Methodology of Application of the Black Sea Three-Dimensional Temperature and Salinity Fields Reconstructed on the Basis of Altimetry and Scanty Measurements in the Operational Prognostic Model

V.V. Knysh✉, G.K. Korotaev, P.N. Lishaev

Marine Hydrophysical Institute, Russian Academy of Sciences, Sevastopol, Russian Federation

✉ e-mail: odop_mhi_nanu@mail.ru

Abstract

The Black Sea condition nowcast and forecast system was developed in Marine Hydrophysical Institute according to MyOcean and MyOcean2 projects and it is still functioning. The developed system includes two modules: hydrophysical, hydrobiological, optical and hydrochemical field nowcast, forecast and reanalysis module and the module of propagation and representation of system products. The module of the sea dynamics nowcast and forecast is the main one in the system as nowcast and forecast hydrophysical fields are used in other modules of the system. Due to paucity of contact measurements of seawater temperature and salinity profiles (certain hydrologic stations and Argo floats), currently these observations are not assimilated in the operative model. The results of prognostic calculations reveal inaccuracies of representation of basin waters mean stratification. A technique for reconstruction and assimilation of three-dimensional temperature and salinity fields in 100–500 m layer (in the conditions simulating operative mode of hydrophysical field nowcast and forecast) is implemented in order to correct the shifts of averaged temperature and salinity modeling profiles in the Black Sea circulation model in the given paper. Three-dimensional temperature and salinity fields are reconstructed for each day of 2012–2013 according to known for these days altimetry level and Argo float measurements accumulated on the horizons of 100–500 m layer over the past 45 days. It is obtained that synoptic structures in the fields of salinity, sea level and current velocity in nowcast and forecast are qualitatively reconstructed quite well. It is revealed that in 0–100 m layer root-mean-square (RMS) deviations between the modeling and observed temperatures are higher than natural variability of the fields. Salinity RMS deviations are lower than its natural variability, except for the layer 45–75 m which is characterized by the presence of cold intermediate layer. For achieving higher accuracy of nowcast and forecast it is necessary to improve the model of the sea upper layer thermodynamics for the depths from the surface down to 100 m. In addition to assimilation of three-dimensional thermohaline fields in the model, it is necessary to assimilate altimetry level and satellite data on sea surface temperature. It is shown that the proposed method can be effectively used in the operational system of the Black Sea hydrophysical field nowcast and forecast.

Keywords

assimilation, three-dimensional fields, operational mode, altimetry, Argo floats, nowcast and forecast accuracy

For citation

Knysh, V.V., Korotaev, G.K. and Lishaev, P.N., 2016. Methodology of Application of the Black Sea Three-Dimensional Temperature and Salinity Fields Reconstructed on the Basis of Altimetry and Scanty Measurements in the Operational Prognostic Model. Physical Oceanography, (2), pp. 46-61. doi:10.22449/1573-160X-2016-2-46-61

DOI

10.22449/1573-160X-2016-2-46-61

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