Ocean Response for a Typical Leftward-Biased Cold Wake Induced by Hurricane Jova (2005) in the Northeast Pacific

In the Northern Hemisphere, cold wakes induced by tropical cyclones (TCs) are generally biased to the right of the storm track. However, a recent study found that a non-negligible proportion of cold wakes is actually leftward-biased. To further reveal the underlying physical mechanisms, the three-dimensional dynamic processes for the typical leftward cold wake of Hurricane Jova (2005) are investigated through a sequence of numerical simulations. Results reveal that the vertical advection in response to Jova (2005) is biased to the left of its track in the upper layer. In cooperation with the heterogenous ambient oceanic temperature stratification, the rightward vertical mixing is suppressed while the leftward feature of vertical advection is further intensified, which effectively promotes the formation of leftward cold wake. Additionally, the currents induced by Jova (2005) drive colder (warmer) water to the left (right) when coupled with background horizontal temperature gradients and then strengthen the leftward distribution of the temperature anomaly. These conclusions are substantiated by the control simulation, as the upper-layer temperature anomaly is restored to rightward disposition with homogeneous initial thermal structures. Based on three groups of sensitivity experiments, the leftward pattern of upwelling is found to be inextricably accompanied by the curl of wind stress caused by the movement of TCs. With the increase in translation speed from the stationary state, the symmetric structure of vertical velocity is gradually distorted to be leftward. Furthermore, the leftward bias distance of the upwelling center in the upper layer positively correlates with the radius of maximum wind, indicating that the wind structure can significantly influences the oceanic responses to TCs.