What is a north wind day and a south wind day?

The north wind blew, and he said to the fallen leaves, "I am autumn." "The north wind day is the northwest wind prevailing in winter in China, and the south wind day is the southeast wind prevailing in summer. Because the northwest wind comes from Siberia, it is cold and dry; The southeast wind comes from the ocean, so it is humid.

When the wind blows from the north, it is a northerly day. The weather is cool and sunny most of the time. The wind in the south is southerly, and the air is humid and warm. It is mostly rainy.

Extended data:

When the blade is at a certain angle to the direction of air flow, the air flow produces a pressure f at the tail of the blade. Its size is in direct proportion to the projection of the geometric shape of the wind vane on the vertical plane in the air flow direction. The windward area of the wind vane head is small and the windward area of the tail is large.

The wind pressure moment is generated by the component f of this pressure difference in the vertical direction of the wind vane, which makes the wind vane rotate around the vertical axis until the wind vane is parallel to the airflow. The wind direction can be easily observed from the relative position between the wind vane and the fixed main azimuth indicator.

Wind vane transmits wind direction signal through vertical axis and angle sensor. There are many ways for the wind vane to transmit and indicate the direction, including electric contact plate, annular potential, synchro and photoelectric code wheel, among which photoelectric code wheel is the most commonly used.