Atmospheric Responses To The Sea Surface Temperature Front Over The East China Sea Under The Different Direction And Speed Of Prevailing Surface Winds During The Spring Season

Various high resolution satellite datasets are used to investigate atmospheric responses to the sea surface temperature (SST) front over the East China Sea under the different direction and speed of prevailing surface winds during the spring season. Results exhibit a significant positive correlation between sea surface temperature and sea surface wind speed under three different kinds of prevailing wind, indicative of ocean-to-atmosphere influences. The characteristics of the atmospheric responses to the SST front over the East China Sea under three kinds of prevailing surface wind are different. Under the northwest and southeast prevailing surface winds, i.e., the wind direction is perpendicular to the SST front from the colder (warmer) flank of the front to the warmer (colder) flank of the front, sea surface wind diverges (converges) over the SST front. At the same time, the influence of the SST front on sea level pressure (SLP), precipitation and convection is relatively weak, showing that the atmospheric responses to the SST front are confined in the atmospheric boundary layer. Under the northeast prevailing surface wind, i.e., the wind direction is parallel to the SST front, the sea surface wind converges (diverges) over the warmer (colder) flank of the SST front, accompanied by the low (high) SLP anomalies. A rainband extends along the Kuroshio Current in the East China Sea. In terms of the distribution of the total precipitation, stratiform precipitation frequency and convective precipitation frequency, the effect of the SST front on rainfall is most obvious under the northeast prevailing sea surface wind. It is also found that different mechanisms are responsible for the air-sea relationship over the SST front under the different prevailing surface winds. The SLP mechanism is at work as the prevailing surface wind direction is parallel to the SST front, while the vertical mixing mechanism is at work as the prevailing surface wind direction is vertical to the SST front.Observation analysis also showed that when SST frontal average wind speed is about6to9m/s, the positive correlation of SST and sea is better, the intensity of the oceanic front is stronger when wind speed is small. The change of vertical circulation and temperature humidity structure with wind speed is strong.A mesoscale atmospheric model with physical parameterizations is used to investigate the mechanisms by which the ocean can influence the atmosphere. The control run successfully reproduces the positive correlation of SST and wind in the vicinity of the oceanic front. By comparing the control and smoothed SST (SMSST) runs, results indicate that the influence of the SST front on SLP, air temperature and precipitation is relatively weak and shift downstream along the downwind direction under the northwest and southeast prevailing surface winds, i.e., the wind direction is perpendicular to the SST front. At the same time, the influence of the SST front on SLP, air temperature and precipitation is relatively strong under the northeast prevailing surface winds, i.e., the wind direction is vertical to the SST front.