下面哪一种资料不属于一体化航行情报系列资料（）。

An area of severe weather often forms well （ ） the fast-moving cold front.

（ ） would decrease the stability of an air mass.

When the temperature rises, first of all,

Airmasses are classified according to the regions where they originate. They are generally divided into polar or tropical to identify （ ） characteristics.

Which of the following is not a general weather characteristic associated with cold fronts?

When flight speed is constant, the greater the air density,

A warm front is one where （ ） ．

A cold front is one where （ ） ．

When judging the wing speed by wind sock, if the wind sock is at aclinic level, then the wind speed can be up to（ ）m/s.

（ ） cannot be an indication to the passage of a frontal system.