lfwhy@neigae.ac.cn J. Xu Graduate School of Chinese Academy of Sciences, 100049, Beijing, China to be at 664, 684 and 705 nm, respectively. The model allowed accurate Chla estimation with a determination coefficient (R2) close to 0.98 and a root mean square error (RMSE) of 0.87 μgl?1. Comparison of different models further showed the stability of the improved model, implying its potential