To lift the heavy fog

 At 10 o 'clock on March 31, the visibility in the Shanghai section of the Yangtze river was improved, and the wu song maritime bureau lifted the orange alert for fog, and began to implement the partial navigation of the ship. As of 17:42 on the same day, wusong maritime bureau organized the ship to reach 500 vessels. However, the visibility of the Shanghai section of the Yangtze river was less than 200 meters, and the wu song maritime bureau started the visibility orange plan again to implement temporary traffic control.