Deep Atmospheric Response to the Spring Kuroshio over the East China Sea*

Abstract

The atmospheric response to the spring Kuroshio Front over the East China Sea is investigated using a suite of high-resolution satellite data and a regional atmospheric model. The atmospheric response appears to extend beyond the marine atmospheric boundary layer, with frequent occurrence of cumulus convection.In spring, Quick Scatterometer (QuikSCAT) wind speed shows a clear effect of sea surface temperature (SST), with high (low) wind speed observed over the warm (cold) tongue. This in-phase relationship between SST and surface wind speed is indicative of SST influence on the atmosphere. Wind convergence is found on the warmer flank of the Kuroshio Front, accompanied by a narrow rainband. The analysis of satellite-borne radar measurements indicates that deep convection appears over the Kuroshio warm tongue in the spring season, with enhanced convective precipitation, frequent occurrence of cumulus convection, and increased precipitation (cloud) tops in altitude. These deep convective activities along the Kuroshio warm tongue are further supported by enhanced lightning flash rate observed by satellite and atmospheric heating estimated by a Japanese reanalysis.The Weather Research and Forecasting (WRF) model is used to investigate the precipitation response to the spring Kuroshio SST front over the East China Sea. Forced by observed SST [control (CTL)], the model well simulates a narrow band of precipitation, high wind speed, and surface wind convergence that closely follows the Kuroshio warm current, consistent with satellite observations. This narrow rainband completely disappears in the model when the SST front is removed by horizontally smoothed SST (SmSST). The results show that it is convective precipitation that is sensitive to the Kuroshio SST front. A case study for an eastward-moving extratropical cyclone indicates that convective precipitation increases its intensity and duration in the CTL run compared to the SmSST run. Local enhancement of upward sensible and latent heat fluxes and convective instability in the lower atmosphere are the key to anchoring the narrow band of convective precipitation that closely follows the Kuroshio.

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).…”

Northern Hemisphere Winter Atmospheric Transient Eddy Heat Fluxes and the Gulf Stream and Kuroshio–Oyashio Extension Variability

“…They found that deep heating dominates along the Florida Current and upstream GS in summer, while the shallow heating dominates in winter along the GS. Several subsequent studies showed similar influence of the Kuroshio in the North Pacific (Toginaga et al 2009;Xu et al 2011;Sasaki et al 2012).…”

Investigating the Local Atmospheric Response to a Realistic Shift in the Oyashio Sea Surface Temperature Front

“…Some recent modeling and observational evidence supports the view that extratropical SST fronts affect the climatological atmospheric state and its variability in the North Pacific (Xu et al 2011;Sasaki et al 2012), North Atlantic (Minobe et al 2008;Minobe et al 2010), Southern Ocean Small et al 2014), and idealized aquaplanet experiments (Brayshaw et al 2008;Nakamura et al 2008), although how this impact compares to other topographic effects, including land-sea contrasts, remains unclear (e.g., Saulière et al 2012;Kaspi and Schneider 2013). Furthermore, a better depiction of an SST front improved the numerical simulation of observed cyclones in several studies (Jacobs et al 2008;Booth et al 2012).…”