Mogilany '03

Second Workshop

DEVELOPMENT OF SATELLITE METHOD OF THE BALTIC ECOSYSTEM MONITORING

A national project funded

by State Committee for Scientific Research

PBZ-KBN-056/P04/2001

Sopot - Mogilany

22-26 September 2003

1. Basic information, 2. Preliminary schedule, 3. Some abstracts, 4. Authors of lectures

Dariusz Ficek - Department of Environmental Physics, Pomeranian Pedagogical University

Piotr Struzik - Satellite Research Department, Institute of Meteorology and Water Management

Ł. Kozłowski, A. Krężel Parametrization of aerosols contribution to light attenuation in the Baltic atmosphere

A. Rozwadowska, A. Krężel A preliminary algorithm for estimation of spectral solar radiation on the Baltic sea surface from satellite data (AVHRR)

J. Urbański, K. Bratke, L. Szymanek The procedure for estimation of variables of sea surface temporarily invisible from satellite level

J. Olszewski, M. Darecki Preliminary remote sensing reflectance model for the Baltic Sea

S.B. Woźniak, M. Darecki, B. Woźniak Theoretical model of upward light field formation in natural conditions above sea surface for remote sensing purposes

S.B. Woźniak, D. Stramski Modeling the effect of mineral particles on ocean reflectance.

M. Darecki, B. Woźniak, S.B. Woźniak Variability in the light backscattering coefficient in the Baltic estimated from the irradiance and reflectance measurements

M. Ostrowska, B. Woźniak, S. Kaczmarek, R. Majchrowski Some aspects of modelling of vertical chlorophyll a profiles in Baltic Sea

S. Kaczmarek, B. Woźniak, M. Ostrowska, D. Ficek Some aspects of propagation of natural light in Baltic Sea

M. Majchrowski, B. Woźniak, J. Dera, S. Kaczmarek, D. Ficek, J. Stoń The model of light absorption by algae in Baltic; the current state of investigations

D. Ficek, B. Woźniak, M. Ostrowska, R. Majchrowski, J. Dera The model of quantum yield of photosynthesis in Baltic; the current state of investigations

M. Kowalewski, A. Krężel An automatic system for precise georeferencing of AVHRR data

M. Ostrowski, A. Krężel Comparison between in situ temperature measurements and NOAA/AVHRR based SSTs in Baltic area

A. Krężel, A. Rozwadowska The use of satellite data to estimation of solar spectral irradiance at the sea level

M. Darecki, S.B. Woźniak, B. Woźniak Validation of the model of the upwelling light fields above the real water surface for the remote sensing application

The participants of conference are invited to visit Satellite Research Department, Institute of

Ł. Kozłowski, A. Krężel Parameterization of aerosols contribution to light attenuation in the Baltic atmosphere

Statistical analysis of aerosol optical thickness (AOT) measured by the AERONET network within the Baltic region has been carried out. AOT data recorded by the station on Gotland Island was compared with satellite derived, calculated with standard SeaDAS procedure on the basis of SeaWiFS data. Taking into account accessibility of independent satellite measurements of AOT, an attempt to reconstruct its spectrum on the basis of known value in single spectral channel (e.g. 500 nm) was undertaken.

A. Rozwadowska, A. Krężel A preliminary algorithm for estimation of spectral solar radiation on the Baltic sea surface from satellite data (AVHRR)

A preliminary algorithm for estimation of spectral solar radiation on the Baltic sea surface from AVHRR data is presented. Moreover, a model of the atmosphere used in the algorithm is described. The algorithm consists of the following parts:

The algorithm uses preprepared LUTs (lookup tables) which relate the following parameters:

A complex code for solar and thermal radiative transfer in the atmosphere MODTRAN4 (v2r1) is used for LUT computations. Horizontal uniformity of the atmosphere within a pixel is assumed.

Additionally, errors in surface solar radiation estimates due to the assumption on atmospheric horizontal uniformity within a pixel are determined using 3D Monte Code for radiative transfer in the atmosphere.

J. Urbański, K. Bradtke, L. Szymanek The procedure for estimation of variables of sea surface temporarily invisible from satellite level

Geostatistical co-kriging and linear regression has been combined to create a reliable and operational procedure. The application of geostatistical method of estimation was followed by a structural analysis of data obtained from SST images. The results of this analysis show whirl structure of anisotropy in the SST field. The variability of surface temperature can be modeled by a spherical function. The maximum average decorrelation scale is 26 km. The co-kriging uses neighboring images in time series as additional data. The regression method combined with co-kriging is used when cloud cover is widespread.

J. Olszewski, M. Darecki Preliminary remote sensing reflectance model for the Baltic Sea

The main assumptions of the proposed model for estimating the remotely sensed reflectance in the Baltic from the measurements of chlorophyll a concentration and absorption by coloured dissolved organic matter (CDOM) were discussed. The model is based on the extended bio-optical data set collected in the Baltic Sea during years 1993-2002. Spatial and temporal variability of the used data set is also presented and analysed.

The modest version of the model is compared with the previously ones. The new model parameterisation, include new approach to the detritus absorption and to the backscattering by particles and also efficiency of taking into account of the wavelength dispersion of the geometrical coefficient of the downwelling radiance distribution on the sea - atmosphere boundary are discussed. Still existing, small discrepancies between model predicted and measured values of the remote sensing reflectance can be reduced in the further developing of the model and some ideas for achieving this goal are proposed.

S.B. Woźniak, M. Darecki, B. Woźniak Theoretical model of upward light field formation in natural conditions above sea surface for remote sensing purposes

The authors adopted previously developed spectral models of light reflection and transmission through the sea surface for the remote sensing purposes. The new model takes into account the influence of the sky irradiance reflection from the wind-ruffled sea surface partially covered with foam, and transmission of light backscattered in water through the surface on the upward light field formation above sea surface. The remote sensing reflectance (RSR) just above sea surface may be calculated as a function of environmental factors such as: sun zenith angle, difusensess and cardioidal distribution factors of sky irradiance, wind speed, backscattering and absorption coefficents of seawater. The model allows to perform "surface correction" of remotely sensed data i.e. to distinguish between the radiance generated by the surface reflection and radiance that carries information about optically active constituents of seawater.

S.B. Woźniak, D. Stramski Modeling the effect of mineral particles on ocean reflectance

(A presentation of the material from Ocean Optics XVI conference, Santa Fe 2002).

We examined the effects of suspended mineral particles on ocean reflectance based on theoretical modeling. The Mie scattering calculations were made for polydisperse systems of mineral particles suspended in seawater to obtain the spectral absorption and backscattering efficiency factors and cross-sections of particles. Different slopes of the Junge-type particle size distribution (the slope values between -3.2 and -4.8 within the size range from 0.05 to 500 μm) and different values of the real part of refractive index (1.15 to 1.22 relative to water) and the imaginary part of refractive index (low and high absorption cases) were used in the calculations. The link between the refractive index and density of particles allowed us to calculate the mass-specific absorption and backscattering coefficients. As a first approximation, we assumed that the ocean reflectance varies as the ratio of backscattering coefficient to the sum of absorption and backscattering coefficients, and that these coefficients can be represented as a sum of contributions from two components only, mineral particles and pure seawater. With these assumptions, we analyzed the spectral behavior of ocean reflectance under varying concentration of suspended mineral particles (between 0.01 and 100 g m^-3) and for different properties of particulate assemblages, that is for different size distributions and refractive index.

M. Darecki, B. Woźniak, S.B. Woźniak Variability in the light backscattering coefficient in the Baltic estimated from the irradiance and reflectance measurements

The knowledge about inherent optical properties of the water like absorption and backscattering is necessary for effective remote sensing of plankton related parameters. The sufficient knowledge, especially regarding backscattering, is relatively poor in coastal waters or semi-enclosed seas – where the Baltic is a typical example. Such situation results from difficulties in direct measurements of the backscattering function both with in situ and in vitro techniques. The study presents an indirect estimation of the backscattering coefficients, where vertical profiles of the diffuse attenuation coefficient for downwelling irradiance and remote sensing reflectance were used. The used data were collected on 27 cruises in the years 1993 – 2002, mainly in the southern part of the Baltic Sea, under various environmental conditions and in different seasons of the year. Nearly 1000 spectra of backscattering coefficients were calculated and later analyzed. The range of seasonal and spatial variability and also dependency on other optical parameters of the seawater are presented.

M. Ostrowska, B. Woźniak, S. Kaczmarek, R. Majchrowski Some aspects of modelling of vertical chlorophyll a profiles in Baltic Sea

The statistical analyses of empirical database of vertical profiles of chlorophyll a concentrations in Baltic are carried on at present. The aim of work is to establish the statistical relationship that allows the chlorophyll a vertical profiles to be estimated using its surface concentration, sea region and season (the number of the day in the year is used as indicator of season). The analyses are not finished yet. The results obtained until now will be presented during the conference in Mogilany.

S. Kaczmarek, B. Woźniak, M. Ostrowska, D. Ficek Some aspects of propagation of natural light in Baltic Sea

The aim of empirical investigations and modeling is to work out the statistical description of downward irradiance attenuation spectral coefficients in Baltic waters. This statistical description allows the attenuation coefficients to be estimated using selected optical characteristics of surface layer which are possible to determine with satellite observations. The analyses are not finished yet. The results obtained until now will be presented during the conference in Mogilany.

M. Majchrowski, B. Woźniak, J. Dera, S. Kaczmarek, D. Ficek, J. Stoń The model of light absorption by algae in Baltic; the current state of investigations

The aim of this study is adaptation of worked out earlier "remote sensing" model of phytoplankton light absorption for oceanic waters to baltic conditions. The analyses are not finished yet. The results obtained until now will be presented during the conference in Mogilany.

D. Ficek, B. Woźniak, M. Ostrowska, R. Majchrowski, J. Dera The model of quantum yield of photosynthesis in Baltic; the current state of investigations

The aim of the study is to adapt to Baltic Sea conditions the developed model of quantum yield of photosynthesis for oceanic waters. The analyses are not finished yet. The results obtained until now will be presented during the conference in Mogilany.

M. Kowalewski, A. Krężel An automatic system for precise georeferencing of AVHRR data

Results of calculations with the use of standard algorithms of georeferencing of the AVHRR data basing on the standard Two-Line Orbital Element Set are burden with comparatively high error of up to 10 km order. It is due to imprecise information of exact position and spatial orientation of the satellite in real time. A navigation method that combine a precise image deformation model and an automatic adjustment on coastal landmarks (ASDIK) was prepared for operational use at the AVHRR imagery. The paper presents the principles of the method and preliminary data of its verification.

M. Ostrowski, A. Krężel Comparison between in situ temperature measurements and NOAA/AVHRR based SSTs in Baltic area

Sea Surface Temperature (SST) algorithms have been checked and verified for polar orbiting satellites NOAA-12, 14, 15, 16 and 17. In situ temperature measurements carried out in the years 2000 - 2003, in southern and central Baltic regions, were taken into account. Performed statistical analysis enabled one to find the best shape of algorithm for given satellite and given part of a day. The multichannel linear SST algorithms were found as the best fitting for the night-time AVHRR SST estimations, whereas non-linear ones better fitted to the day-time images. Proper coefficients for all algorithms were developed for the Baltic Sea.

A. Krężel, A. Rozwadowska The use of satellite data to estimation of solar spectral irradiance at the sea level

Meteosat visible channel data were used for calculation of “cloudiness coefficient” over the Baltic Sea area. The raw data from the Eumetsat data base were processed to the maps of cloudiness coefficient. Obtained in this way measure of cloudiness has replaced the standard cloudiness in simple model of solar energy transmission in terrestrial atmosphere as input parameter. Calculated solar irradiance at the sea level was compared to the actinometric measurements conducted from the autonomic buoy off the Polish coast and similar calculation using ICM meteorological model results as input data.

M. Darecki, S.B. Woźniak, B. Woźniak Validation of the model of the upwelling light fields above the real water surface for the remote sensing application

Commonly developed models of the upwelling radiance for the remote sensing application usually concentrate on the relationships between remote sensing reflectance and inherent optical properties (IOP) of the water like absorption and backscattering. Less emphasis is being placed on geometrical aspects of the upwelling radiance flux depended on ambient light conditions and optical properties of the water. Also the transmission through the roughness sea surface is often considered as marginal.

In this work the preliminary validation of the developed model which accounts for all the above mentioned parameters is made. The emphasis is on validation of the upwelling radiance transmission through the water-air interface. The filed measurements of the remote sensing reflectance from the above and just below the water surface is compared and analysed in the context of the model parameterisation. The results generally confirm the correctness and importance of the model assumptions.

B. Woźniak et al. Preliminary verification of the "remote sensing" algorithm for marine primary production

We are currently working on preliminary verification of the accuracy of remote sensing algorithm for marine primary production, which was developed in frame of our grant project. The latest results of verification will be presented at the workshop.

Pomeranian Pedagogical Academy (Depart. of Environment. Physics), Słupsk, Poland

Satellite Research Department, Institute of Meteorology and Water Management, Kraków, Poland