статья в журнале

En

Physical Oceanography

ISSN:0928-5105
eSSN:1573-160X

2018

10.22449/1573-160X-2018-5-380-389

Mathematical method combining optimal interpolation and expansion into the empirical orthogonal functions is developed to implement a retrospective analysis of the Black Sea thermohaline structure using incomplete archival oceanographic data. In order to increase spatial consistency of the resulted hydrologic structure, the earlier applied reconstruction method based on the horizontal empirical orthogonal functions was transformed to the combined one in which the vertical empirical orthogonal functions were the basic elements. The results of computing experiments make it possible to limit the number of the modes by 5 both for horizontal and vertical empirical orthogonal functions. Such a combination significantly reduces the calculation time and lowers the error level. This method was applied to reconstruct the monthly fields (spatial resolution is 10' latitude x 15' longitude) for almost a hundred-year period from 1923-2015. The relative part of the monthly average fields' successful reconstruction constitutes about 70 %. Based on the reanalysis data, the temperature and salinity climatic fields were calculated by various methods both for the entire observational period and for certain decades. It is revealed that in the XX century the gain-phase climatic characteristics of the Black Sea remain very stable whereas general tendencies in the long-term variations of the temperature and salinity seasonal cycles are opposite: when the sea temperature seasonal range rises the phase of annual harmonic of seasonal oscillations diminishes, and in the case of salinity, it increases, i. e. the salt content maximum shifts for the later period. The reanalysis data were used to study various aspects of the inter-annual and inter-decadal variability of the Black Sea thermohaline structure, density stratification, geostiophic circulation etc. The future trends imply application of the thermohaline fields' reanalysis array for studying long-term changes in the Black Sea basin as well as for assimilating observational data in the hydrophysical fields' reconstructions by the hydrodanamic models.

BLACK SEA, THERMOHALINE STRUCTURE, REANALYSIS, CLIMATE, EMPIRICAL ORTHOGONAL FUNCTIONS, INTERANNUAL VARIABILITY, IN-SITU, RECONSTRUCTION, REANALYSIS

2018-12-12 15:49:00