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Coastal upwelling by wind-driven forcing in the Caspian Sea: A numerical analysis

Fallah Fatemeh, Mansoury Dariush

Oceanologia

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2022

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No. 64 (2)

363--375

EN

In this study, wind-driven coastal upwelling in the Caspian Sea was investigated using a developed three-dimensional hydrodynamic numerical model based on the Princeton Ocean Model (POM). The model was forced with wind fields and atmospheric fluxes from the ECMWF database and it considers freshwater inflows from the Volga, Kura and Ural Rivers. This model was implemented for 10 years (2008–2018). Findings indicated that the upwelling in the Caspian Sea was due to effects of wind and bottom topography, often occurring from May to September. In June and July, in the eastern part of the middle and sometimes southern basins, up to 3°C water temperature difference occurs between coastal and offshore areas. The vertical temperature gradient in the middle basin was larger than that in the southern basin. Upwelling in August in the eastern coasts of the middle basin within 25 km of coast from the depth of 15 m to the surface was shown, which was due to the effects of wind and bottom topography. In the middle basin, the highest vertical velocities caused by upwelling in June, July and August were 12, 13.82, and 10.36 m/day, respectively.

2

Symulacja pola przepływu powietrza nad aglomeracją miejską na przykładzie Krakowa

Kamiński K., Petera J., Tomczak E.

Inżynieria i Aparatura Chemiczna

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2006

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Nr 5s

52-54

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Fale termiczne nad Polską w zimie w zależności od pola wiatru w Europie

Degirmendzić J.

Przegląd Geofizyczny

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2004

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Z. 1-2

11-23

EN

The main goal of this paper is to analyze transformation of wind field over Europe associated with change of intensity of thermal wave in Poland during winter. Thermally anomalous periods were distinguished on the basis of daily mean temperature record at 52.5°N, 20°E grid point. Wind field was defined by meridional and zonal wind components. Both, temperature and wind data were retrieved from NCEP/NCAR Reanalysis. The analysis was performed for the period of 1950-2001 and 850 hPa isobaric level. Cold/heat waves were categorized into three thermal classes - extreme, moderate and weak. In order to analyze wind field the following parameters were employed: relative vorticity, wind speed and directional steadiness of wind vector. Additionally, the structure of streamlines was analyzed. Temperature rise in Poland is forced by the development of dipole-like structure, clearly seen on the map of anomalies of relative vorticity. Positive anomalies are situated over Norwegian See, eastern Atlantic and Scandinavia, while negative vorticity advection is observed in southern Europe. Simultaneously with dipole development the increase of wind speed in middle Europe is also noted - supposedly it constitutes significant feature of wind field responsible for temperature increase in Poland in winter. In case of extreme heat waves the source region of warm advection is shifted southwards. Streamline pattern indicates more parallel flow over the Atlantic to the Iberian Peninsula and change of wind direction over Poland, from westerly to south-westerly. Intensive transport of heat over the northern Europe reduces temperature contrast at the Mediterranean front, which consequently decelerates western flow and lowers directional steadiness of wind vector down to 50% over the southern part of continent. Field of vorticity anomalies corresponding to the cold waves occurrence over Poland posseses dipole-like structure, however its polarization is reversed. Anticyclonic vorticity advection occurs in northern Europe and northern Atlantic while southern Europe experiences increase of cyclonic vorticity. Cooling in central Europe is associated with transformation of circulation field into blocking type - simultaneously the source region of cold advection shifts northwards over the Scandinavia (around 70°N). Enhanced thermal contrasts over southern Europe together with air masses inflow from the north, i.e. possessing surplus of cyclonic vorticity, strengthen the Mediterranean front.