ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa


Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2014, Vol. 11, No. 3, pp. 9-18

Temporal variability of the phase velocity of Rossby waves in the North Pacific

T.V. Belonenko1 , A.A. Kubrjakov2 
1 Saint-Petersburg State University, Saint-Petersburg, Russia
2 Marine Hydriophysical Institute, Sevastopol, Russia
Saint-Petersburg State University, Saint-Petersburg, Russia
Examination is carried out of the AVISO satellite data set on absolute dynamic topography MADT for the period 1992 - 2013 over water area of 25-50 N, 140 – 180 E. The zonal isopleths display varying inclination, which corresponds to the time change of phase velocity of the Rossby waves propagating westward. In this paper we propose a method for analyzing variability of the phase velocities of Rossby waves, which allows studying the temporal variability of Rossby waves in the north-western Pacific Ocean. Empirical phase velocities of Rossby waves are derived by applying the Radon transformation for each space-time segment within a window scale: 90 days of time and 2 degrees of longitude. Further, the window is sequentially shifted on a step in time and space. In such a way, we obtain window-scaled smoothed characteristics of the space-time variability of Rossby waves phase velocity. Based on the Radon transformation with constructing of a relevant space-time window, the suggested method for analyzing the phase velocity variability has been used for the first time. Curves of the Rossby wave phase velocities calculated from altimetry data by a method using the Radon transformation have shown substantial variability in time. Meanwhile, the seasonal and inter-annual change of the Rossby wave phase velocities differ at different latitudes. To estimate the baroclinic Rossby deformation radius either the continuous stratification approximation is used, where the Brunt-Vaisala frequency is defined as an integral over the entire water column, or for the two-layer fluid approximation. It is shown that seasonal variability of the phase velocity of Rossby waves is caused mostly by changes in ocean stratification and depends on the depth of upper mixed layer. This dependence actually exists, as is proved on the basis of ARGO data for 2002-2013.
Keywords: Pacific, Rossby waves, baroclinic Rossby deformation radius, altimetry, AVISO, MADT, Radon transformation, phase velocity
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