What does the wind direction in the weather forecast mean? Forecasted south wind, north wind and so on.

Meteorology, the direction of the wind is determined as the wind direction. So the wind from the north is called the north wind and the wind from the south is called the south wind. When the meteorological observatory forecasts the wind, the wind direction will swing from side to side in a certain direction, and it will be "biased", such as the northerly wind. When the wind is very small, it will be explained by "uncertain wind direction"

The unit of measurement of wind direction is azimuth. For example, on land, it is generally indicated by 16, and at sea, it is generally indicated by 36. At high altitude, it is expressed by angle. To express the wind direction by angle is to divide the circumference into 360 degrees, north wind (N)0 degrees (that is, 360 degrees), east wind (E)90 degrees, south wind (S) 180 degrees, west wind (270 degrees), and the rest wind directions can be calculated from this, as shown in the left figure.

In order to express the frequency of wind in a certain direction, the quantity of wind direction frequency is usually used, which refers to the percentage of the frequency of wind in a certain direction to the total frequency of wind in all directions in a year (month), namely:

Wind direction change = frequency of occurrence of a certain wind direction/total observed frequency of wind direction × 100%.

From the calculated wind direction frequency, we can know which wind direction is more and which wind direction is less in a certain area. It is observed that northerly winds (north wind, northeast wind, northwest wind) blow in winter and southerly winds (south wind, southeast wind, southwest wind) blow in summer in North China, Yangtze River valley, South China and coastal areas.

One of the instruments for measuring wind direction is the wind vane, which is generally 10- 12 meters high from the ground. If there is an obstacle nearby, its installation height should be at least 6 meters higher than the obstacle, and the short stick pointing north should face north. In which direction the wind arrow points, it means what direction the wind direction is at that time. There is also a rectangular wind pressure plate (800g in weight and 200g in weight) on the anemometer. An arc frame with long and short teeth is installed next to the air pressure plate. The number of long and short teeth raised by the air pressure plate indicates the magnitude of wind force. At present, the EIJ anemometer designed and manufactured by our country has been widely used in various meteorological stations.