Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements

Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide an opportunity to study horizontal inhomogeneities of the humidity field in the troposphere and of the cloud liquid water path (LWP) spatial distribution. However, practical applications are difficult and require thorough analysis of the information content of measurements, assessment of errors of data processing algorithm and the development of the quality control procedures. In this study we analyse the application of our LWP retrieval algorithm based on the inversion of the radiative transfer equation to the problem of detection of the LWP horizontal inhomogeneities by means of ground-based microwave observations in the vicinity of a coastline of a water object of medium size. The study is based on data acquired by the microwave radiometer RPG-HATPRO which is located in the suburbs of St.Petersburg, Russia, at 2.5 km distance from the coastline of the Neva Bay (the Gulf of Finland) and is operating in angular scanning mode in the vertical plane. The retrieval setup is organised in such a way that zenith and off-zenith measurements provide equal sensitivity to atmospheric parameters. The optimal elevation angles for off-zenith observations are selected. The possibility to detect LWP horizontal inhomogeneity, namely the LWP land-sea contrast, for different measurement geometries (elevation angles) and values of cloud base height is analysed. It is shown that ground-based microwave observations in the vicinity of a coastline can be a valuable tool for validation of the space-borne measurements of the LWP land-sea contrast if three principal requirements are met: (a) the multi-parameter physical inversion method is used for retrieving LWP; (b) rigorous bias correction and quality control procedures are applied to the retrieval results; (c) the information on the cloud base height is available. As a result of processing the microwave measurements at the observational site of St.Petersburg State University, the monthly-averaged values of the LWP land-sea difference have been obtained for summer months within the period 2013–2021. For 24 out of 25 months of high quality observations, the LWP land-sea monthly difference is positive (larger values over land and smaller values over water) and can reach 0.06–0.07 kg m−2. The estimations of the LWP land-sea contrast obtained from the ground-based microwave measurements at the observational site of St.Petersburg University are in very good agreement with the values of the LWP land-sea contrast obtained from the multi-year space-borne measurements by the SEVIRI instrument (Spinning Enhanced Visible and InfraRed Imager) in the region of the Neva Bay (the Gulf of Finland) in June and July. For August, the so-called “August anomaly” detected by space-borne observations is not confirmed by the ground-based measurements.

Three new chrysophycean stomatocysts with long spines from the Gulf of Finland, Baltic Sea

Three new morphotypes of chrysophycean stomatocysts with long spines are described following International Statospore Working Group (ISWG) guidelines and illustrated by SEM micrographs. Differences of our new morphotypes from known stomatocysts are discussed. Their biological affinity is currently unknown.

New data on the flora of Centrophyceae (Bacillariophyta) in the Neva Bay of the Gulf of Finland (Russia)

This scanning electron microscopy study of phytoplankton from the Neva Bay and analysis of valve images from S.I. Genkal’s iconotheka have provided new data on centric diatoms of the Neva Bay. Representatives of the genera Aulacoseira scalaris and Stephanodiscus lacustris, new to the flora of the Bay, have been identified. The systematic position and distribution of 14 species and varieties of Centrophyceae from the genera Aulacoseira, Conticribra, Cyclostephanos, Ellerbeckia, Handmannia, Pantocsekiella, Stephanodiscus, Thalassiosira have been refined and specified. The species composition of the class Centrophyceae of the Neva Bay has been expanded. Now it includes 42 species and varieties from 17 genera.

Year-round movements of Long-tailed Ducks Clangula hyemalis from Kolguev Island, Barents Sea

Arctic birds migrating southwards face a multitude of challenges such as habitat loss, pollution, overexploitation of food resources and climate change impacts. Long-tailed Duck winter populations in the Baltic Sea have declined in recent decades. However, precise spatial data are lacking, especially from males. Thus, we aimed to identify the wintering grounds, timing of migration and stopover sites of males and females. We studied spatiotemporal distribution patterns of eight male and five female Long-tailed Ducks using implanted ARGOS satellite transmitters. Birds were tagged in the breeding season on Kolguev Island, Russia. After the breeding period, Long-tailed Ducks from Kolguev used three main post-breeding areas: most males undertook long distance eastward post-breeding migration to areas around the Yamal and Gydan peninsulas, while one male and four females moved short to the southeast coast of Kolguev, and one female moved to Mezhdusharsky Island in the Novaya Zemlya Archipelago. Autumn migration included stopover sites in the White Sea, Lake Ladoga, the Gulf of Finland and the Gulf of Riga, and all birds except one spent the winter in the southern part of the Baltic Sea, from the Pomeranian coast and Hoburgs bank to the Gulf of Finland. Only one female stayed in the White Sea for the winter. All but one bird used the White Sea as a stopover site in May, suggesting that this area is of special importance.

A second-hand shipwreck market: Salvage auctions in mid-eighteenth-century Helsinki

When a merchant ship was wrecked in the Gulf of Finland in the eighteenth century it was salvaged (mainly its running rigging), together with its cargo. In eighteenth-century Sweden, salvage was the monopoly of the Northern Diving and Salvage Company (1729–1802). In Helsinki, several salvage auctions were held each year. Salvage documents are useful sources not only for investigating the demand for ship parts, but also for identifying ships and explaining past marine accidents. The detailed technical knowledge provided by auction protocols offers insight into ships and their equipment in the early modern Baltic. Many ships were on their way to St Petersburg (established in 1703), the home port of European naval stores, but many of them were wrecked on the rocky coasts of Helsinki. This gave rise to a strange kind of shipping based on random imports and the use of recycled cordage, sails and anchors from the shores blessed by unfortunate ships.