Sensitivity of the Mediterranean sea level to atmospheric pressure and free surface elevation numerical formulation in NEMO

Abstract

Abstract. The sensitivity of the dynamics of the Mediterranean Sea to atmospheric pressure and free surface elevation formulation using NEMO (Nucleus for European Modelling of the Ocean) was evaluated. Four different experiments were carried out in the Mediterranean Sea using filtered or explicit free surface numerical schemes and accounting for the effect of atmospheric pressure in addition to wind and buoyancy fluxes. Model results were evaluated by coherency and power spectrum analysis with tide gauge data. We found that atmospheric pressure plays an important role for periods shorter than 100 days. The free surface formulation is important to obtain the correct ocean response for periods shorter than 30 days. At frequencies higher than 15 days −1 the Mediterranean basin's response to atmospheric pressure was not coherent and the performance of the model strongly depended on the specific area considered. A large-amplitude seasonal oscillation observed in the experiments using a filtered free surface was not evident in the corresponding explicit free surface formulation case, which was due to a phase shift between mass fluxes in the Gibraltar Strait and at the surface. The configuration with time splitting and atmospheric pressure always performed best; the differences were enhanced at very high frequencies.

Sea-level variability in the Mediterranean Sea from altimetry and tide gauges

“…5). This in agreement with Oddo et al (2014) who, looking at the sensitivity of the Mediterranean sea level to atmospheric pressure, observed a large scale zonal gradient, which produces higher sea-level values and a larger variance in the sea-level signal in the Levantine basin. These events have already been observed at the basin scale (Calafat et al 2010(Calafat et al , 2012Tsimplis et al 2013) and defined as non-steric fluctuations due to mass transport through the Strait of Gibraltar driven by wind, occurring during a strong negative phase of the North Atlantic Oscillation (Landerer and Volkov 2013).…”

The diurnal cycle of sea-surface temperature and estimation of the heat budget of the Mediterranean Sea

“…6.5 km) covering the whole Mediterranean Sea. The Ocean General Circulation Model is based on the Nucleus for European Modelling of the Ocean (NEMO), implemented for the Mediterranean Sea at 1/168 horizontal resolution with 72 vertical levels as described by Oddo et al [2014Oddo et al [ , 2009 and Tonani et al [2008]. The model solutions are corrected by the variational assimilation scheme based on 3DVAR, see Dobricic and Pinardi [2008], of vertical profiles of temperature and salinity from CMEMS In-Situ-TAC (Thematic Assembly Center) and along track satellite Sea Level Anomaly observations from CMEMS-Sea Level-TAC.…”

Multi-nest high-resolution model of submesoscale circulation features in the Gulf of Taranto

“…The MFS model has a horizontal resolution of 1/16 • , contains 72 unevenly distributed layers in the vertical direction (Oddo et al 2014) and includes a variational assimilation scheme based on the 3D-VAR method of Dobricic and Pinardi (2008). We used MFS data where only the LS1 observations were assimilated by the 3D-VAR scheme.…”