What is the phenomenon of continuous rainy weather called?

Plum rains and rainy days refer to the rainy weather process for several days in a row. Generally, it rains continuously for 6 days or more without sunshine, and the daytime rainfall for any 4 days is 0. 1 mm or more; The severe continuous rain is ≥ 10 days with continuous rain and no sunshine, in which the daytime rainfall is ≥0. 1 mm in any 7 days. ..

When it rains continuously, there is less sunshine and high air humidity. In spring and autumn, continuous rain is often accompanied by low temperature, which often leads to mildew and germination of seeds, the spread of pests and diseases, and the reduction of agricultural production.

cause

The occurrence of continuous rain is related to the seasonal changes of westerly belt and subtropical high system that affect the migration of rain belt in China, and even the areas with rainy weather have obvious seasonal changes. During the transition from winter to summer, the continuous rainy area moves from south to north; From summer to winter, from north to south, it conforms to the characteristics of rain belt displacement.

In spring, the warm and humid airflow in the south began to be active, and the cold air in the north began to decay, but it still had a certain intensity and was active frequently. The intersection of cold and warm air (that is, the front) often stagnates or lingers between the Yangtze River and South China. A quasi-static front appears on the ground weather map, and an east-west shear line appears on the 700 HPA isobaric map, which is located on the north side of the ground quasi-static front. There is continuous rainy weather between the ground front and the shear line on the 700 HPA isobaric surface.