In the Northern Hemisphere，what type of cloud formations would you expect to see to the west of an approaching tropical wave?（）.

单项选择题In the Northern Hemisphere，the largest waves or swells created by a typhoon or hurricane will be located（）.

A.in the southeast quadrant of the storm
B.directly behind the storm center
C.forward and to the right of its course
D.behind and to the left of its course

单项选择题In the Northern Hemisphere，gusty winds shifting clockwise，a rapid drop in temperature，thunderstorms or rain squalls in summer (frequent rain snow squalls in winter) then a rise in pressure followed by clearing skies，indicate the passage of a(n)（） .

A.warm front
B.tropical cyclone
C.anticyclone
D.cold front

单项选择题In the Northern Hemisphere，an area of counterclockwise wind circulation surrounded by higher pressure is a（）.

A.low
B.high
C.warm front
D.cold front

单项选择题In many areas atoll clouds (clouds of vertical development) are produced over small islands. These are the result of（）.

A.rising air currents produced by the warm islands
B.warm air from the sea rising over higher land areas
C.cool land air mixing with warm sea air
D.descending air over the islands

单项选择题In a microbarograph，the pen should be checked and the ink well filled（）.

A.each time the chart is changed
B.once per month
C.once per week
D.daily