When is the rainy season at its peak?

The formation mechanism of rime and rime is similar, generally appearing on cloudy days, mostly caused by cold rain, generally lasting for a long time, with no obvious diurnal variation, and can be produced day and night. Rime is a precipitation phenomenon under a specific weather background. The typical weather of rime formation is mild cold (0-3℃), with rain, strong wind and heavy fog drops, which usually occurs when cold air meets warm air, which is very powerful. During this period, the northwest airflow and southwest airflow over the Jianghuai basin were very strong, and cold air invaded the ground. At this time, the temperature of the ground layer is low (slightly lower than zero degrees Celsius), and there is a warm air layer or cloud over 1500 to 3000 meters, forming a warm air layer or cloud. More than 3000 meters, there is an upper atmosphere, the temperature is below zero degrees Celsius, and the cloud temperature is often -65433. That is, there is an inversion layer near the ground The vertical structure of the atmosphere is cold from top to bottom and warm in the middle, with ice crystal layer, warm layer and cold layer from top to bottom.

Snowflakes falling from the ice crystal layer melt into raindrops when passing through the warm layer, and then enter the cold air layer near the ground, and the raindrops quickly cool down and become supercooled raindrops (there is a physical property in the atmosphere that they are still in liquid state when the temperature is tens of degrees below zero (℃), which is called "supercooled" water drops, such as supercooled raindrops and supercooled fog drops). The fog droplets and water droplets that form rime are large and the condensation speed is fast. Because the diameter of these raindrops is very small, although the temperature dropped below zero degrees Celsius, they fell before freezing.

When these supercooled raindrops fall on the ground with a temperature below 0℃ and on objects such as branches and wires, they will gather on the whole surface of the objects and freeze immediately. Frozen into a transparent or translucent ice layer of ground glass, making branches or wires become thick popsicles, which are generally smooth or slightly prominent. Sometimes dripping water freezes and forms long icicles. This has become what we call "rainy days". If the rime is caused by non-supercooled raindrops falling on the ground or objects with poor cooling, and sleet condenses and freezes, that is, the ice layer formed by the mixture of amorphous appearance and crystal icing, generally this rime is very thin and will not exist for a long time.