Circulation in the Tsushima Strait has been studied with variational approach based on recently developed ocean general circulation model. Optimized solution describing the climatological mean circulation and synoptic circulation during 1999-2000 were obtained through the assimilation of climatological temperature/salinity, estimates of the total transport and field temperature/salinity and mooring observations during 1999-2000. Variational algorithm was implemented on the basis of modification of OGCM developed at the Laboratorie d'Oceanograpie Dynamique et de Climatologie (Madec et al., 2XXX). Semi-implicit formulation of the finite difference sheame significantly simplifies the assimilation of the data into the OGCM. The obtained solutions desrcibe optimazed climatological circulation and circulation during 9 month period.
Collaborators:
D.Nechaev (USM), M.Yaremchuk (IPRC)Reference:
Nechaev D., G.Panteleev, M.Yaremchuk. Reconstruction of the circulation in Limited regions of an Ocean with open boundaries: climatologicl circulation in the tsushima strait. Oceanology, Vol. 45, No. 6, 2005, pp. 761.780. Translated from Okeanologiya, Vol. 45, No. 6, 2005, pp. 805.825. Original Russian Text Copyright c 2005 by Nechaev, Panteleev, Yaremchuk. English Translation Copyright c 2005 by Pleiades Publishing, Inc.
The *.pdf file can be douwloaded here
All results of this study are available upon request: gleb@iarc.uaf.edu
Summary
Goals:
(1) Reconstruction of the climate circulation; (2) Reconstruction of the circulation during 1999-2000.
Figure 1. Bottom topography in the Tsushima Strait. Solid line - model domain. Triangles - mooring locations.
Cliamtoilogical circulation. Utilized data:
1. Climatological T/S data. 2. Cliamtological heat/salt/ momentum fluxes. 3. Estimates of the total transport through the Tsushima Strait (Figure 2).
Figure 2. Estimates of the total transport through the Tsushima Strait.
Figure 3. Evolution of the mean climatological (red dots), first guess (asterisk), and optimized (circles) fields. Evolution of temperature is shown on the left panel, salinity on the right panel. The optimized mean T/Sfields are in a good agreement with the climatological data.
Figure 4. Evolution of the optimized temperature and velocity derived through the assimilation of the climatological data.
1999-2000 circulation. Utilized data:
For the reconstruction of large scale circulation for the 10-monthsperiod of velocity measurements ( Perkins et al., 2000).we utilized: velocity observation at 11 moorings; NCEP/NCAR wind stress, heat and salt fluxes at the surface; ~ 100 T/S profiles in the region; d) climatological T/S data. The climatological model state was used as the First Guess solution. The evolution of the optimized velocity fields for the period 1999-2000 is shown in Figure 5. Analysis of the hindcast solution shows that: 4Dvar data assimilation approach allows to derive realistic evolution of the local circulation; (2) Assimilation of the velocity observations allowed us to capture the events of water inflow through the northern model boundary in June, 1999 and November- December, 1999, which is the well known local phenomenon; (3) Assimilation of the velocity observations intensifies the counter-current along the Japanese coast; (4) There is a noticeable decrease of the inflow through the western boundary in the optimized 1999-2000 solution in comparison with the optimal climatological state. (5) Most of T/S data were collected at the beginning and at the end of the investigated period. The amount of T/S data is insufficient for obtaining realistic T/S fields during the major part of the investigated period.
Figure 5. Evolution of the optimized temperature and velocity derived through the assimilation of the 1999-2000 data.
Figure 6. Reconstructed circulation at 22.5m during 1999-2000. Black arrows – model results. Triangles and white arrows – moorings and observed currents.
Figure 7. Reconstructed circulation at 60m during 1999-2000. Black arrows – model results. Triangles and white arrows – moorings and observed currents.