Recent weather forecast of pear tree

A, ① The air circulation formed by uneven ground heat and cold is thermal circulation, so it is correct;

B, ② is the phenomenon of burning wind, so it does not meet the meaning of the question;

C, ③ vertical airflow sinking is an anticyclone, which does not conform to the meaning of the question;

The cold air mass at D and ④ moves to the warm air mass, forming a cold front.

So choose: a.