Naslov
Observations and modeling of the Po River inflow to the Northern Adriatic (the case of 16 - 20 January 1987)

Autori
Beg Paklar, Gordana ; Isakov, Vlad ; Koračin, Darko ; Kourafalou, Vily ; Orlić, Mirko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Oceanography of the Eastern Mediterranean and Black Sea / NN - Atena : Institute of Oceanography, 1999, 183-183

Skup
Oceanography of the Eastern Mediterranean and Black Sea

Mjesto i datum
Atena, Grčka, 1999

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
observations; modeling; Po River inflow to the Northern Adriatic
(observations; modeling; Po River inflow to the Northern Adriatic)

Sažetak
Sea surface temperature obtained from Advanced Very High Resolution Radiometer (AVHRR) in the Northern Adriatic shows Po River water advected off the coast after a long lasting bora episode of 16-20 January 1987, contrary to the usual coastal confinement of the Po River plume in winter. In a climatological sense Po-influenced water has lower temperature than sea water during January and therefore can easily be observed on AVHRR satellite images. Being of NE direction, the bora may be expected to prevent spreading of the Po River water, but due to its longshore variability it actually advects low-salinity water towards the eastern Adriatic coast. Importance of the bora longshore variability for the current and density fields on the Adriatic shelf has been amply documented by in situ and remotely sensed data and by several numerical models. To simulate the bora induced currents correctly it is crucial to have fine horizontal resolution which resolves the bora longshore variability. However, previous fine-resolution numerical models were forced with climatological wind which was suddenly applied and thereafter kept constant. These time constant wind fields excluded inertial effects which are important for transient forcing like bora. In this study, thermodynamic properties of the Adriatic shelf waters during the bora event of 16-20 January 1987 are reproduced with the Princeton Ocean Model (POM). Horizontal resolution in the experiment was 5 km, while in the vertical direction 16 sigma levels were used. POM has been forced with the wind field obtained from Mesoscale Model 5. Horizontal resolution in the meteorological model was 9 km. Hourly values of the bora wind field from meteorological model were used to derive the oceanographic model, whereas wind values at intermediate time steps were obtained by linear interpolation. By using this space and time varying wind field it was possible to model the horizontal variability of the current field correctly and to follow its temporal evolution and decay. The Po River was introduced in the model as a source term in the continuity equation. Moreover, it was assumed that the Po River water has zero salinity and 5 degrees C lower temperature than the ambient sea water. Initial sea surface temperature was obtained from AVHRR scene of 9 January 1987, whereas temperature was assumed to be vertically uniform in accordance with some simultaneous bathythermograph measurements. The initial salinity field was obtained via a 10 day simulation of river discharge with no wind and temperature changes. AVHRR satellite images of 21 and 22 January, when the bora slackened, were used for verification of the oceanographic model results. Model results show spreading of the Po cold and fresh waters away from the river mouth. Horizontal variability of current field during the bora episode and after it agrees with the shape of the cyclonic gyre that is visible on the infrared satellite images. Several numerical experiments are performed to demonstrate the importance of the horizontal and vertical mixing, thickness of the first sigma layer and initial conditions on the computed transport patterns.

Izvorni jezik
Engleski

Znanstvena područja
Geologija, Biologija

POVEZANOST RADA