DEPRESSIONS – Air – DGCA Question Bank For Politics

#1. A thermal depression is likely to form:

over the Iberian peninsular during the summer

in the lee of the Alps over Northern Italy in winter

in association with a marked trough of low pressure over the USA

on the trailing edge of a warm sector mid latitude depression

As the air at the surface is heated, it will expand, causing the pressure surface to be lifted. This higher pressure at height will result in an outflow of air. In turn this will cause a fall in surface pressure and the air will move cyclonically.This is thermal depression

Thermal depressions are most frequent over land masses like Iberia in summer

The Polar Air Depression can be classified as a thermal depression because it is essentially created by warming its lower layers.

#2. Tropical revolving storms usually:

form close to one side of the equator and while moving slowly in a westerly direction, cross over to the other hemisphere

move in a westerly direction before re-curving towards the equator

move in an easterly direction before re-curving towards the nearest pole

do not form within 5° of the equator

These are cyclones that develop over the warm tropical oceans and have sustained wind speeds in excess of 64 knots

Requirements

 Must be within 5  and 25  latitude. Below 5  coriolis force is too small, above 25  latitude the sea is usually too cold.

#3. With reference to tropical revolving storms, which of the following statements is correct:

typhoons are found in the South China sea in January

cyclones, occur in the Bay of Bengal in winter

hurricanes, in the South Atlantic sometimes affect the east coast of Brazil

hurricanes affect the south east of the USA in late summer

Hurricanes.
Hurricane is the name given to Tropical Revolving Storms in the Caribbean/Gulf of Mexico Area. Frequency of developed Hurricanes is average 3 per year. They occur from August to October, tracking westwards across the Atlantic near 10°N-15°N latitude and at 10-15 knots. Internal windspeeds can exceed 100 knots. They then cross the Bay of Mexico or turn right around the sub tropical high to track NW, N, NE up the USA East Coast. They are energised by the latent heat of condensation and are therefore more active over the sea. Each season they are named alphabetically in order of occurrence using alternate male/female first names.

#4. Which of the following statements accurately describes the “West African Tornado”:

the West African Tornado is similar to the North American and European tornadoes

it is a line of thunderstorms producing a line squall aligned roughly north/south

it is another name for the cyclones that affect the West African coast in summer

it is the name given to a line of thunderstorms that lie along the ITCZ but some 200 miles to the south

West African Tornadoes are associated with the passage of the ITCZ through countries bordering the Gulf of Guinea. They are thundersqualls which form in a line North-South and move from East to West in March to May and October to November.

#5. Extensive cloud and precipitation is often associated with a non-frontal thermal depression because of

Surface divergence and upper level convergence causing widespread descent of air in the depression

Surface convergence and upper level divergence causing widespread descent of air in the depression

Surface convergence and upper level divergence causing widespread ascent of air in the depression

Surface divergence and upper level convergence causing widespread ascent of air in the depression

#6. In comparison with a primary depression a secondary depression is:

Always more active

Sometimes more active

Never more active

Unlikely to produce gale force winds

#7. A Secondary Depression would form in association with:

A Polar Depression

A Col

A Summer Thermal Depression over the Mediterranean or Caspian Sea.

A Polar Front Low

When a small depression is enclosed within the circulation of a larger depression it is called a secondary. The isobars need not show a closed centre. Secondaries are particularly associated with frontal depressions and form

#8. Tropical Revolving Storms:

Are always given a male first name beginning with “A” for the first of the season and thereafter named in alphabetical order of occurrence

Have internal wind speeds of 10-20 knots rotating cyclonically round a subsiding clear air core known as the eye

Usually have the most severe weather in the quadrant to the right of the track in a Hurricane

Regenerate after crossing the coast from sea to land

#9. A Secondary low pressure system rotates around a Primary low:

Cyclonically

Anticyclonically.

Into the primary

At a constant distance

This secondary may deepen and form the next depression along the PF and equal the size of the primary. At this stage, the depressions tend to rotate around each other cyclonically

#10. Flying conditions in a Secondary low pressure system are:

Always more severe than in a Primary low

Sometimes more severe than in a Primary low

Less severe than in a Primary low

Relatively calm

On a trailing front from an occluded primary. This secondary may deepen and form the next depression along the PF and equal the size of the primary. At this stage, the depressions tend to rotate around each other, until eventually the primary and the sec-ondary has become the new primary.

secondary depression are stronger than primary

#11. Tropical Revolving Storms:

Do not occur in the South Atlantic.

Generally move from east to west before turning towards the equator.

Intensify after crossing coasts.

Occur principally in spring and early summer.