Introduction


A new, 7th, issue of the electronic atlas “Bio-optical characteristics of the Russian seas from satellite ocean color data”, as the previous ones, contains color maps with the mean monthly distributions of the bio-optical characteristics in the Barents, White, Black, and Caspian seas; diagrams, demonstrating variability of the monthly means in different sub-regions and in the whole basins; tables with parameters of the inter-annual changeability of different characteristics. The set of bio-optical parameters includes chlorophyll concentration, the particle backscattering coefficient and the absorption coefficient of yellow substance – they display the spatial and temporal variability of three important seawater constituents – photosynthetic phytoplankton, suspended particulates and colored organic matter. The above parameters were derived from SeaWiFS and MODIS-Aqua data collected over the period of 1998-2012.

This release continues the series of issues, which started since 2002 – the first issue was prepared in Russian and included data of 1998-2002 (
Kopelevich et al. 2002a); the next ones were issued in English with adding new data every two years; the last, 6th, issue was presented in 2011 and included data of 1998-2010 (Kopelevich et al. 2011c). As compared with the 6th issue, the new release has some changes and additions.

The design of the website has been modified for the convenience of the user. The main goal of modification was improvement of the accessibility to the required information for the user. For that, the access from the home page to pages with basic information was restructured. Now the user can find the general information of his interest at the home page and then proceed to more detailed topics of his choice. An advantage of the new interface is accessibility of the material from any page at the site. An interactive site provides the user with more detailed information on each topic. Charts, maps, tables are indicated in the text as small pictures. Clicking on them, the user gets to its larger version. It is possible to view a map from the text by clicking the reference placed on each page. Such links provide the user with the option to view illustration concerning the sea or the specific product of his interest. If one would like to read the Atlas as a book, the site provides a version for reading.

The new issue includes data of 2011-2012. For joining them with the previous data, it was necessary to solve the question of a need of recalculation of data of 1998-2010 (calculated with old SeaDAS version l2gen 6.2.5) by means of new version 6.5.7 or 6.6.3. To address this issue, a direct comparison of the values of the radiance reflectance
R rsi) for the Barents, Black and Caspian Seas, derived with the new and old versions, was performed. Results of the comparison showed that the differences between the above versions were not significant, except for the channel 412 nm; the versions 6.5.7 and 6.6.3 coincided almost completely. Based on these results, version l2gen 6.2.5 was used for processing MODIS-Aqua data in the Barents Sea and Black Sea from July 2002 to December 2010; version l2gen 6.5.7 or 6.6.3 - for data of 2011-2012. For the Caspian Sea, the last version was used for all MODIS data of 2002-2012, since the algorithm for calculating the yellow substance absorption needs correct data for all wavelengths. For 1998-2002, SeaWiFS data, transformed to the MODIS-like monthly averages as a result of joining with MODIS data were used (Kopelevich et al. 2011c).

The time series of bio-optical characteristics of the White Sea have been extended by including SeaWiFS data since 1998 (the MODIS-Aqua data only since July 2002 were used in the previous issue). The procedure for linking the data from SeaWiFS and MODIS-Aqua was developed and applied in the previous issue for all considered seas, except the White Sea, where all computations were performed only with MODIS-Aqua data (
Kopelevich et al., 2011c). Now the similar procedure was applied to the White Sea (see Section White Sea, Satellite data).

In the new issue, a greater attention, than in the previous ones, is paid to the coccolithophore blooms. The coccolithophore concentration is given not only for the Black Sea, as before, but also for the Barents Sea; where it was calculated with a regional algorithm (see Sections Barents Sea
Satellite data and Results and discussion ).

As in the previous issue, the monthly and annually averaged data on SST from MODIS-Aqua were added in this release to provide an opportunity for analysis of connection between changes of bio-optical characteristics and SST (
Burenkov et al 2011a, Kopelevich et al. 2011a). The SST data were downloaded from the NASA web site http://oceancolor.gsfc.nasa.gov. The daytime level 2 MODIS Aqua files were used. The quality level qual_sst varied between 0 and 4, where 0 indicated the best quality and 4 – the complete failure (usually, land). When averaging, the pixels with values of qual_sst exceeding 2 were filtered out. The MODIS-Aqua data on SST in 2003 were of a bad quality, so we used, instead of them, the data from MODIS-Terra with a quality level less or equal to 3 for 2003.

The daily Level-3 values from MODIS-Aqua data were generated by averaging the Level-2 values within a given bin of 3 x 3 km, and filtering out pixels flagged for land, clouds, and straylight. The monthly of other Level-3 files were created by averaging the daily Level-3 values over the corresponding period.