401.1b - general weather associated with each air mass

Factors to consider with air mass weather:

• _____ of the air

• __________ of the air

• Presence of lifting agents

• Stability

Temperature, moisture content

What are the three lifting agents that can be considered with air mass weather?

Convection, orographic lift, mechanical turbulence

Continental arctic air masses are ______. _____ temperatures and ____ moisture are characteristics of this air mass.

the most stable, cold, low

If any moisture is introduced to Continental Arctic air masses, it is generally trapped in the low levels, causing ________.

fog or low stratus

Maritime Arctic air masses are ____ in temperature and _____ in moisture.

cold, high

Maritime Arctic air masses form from ________ as it moves South out of the frozen ice and tundra and over ________ in winter or South over _______ in summer.

the Continental Arctic, the North Pacific Ocean, the Canadian North

Maritime Arctic air masses are slightly less cold as it is formed when Continental Arctic air is _____ by moving over the open ocean. This increases __________, reducing stability.

modified, temperature and moisture content

Showers of snow and even cooler weather thunderstorms are possible with Maritime Arctic air masses, depending on ______ and ______.

the lifting agents, underlying topography

Maritime Polar air starts relatively cold and dry, but during its passage over the warm waters of the ocean, it increases in temperature and becomes ______ to a great depth.

It is characterised by _____ at any time of the year.

unstable, frequent showers

In the winter months when instability (convection) is most vigorous over the sea, ________ are common as soon as _______ air masses makes landfall.

hail and thunder, Maritime Polar

During the summer, land temperatures are higher than sea temperatures and the heaviest showers occur after the ______ air mass is modified by _____ from the earth.

Maritime Polar, the terrain and radiation

Maritime Tropical air is _______ in its lower layers and, although unstable over its source region, during its passage over cooler water becomes more stable and the air becomes ______.

warm and moist, saturated

As ______ air moves over cooler waters and becomes saturated, it brings with it ______, and perhaps also _____ around windward coasts and across hills.

To the lee of high ground, the cloud may break up and here the weather, particularly in the summer months, can be fine and sunny, if humid.

Maritime Tropical, low cloud and drizzle

_______ is a mild air stream and during the winter months, can raise air temperature several degrees above the average.

Maritime Tropical air

With regards to stability, what happens when an air mass is heated from below?

Destabilises the air

Does heating from below favour layer type clouds or vertical development clouds?

Vertical development clouds

Characteristics from heating from below:

• ________ the air

• Favours _______

• ______ visibility

• Turbulence

Destabilises, vertical development clouds, good

Characteristics from cooling from below:

• ________ the air

• Favours _______

• ______ visibility

• Little turbulence

Stabilizes the air, layer type clouds, Poor (FG and HZ)

Would the visibilities normally be good or poor during unstable conditions?

Good visibilities

Would an air mass be more turbulent in stable or unstable conditions?

Unstable

True or False: During unstable condition the air is more turbulent due to the horizontal movement of the air.

False, it is vertical movement

True or False: Inversions will tend to block vertical movement and visibilities would tend to be poor.

True