Numerical Modelling of Freshwater Inputs in the Shelf Area of the Ofanto River (Southern Italy)

Giorgia Verri1,2, Nadia Pinardi1,2, Joseph J Tribbia3, David Gochis3, Frank Bryan3, Yu-heng Tseng3, Antonio Navarra4,5 and Giovanni Coppini2, (1)University of Bologna, Physics, Bologna, Italy, (2)Centro Euro-Mediterraneo sui Cambiamenti Climatici, Italy, (3)National Center for Atmospheric Research, Boulder, CO, United States, (4)Istituto Nazional di Geofisica e Vulcanologia, Italy, (5)Fondazione CMCC, Bologna, Italy
Abstract:
The aim of this study is to understand and to assess the effects of river freshwater release on the ocean circulation and dynamics focusing on the shelf area near estuaries.

A sensitivity study to different modelling approaches, which point to the representation of the dynamics of the river inflow, are presented. The modeling strategy we chose consists of an integrated modeling chain including the atmosphere, the hydrology/hydraulics and the estuarine dynamics in order to force our regional ocean model at the Ofanto outlet in a reliable way. This meteo-hydrological modeling chain allows us to take into account all the physical processes involved in the local water cycle of the Ofanto catchment such as the rainfall, the land surface infiltration/evaporation, the partitioning of total runoff into surface and subsurface runoff and the channel streamflow.

In order to achieve our goal, we chose the Ofanto river catchment and its estuary as case study. The Ofanto river is a torrential river flowing across the Southern Italy and ending in the Adriatic Sea; its annual averaged discharge is low (15 m3s-1 following Raicich, 1996) but may significantly increase when heavy rain events occur.

In details our regional ocean model is a finite difference numerical model based on NEMO code (Madec, G., 2008) and implemented in the Central Mediterranean Sea with 2km as horizontal resolution. The meteo-hydrological modeling chain consists of: 1) the WRF-ARW model (Skamarock et al., 2008) including NOAH-MP as Land Surface Submodel,; 2) WRF-HYDRO model (Gochis D., et al., 2013) representing the hydrology/hydraulics component with 200m as horizontal resolution, simulating the streamflow discharge along the Ofanto river network.; 3) finally an estuarine box model (Garvine et al., 2006) is inserted downstream of WRF-Hydro and upstream of the regional ocean model.

A set of sensitivity experiments has been performed aiming to evaluate the capability of the regional ocean model to decribe the Ofanto river plume by providing hindcast discharge and salinity from the estuary model at the river mouth with different methods. The time window of the simulations covers the first three months of year 2011, since 4 heavy rain events affected the Ofanto catchment in this period.

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