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1

The impact of repeated water soaking of cereal straw on the slagging index and the formation of deposits on heating surfaces of power boilers

Rozwadowska A., Dziok T.

Polityka Energetyczna

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2018

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T. 21, z. 2

125--137

EN

The article presents the results of the analysis of straw obtained from ripening wheat, which was subjected to four water soaking cycles in demineralized water. The soaking was carried out under laboratory conditions at 20°C. As a result, part of mineral matter, including a significant amount of alkaline sodium and potassium salts and substances containing sulfur and phosphorus, was washed out. The process of soaking has a great impact on the chemical composition of ash obtained from water-treated straw, which increased its acidity. The Na2O content in the analyzed ash has decreased by 78%, while the K2O content has decreased by 60%. In turn, the content of water-insoluble, acid-forming SiO2 has increased by 80%. As a consequence, a positive change in the values of indices, on the basis of which the tendency of straw to slagging and deposit formation during the combustion and gasification processes is assessed, has been observed. Already after the second water soaking cycle it became apparent, based on the AI alkali index, that the examined fuel should not cause difficulties resulting from the increased intensity of use of the boiler during the combustion process. Meanwhile, the value of the BAI bed agglomeration index was considered to be safe, indicating a low possibility of bed agglomeration during the combustion or fluidized bed gasification, after the third water soaking cycle. The third of the analyzed indices, the Fu fouling index, did not indicate any tendency to deposit formation during the combustion; however, four water soaking cycles reduced its initial value by 80%. The last of the analyzed indexes, the SR, slag viscosity index did not change its value during the experiment, which, both for the raw straw and after subsequent soaking cycles, indicated that the fuel should have a low tendency to accumulate slag during the combustion process.

PL

W artykule przedstawiono wyniki badań słomy pozyskanej z dojrzewającej pszenicy, którą poddano procesowi czterokrotnego moczenia w wodzie demineralizowanej. Operację moczenia prowadzono w warunkach laboratoryjnych w temperaturze 20°C. W wyniku moczenia ze słomy została usunięta część substancji mineralnej, w tym znaczna ilość alkalicznych soli sodu i potasu oraz substancji zawierających siarkę i fosfor. Proces moczenia w wyraźny sposób wpłynął na zmianę składu chemicznego popiołu otrzymanego z preparowanej wodą słomy, który zwiększył swoją kwasowość. W popiele o 78% zmalała zawartość Na2O, o 60% zawartość K2O, do 80% wzrósł natomiast udział nierozpuszczalnego w wodzie, kwasotwórczego SiO2. W konsekwencji korzystnie zmieniły się wartości wskaźników, za pomocą których oceniana jest skłonność słomy do deponowania zanieczyszczeń podczas spalania i zgazowania. Już w wyniku dwukrotnego moczenia indeks alkaliczności AI przyjmował wartość sugerującą, że paliwo to nie powinno sprawiać trudności podczas spalania z powodu zwiększonej intensywności żużlowania kotła. Natomiast wskaźnik aglomeracji złoża BAI bezpieczną wartość wskazującą na niewielkie prawdopodobieństwo wystąpienia zjawiska aglomeracji złoża podczas spalania lub zgazowania fluidalnego osiągnął po trzecim cyklu moczenia słomy. Trzeci z ocenianych wskaźników, Fouling-Index Fu nie osiągnął wprawdzie wartości wskazującej na brak skłonności paliwa do deponowania zanieczyszczeń podczas spalania, ale w wyniku czterokrotnego moczenia nastąpiła 80% redukcja jego początkowej wartości. Ostatni z analizowanych wskaźników, wskaźnik lepkości żużla SR, w trakcie prowadzonego eksperymentu nie zmieniał swojej wartości, która dla zarówno dla słomy surowej, jak i po kolejnych cyklach moczenia, wskazywała, że paliwo to powinno charakteryzować się małą skłonnością do odkładania żużlu podczas spalania.

2

Aerosol physical properties in Spitsbergen's fjords: Hornsund and Kongsfjorden during AREX campaigns in 2014 and 2015

Markuszewski P., Rozwadowska A., Cisek M., Makuch P., Petelski T.

Oceanologia

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2017

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No. 59 (4)

460--472

EN

We present results of measurements of aerosol physical properties conducted on board of r/v Oceania during two cruises to the Spitsbergen region in 2014 (AREX 2014) and 2015 (AREX 2015). Measurements of aerosol size distribution, aerosol scattering coefficient and black carbon concentrations were made in two different Spitsbergen fjords: Hornsund and Kongsfjorden. The aerosol size distribution was measured in the size range from 0.09 μm to 47 μm using two aerosol size distribution spectrometers and a standard condensation particle counter. For the scattering coefficient an integrating nephelometer was used. Black carbon concentration was measured by an aethalometer. Temporal variabilities in physical properties of aerosol observed during the AREX 2014 and AREX 2015 campaigns were much higher than the differences between both fjords. The basic factors influencing aerosol conditions were advection and local generation of marine aerosol. In 2015 an episode of smoke advection was observed in both fjords causing an increase in the mean black carbon concentration from 7–12 ng m−3 to about 60 ng m−3, and an aerosol scattering coefficient at 550 nm from 2–4 Mm−1 to 12–17 Mm−1. Moreover, under certain conditions statistically significant gradients in aerosol optical properties were observed along the fjord axis reflecting an impact of mountains surrounding the fjords.

3

Aerosol Optical Depth variations due to local breeze circulation in Kongsfjorden, Spitsbergen

Cisek M., Petelski T., Zieliński T., Makuch P., Pakszys P., Rozwadowska A., Markuszewski P.

Oceanologia

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2017

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No. 59 (4)

422--430

EN

This paper presents the results of Aerosol Optical Depth (AOD) studies which took place in Ny-Ålesund in the spring of 2014 during the iAREA campaign. The measurements were taken using Microtops II hand-held sunphotometers along the Kongsfjorden, on a path leading from the research village to the fjord opening. Local breeze circulation was observed during the measurement campaign which resulted in an evident increase of AOD along the measurement profile towards the open sea. Using the observed AOD, changes over the open sea have been calculated and the location of the breeze front has been determined.

4

Studies of vertical coarse aerosol fluxes in the boundary layer over the Baltic Sea

Petelski T., Markuszewski P., Makuch P., Jankowski A., Rozwadowska A.

Oceanologia

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2014

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No. 56 (4)

697--710

EN

The results of studies of the vertical gradient of aerosol concentration measurements made during cruises of r/v "Oceania" between 2008 and 2012 are presented. Using the results from those experiments, sea spray emission fluxes were calculated for all particles of sizes in the range from 0.5 µm to 8 µm, as well as for particles of sizes from fifteen channels of 0.5 µm width. The information obtained was further used to calculate the Sea Salt Generation Function (SSGF) for the Baltic Sea depending on the wind speed and the aerosol size distribution.

5

Studies of aerosol optical depth with the use of Microtops II sun photometers and MODIS detectors in coastal areas of the Baltic Sea

Zawadzka O, Makuch P, Markowicz K.M, Zieliński T, Petelski T., Ulevičius V, Strzałkowska A., Rozwadowska A., Gutowska D.

Acta Geophysica

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2014

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Vol. 62, no. 2

400--422

EN

In this paper we describe the results of a research campaign dedicated to the studies of aerosol optical properties in different regions of both the open Baltic Sea and its coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with the use of the hand-held Microtops II sun photometers. The studies were complemented with aerosol data provided by the MODIS. In order to obtain the full picture of aerosol situation over the study area, we added to our analyses the air mass back-trajectories at various altitudes as well as wind fields. Such complex information facilitated proper conclusions regarding aerosol optical depth and Ångström exponent for the four locations and discussion of the changes of aerosol properties with distance and with changes of meteorological factors. We also show that the Microtops II sun photometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results.

6

The impact of a non-uniform land surface on the radiation environment over an Arctic fjord - a study with a 3D radiative transfer model for stratus clouds over the Hornsund fjord, Spitsbergen

Rozwadowska A., Górecka I.

Oceanologia

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2012

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No. 54 (4)

509-544

EN

This paper estimates the influence of land topography and cover on 3D radiative effects under overcast skies in the Arctic coastal environment, in particular in the Hornsund fjord region, Spitsbergen. The authors focus on the impact of a non-uniform surface on: (1) the spatial distribution of solar fluxes reaching the fjord surface, (2) spectral shortwave cloud radiative forcing at the fjord surface, (3) the solar flux anomaly at the domain surface resulting from the assumption of a uniform surface, i.e. the error due to plane parallel assumptions in climate models, and (4) remote sensing of cloud optical thickness over the fjord. Their dependence on spectral channel, cloud optical thickness, cloud type, cloud base height, surface albedo and solar zenith angle is discussed. The analysis is based on Monte Carlo simulations of solar radiation transfer over a heterogeneous surface for selected channels of the MODIS radiometer. The simulations showed a considerable impact of the land surrounding the fjord on the solar radiation over the fjord. The biggest differences between atmospheric transmittances over the fjord surface and over the ocean were found for a cloud optical thickness τ = 12, low solar zenith angle υ, high cloud base and snow-covered land. For τ= 12, υ = 53°, cloud base height 1.8 km and wavelength λ= 469 nm, the enhancement in irradiance transmittance over the fjord was 0.19 for the inner fjords and 0.10 for the whole fjord (λ = 469 nm). The land surrounding the Hornsund fjord also had a considerable impact on the spectral cloud radiative forcing on the fjord surface and the solar flux anomaly at the domain surface due to the uniform surface assumption. For the mouth and central part of the fjord the error due to the use of channel 2 of the MODIS radiometer (λ = 858 nm) for cloud optical thickness retrieval was < 1 in the case of low-level clouds (cloud base height 1 km, nadir radiance, υ = 53°, cloud optical thickness retrieved solely from MODIS channel 2). However, near the shoreline (up to 2 km from it), especially over the inner fjords, the cloud optical thickness was then overestimated by > 3 for τ = 5 and by > 5 for τ = 20.

7

Seasonal variability in the optical properties of Baltic aerosols

Zdun A., Rozwadowska A., Kratzer S.

Oceanologia

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2011

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No. 53 (1)

7-34

EN

A five-year dataset of spectral aerosol optical thickness was used to analyse the seasonal variability of aerosol optical properties (the aerosol optical thickness (AOT) at wavelength λ=500 nm, AOT(500) and the Angström exponent for the 440-870 nm spectral range, α(440, 870)) over the Baltic Sea and dependence of these optical properties on meteorological factors (wind direction, wind speed and relative humidity). The data from the Gotland station of the global radiometric network AERONET (Aerosol Robotic Network, http://aeronet.gsfc.nasa.gov) were taken to be representative of the Baltic Sea conditions. Meteorological observations from Farosund were also analysed. Analysis of the data from 1999 to 2003 revealed a strong seasonal cycle in AOT(500) and α(440, 870). Two maxima of monthly mean values of AOT(500) over the Baltic were observed. In April, an increase in the monthly mean aerosol optical thickness over Gotland most probably resulted from agricultural waste straw burning, mainly in northern Europe and Russia as well as in the Baltic states, Ukraine and Belarus. During July and August, the aerosol optical thickness was affected by uncontrolled fires (biomass burning). There was a local minimum of AOT(500) in June. Wind direction, a local meteorological parameter strongly related to air mass advection, is the main meteorological factor influencing the variability of aerosol optical properties in each season. The highest mean values of AOT(500) and α(440, 870) occurred with easterly winds in both spring and summer, but with southerly winds in autumn

8

Variability in aerosol optical properties at Hornsund, Spitsbergen

Rozwadowska A., Sobolewski P.

Oceanologia

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2010

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No. 52 (4)

599-620

EN

Spectra of the aerosol optical thickness from the AERONET station at Hornsund in 2005-2008 were employed to study the interseasonal and intraseasonal variability in aerosol optical thickness for λ=500 nm (AOT(500)) and the Angström exponent in the southern part of Spitsbergen in spring and summer. The dependences of aerosol optical properties on long-range transport and local meteorological conditions, i.e. wind direction and speed and humidity, were analysed. Backward trajectories computed by means of NOAA HYSPLIT model (Draxler & Rolph 2003) were used to trace the air mass history. The mean values of AOT(500) for spring and summer were 0.110 ± 0.007 (mean and standard deviation of the mean) and 0.048 ± 0.003 respectively. The average values of the Angström exponent do not differ and take respective values of 1.44 ± 0.03 and 1.45 ± 0.03. In both seasons, the highest AOT(500) cases (the highest 20% of AOT values) can be explained by long-range transport from Europe, Asia (spring and summer) and North America (summer). In summer, the impact of distant sources on AOT is strongly modified by cleansing processes en route to Hornsund. Local meteorological conditions at the station are of secondary importance as regards the intraseasonal variability of aerosol optical properties in the southern part of Spitsbergen.

9

Zlodzenie Hornsundu i jego przedpola (SW Spitsbergen) w sezonie zimowym 2006/2007

Styszyńska A., Rozwadowska A.

Problemy Klimatologii Polarnej

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2008

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nr 18

141-160

PL

W sezonie zimowym 2006/2007 przebieg zlodzenia Hornsundu był odmienny od przeciętnego. Od listopada do marca średnia miesięczna temperatura powietrza była o 3.6–6.3 deg wyższa od średniej klima-tycznej (1978–2006). Ujemna temperatura wody powierzchniowej przy brzegu Isbjornhamny występowała od 28 IX 2006 do 27 V 2007 r. Najniższe wartości temperatury wody mierzono w drugiej i trzeciej dekadzie października (–1.8°C). Latem i jesienią 2006 r. dochodziło do bardzo intensywnego obłamywania się lodu lodowcowego, który okresowo tworzył zwarte skupienia wzdłuż brzegu. Rozwój lodu morskiego w Isbjornhamnie cechuje się stadial-nością. Pierwszy okres tworzenia się lodu morskiego miał miejsce między 6 października a 3 listopada, drugi – od połowy stycznia. W tym samym czasie dryfujący lód allochtoniczny pojawił się również na przedpolu fiordu. Od trzeciej dekady lutego do drugiej dekady kwietnia prawie cała powierzchnia Hornsundu pokryta była lodem dryfu-jącym o zmiennej zwartości. Na osiowej partii fiordu lód morski zanikł po 25 kwietnia, a w Brepollen – w trzeciej dekadzie czerwca 2007 r. Maksymalna wysokość wału lodu nabrzegowego w Isbjornhamnie osiągnęła 2.5 m.

EN

This article presents the development of sea ice cover in the waters of central and western part of the Hornsund Fjord, as well as in its foreshore during winter season 2006–2007. Due to long lasting (November-March) high air temperatures (Fig. 1) the sea ice cover development of Hornsund was different from the average one. Significant decrease in air temperature was observed only in April (mean monthly –8.7°C). In such thermal conditions the maximum thickness of sea ice which might have been formed in the outer, sheltered from high seas areas of the fjord, estimated with the help of Zubov formula, could reach 47cm in January, 58cm in February, 66cm in March, up to 77–80cm in the period from April to May 2007 (Tab.1). In summer and autumn 2006 only brash glacier ice and small icebergs broken off the glaciers endings on the sea in Hornsund drifted in the waters of the fjord. At this time brash glacier ice and growlers broken off the Hans Glacier periodically concentrated densely along the coast of Isbjorhamna. The first forms of new ice (slush and grease ice as well as shuga) were observed close to the west coast of Isbjornhamna from 6th October till 3rd November. The second period of sea ice formation started on 7th December. However, the ice disappeared quickly because of strong winds. Not sooner than in the middle of January when severe frost was noted, a permanent ice cover was formed (young ice). But also this ice was broken and diverged in most part of the fjord. Fast ice was only observed in the internal waters of Hornsund, in the Brepollen, Burgerbukta and Samarinvagen bays. From the third decade of February till the end of April the ice cover of Hornsund experienced large fluctuations. During that period the entire area of Hornsund was covered with sea ice a few times. This phenomenon was noted when the allochtonic ice drifting in the waters of the Sorkapp Current entered western and central part of the fjord and when the central and inner parts were covered with ice formed in situ. This sea ice cover was several times destroyed by very strong east winds causing that most of ice was moved outside the fjord. At the beginning of May very strong E and SE winds caused ice removal from the axial part of Hornsund. Later, apart from two short episodes (19-29 May and 22-23 June) when open strips of allochtonic ice entered west and central part of the fjord, only single floes of broken-off the fast ice from Brepollen, Burgerbukta and Samarinvagen drifted in the waters of Hornsund. The ice season 2006/2007 ended on 19th July when the last floes of very rotten ice were observed drifting from the inside of the fjord with the tidal stream to its foreshore.

10

Pomiary aerozolowe w Hornsundzie w trakcie XXIX Wyprawy Polarnej PAN

Rozwadowska A., Petelski T., Zieliński T.

Problemy Klimatologii Polarnej

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2008

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nr 18

161-170

PL

W pracy przedstawiono wyniki pomiarów przeprowadzonych na stacji Hornsund podczas międzynarodowego eksperymentu ASTAR 2007 (Arctic Study of Tropospheric Aerosol, Clouds and Radiation). Stwierdzono, że zjawisko zamglenia arktycznego (ang. Arctic Haze) wystąpiło w czasie kampanii pomiarowej ASTAR 2007 na południowym Spitsbergenie tylko jednego dnia. Przypuszcza się, że ograniczenie wystąpienia zamglenia arktycznego na południowym Spitsbergenie wiosną 2007 roku może być spowodowane m.in. przesu-nięciem się na północ granicy zamarzania morza.

EN

Intensive measurement periods within the ASTAR Project were carried out in spring 2004 and 2007. Spring is the season in the Arctic when the so-called Arctic Haze phenomenon occurs. The ASTAR 2007 measurement period lasted from 28 March to 16 April. During the campaign at the station in Hornsund the following instruments were used: laser particle counter, sunphotometers, radiometers and pyranometers. Such instrumentation set-up facilitated the determination of the aerosol optical thickness, aerosol concentration and size distribution, upward and downward radiation fluxes. During the 2007 ASTAR campaign the Arctic Haze conditions were observed only one day in the southern Spitsbergen area. A hypothesis was set forth that due to higher up north shift of frozen sea surface areas marine aerosols may noticeably contribute to cleaning of the Arctic atmosphere.

11

Influence of aerosol vertical profile variability on retrievals of aerosol optical thickness from NOAA AVHRR measurements in the Baltic region

Rozwadowska A.

Oceanologia

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2007

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No. 49 (2)

165-184

EN

The expected influence of variability in atmospheric aerosol profiles on retrievals of aerosol optical thickness (AOT) from NOAA AVHRR measurements is analysed. In particular, the bias in the AOT retrieval due to the assumption of a climatological aerosol profile in the retrieval algorithm is studied. The bias is defined as the difference between AOT retrieved with an algorithm using a climatological aerosol profile, and the actual AOT employed in the calculations of radiances at the top of the atmosphere (TOA). The TOA radiances are simulated by means of the MODTRAN code for different aerosol profiles. Atmospheric conditions and solar and satellite angles used in the bias simulations are typical of the Baltic region. In the simulations, the maximum absolute value of the bias amounts to nearly 40% in channel 2 and 14% in channel 1 of AVHRR.

12

Uncertainty in stratiform cloud optical thickness inferred from pyranometer measurements at the sea surface

Rozwadowska A.

Oceanologia

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2004

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No. 46 (2)

155-174

EN

The relative "plane-parallel" error in a mean cloud optical thickness retrieved from ground-based pyranometer measurements is estimated. The plane-parallel error is defined as the bias introduced by the assumption in the radiative transfer model used in cloud optical thickness retrievals that the atmosphere, including clouds, is horizontally homogeneous on the scale of an individual retrieval. The error is estimated for the optical thickness averaged over the whole domain, which simulates the mean cloud optical thickness obtained from a time series of irradiance measurements. The study is based on 3D Monte Carlo radiative transfer simulations for non-absorbing, all-liquid, layer clouds. Liquid water path distributions in the clouds are simulated by a bounded cascade fractal model. The sensitivity of the error is studied with respect to the following factors: averaging time of irradiance used in an individual retrieval, mean cloud optical thickness, cloud variability, cloud base height and solar zenith angle. In the simulations presented in this paper, the relative bias in the domain averaged cloud optical thickness retrieved from pyranometer measurements varies from +1% for optically thin clouds to nearly -20%. The highest absolute value of the relative bias is expected for thick and variable clouds with high bases (e.g. 1 km) and retrievals based on long-term mean irradiances (averaging time of the order of several tens of minutes or hours). The bias can be diminished by using short-term irradiance averages, e.g. of one minute, and by limiting retrievals to low-level clouds.

13

Uncertainty in estimating mean solar radiation fluxes at the Baltic surface from irregular ship-borne meteorological observations

Rozwadowska A.

Oceanologia

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1999

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No. 41 (1)

25-50

EN

The influence of the technique of sampling of meteorological conditions and the number of observations on uncertainties in estimates of the solar radiation flux in the Baltic region is analysed. A semi-empirical model, applied to regular meteorological observations from two Baltic island stations, Gotska Sandon and Arkona, was employed to derive solar radiation fluxes (downward irradiances) for error analysis. The impact of several factors, i.e. consistent sampling at one observation time, using both daytime and night-time observations in the flux calculations, and consistent oversampling during the same part of a month on systematic uncertainties in the monthly mean flux estimates are discussed. The random errors resulting from an insufficient number of observations used in the flux calculations and error reduction with an increasing number of observations are analysed with respect to batch and random sampling. The statistical correlation of consecutive meteorological observations (meteorological conditions represented by the zenithal transmittance of irradiance) was also investigated with respect to errors in the estimation of the solar radiation flux for the Baltic Sea region.

14

Solar radiation fluxes at the surface of the Baltic Proper. Part 2. Uncertainties and comparison with simple bulk parametrisations

Isemer H. J., Rozwadowska A.

Oceanologia

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1999

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No. 41 (2)

147-185

EN

An adjusted version of the semi-empirical model developed by Rozwadowska (1991) was applied to calculate monthly and annual estimates of incident solar radiation fluxes at the surface of the Baltic Proper during 1980 to 1992 using voluntary observing ship meteorological observations from COADS as input data. The semi-empirical model was specifically calibrated using measurements from the Baltic Proper region. In Part 1 of this study we described the resulting solar radiation flux climatology for the Baltic Proper as well as for its three sub-basins. In this second part, we give estimates of the overall random and systematic errors of the climatological flux results, apply simple bulk parametrisations to the same COADS ship observations, and compare the results with those of the semi-empirical model presented in Part 1. This comparison shows that bulk parametrisations calibrated both in purely marine and in continental environments elsewhere on the globe produce surface radiation climates over the Baltic Proper which deviate systematically, in a seasonally and regionally varying manner, from the results of the semi-empirical model. We present evidence to show that the differences found may be due both to physical reasons and to problems with the calibration methodology. This indicates that the atmospheric conditions over the Baltic Sea require specific, regionally calibrated models and parametrisations for solar surface radiation. We suggest that international efforts be made in order, firstly, to build up inventories and accessible data compilations of existing surface radiation records from the Baltic Sea, and secondly, to initiate additional surface radiation measurement activities based on internationally accepted and co-ordinated strategies. The planned intensive observational and modelling phase of BALTEX scheduled for the years 1999 to 2001 (BRIDGE) would be an ideal start for such initiatives.

15

Seasonal changes of the aerosol optical thickness for the atmosphere over the Baltic Sea - preliminary results

Kuśmierczyk-Michulec J., Rozwadowska A.

Oceanologia

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1999

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No. 41 (2)

127-145

EN

A statistical analysis of the aerosol optical thickness and the Angstrom parameters derived from measurements of spectral solar radiation at the surface of the southern and western Baltic Sea is presented. The experimental data were collected on cloudless days during over 20 cruises from March to September within a 4-year period (1994-1998). The monthly and seasonal variability of the aerosol optical thickness for two wind direction sectors - northern sector 270o-N-90o and southern sector 90o-S-270o - is analysed.

16

Solar radiation fluxes at the surface of the Baltic Proper. Part 1. Mean annual cycle and influencing factors

Rozwadowska A., Isemer H. J.

Oceanologia

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1998

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No. 40 (4)

307-330

EN

Meteorological observations made on board Voluntary Observing Ships in the period 1980-1992 are used to estimate the climatological characteristics of the solar radiation flux at the surface of the Baltic Proper. A semi-empirical model developed for the Baltic region is used. Monthly and annual means of solar radiation fluxes reaching the sea surface, averaged over the northern, southern and western parts of the Baltic Proper are calculated. Seasonal and interannual variability of the fluxes as well as the impact of both meteorological and astronomical factors on the monthly and annual means of the fluxes are also analysed. The annual mean irradiance for the entire Baltic Proper is estimated at 117 ( ±4) W m-2. The long-term monthly means for this area vary from 12 (±4) W m-2 in December to 241 (±21) W m-2 in June.

17

Finding the aerosol optical thickness over the Baltic Sea - comparison of two methods

Rozwadowska A., Kuśmierczyk-Michulec J.

Oceanologia

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1998

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No. 40 (3)

165-182

EN

The results of two methods used to estimate the aerosol optical thickness over the Baltic Sea are compared. The standard method is based on measurements of the direct component of the downward irradiance at the sea surface in 8 spectral bands (412, 443, 490, 510, 555, 670, 765, 865 nm - the same as SeaWiFS). In the pyranometric method, Baltic aerosols are assumed to be a mixture of model aerosol types with strictly defined optical properties, i.e. maritime, continental and stratospheric types. Their proportion in the Baltic aerosol is found from broadband spectral downward irradiance measurements (VIS, IR) using the radiative transfer model. Simultaneous measurements of the spectral downward irradiance and its direct component on cloudless days in the southern Baltic were used in the comparison. The pyranometric method of estimating the aerosol optical thickness proved to be a satisfactory tool. Depending on the wavelength, the statistical errors in it are not in excess of plus_min.0.06 - 0.08.