A fine resolution hybrid coordinate ocean model (HYCOM) for the Black Sea with a new solar radiation penetration scheme

A 1/25° x 1/25° cos(lat), (long x lat) resolution eddy-resolving HYbrid Coordinate Ocean Model (HYCOM) is introduced for the Black Sea and used to examine the effects of ocean turbidity on upper ocean circulation features including sea surface height (SSH) and mixed layer depth (MLD) on annual mean and seasonal climatological time scales. HYCOM is a primitive equation model with a K-Profile Parameterization (KPP) mixed layer sub-model, and it uses a hybrid vertical coordinate that combines the advantages of isopycnal, terrain-following (sigma) and z-level coordinates in optimally simulating coastal and open-ocean circulation features. This model approach with ≈3.0 km resolution is applied to the Black Sea for the first time in the literature.; A newly-developed time-varying solar penetration scheme that treats attenutation as a continuous quantity is added to the model as will be described in this dissertation. This new scheme involves two bands for the top 10 m of the water column; thus, it is suitable for any Ocean General Circulation Model (OGCM) that has fine vertical layer resolution near the surface. With the new parameterization, the depth-dependent attenuation of subsurface heating in HYCOM is given by monthly mean fields for the attenuation of Photosynthetically Available Radiation (k_PAR) during 1997–2001 as constructed from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite data. Climatologically-forced HYCOM simulations with no assimilation of any ocean data are then used to show the importance of including spatial and temporal varying attenuation depths for the annual and monthly mean predictions of upper ocean quantities in the Black Sea.; It is first shown that most of the large differences between the basin-wide mean net heat flux at the sea surface and flux entering the mixed layer (mixed layer flux) in the Black Sea occur from April to October on the climatological time scales, and there is almost no difference between the two during the remaining months. The difference between the net heat flux at the sea surface and mixed layer flux is shortwave radiation absorbed below the mixed layer, which can be as large as 50 W m−2 in summer because the MLD is very shallow (<4 m) over the most of Black Sea. In particular, the model simulations reveal that the basin-wide mean flux below the mixed layer can be as large as 100 W m−2 regardless of the atmospheric forcing used.; Finally, the results in this dissertation suggest that, if the Black Sea turbidity is entirely or largely due to biology, a lack of nutrients (or other caus for loss of biomass) will have a significant effect on the overall circulation of the Black Sea. In this dissertation, it is not specifically examined how likely this is (i.e., how robust the bio-system is in the Black Sea).