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Whitehorse Master 3000 Oral Prep > Meteorology > Flashcards

Meteorology Flashcards

(106 cards)

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1
Q

Atmosphere:

If an unsaturated parcel of air is cooled beyond its dew point, what will happen?

A

It will become saturated and some of the water vapor will condense out, forming clouds.

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2
Q

Atmosphere:

What is the difference between absolute and relative humidity?

A

Absolute humidity is the quantity of water in the air, expressed in grams per cubic meter.

Relative humidity is the absolute humidity in relation to the quantity required for the air to be saturated, expressed as a percentage.

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3
Q

Atmosphere:

What is the dew point?

A

The temperature at which a parcel of air is saturated.

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4
Q

Atmosphere:

What is the troposphere?

A

The lowest layer of the atmosphere. It is the layer which contains almost all the water and most of what we think of as weather.

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5
Q

Atmosphere:

Complete the sentence: When air rises, it…

A

Cools, due to expansion

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6
Q

Atmosphere:

At what rate does unsaturated air cool with altitude?

A

10°C/km

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7
Q

Atmosphere:

What type of atmospheric stability results in clear skies?

A

Absolute stability, where the parcel of air is always cooler than the surrounding air and therefore wants to sink back down to its original altitude.

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8
Q

Atmosphere:

What does SALR stand for?

A

Saturated Adiabatic Lapse Rate

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9
Q

Atmosphere:

What is called when air is forced to rise because of two or more air flows meeting?

A

Convergence

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10
Q

Atmosphere:

What is it called when air is forced to rise due to land?

A

Orographic uplift

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11
Q

Atmosphere:

What is a fluffy cloud at low altitude called?

A

Cumulus

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12
Q

Atmosphere:

What does a nimbostratus cloud look like?

A

Flat layer of cloud at low altitude which brings rain

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13
Q

Atmosphere:

How might clouds change when a depression is approaching?

A

As a depression approaches, high cloud will appear and it will thicken and lower as the depression gets closer.

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14
Q

Atmosphere:

What are squalls?

A

A sudden and dramatic increase in the wind speed, which lasts longer and is more significant than a regular gust. It can also cause a significant shift in the wind direction.

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15
Q

Weather Patterns:

Which air mass forms over northern Canada and Greenland and moved directly across the North Atlantic to the UK?

A

Polar Maritime

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16
Q

Weather Patterns:

How is an air mass which originates over land termed?

A

Continental

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17
Q

Weather Patterns:

What are the characteristics of maritime air?

A

More humid (contain more water) than continental air masses.

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18
Q

Weather Patterns:

What are the expected weather conditions when the UK is under the influence of a tropical maritime air mass?

A

This air mass is warm and moist. As it moves towards the UK and cools a little, it will become stable and saturated. When it reaches the UK, it will cause low cloud and drizzle and perhaps some fog.

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19
Q

Weather Patterns:

What are the expected weather conditions when the UK is under the influence of a tropical continental air mass?

A

A tropical continental air mass brings warm and dry weather and clear skies because it originates in a warm place and doesn’t carry much moisture with which to form clouds or rain.

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20
Q

Weather Patterns:

Which type of breeze occurs because land absorbs heat more quickly than water?

A

Sea/onshore breeze

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21
Q

Weather Patterns:

What causes a land/offshore breeze?

A

At night, the land cools more quickly than the sea. The air over the land is cooled and sinks, creating a high pressure, in contrast to the low pressure over the sea. This creates a pressure gradient which results in the land/offshore breeze.

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22
Q

Weather Patterns:

What drives the north-east monsoon?

A

The intense winter cold across the Tibetan Plateau and Central Asia.

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23
Q

Weather Patterns:

Why is the summer monsoon south-westerly when the pressure gradient is north-south?

A

Because the Coriolis Effect bends/deflects the airflow to the right in the northern hemisphere, resulting in a south-westerly wind.

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24
Q

Weather Patterns:

What is the pressure over central Australia in the wet season and what is the effect of that pressure?

A

The wet season is the result of the intense heat in central Australia causing air to rise and thus creating a low pressure. This draws warm, humid air from the Indian Ocean over northern Australia, which causes the wet season.

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25
**Weather Patterns:** Why are the seas in the Arabian Sea rougher during the southwest monsoon than during the northeast monsoon?
Two reasons: 1. Wind speeds are higher during the more powerful SW monsoon 2. SW‘ly winds have a much greater ‘fetch’ (distance travelled) and are this larger
26
**Weather Patterns:** What are the weather conditions along India’s SW coast during the SW monsoon?
The SW monsoon draws warm humid air from the Indian Ocean, so the weather is very unstable with high levels of precipitation and squally conditions.
27
**Weather Patterns:** Which of the jet streams drives the weather experienced in Northern Europe?
The polar jet
28
**Weather Patterns:** What causes El Niño?
Weaker than normal trade winds allow the warm water that is normally pushed over to the west Pacific Ocean to spread more evenly across the ocean. This reduces the normal temperature gradient.
29
**Weather Patterns:** What does ITCZ stand for?
Inter tropical Convergence Zone
30
**Weather Patterns:** Which cell is driven by the intense heat of the sun causing air to rise at the equator?
The Hadley Cell
31
**Weather Patterns:** Why are there often desserts at approximately 30-40° latitude?
Because that is the latitude at which the air descends between the Hadley and Ferrel cells. This air is typically cool, dry and stable, so there is very little rainfall.
32
**Weather Patterns:** What are created along the polar front and blown towards Northern Europe by the polar jet?
Depressions (low pressure systems)
33
**Pressure Systems:** What is the average global atmospheric pressure?
1013mb
34
**Pressure Systems:** What is ‘pressure gradient’?
The change in air pressure per unit of horizontal distance.
35
**Pressure Systems:** Which unit of pressure is equivalent to millibars?
Hectopascals (hPa)
36
**Pressure Systems:** What does an isobar show?
Isobars link areas of equal pressure on a pressure chart in much the same way that contours link areas of equal depth or height on charts and maps.
37
**Pressure Systems:** What is the difference between geostrophic wind and gradient wind?
Geostrophic wind blows parallel to the isobars, at altitude. Gradient wind (aka Real wind) is the result of friction slowing Geostrophic wind and causing it to cross the isobars by the angle of indraft.
38
**Pressure Systems:** Which way does a low pressure system rotate in the southern hemisphere?
Clockwise
39
**Pressure Systems:** What is a depression?
Often used to describe mid-latitude low pressure systems.
40
**Pressure Systems:** Which way does a low pressure system rotate in the northern hemisphere?
Anti-clockwise
41
**Pressure Systems:** Which way does a depression rotate in the southern hemisphere?
Clockwise
42
**Pressure Systems:** How does front symbology indicate the motion of the front?
The triangles/semi-circles point in the direction of motion of the front
43
**Pressure Systems:** What happens when the cold front catches up with the warm front?
It lifts the warm air mass off of the ground and causes an occlusion
44
**Pressure Systems:** Where do depressions form?
They typically form along the polar front, which is the boundary between the ferrel and polar cells.
45
**Pressure Systems:** What causes a depression to dissipate?
Once most of the warm air on the warm sector has been forced upward, the temperature gradient between the two sectors will reduce because the warm air cools as it rises. At this point the air stabilizes and the system dissipates.
46
**Pressure Systems:** Does an occluded front occur when a cold front catches up with a warm front, or when a warm front catches up with a cold front?
Cold front catches up with a warm front
47
**Pressure Systems:** How will cloud cover and precipitation change as a warm front approaches?
As a warm front approaches, cloud cover will increase and lower. Precipitation will initially be light and intermittent, but it will become moderate or heavy in the vicinity of the front.
48
**Pressure Systems:** Which front is steeper?
The cold front
49
**Pressure Systems:** What happens to the wind as the cold front passes in the northern hemisphere?
The wind will veer dramatically and sudden squalls may occur
50
**Pressure Systems:** What is the warm sector?
The warmer air mass wedged between colder air ahead and behind.
51
**Pressure Systems:** Why are conditions in anticyclones typically stable with clear skies?
Because the descending air is generally cool and dry
52
**Pressure Systems:** Why does the temperature in an anticyclone differ with the season?
It’s warmer in summer because clear skies mean that there’s nothing to block the intense infrared radiation from the sun. In winter, it’s colder because there’s not a lot of infrared radiation, but there’s also no cloud cover to prevent what warmth there is from escaping into the atmosphere.
53
**Pressure Systems:** Which way does an anticyclone rotate in the northern hemisphere?
Clockwise
54
**Pressure Systems:** Is air riding or falling in an anticyclone?
Falling
55
**Tropical Storms:** Why do tropical storms not normally form on the equator?
They need the Coriolis effect to begin rotating and there is insufficient Coriolis effect below approximately 5 degrees of latitude.
56
**Tropical Storms:** What are tropical storms called in the Indian Ocean?
Cyclones
57
**Tropical Storms:** What is the minimum sea temperature for tropical storms to form?
The sea temperature needs to be more than 26°C for tropical storms to form.
58
**Tropical Storms:** What is a tropical storm?
A tropical storm is a rapidly rotating low pressure system which develops within tropical areas of the world.
59
**Tropical Storms:** Why can’t tropical storms form over land or higher latitudes?
They can only form in an area where there is warm, moist air. There isn’t enough moisture over land and it’s not warm enough (more than 26°C) at higher latitudes.
60
**Tropical Storms:** What is the approximate Hurricane season in the Caribbean Sea?
Hurricane season in the Caribbean Sea can be summarized as JASON or JJASON, I.e (June), July, August, September, October and November.
61
**Tropical Storms:** How can El Niño and La Niña affect tropical storm formation and strength
Multi-annual fluctuations in Pacific Ocean sea surface temperatures caused by El Niño and La Niña, can lead to weaker and stronger tropical storms in different parts of the world.
62
**Tropical Storms:** What magnitude of a fall in atmospheric pressure is confirmation that a tropical storm is in the vicinity?
5mb
63
**Tropical Storms:** What change in the wind might signal that a tropical storm is inbound?
If the wind strength to a degree and/or was coming from direction which is not normal for the region (I.e. trade winds)
64
**Tropical Storms:** At what wind speed (in knots and on the Beaufort scale) is a hurricane declared?
Wind speeds of over 64knots (Force 12) are hurricane force.
65
**Tropical Storms:** Which organization is the primary source of hurricane forecasting in the Caribbean?
The National Hurricane center of the United States National Oceanic and Atmospheric Administration (NOAA)
66
**Tropical Storms:** How can swell indicate the presence of a tropical storm?
A long low swell, traveling outward from the center of the storm, may be the first indication of a tropical storm’s approach. Particular attention should be paid when the swell direction and height differs from the norm in the region.
67
**Tropical Storms:** In the northern hemisphere, if the wind is veering and the pressure is falling, where should the relative wind be positioned in order to take avoiding action?
Starboard bow
68
**Tropical Storms:** What is the average speed of a tropical storm prior to it recurving?
Tropical storms tend to move at approximately 10 knots in their early stages. As they gain latitude, this may increase but rarely exceeds 15 knots before they have recurved.
69
**Tropical Storms:** What is Buys Ballot’s Law and how can it be used in the southern hemisphere?
Buys Ballot’s Law can be used to determine the Centre of an area of low pressure from the perspective of the observer. In the southern hemisphere, if the observer faces the wind the center of the low will be 100° to 125° to their left or 10° to 35° over their left shoulder.
70
**Tropical Storms:** If the pressure is falling and the wind is backing, where are you in relation to the tropical storm?
Advance left
71
**Tropical Storms:** Where is the dangerous quadrant in the Northern Hemisphere?
Advance right
72
**Tropical Storms:** What is the correct action to take if you find yourself in the dangerous quadrant in the southern hemisphere?
Place the wind on the port bow and make best speed. Maintain the relative wind direction as the wind backs.
73
**Tropical Storms:** Describe, in general terms, the movement of a standard tropical storm in the North Atlantic.
Having formed in low latitudes in the mid or eastern-Atlantic, tropical storms tend to move roughly W’ly to WNW’ly across the Atlantic before recurving away from the equator in the vicinity of 25°N latitude and eventually settling on to a north-easterly track.
74
**Tropical Storms:** Why is the dangerous quadrant so called?
The dangerous quadrant is so named because the storm is more likely to recurve that way, the wind and waves push any nearby vessels into the path of the storm and the wind speed is higher.
75
**Forcast:** Which sea state is worse; Rough or high?
High
76
**Forecasting:** What is the Beaufort scale used to quantify
Wind speed, based on observed sea conditions
77
**Forecasting:** Which meteorological instrument is used to measure humidity?
A hygrometer
78
**Forecasting:** Which hygrometer should be used when taking temperature readings?
The one on the windward side of the vessel.
79
**Forecasting:** What is the difference between a barograph and a barometer?
A barometer measures pressure at a point in time, whereas a barograph records pressure change over time.
80
**Forecasting:** How do you take a pressure reading with a precision aneroid barometer?
The micrometer dial on the right hand side is rotated whilst the black button is compressed until the indicator light jumps from one setting to another to indicate that the value indicated matches ambient pressure. The pressure is then read from the read-out.
81
**Forecasting:** What must the OOW be cautious about when measuring the wind speed?
They must understand weather the wind speed being fed into the bridge equipment is relative or true and, when more than one anemometer is fitted, they must ensure that the windward one is being used.
82
**Forecasting:** What causes depression of the wet bulb?
The tip of the wet bulb thermometer is wrapped in clean muslin which is dipped into a reservoir of distilled water. The evaporation from the muslin absorbs heat from the thermometer, lowering the temperature recorded. The drier the air, the greater the evaporation and the greater the depression.
83
**Forecasting:** Which series of publications should be consulted during NAVTEX setup?
Admiralty List of Radio Signals
84
**Forecasting:** How many routing charts are there?
Each ocean has 12 routing charts, one for each month of the year
85
**Forecasting:** What is weather routing?
The use of weather info to determine a safer, quicker and/or more economical route between two ports
86
**Forecasting:** What are Viking, Fair Isle and Forties?
Sea areas in the Met Office’s shipping forecast
87
**Forecasting:** Why does geostrophic wind not correctly predict the wind speed at ground level?
Geostrophic wind speed is reduced at the surface due to friction between the moving air and the water or land below.
88
**Forecasting:** By how much is geostrophic wind reduced to get the real/gradient wind at the surface?
Half over land or a third over water, to determine the real wind speed at the surface
89
**Forecasting:** What is frontolysis?
Means that the front is dissipating because the temperature gradient is decreasing at the surface
90
**Forecasting:** What is the change in pressure from one isobar to the adjacent one?
4mb
91
**Forecasting:** What is the symbology and direction of travel for a cold front?
Blue line with blue triangles pointing in the direction of travel of the front
92
**Fog:** Which type of fog occurs when warm, moist air passes over cold water?
Advection fog
93
**Fog:** Which type of fog occurs at the boundary between warm and cold air masses?
Frontal fog
94
What causes advection fog?
Occurs when warm moist air passed over a colder surface. The colder surface cools the warm moist air to below its dew point which causes condensation.
95
**Fog:** What is the definition of fog?
A cloud at ground level, which reduces visibility to below 1000m
96
**Fog:** What causes radiation fog?
As the land cools during the night, it cools the air close to the surface. This air is cooled to below its few point, causing condensation, forming fog. Although it has formed over land, it can flow out over the sea, although not normally further than 10-15nm and is normally burnt off fairly quickly once the sun rises.
97
**Fog:** Using the dew point table above, can fog form under the following conditions? Dry bulb temp = 20°c Wet bulb temp = 17°c Sea temp = 14°c
Yes. The dew point temp is 15°c and the lower sea water temp make cool the air below that
98
**Fog:** What is the ‘depression of the wet bulb’?
The difference between the dry and wet bulb temp
99
**Fog:** Where can the ‘dew point table’ be found?
Mariners handbook NP100
100
**Fog:** What is plotted against the dew point to determine the likelihood of fog forming in the future?
The sea surface temp
101
**Ice Accretion:** What are the two types of ice accretion?
Salt water and fresh water
102
**Ice Accretion:** Below what air temperature does salt water ice accretion occur?
-2°C
103
**Ice Accretion:** Which factors must be present for salt water ice accretion to occur?
1. Air temperature of less than -2°C 2. Adverse weather conditions 3. Vessels motion causing significant amount of spray and/or water on deck.
104
**Ice Accretion:** Which type of ice accretion creates equipment and safe access issues but is unlikely to place the vessel in danger?
Fresh water ice accretion
105
**Ice Accretion:** How can ice accretion affect GNSS and radio antennas?
GNSS antennas covered in a layer of insulating ice may not receive the relatively weak signals from orbiting satellites, so position accuracy may suffer. Radio antennas may suffer from reduced effective range and whip aerials could snap if the ice becomes too heavy.
106
**Ice Accretion:** Which factors must be present for fresh water ice accretion to occur?
Air temperature below 0°C and moisture in the air from either rain, snow or fog.

Whitehorse Master 3000 Oral Prep (12 decks)

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