Influence of the Kuroshio in the East China Sea on the Early Summer (Baiu) Rain

Abstract

Influence of the Kuroshio in the East China Sea on the baiu rainband is examined using satellite observations, a reanalysis dataset, and a regional atmospheric model from 2003 to 2008. Satellite observations and reanalysis data reveal that precipitation over the Kuroshio is the highest in early summer (June), when the baiu rainband covers the East China Sea. The high rainfall is collocated with the warm sea surface temperature (SST) tongue of the Kuroshio. This locally enhanced precipitation is embedded in the large-scale baiu rainband, so that the amplitude of precipitation over the Kuroshio is twice as large as that in its surrounding area. The Kuroshio is also accompanied by high surface wind speed, energetic evaporation, and wind convergence. This wind convergence likely results from the SST influence on atmospheric pressure through not only temperature changes, but also humidity changes. Furthermore, the Kuroshio anchors the ascent motion and large diabatic heating with a peak in the midtroposphere, suggesting that the influence of the Kuroshio extends to the upper troposphere. It is also found that the East China Sea in June is the region of the strongest deep atmospheric response to western boundary currents along with the Gulf Stream region in summer. The observational results are well reproduced by the regional atmospheric model. The model indicates that when the SST tongue of the Kuroshio is smoothed, the enhanced precipitation, the energetic evaporation, and the wind convergence over the Kuroshio disappear, although the large-scale structure of the baiu rainband is not essentially changed.

Assessing the impact of the Kuroshio Current on vertical cloud structure using CloudSat data

“…Strong updrafts occurred in the ECS during the target period and were strongest at 400 hPa. This observation was consistent with a previous report (Sasaki et al, 2012). Figure 1c shows the mean relative humidity of the MSM at 400 hPa.…”

“…Evaporation from the sea surface in the Kuroshio region enhances the formation of convectively unstable air masses, which can produce deep convection Tsuguti and Kato, 2014;Manda et al, 2014;Kunoki et al, 2015;Sato et al, 2016). The Kuroshio also impacts the surface wind convergence, which in turn helps form the deep convective clouds (Xu et al, 2011;Sasaki et al, 2012;Miyama et al, 2012). Recent studies reported the impact of the Kuroshio on the cloud vertical structure.…”

Seasonal Migration of the Baiu Frontal Zone over the East China Sea: Sea Surface Temperature Effect

“…3a). This correspondence of the positions of the Baiu frontal zone and the Kuroshio Front in May is consistent with several recent studies (Xu et al 2011;Sasaki et al 2012;Miyama et al 2012).…”

Spatial Patterns and Intensity of the Surface Storm Tracks in CMIP5 Models

“…The North Atlantic and North Pacific WBCs, the Gulf Stream, and KuroshioOyashio Extension (KOE) influence the atmosphere through the entire troposphere during spring and summer (Minobe et al 2008(Minobe et al , 2010Xu et al 2011;Sasaki et al 2012) and modify low-level atmospheric baroclinicity, shifting the free-tropospheric storm track and altering the poleward heat and moisture transport (e.g., Tokinaga et al 2009;Frankignoul et al 2011;Ogawa et al 2012;Taguchi et al 2012;Kwon and Joyce 2013;O'Reilly and Czaja 2015). In the Southern Ocean, south of the Indian Ocean, the Agulhas Return Current (ARC) helps to anchor the climatological location of the free-tropospheric storm track (Nakamura et al 2004).…”