What is the reason for the formation of black rain?

Black Rain 65438+1On the morning of March 5, 990, black rain suddenly fell in parts of Hutang District and Lu Zheng District of Wujin County, Changzhou City, Jiangsu Province, lasting for 10 minute. It is found that black rain contains many fine powders such as fibrous substances. At that time, the citizens were very surprised by the arrival of the black rain. Some people think this is a special phenomenon in celestial bodies, but others think that the appearance of black rain is an ominous sign that the weather may suddenly change. According to the analysis of Changzhou Meteorological Bureau, the reason for the formation of black rain may be that the cyclone passes through a grassland or lake, which rolls grass seeds, pollen or algae plants in the lake into the air, moves with the airflow, and then falls under the action of high-altitude airflow.