Urban weather 200 1

(1) According to the data and sparsity of isobar in the figure, judge the distribution characteristics of air pressure. In the southwest and southeast of the figure, the pressure is high, there is a high pressure center, the isobar is sparse, and the pressure gradient is small; The air pressure in the north of the central part is low, the air pressure center is low, the isobars are dense, and the air pressure gradient is large.

(2) According to the latitude and longitude analysis, this area is the northwest of China, and the time in the picture is April and spring. According to the weather characteristics when the cold front passes, it is expected that there will be windy weather within the dotted line. "Before this, the topsoil in most areas of the illustrated area was thawed and the surface was dry. The dotted line shows the meteorological disasters caused by the weather system. " Combined with the information in the materials, the disaster should be a sandstorm. The natural causes of sandstorms are: thawing of topsoil, intensified evaporation and surface. The warm air mass before the cold front is dry and it is difficult to form precipitation; The cyclone is strong, the airflow rises, forming sand blowing, and the west wind is strong, forming a large-scale sandstorm.

So the answer is:

(1) There is high pressure in the southwest and southeast, with high pressure center, sparse isobar and small pressure gradient; The air pressure in the north of the central part is low, the air pressure center is low, the isobars are dense, and the air pressure gradient is large.

(2) Sandstorm?

Weather conditions: rising temperature leads to thawing of topsoil, enhanced evaporation, dry surface and abundant sand sources; The warm air mass before the cold front is dry and it is difficult to form precipitation; The cyclone is strong, the airflow rises, forming sand blowing, and the west wind is strong, forming a large-scale sandstorm.