Parameterization of the light absorption by components of sea water - PowerPoint PPT Presentation

Parameterization of the light absorption by components of sea water in the Black sea coastal zone E.V. Dmitriev, T.Y. Churilova, M. Chami, G. Khomenko, G.A. Berseneva, O.V. Martynov, E.B. Shybanov, M. E-G. Lee, G.K. Korotaev

Light absorption in coastal sea waters λ = λ + λ + λ + λ a ( ) a ( ) a ( ) a ( ) a ( ) Four-component model: φ w CDOM NAP 1) Pure sea water - w Measuring of phytoplankton absorption coefficient 2) phytoplankton - φ λ = λ − λ 3) colored dissolved organic matter - CDOM ( ) ( ) ( ) a a a φ p NAP 4) nonalgal particles - NAP Parameterizations of the spectral absorption for different sea water components λ λ = λ E ( ) φ a ( ) A ( ) Chl by phytoplankton φ φ − λ − λ λ = λ ( S ( )) ˆ a ( ) a ( ) e NAP r by nonalgal particles NAP NAP r − λ − λ by colored dissolved λ = λ ( S ( )) ˆ a ( ) a ( ) e CDOM r organic matter CDOM CDOM r

The oceanographic platform near Katsiveli Observations were made in summer 2002 (from July 27 until August 15) Coordinates 44°23’N and 33°59’E The platform located 600 meters from the southern Crimea coast The deck of the platform in the Black Sea is 12 meters high from the sea level The bottom depth of the sea increases from 28 to 33 meters in the offshore direction

Concentration of phytoplankton Variability of the wind speed and pigments in the Black Sea as derived Secchi disk depth near the platform by SeaWiFS satellite sensor during the experiment. (top) on July 26 2002 16 wind speed and (bottom) on August 11 2002. secchi disk depth 12 Secchi disk depth (m) Wind speed (m s -1 ) 8 4 0 26.07 30.07 03.08 07.08 11.08 15.08 Date : Day.Month.2002 Temporal variation of the vertical profile of the temperature along the experiment. 0 0 25 5 -50 23 Depth z (m) 21 10 -100 19 15 17 -150 15 -200 20 13 11 25 -250 9 28.07 30.07 01.08 03.08 05.08 07.08 09.08 11.08 13.08 15.08 26.07 Temperature (°C) Date: Day.Month.2002

Relative contribution of phytoplankton, nonalgal particles and CDOM absorption to the total absorption August 3 August 2 100 100 CDOM 80 80 Relative contribution (%) Relative contribution (%) 60 CDOM 60 NAP The absorption 40 40 NAP budget reveales 20 20 that the Crimea Phytoplankton pigment Phytoplankton pigment coastal waters 0 0 clearly fall in the 360 400 440 480 520 560 360 400 440 480 520 560 Wavelength, nm 100 Wavelength, nm 100 case II water August 10 August 14 type with a CDOM 80 80 Relative contribution (%) Relative contribution (%) yellow substance dominated 60 60 CDOM regime. NAP 40 40 NAP 20 20 Phytoplankton pigment Phytoplankton pigment 0 0 360 400 440 480 520 560 360 400 440 480 520 560 Wavelength, nm Wavelength, nm

Parameterization of the light absorption by particles and phytoplankton [ Bricaud et al, JGR, 1998] Parameterization of the specific absorption Calibration for "CASE I" waters [ Bricaud et al, JGR, 1998] [ Bricaud et al, JGR, 1998] ( λ λ = λ E ) ph a ( ) A ( ) Chl , ph ph λ − λ = λ E ( ) 1 * a ( ) A ( ) Chl ph ph ph Calibration for "CASE II" waters of the Black Sea coastal zone 1 a ph (443)=0.0514*Tchla0.566, r 2 =0.58 0.1 a ph (443), m -1 0.01 0.001 0.1 1 10 Tchla, mg/m 3

Parameterization of light Spectral values of numerical coefficients A ph - top and E ph -bottom defining the absorption by phytoplankton parameterization of light absorption by ( λ λ = λ E ) phytoplankton as a function of the sum of a ( ) A ( ) Chl ph , ph ph chlorophyll a and phaeopigment concentration where λ = λ − λ A ( ) exp( ln a ( ) E ( ) ln Chl ), ph ph ph Our fitting λ − λ − (ln ( ) ln ( ) )(ln ln ) a a Chl Chl λ = ph ph E ( ) , ph − 2 (ln Chl ln Chl ) Tests of normality of the distribution of a ph ( λ ). Bricaud et al 1998 The upper bar - Jarque-Bera test, the middle bar - Lilliefors test, the lower bar - hybrid test. The significance level 0.05.

Parameterization of absorption The spectral distribution by phytoplankton for different values of the determinate and random errors of Tchla concentrations of the absorption parameterization Spectral distributions of the specific absorption by phytoplankton in different waters [Babin et al, JGR, 2003]

Variations of the spectral absorption at fixed value of Tchla concentration. Thin grey curves (5 in total) are spectral absorption measured for different water at the chlorophyll concentration 0.65 mg/m3. The correlation coefficients between the distributions of spectral absorption at fixed value of Tchla

Parameterization of light absorption by nonalgal particles (NAP) and color dissolved organic matter (CDOM) The root-mean-square approximation The general form errors of DLM (solid grey curve) and − λ − λ λ = λ S ( ) ˆ ( ) ( ) a a e NAP r NLSM (solid black curve). NAP NAP r λ = λ − λ − λ Fitting in the spectral region from S ( ) ˆ a ( ) a ( ) e CDOM r 380 to 730 nm, excluding the intervals CDOM CDOM r 400-480 and 620-710 nm λ (nm) is a reference wavelength r The exponential fit of the NAP absorption by different methods The example corresponds to the largest error of nonlinear least-square fitting method August 14, depth 16 m Fitting in the spectral region from 350 to 700 nm

Histograms of the exponential slope parameter of parameterization S NAP of the NAP absorption spectrum DLM, 118 samples NLSM, 118 samples The fitting is done for the spectral region from 380 to 730 nm, excluding the intervals 400-480 and 620-710 nm Average slopes 2 σ =0.002 presented in [Babin 2 σ =0.0024 et al 2003] for different coastal waters range from 0.0116 up to 0.0130 Scatter plots of - S the slope NAP parameter estimated by DLM - squares and by NLSM - stars, with S NAP respect to the NAP absorption at the wavelength 443 nm. The black solid and dash curves signify the S S NAP NAP corresponded mean values of . S NAP

The exponential fit of the CDOM Parameterization obtained from our absorption using NLSM measurements in the Black Sea 2002 − λ − λ = 0 . 0179 ( 443 ) a ( ) a ( 443 ) e CDOM CDOM − ± λ − λ = ( 0 . 0104 0 . 0024 ) ( 443 ) a ( ) a ( 443 ) e NAP NAP Parameterization derived in [Babin et al, JGR, 2003] − λ − λ = 0 . 0176 ( 443 ) a ( ) a ( 443 ) e CDOM CDOM − λ − λ = 0 . 0123 ( 443 ) a ( ) 0 . 75 a ( 443 ) e NAP NAP The spectral curves are fitted by exponential function in the spectral region from 350 to 500 nm.

� � � Conclusions The presented results show that the Crimea coastal waters fall in the case II water type with a CDOM dominated regime and clearly have their own optical particularities. We demonstrated that the parameterization of phytoplankton absorption obtained from our measurements is significantly different from the published one in [Bricaud et al. 1998] and have proofed that this cannot be explained by poor statistic. Our fitting of E ph reveals a strong minimum at the wavelength 580 nm, which can not be observed in the parameterization of Bricaud at al. The absorption by NAP and CDOM can be parameterized well using an exponential regression. We compared two different techniques of estimating slope parameter: the data linearization method (DLM) and the nonlinear least-square method (NLSM). It is shown that the NLSM is more preferable. The mean value of S NAP obtained by NLSM, is amounted to 0.0104±0.0024, that is less than all average slopes represented in [ Babin et al. , 2003] for different coastal waters. We would like to underline that the difference between mean values of slope parameters for DLM and NLSM is comparable with the range of the average slopes for different waters. 2 of 4 our measurements of CDOM spectral absorption are significantly go out the uncertainty intervals for the parameterization constructed in [ Babin et al. , 2003]. Thus it should be calculated more exact employing additional measurements.