Improvement of the Method for Reconstructing the Temperature and Salinity Three-Dimensional Fields of the Black Sea Based on Insufficient Measurements and Altimetry

Abstract

The article represents the results of two special numerical experiments aimed at improving the previously proposed procedure of reconstructing salinity and temperature three-dimensional fields based on the altimetry data and the insufficient measurements performed at the stations and the Argo buoys in 2012. In the Experiment 1, the monthly average coefficients of sea level linear dependence and depths where the salinity values of the "zero" gradation altimetry level profile lie within the salinity profiles of positive and negative gradations are applied. The procedure for calculating the daily average coefficients of the depth linear trends is realized in the Experiment 2. It is shown that the thermohaline fields reconstructed in the Experiment 2 for the deepwater area are more accurate; on the horizons of the 100-500 m layer their values range smoothly from one day to another. The Black Sea hydrophysical fields are reconstructed by assimilation in the model of three-dimensional thermohaline parameters in the reanalysis for 2012. It is revealed that, as compared to the observations on the overwhelming majority of horizons in the 0-500 m layer (the Experiment 2), the standard root-mean-square deviations of temperature and salinity are lower than those in Experiment 1. The root of the measured salinity field dispersion exceeds the standard deviations on all the horizons within 0-500 m, inclusive. Application of the daily average coefficients of the linear trends for reconstructing three-dimensional fields of temperature and salinity, and their subsequent assimilation in the model is preferable. It is revealed that the model of the upper 0-100 m layer thermodynamics requires improvement. Introduction. In order to improve the system functioning in Marine Hydrophysical Institute (MHI) in operative mode of nowcast, forecast and reanalysis of the Black Sea condition [1], it is necessary to develop a special procedure of temperature and salinity three-dimensional field reconstruction applying altimetry and rare contact measurements of these parameters performed at hydrologic stations and Argo buoys. Such sea measurements are characteristic for the period from 1993 to the present time. Solution of this problem is dictated by the fact that the results of circulation prolonged forecast calculations in the entire area of the sea according to MHI model [2] and short-term forecasts in the local coastal region according to high-resolution POM model [3 -6] point to inaccuracies in the reconstruction of the basin water average stratification. Inadequacy of turbulent exchange process parameterization, errors of atmospheric effect fields and approximate character of initial conditions may be the causes for them. Threedimensional temperature and salinity fields of sea water are not assimilated in the

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“…The differences between the values of level field RMS in the considered reanalyses can be also due to the fact that different methods for the sea altimetry level assimilation in the model are used. The location of the main structures in the sea level (western and eastern cyclonic gyres, cyclonic and anticyclonic eddies) in our reanalysis and in altimetry level, reconstructed for each day by AVISO data on level anomalies [19], is close as temperature and salinity pseudo-measurements are tied to altimetry level [3,4]. The location of the mentioned level structures in the reanalysis of the sea fields carried out in [17,18] can be somewhat different from the location of structures in the altimetry level.…”

“…limited measurement data of Argo profiling floats 3D fields of temperature and salinity pseudo-measurements over 1993-2002 were reconstructed earlier on the horizons of Marine Hydrophysical Institute (MHI) model in 100-500 m sea level in its deep part (bounded by 500 m isobath) on the basis of joint analysis of altimetry data and shipboard measurements using the methodology described in [3]. In [4] the proposed method was adapted to the measurements of salinity and temperature profiles by Argo floats. This provided the reconstruction of 3D fields of temperature and salinity pseudo-measurements over 1993-2014 period.…”

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“…The differences between the values of level field RMS in the considered reanalyses can be also due to the fact that different methods for the sea altimetry level assimilation in the model are used. The location of the main structures in the sea level (western and eastern cyclonic gyres, cyclonic and anticyclonic eddies) in our reanalysis and in altimetry level, reconstructed for each day by AVISO data on level anomalies [19], is close as temperature and salinity pseudo-measurements are tied to altimetry level [3,4]. The location of the mentioned level structures in the reanalysis of the sea fields carried out in [17,18] can be somewhat different from the location of structures in the altimetry level.…”

“…limited measurement data of Argo profiling floats 3D fields of temperature and salinity pseudo-measurements over 1993-2002 were reconstructed earlier on the horizons of Marine Hydrophysical Institute (MHI) model in 100-500 m sea level in its deep part (bounded by 500 m isobath) on the basis of joint analysis of altimetry data and shipboard measurements using the methodology described in [3]. In [4] the proposed method was adapted to the measurements of salinity and temperature profiles by Argo floats. This provided the reconstruction of 3D fields of temperature and salinity pseudo-measurements over 1993-2014 period.…”

Modelling of Water Pollution Propagation in the Sevastopol Bay

“…It is based on a combined analysis of altimetry and numerically insignificant ship hydrological observations in the Black Sea over 1993-2002. This technique was refined and applied in [8] to the salinity and temperature measurements carried out by Argo buoys. This provided the reconstruction of three-dimensional fields of temperature and salinity pseudomeasurements on a regular grid in 63-500 m layer over 1993-2014.…”

“…Here N is a number of grid nodes at 2.5-150 m layer horizons in the deepwater sea area, (7) (8) the line denotes averaging over horizon.…”

“…In the first iteration, daily salinity (temperature) pseudo-measurements are reconstructed in 63-125 m layer in the nodes that belong only to the zones located to the right of the Black Sea RC front and anticyclonic eddies, as well as at the horizons of 2.5-50 m layer in all model grid nodes. In this case we use: an initial field of salinity (temperature) pseudo-measurements at 150 m basic horizon, its calculated dispersion 2 * σ ( , ) Sl zt (the dispersion of "measurement" errors was assumed to be equal to 2 * 0,05 σ ( , ) Sl zt ), model prognostic fields in 2.5-125 m layer and also covariance functions estimated by the formulas ( 6) - (8).…”

Untitled

“…The differences between the values of level field RMS in the considered reanalyses can be also due to the fact that different methods for the sea altimetry level assimilation in the model are used. The location of the main structures in the sea level (western and eastern cyclonic gyres, cyclonic and anticyclonic eddies) in our reanalysis and in altimetry level, reconstructed for each day by AVISO data on level anomalies [19], is close as temperature and salinity pseudo-measurements are tied to altimetry level [3,4]. The location of the mentioned level structures in the reanalysis of the sea fields carried out in [17,18] can be somewhat different from the location of structures in the altimetry level.…”

“…limited measurement data of Argo profiling floats 3D fields of temperature and salinity pseudo-measurements over 1993-2002 were reconstructed earlier on the horizons of Marine Hydrophysical Institute (MHI) model in 100-500 m sea level in its deep part (bounded by 500 m isobath) on the basis of joint analysis of altimetry data and shipboard measurements using the methodology described in [3]. In [4] the proposed method was adapted to the measurements of salinity and temperature profiles by Argo floats. This provided the reconstruction of 3D fields of temperature and salinity pseudo-measurements over 1993-2014 period.…”

Modelling of Water Pollution Propagation in the Sevastopol Bay

“…It is based on a combined analysis of altimetry and numerically insignificant ship hydrological observations in the Black Sea over 1993-2002. This technique was refined and applied in [8] to the salinity and temperature measurements carried out by Argo buoys. This provided the reconstruction of three-dimensional fields of temperature and salinity pseudomeasurements on a regular grid in 63-500 m layer over 1993-2014.…”

“…Here N is a number of grid nodes at 2.5-150 m layer horizons in the deepwater sea area, (7) (8) the line denotes averaging over horizon.…”

“…In the first iteration, daily salinity (temperature) pseudo-measurements are reconstructed in 63-125 m layer in the nodes that belong only to the zones located to the right of the Black Sea RC front and anticyclonic eddies, as well as at the horizons of 2.5-50 m layer in all model grid nodes. In this case we use: an initial field of salinity (temperature) pseudo-measurements at 150 m basic horizon, its calculated dispersion 2 * σ ( , ) Sl zt (the dispersion of "measurement" errors was assumed to be equal to 2 * 0,05 σ ( , ) Sl zt ), model prognostic fields in 2.5-125 m layer and also covariance functions estimated by the formulas ( 6) - (8).…”

Untitled

“…The differences between the values of level field RMS in the considered reanalyses can be also due to the fact that different methods for the sea altimetry level assimilation in the model are used. The location of the main structures in the sea level (western and eastern cyclonic gyres, cyclonic and anticyclonic eddies) in our reanalysis and in altimetry level, reconstructed for each day by AVISO data on level anomalies [19], is close as temperature and salinity pseudo-measurements are tied to altimetry level [3,4]. The location of the mentioned level structures in the reanalysis of the sea fields carried out in [17,18] can be somewhat different from the location of structures in the altimetry level.…”

“…limited measurement data of Argo profiling floats 3D fields of temperature and salinity pseudo-measurements over 1993-2002 were reconstructed earlier on the horizons of Marine Hydrophysical Institute (MHI) model in 100-500 m sea level in its deep part (bounded by 500 m isobath) on the basis of joint analysis of altimetry data and shipboard measurements using the methodology described in [3]. In [4] the proposed method was adapted to the measurements of salinity and temperature profiles by Argo floats. This provided the reconstruction of 3D fields of temperature and salinity pseudo-measurements over 1993-2014 period.…”

Modelling of Water Pollution Propagation in the Sevastopol Bay

“…It is based on a combined analysis of altimetry and numerically insignificant ship hydrological observations in the Black Sea over 1993-2002. This technique was refined and applied in [8] to the salinity and temperature measurements carried out by Argo buoys. This provided the reconstruction of three-dimensional fields of temperature and salinity pseudomeasurements on a regular grid in 63-500 m layer over 1993-2014.…”

“…Here N is a number of grid nodes at 2.5-150 m layer horizons in the deepwater sea area, (7) (8) the line denotes averaging over horizon.…”

“…In the first iteration, daily salinity (temperature) pseudo-measurements are reconstructed in 63-125 m layer in the nodes that belong only to the zones located to the right of the Black Sea RC front and anticyclonic eddies, as well as at the horizons of 2.5-50 m layer in all model grid nodes. In this case we use: an initial field of salinity (temperature) pseudo-measurements at 150 m basic horizon, its calculated dispersion 2 * σ ( , ) Sl zt (the dispersion of "measurement" errors was assumed to be equal to 2 * 0,05 σ ( , ) Sl zt ), model prognostic fields in 2.5-125 m layer and also covariance functions estimated by the formulas ( 6) - (8).…”