Impact of a fine scale SST over the Kuroshio Extension region to wintertime rainfall

In the present study, the winter precipitation in the vicinity of Japan is simulated by the Weather Research Forecasting model by using two sets of sea surface temperatures (SSTs) data with different spatial resolutions. It is found that the difference in the SST resolutions influences the interannual variance of the local precipitation over the Kuroshio–Oyashio Extension (KOE) region. The warm (cold) SST anomaly in the KOE region near Japan, caused by ocean processes, induces an increase (decrease) in the local precipitation to the east of the SST anomaly. This increase is accompanied by the enhancement of surface wind convergence (divergence). Furthermore, the anomalous ascent associated with the enhanced surface wind convergence in response to the warm SST anomalies extends to the mid-troposphere up to around 500 hPa; this is accompanied by an increase in the cloud ice. This suggests that the SST in the KOE region can affect the atmosphere above the planetary boundary layer. Moisture budget analysis indicates the influence of moisture advection by mean wind on the spatial phase difference between the SST and precipitation anomalies.