Remote passive optical measurements of the state of waters in water basins studied from ships, airborne platforms, or satellites are most informative because they cover a large territory and are performed at a high frequency. At the same time, for correct estimation of the remotely obtained data some in situ measurements of the state of waters in water samples, taken at a limited number of points, should be performed. Studies carried out in the coastal regions of the Middle Caspian Sea were used as an example to identify the conditions when such point-like measurements are suitable for calibrating the remote hydro-optical measurements by the Ecological Monitoring of Marine Waters (EMMA) complex onboard a cruising vessel. The limitations identified were explained through analysis of the structure of coastal waters; this structure was measured through vertical sensing of water at stations and by operating a flow-through system for determining the temperature and salinity of surface waters. An algorithm is proposed for selecting water samples suitable for calibration of remote measurement by correlating them with Secchi disk depth, and the efficiency of this method is demonstrated. We showed what hydrophysical conditions should be taken into consideration for the preliminary selection of water sampling sites for calibrating remote measurements.

Results of the study of water exchange between the Azov and Black seas based on the data of contact measurements in 2019 are presented. Estimates of the scale of the Sea of Azov plume were obtained under conditions of a strong northeasterly wind (9–10 m/s). The results of field measurements confirmed the determining role of wind in water exchange through the Kerch Strait, which made it possible to form statistics on the flow of the Sea of Azov waters into the Black Sea based on wind reanalysis data over the past twenty years. A new method for calculating the flow of the Sea of Azov water through the Kerch Strait based on the comparison of satellite and field data is proposed and applied. The calculation of the Sea of Azov water transport is generally based on the assessment of the spatial characteristics of the Sea of Azov plume in the Black Sea and, in particular, on the determination of the dependence of its area on wind parameters. The average annual transport of the Sea of Azov water estimated using the new method practically coincides with the average value of all estimates of water exchange through the Kerch Strait, obtained using other calculation methods. We also considered the reverse case of the inflow of the Black Sea waters into the Sea of Azov after the end of the period of intense flow of the Sea of Azov waters into the Black Sea.

Ship-based measurements of the biooptical characteristics of Lake Issyk-Kul waters with the passive remote sensing complex Ecological Monitoring of Marine Areas (EMMA), as well as measurements in water samples, were used to develop and test a new technique for estimating the composition of oligotrophic waters. It is the third part of the method for remote estimation of the concentrations of the main natural constituents in sea or lake waters using the spectrum of light absorption by pure sea water which we developed earlier for mesotrophic and eutrophic waters. This technique was used to estimate the concentrations of pigments of phytoplankton, colored organic matter, and suspension and their distribution over the lake water basin during three-day experiment in July 2018.

Наибольшая изменчивость экологического состояния прибрежных вод наблюдается в районах впадения рек. Плюмы рек могут отличаться от окружающей морской воды как по составу примесей, так и по их концентрации. При этом размеры и положение плюмов характеризуются сильной изменчивостью. Для мониторинга таких акваторий требуется проведение измерений с хорошим пространственным и временным разрешением. Продемонстрирована возможность оперативной оценки распределения естественных компонент морской воды в районе речного плюма у Кавказского побережья Черного моря методом пассивного оптического зондирования с борта судна. Для этого использовался портативный трехканальный гиперспектральный комплекс ЭММА - экологический мониторинг морских акваторий, установленный на гиростабилизированной платформе. Данные комплекса ЭММА были обработаны специальным алгоритмом, позволяющим получить спектры поглощения света морской водой и оценить концентрации природных компонент в ее составе. Обсуждается эффективность работы гиростабилизированного комплекса по сравнению с измерениями без стабилизации. Показана возможность получения оценок концентрации основных естественных составляющих морской воды гиростабилизированным комплексом ЭММА в условиях неравномерного освещения при низком положении солнца, что существенно расширяет временные рамки проведения измерений. Представленный комплекс может быть полезен при проведении подспутниковых измерений в прибрежных районах океана и внутренних морях, включающих речные плюмы.

We report results of a field survey conducted in the buoyant, sediment-carrying coastal plume generated by the discharge from the Patos Lagoon, the World's largest choked lagoon. The concentration of total suspended matter (TSM) and organic matter (as represented by total organic carbon, TOC) were mapped using an ultraviolet fluorescent LiDAR, which allowed for extensive data coverage (total of 79,387 simultaneous determinations of TSM and TOC) during 3 consecutive days. These observations were accompanied by hydrographic measurements from the ship and at a mooring station. We first describe synoptic variability of the plume, which responded energetically to wind forcing. We then analyze the TSM, TOC and hydrographic data jointly and develop a simple approach to estimate the rates of suspended matter removal from the upper layer due to gravitational settling and turbulent mixing based on relative changes in TSM and TOC concentrations. Four distinct regions within the plume exhibiting different dynamics of suspended and dissolved constituents were identified on this basis.

The study of the ecological state of coastal areas often requires rapid acquisition of detailed data. In this work, sea radiance coefficient spectra are analyzed, which were measured with a new three-channel passive optical complex for ecological monitoring of marine aquatoria (EMMA), developed by us, which operates semiautomatically on board a moving ship. The measurements were carried out near the Brazilian coast at the Rio Grande river mouth. The spectra are processed using an original technique which is based on intrinsic properties of the pure sea water absorption spectrum (WASM – water absorption step method) and has been modified for eutrophic Case II waters. This enables us to estimate the absorption indices of the suspended matter and colored organic matter. The comparison of these remote estimates with the estimates made from water samples taken at special stations shows their high correlation. The distributions of the suspended matter and colored organic matter are retrieved from remote measurement data and compared to the satellite imagery for the water area under study.

Оценка экологического состояния прибрежных вод или вод внутренних морей требует оперативного получения подробных данных об акватории. Разработанный нами новый трехканальный пассивный оптический комплекс для экологического мониторинга морских акваторий позволяет получать спектры коэффициента яркости моря с борта движущегося судна. Для обработки результатов измерений с целью получения данных о концентрации имеющихся в воде естественных примесей используется оригинальный метод решения обратной задачи, основанный на учете особенностей спектра поглощения света чистой водой, - метод водной адсорбционной ступеньки. Комплекс для экологического мониторинга морских акваторий совместно с программой метода водной адсорбционной ступеньки был использован для изучения зон смешения различных типов вод в Черном море. Производя измерения с пространственным разрешением 3 метра с борта движущегося судна, он позволил получить подробную картину распределения примесей по двум исследуемым акваториям прибрежных районов Черного моря различной трофности. Данные дистанционного зондирования были верифицированы результатами измерений, полученными на станциях.

The paper discusses spectra of the radiance coefficient of the sea surface measured in the open ocean and in coastal waters, and different kinds of these spectra corresponding to the water types are revealed. The focus is the method of measuring the radiance coefficient from a moving ship with a hyperspectral spectrophotometer. The results of studying a water area of Russia's Black Sea coast at river mouths are presented. A new calibration method that can process measurement results taking into account the impact of cloudiness and wind has been proposed and tested. The concentrations of the main admixtures in natural seawater in the studied water area are estimated according to the obtained spectra; these estimates are compared to the results of direct analysis of water samples. It has been shown that the method of remote measurement of the sea radiance coefficient from on board a ship makes it possible to obtain operative maps of the spatial distribution of the main seawater admixtures.

Latest data on the hydrophysical and biological state of the residual basins of the Aral Sea are presented and compared. Direct, quasi-simultaneous observations were carried out in the central part of the Western Large Aral Sea, the northern extremity of the Large Aral known as Chernyshev Bay, Lake Tshchebas, and the Small Aral Sea in October 2014. The Large Aral Sea and Lake Tshchebas transformed into hyperhaline water bodies with highly special taxocene structure. The Small Aral Sea was a relatively diverse brackish ecosystem, which was rather similar to the pre-desiccation environment. The Small Aral Sea and Lake Tshchebas exhibited a fully-mixed vertical structure, whereas the Western Large Aral Sea was strongly stratified. Our data show that during desiccation, different parts of the Aral Sea experienced different environmental conditions, resulting in qualitative and quantitative differences in the physical and biological regimes among the different residual basins.

This paper presents the results of long-term in situ and satellite measurements at shelf areas adjacent to the estuaries of the small rivers of the Russian coast of the Black Sea (Mezyb, Pshada, Vulan, Tuapse, Bitkha, Sochi, Cudepsta, Mzymta). The quantitative characteristics of the response of the hydrophysical and hydrochemical fields at the sea shelf on the influence of the continental river discharge are presented for each of these areas. A number of indicators of the water quality (the concentrations of the nitrate and nitrite forms of nitrogen, the phosphorus, the silica, the dissolved oxygen, the value of the total alkalinity and pH, the mineral and organic suspended matter, and the chlorophyll a) are considered in the context of the anthropogenic and terrigenous influence. In this paper, the emphasis was placed on the Mzymta River plume at the shelf area adjacent to the city of Sochi, where the measurements were repeatedly performed during the spring flooding conditions in the period from 2007 until 2012. The interannual variability of the water quality indicators and the seasonal and short-term variability of the area and the configuration of the plume, which transports suspended matter and anthropogenic pollution, were considered.

В статье предложен температурно-влажностный критерий (ТВ-критерий), который может быть рассчитан по оперативной информации со спутников для изучения районов Мирового океана, где формируется или действуют тропические циклоны. Для его получения оценивалось интегральное количество водяного пара в тропосфере в предциклонном состоянии. Исследование статистических свойств критерия в Северной Атлантике показало его высокую корреляцию с количеством зародившихся циклонов. Однако характерная величина ТВ-критерия менялась в разные годы. Причины этих изменений и их связь с активностью циклогенеза были исследованы с использованием баз данных по вертикальному профилю температуры и влажности атмосферы в Атлантическом океане для двух лет (2004 и 2009 гг.), характеризующихся высокой и низкой активностью циклогенеза. Было выявлено некоторое увеличение температуры атмосферы на значительном интервале высот в 2009 г. по сравнению с 2004 г., зафиксированное в июле, т.е. до начала сезона ураганов. ТВ-критерий был пересчитан с учетом измененного профиля температуры атмосферы. Его статистические свойства и корреляция с частотой циклогенеза подтвердили высказанное предположение о том, что одной из причин, уменьшающей активность циклогенеза, является “потепление” значительного слоя тропосферы.

Despite longstanding contributions to oceanography, similar use of fluorescence light detection and ranging (LiDAR) in lake settings is not routine. The potential for ship-mounted, multispectral Ultraviolet Fluorescence LiDAR (UFL) to provide rapid, high-resolution data in variably turbid and productive lake conditions are investigated here through a series of laboratory tank and field measurements carried out on Lake Balaton, Hungary. UFL data, calibrated empirically to a set of coinciding conventionally-analyzed samples, provide simultaneous estimates of three important parameters-chlorophyll a(chla), total suspended matter (TSM) and colored dissolved organic matter (CDOM). Successful UFL retrievals from both laboratory and field measurements were achieved for chla (0.01–378 mg∙m−3; R = 0.83–0.92), TSM (0.1–130 g∙m−3; R = 0.90–0.96) and CDOM (0.003–0.125 aCDOM(440); R = 0.80–0.97). Fluorescence emission at 685 nm is shown through tank measurements to display robust but distinct relationships with chla concentration for the two cultured algae species investigated (cyanobacteria, Cylindrospermopsis raciborskii, and chlorophyta, Scenedesmus armatus). The ratio between fluorescence emissions measured at 650 nm, related to the phycocyanin fluorescence maximum, to that at 685 nm is demonstrated to effectively distinguish these two species. Validation through both laboratory measurements and field measurements confirmed that site specific calibration is necessary. This study presents the first known assessment and application of ship-mounted fluorescence LiDAR in freshwater lake conditions and demonstrates the use of UFL in measuring important water quality parameters despite the more complicated hydro-optic conditions of inland waters.

(1) Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany, Hungary (azlinszky@gmail.com), (2) Shirshov Institute of Oceanology of the Russian Academy of Sciences, Moscow, Russia„ (3) Marine Hydrophysical Institute, Sevastopol, Ukraine„ (4) Institute for Photogrammetry and Remote Sensing, Vienna University of Technology, Wien, Austria„ (5) Space Research Group, Department of Geophysics, Institute of Earth Sciences, Eötvös Loránd University, Budapest, Hungary