CN-122024895-A - Remote sensing estimation method for pigment concentration in lake

CN122024895ACN 122024895 ACN122024895 ACN 122024895ACN-122024895-A

Abstract

The invention relates to the technical field of lake eutrophication monitoring, in particular to a remote sensing estimation method for lake pigment concentration, which comprises the steps of firstly obtaining remote sensing reflectivity data of a target water body, reflectance values of at least four characteristic wave bands 665nm, 710nm, 620nm and 750nm related to pigment absorption and fluorescence characteristics are extracted, and water absorption coefficients of at least two pigment sensitive wave bands are estimated. Based on the method, a four-band combination index UMEP is constructed, and the biological optical model is transformed according to the water body radiation transmission, so that the influence of environmental parameters is eliminated. By introducing dynamic decomposition factor beta and absorption coefficient difference epsilon, the mixed pigment absorption signal is decomposed into independent contributions of chlorophyll a and phycocyanin, and the concentrations of the chlorophyll a and the phycocyanin are finally calculated by using the specific absorption coefficients of the chlorophyll a and the phycocyanin. The method has definite physical mechanism, can adapt to the change of the optical characteristics of the water body, can be directly applied to multi-source satellite remote sensing images, and realizes the synchronous and high-precision business inversion of the concentration of two key pigments in the water body of a large-scale lake.

Inventors

TANG BOHUI
WANG DONG
LIU YITING
CHEN XIAOXI
LI YANFANG
HUANG LIANG
FAN DONG

Assignees

昆明理工大学

Dates

Publication Date: 20260512
Application Date: 20260129

Claims (9)

1. A remote sensing estimation method for the pigment concentration in a lake is characterized by comprising the following steps: S1, acquiring remote sensing reflectivity data and corresponding measured pigment concentration data of a target lake water body; S2, identifying and extracting reflectivity values of at least four characteristic wave bands related to pigment absorption and fluorescence characteristics based on the remote sensing reflectivity data, and estimating total absorption coefficients of water bodies and absorption coefficients of pigment components at the at least two characteristic wave bands; S3, constructing a four-band combination index UMEP for inverting pigment concentration based on the reflectivity values of the at least four characteristic bands, wherein the expression is as follows: Wherein, R rs (λ 1 ),R rs (λ 2 ),R rs (λ 3 ) and R rs (λ 4 ) are remote sensing reflectivities at bands λ 1 ,λ 2 ,λ 3 and λ 4 , respectively; S4, carrying out mathematical transformation on the four-band combination index (UMEP) according to a biological optical model of water body radiation transmission, eliminating parameter influences related to water-gas interface transmittance, water body refractive index and solar zenith angle, and expressing the parameter influences as functions directly related to pigment absorption coefficients; s5, based on the estimated absorption coefficient, introducing a decomposition factor beta and an absorption coefficient difference epsilon, decomposing a mixed pigment absorption signal at the wave band lambda 3 into chlorophyll a absorption contribution and phycocyanin absorption contribution, and respectively calculating chlorophyll a concentration and phycocyanin concentration by utilizing respective specific absorption coefficients; and S6, applying the four-band combination index UMEP, the decomposition factor beta and the absorption coefficient difference epsilon to the satellite remote sensing image which is subjected to atmosphere correction and contains at least four characteristic bands to realize synchronous inversion of chlorophyll a and phycocyanin concentration in a large-scale lake water body.
2. The method for remote sensing estimation of lake pigment concentration of claim 1, wherein the remote sensing reflectivity data in step S1 is obtained by the following formula: Where L W denotes the leaving irradiance, E d (0 + ) denotes the downstream irradiance, L u denotes the total radiation intensity measured by the instrument, r sky is the Fresnel reflection on the water surface, and ρ p denotes the reference whiteboard reflectivity.
3. The method of claim 1, wherein the at least four characteristic bands in the step S2 include a band lambda 1 at the absorption valley of chlorophyll a, a band lambda 2 at the near-infrared reflection or fluorescence peak region, a band lambda 3 at the characteristic absorption band of phycocyanin, and a reference band lambda 4 at the dominant absorption of pure water, and the center wavelengths are 665nm, 710nm, 620nm, and 750nm, respectively.
4. The method of remote sensing estimation of lake pigment concentration according to claim 1, wherein the estimation of the total absorption coefficient a and the pigment substance absorption coefficient a p is implemented by using a quasi-analytical algorithm QAA in the step S2.
5. The method for remote sensing estimation of lake pigment concentration of claim 1, wherein the bio-optical model in step S4 is: Wherein t is the transmissivity of the water-air interface, n is the refractive index of the water body, f/Q is the weak function of the zenith angle of the sun, b b (lambda) is the total backscattering coefficient of the water body, and a (lambda) is the absorption coefficient of the water body.
6. The method for remote sensing estimation of lake pigment concentration of claim 1, wherein the decomposition factor β in step S5 is calculated by the following formula: Wherein, beta represents the concentration ratio of the lake pigment chlorophyll a at 620nm to the lake pigment phycocyanin, a p (620)、a p (665) is the total absorption coefficient of pigments at 620nm and 665nm, a pc (620) is the absorption coefficient of phycocyanin at 620nm, a chla (665) is the absorption coefficient of chlorophyll a at 665nm, and epsilon is the difference of absorption coefficients between adjacent bands.
7. The method for remote sensing estimation of lake color concentration of claim 6, wherein the difference epsilon in absorption coefficient in step S5 is calculated by the following equation: Wherein a w (620),a w (665) is the absorption coefficient of pure water at 620nm and 665nm, respectively.
8. The method for remote sensing estimation of lake pigment concentration according to claim 1, wherein the chlorophyll a concentration a chla and the phycocyanin concentration a pc in step S5 are calculated by the following formula: Wherein a chla (lambda) and a pc (lambda) respectively represent the UMEP model output chlorophyll a total absorption coefficient and phycocyanin total absorption coefficient, and a chla (lambda) and a pc (lambda) represent the specific absorption coefficients of chlorophyll a and phycocyanin.
9. The method of claim 1, wherein the satellite remote sensing image in step S6 is from a Sentinel-3, MERIS, HJ-1A or GF-5 satellite sensor including the at least four characteristic bands.

Description

Remote sensing estimation method for pigment concentration in lake Technical Field The invention relates to the technical field of lake eutrophication monitoring, in particular to a remote sensing estimation method for lake pigment concentration. Background The concentration of pigment substances in lakes is a key index for measuring the eutrophication degree of water bodies, wherein pigments such as chlorophyll a, phycocyanin and the like not only directly reflect the community structure of phytoplankton, but also can be used for tracing the explosion track and driving mechanism of cyanobacteria bloom. The lake optical environment is complex, the optical characteristic difference of water bodies between different lakes and inside the lakes is obvious, and the universality of the remote sensing inversion algorithm of the pigment substances is low. With the development of multispectral and hyperspectral remote sensing technology, the characteristic reflection information of the pigment substances in the lakes can be captured more finely, so that the content of the pigment substances in the lakes can be extracted more accurately, and more effective technical means are provided for monitoring and managing the eutrophication of the lakes. The method is characterized in that the method comprises the steps of sampling on a lake, carrying a water body back to a laboratory for analysis to obtain a result, wherein the method is high in single-point cost, poor in timeliness, large in spatial extrapolation error and incapable of reflecting pigment content information in a large range, and the method is characterized in that an empirical model is built on the basis of priori apparent lake spectrum and matched satellite wave bands to achieve inversion effect of pigment substances, but the lake is high in types, strong in optical property and space diversity, and difficult to obtain measured spectrum data, so that the model is not generally applicable. In conclusion, the method based on the combination of the biological optical model and the spectral characteristics can effectively and accurately obtain the pigment substance content of the target lake, and the method decomposes dynamic coupling of chlorophyll a and phycocyanin pigment substances in the lake, can improve the generalization application capability of the model at the present stage aiming at different lakes, can seamlessly access multi-source hyperspectral/multispectral images, and enables the physical mechanism and the data driving advantage of the conventional inversion method to be synchronously enhanced. Disclosure of Invention The invention aims to provide a remote sensing estimation method for lake pigment concentration, which realizes synchronous, separation and inversion of chlorophyll a and phycocyanin concentration from satellite remote sensing reflectivity data by constructing a four-band combination index UMEP and combining dynamic decomposition factor beta and absorption coefficient difference epsilon. In order to achieve the technical purpose and the technical effect, the invention is realized by the following technical scheme: A remote sensing estimation method for lake pigment concentration comprises the following steps: S1, acquiring remote sensing reflectivity data and corresponding measured pigment concentration data of a target lake water body; S2, identifying and extracting reflectivity values of at least four characteristic wave bands related to pigment absorption and fluorescence characteristics based on the remote sensing reflectivity data, and estimating total absorption coefficients of water bodies and absorption coefficients of pigment components at the at least two characteristic wave bands; S3, constructing a four-band combination index UMEP for inverting pigment concentration based on the reflectivity values of the at least four characteristic bands, wherein the expression is as follows: Wherein, R rs(λ1),Rrs(λ2),Rrs(λ3) and R rs(λ4) are remote sensing reflectivities at bands λ 1,λ2,λ3 and λ 4, respectively; S4, carrying out mathematical transformation on the four-band combination index (UMEP) according to a biological optical model of water body radiation transmission, eliminating parameter influences related to water-gas interface transmittance, water body refractive index and solar zenith angle, and expressing the parameter influences as functions directly related to pigment absorption coefficients; s5, based on the estimated absorption coefficient, introducing a decomposition factor beta and an absorption coefficient difference epsilon, decomposing a mixed pigment absorption signal at the wave band lambda 3 into chlorophyll a absorption contribution and phycocyanin absorption contribution, and respectively calculating chlorophyll a concentration and phycocyanin concentration by utilizing respective specific absorption coefficients; and S6, applying the four-band combination index UMEP, the decomposition factor beta and the a