I believe following can be one of the factors but would be interested in a more detailed response. :)
In summer land gets heated up faster, creating low pressure and the air rushes from cooler sea to warmer land.
In winter land looses its heat faster and get cooled down, creating higher pressure compared to over sea, which is warmer and the air rushes from land to sea.
The key to wind directions is the geography, the way land mass and sea are placed. This according to me is or is one of the factors for the bidirectional winds and ocean currents in this region. However I would like to know, how this change takes place. Does the orientation of the wind, change suddenly? When does this change take place and how does it happen? Waiting for a more comprehensive response...