封冻: freeze-up◇封冻期 a period of freezing weather; freeze; freeze-up
常年: 1.(终年) throughout the year; perennial 短语和例子常年坚持体育锻炼 persist in physical training all the year round; 夏威夷常年百花盛开。 in hawaii there are flowers all the year round.2.(长期) year in year out 短语和例子