Is the plum rain convective or frontal?

Meiyu is a large-scale precipitation weather process, which belongs to frontal precipitation because of the relatively stable atmospheric circulation. During the meiyu period, the blocking high pressure is often maintained at a higher latitude north of 50 N, so that the cold air cannot go south on a large scale, but at a lower latitude. The ridge line of the western Pacific subtropical high is about 20-25 N, and the middle and lower reaches of the Yangtze River in China are just the intersection of the warm and humid airflow in the southwest and the cold air in the north transported by the western Pacific subtropical high. There are often shear lines and southwest vortex activities in this area, and there are quasi-static fronts and frontal cyclones on the ground, which cause long-term rainy weather and repeated heavy rains. On satellite images, the Meiyu front cloud belt is usually stable.

However, the "in" and "out" dates of Meiyu are different every year. There can be a difference of more than 40 days between morning and evening, sometimes there will be a phenomenon of "less plum" or "empty plum", and sometimes there will be a phenomenon of "abundant plum". For example, 1954 and 199 1 are both special years in the meiyu period, and the rainfall is particularly heavy, causing floods in the Jianghuai basin. However, in 1994, there was an abnormal drought in Shaomei and Jianghuai areas. This abnormal situation in meiyu period is often related to the abnormal change of global atmospheric circulation.

It refers to a period of continuous rainy weather from mid-June to early summer in mid-July, 28°-34° N east of Yichang in the middle and lower reaches of the Yangtze River in China, or from Jianghuai Valley to a narrow area in southern Japan. At this time, it is the season when plums in the south of the Yangtze River are yellow and ripe, so it is called "Meiyu". Meiyu weather is mainly characterized by rainy weather, short sunshine time, high relative humidity and abundant rainfall, often from heavy rain to heavy rain.

Meiyu is a large-scale precipitation weather process, which is caused by relatively stable atmospheric circulation. During the meiyu period, the blocking high pressure is often maintained at a higher latitude north of 50 north latitude, so that the cold air cannot go south on a large scale, but at a lower latitude. The ridge line of the western Pacific subtropical high is about 20-25 N, and the middle and lower reaches of the Yangtze River in China are just the intersection of the southwest warm and humid airflow transported by the western Pacific subtropical high and the small cold air in the north. There are often shear lines and southwest vortices in this area, and there are quasi-static stops and fronts on the ground.

However, the "in" and "out" dates of Meiyu are different every year. There can be a difference of more than 40 days between morning and evening, sometimes there will be a phenomenon of "less plum" or "empty plum", and sometimes there will be a phenomenon of "abundant plum". For example, 1954 and 199 1 are both special years in the meiyu period, and the rainfall is particularly heavy, causing floods in the Jianghuai basin. However, in 1994, there was an abnormal drought in Shaomei and Jianghuai areas. This abnormal situation in meiyu period is often related to the abnormal change of global atmospheric circulation.