Excuse me, a question about geographical weather.

5. Judging the weather system according to the isobar near the ground.

(1) Closed isobar: high pressure center-anticyclone-peripheral airflow from inside to outside, central airflow sinking-sunny weather.

① The northern hemisphere is clockwise, with the north wind blowing in the east and the southerly wind blowing in the west; The southern hemisphere is the opposite. ② The protruding part of isobar is high pressure ridge. Example 3: The weather in autumn in China is crisp; In winter, China is located in the east of the Asian high, with northerly winds.

(2) Closed isobar: low pressure center-cyclone-peripheral airflow from outside to inside, central airflow rising-rainy weather.

(1) counterclockwise in the northern hemisphere, with south wind blowing in the east and north wind blowing in the west; The southern hemisphere is the opposite. ② The protruding part of the isobar is a trough of low pressure, which can form a frontal cyclone in the mid-latitude zone (temperate zone). For example, typhoons in summer and autumn are tropical cyclones.

(3) Isobars on the front are dense.

Cold front: there is rain and strong wind behind the front; Warm front: There is rain before the front. Examples: rain belt in China, cold wave in winter in North China, and rainstorm in summer.

Air pressure refers to the weight of the air column from above the observation height to the upper limit of the atmosphere. For the same place, the air pressure always decreases with the increase of height. A plane composed of points with equal air pressure in space is an isobaric plane, and the unit of air pressure is usually hectopascals or millimeters of mercury.