Inherent optical properties and remote sensing reflectance of Pomeranian lakes (Poland)

• Main Authors: Dariusz Ficek, Justyna Meler, Tomasz Zapadka, Bogdan Woźniak, Jerzy Dera
• Format: Article
• Language: English
• Published: Elsevier 2012-11-01
• Series: Oceanologia
• Subjects: Light absorption; Light scattering; Remote sensing reflectance; Concentrations of optically active components; Pomeranian lakes (Poland)
• Online Access: http://www.iopan.gda.pl/oceanologia/54_4.html#A4

This paper describes the results of comprehensive empirical studies of theinherent optical properties (IOPs), the remote sensing reflectance <i>R_rs</i>(&lambda;) andthe contents of the principal optically active components (OAC) i.e. coloureddissolved organic matter (CDOM), suspended particulate matter (SPM) andchlorophyll <i>a</i>, in the waters of 15 lakes in Polish Pomerania in 2007-2010.It presents numerous spectra of the total absorption <i>a</i>(&lambda;) andscattering <i>b</i>(&lambda;) &#x2248; <i>b_p</i>(&lambda;) of light in the visibleband (400-700 nm) for surface waters, and separately, spectra of absorptionby CDOM <i>a</i>_CDOM(&lambda;) and spectra of the mass-specificcoefficients of absorption <i>a_p</i>^*(SPM)(&lambda;) and scattering<i>b_p</i>^*(SPM)(&lambda;) by SPM. The properties of these lake waters are highly diverse, but all of them can beclassified as Case 2 waters (according to the optical classification by Morel&amp; Prieur 1977) and they all have a relatively high OAC content. The lakeswere conventionally divided into three types: Type I lakes have the lowestOAC concentrations (chlorophyll concentration <i>C_a</i> = (8.76 &plusmn; 7.4) mg m^-3 and CDOM absorption coefficients<i>a</i>_CDOM(440) = (0.57 &plusmn; 0.22) m^-1 (i.e. mean and standarddeviation), and optical properties (including spectra of <i>R_rs</i>(&lambda;)resembling those of Baltic waters. Type II waters have exceptionally highcontents of CDOM (<i>a</i>_CDOM(440) = (15.37 &plusmn; 1.54) m^-1),and hence appear brown in daylight and have very low reflectances<i>R_rs</i>(&lambda;) (of the order of 0.001 sr^-1). Type III waters arehighly eutrophic and contain large amounts of suspended matter, includingphytoplankton ((<i>C</i>_SPM = (47.0 &plusmn; 39.4) g m^-3,<i>C_a</i> = (86.6 &plusmn; 61.5) mg m^-3; <i>a</i>_CDOM(440) = (2.77 &plusmn; 0.86) m^-1). Hence the reflectances <i>R_rs</i>(&lambda;)of these type of waters are on average one order of magnitude higher thanthose of the other natural waters, reaching maximum values of 0.03 sr^-1in &lambda; bands 560-580 nm and 690-720 nm (see Ficek et al. 2011). Thearticle provides a number of empirical formulas approximating therelationships between the properties of these lake waters.