We know when and where the wind is.

When I saw the hair of the goddess standing in the wind fluttering in the wind, we knew that the wind was beside her. When the wind blows into the window and blows the curtains, we will know where the wind is.

Wind is a natural phenomenon caused by air flow, which is caused by solar radiation heat.

Sunlight shines on the earth's surface, causing the surface temperature to rise, and the surface air to expand and become lighter and lighter. After the hot air rises, the cold air with low temperature flows in horizontally, and the rising air falls down because it gradually cools and becomes heavier. Because the surface temperature is high, it will heat up the air, and this airflow will produce wind.

The horizontal movement of air is called wind. Wind is a physical quantity representing the movement of airflow. It has not only the size (wind speed), but also the direction (wind direction). So the wind is a vector. Wind direction refers to the direction of the wind. The surface wind direction is indicated by 16, and the wind direction in the upper air is usually indicated by azimuth degrees, that is, 0 (or 360) means due north, 90 means due east, 180 means due south, and 270 means due west.

At azimuth 16, the angular difference between each adjacent azimuth is 22.5. The units of wind speed are usually expressed as meters per second, knots (nautical miles per hour, also known as knots) and kilometers per hour.