单选题A katabatic wind blows（）.A up an incline due to surface heatingB in a circular patternC down an incline due to cooling of the airD horizontally between a high and a low pressure area

The numeral in the center of a wind rose circle on a pilot chart indicates the ______.

A.total number of observations

B.average wind force on the Beaufort scale

C.average wind force in knots

D.percentage of calms

When recording the wind direction in the weather log，you would report the ______．

A.direction the wind is blowing toward

B.direction the wind is blowing from

C.duration of the maximum gust of wind

D.wind chill factor

B

Have you ever wondered?

1.Why do airplanes take longer to fly west than east?

It can take five hours to go west-east from New York(NY) to London but seven hours to travel east-west from London to NY. The reason for the difference is an atmospheric phenomenon know as the jet(喷射) stream. The jet stream is a very high altitude wind which always blows from the west to the east across the Atlantic. The planes movement a constams air speed thus go faster in the west-east direction when the air moving with the wind than in the opposite direction.

2 What would happen if the gravity on Earth was suddenly turned off?

Supposing we could magically turn off gravity. Would buildings and other structures float away? What happened would depend on how strongly the things were attached to the Earth. The Earth is moving at quite a speed moving at over a thousand miles per hour. If you turn something round your head on a string, it goes around in a circle until you let go of the strong go of the string. Things not attacked to the Earth would fly off in a straight line . People in buildings would suddenly shoot upwards at a great speed until they hit the ceiling. Most things would fly off into space.

60.What information coa we get from the first passage?

A.tis the iet stoomn that affeets how fast airplanes fly.

B.Planes go slower when they are moving with the wind.

C.It takes more time to fly from NY to London than from London to NY.

D.The jet stream always blows from the east to the west across the Atantic.

A wind vane on a moving vessel shows ______.

A.dead reckoning wind direction

B.true wind direction

C.apparent wind direction

D.estimated wind direction

A fire has broken out on the stern of your vessel. You should maneuver your vessel so the wind ______.

A.comes over the bow

B.blows the fire back toward the vessel

C.comes over the stern

D.comes over either beam

The velocity of the apparent wind can be more than the true wind，and come from the same direction，if certain conditions are present．One condition is that the ______．

A.Ship's speed must be less than the true wind velocity

B.True wind must be from dead astern

C.True wind velocity must be faster than the ship's speed

D.True wind must be from dead ahead

SHIFT OF WIND DIRECTION IN AN ANTICLOCKWISE MANNER, FOR EXAMPLE FROM NORTH TO WEST ( OPPOSITE OF VEERING ) defines ______.

A.Backing (of wind)

B.Veering (of wind)

C.Shifting of wind

D.altering of wind

An anemometer on a moving vessel measures ______.

A.apparent wind speed only

B.true wind speed and true wind direction

C.true wind speed only

D.apparent wind speed and true wind direction