Warming of Western North Pacific Ocean and Energetics of Transient Eddy Activity

Abstract

This study examines the increase in the sea surface temperature (SST) in the western North Pacific Ocean (WNPO) during December-February for the period 1959-2008. The relationship of this SST increase with significant interdecadal changes in the baroclinicity and the energetics of transient eddy activity is also examined. These results show that the interannual variations of the WNPO SST and atmospheric conditions including baroclinicity and turbulent heat flux are responses to the upstream atmospheric forcings associated with the East Asian winter monsoon (EAWM). For the interdecadal variations, the intensified baroclinicity downstream of the Pacific storm-track activity is responsible for an increase in the baroclinic energy conversion (BCEC) from the mean available potential energy (MAPE) to the eddy available potential energy (EAPE) to the east of 1808. This in turn increases the BCEC from the EAPE to the eddy kinetic energy (EKE) over this region. The BCEC and generation of EAPE by diabatic heating are enhanced to the east of 1808 as a result of the intensified baroclinicity. This could be responsible for the development of transient eddy activity downstream of the Pacific storm track over the North Pacific.

Long-term variability of sea surface temperature in Taiwan Strait

“…Seasonality of SST warming in the China Seas has been studied by several researchers (Table 1). Mechanisms responsible for the enhanced winter warming in the western North Pacific were investigated by Yeh and Kim (2010), Heo et al (2012) and Park et al (2012). Clearly, the East Asian winter monsoon and its intensification (combined with the concomitant relaxation of the summer monsoon) play key roles.…”

Annual and semiannual cycles of midlatitude near-surface temperature and tropospheric baroclinicity: reanalysis data and AOGCM simulations

“…One of the measures of atmospheric baroclinicity is the maximum growth rate of the linear Eady model, which has been shown to be a useful estimate of the growth rate of the most rapidly growing instability in a wide range of baroclinic instability problems (Lindzen and Farrell, 1980). The maximum Eady growth rate has been found to be a suitable parameter to quantify the geographical location and intensity of the storm tracks (i.e., Hoskins and Valdes, 1990;Wu et al, 2011), to evaluate the impact of increasing greenhouse gases and sulfate aerosols on extratropical cyclone activity (Carnell and Senior, 1998;Geng and Sugi, 2003), and to measure the baroclinicity of the mean state of the atmosphere (e.g., Heo et al, 2012). In the present paper, it is applied to the reanalysis and model data.…”

Annual and semiannual cycles of midlatitude surface temperature and baroclinicity: reanalysis data and AOGCMs simulations

“…One of the measures of atmospheric baroclinicity is the maximum growth rate of the linear Eady model, which has been shown to be a useful 10 estimate of the growth rate of the most rapidly growing instability in a wide range of baroclinic instability problems (Lindzen and Farrell, 1980). The maximum Eady growth rate has been found to be a suitable parameter to quantify the geographical location and intensity of the storm tracks (i.e., Hoskins and Valdes, 1990;Wu et al, 2011), to evaluate the impact of increasing greenhouse gases and sulphate aerosols on extratropical cyclone activity (Carnell and Senior, 1998;Geng and Sugi, 2003), and to measure the baroclinicity of the mean state of the atmosphere (e.g., Heo et al, 2012). In the 15 present paper, it is applied to the reanalysis and model data.…”