WEATHER MAPS

Question 1

Four properties of the atmosphere

Answer 1

Pressure, density, temperature, humidity

Question 2

Define pressure

Answer 2

The total weight of the column of air up to the upper limits of the atmosphere above a reference point.
= 1kg per square cm.
Measured in Hectopascal (Hpa)

Question 3

Define Isobars

Answer 3

Lines on a wx map that joint together areas of equal pressure.
When drawn, wx systems become apparent (Lows, highs etc.)

Question 4

Buys Ballots Law

Answer 4

If you stand with your back to the wind, the Low pressure is on your right. (SH only)

Question 5

Wind flow around pressure systems (SH)

Answer 5

Clockwise around LOW (cyclones)
Anti clockwise around HIGH (anticyclones)

Question 6

Define Anticyclone

Answer 6

A region of relatively high pressure, surrounded by enclosed isobars, at the centre the pressure is highest.

Question 6

Define Cyclone

Answer 6

A region of relatively low pressure, more or less circular & concentric Isobars surrounding central L where pressures are lowest.

Question 7

Define ridge
Associated weather?

Answer 7

A ridge of high pressure is an extension of isobars away from the parent High. Never marked on wx charts.
Associated with wx conditions similar to High pressure systems.

Question 8

Define trough
Associated wx conditions?

Answer 8

A trough of low pressure is an extension of isobars away from the parent Low. The pressure at any point along the trough is LOWER than the pressure either side of the trough.
Sharp change of wind direction, conditions variable - can be like wx associated with a Low pressure system, NSW, or a region of severe TS.

Question 9

Trough vs. front?

Answer 9

Sharp change in wind direction.
All fronts of any kind mark troughs. Other troughs are marked by a solid bold line on a wx chart.
(All fronts are troughs, not all troughs are fronts)

Question 10

Define Col
Associated weather?

Answer 10

Area of opposing Highs and Lows (two of each), where a region of almost even pressure results between the systems.
Light & variable winds, moisture fed into converging axis may produce TS in summer, or fog in winter.

Question 11

Define a front

Answer 11

Fronts mark the boundaries between air masses that have different temp & moisture characteristics.

Question 12

Define a tropical cyclone

Answer 12

A low pressure system in the tropics, that with the right conditions, will develop to become a depression, and may become a tropical cyclone.
Are named (unlike mid-lat/polar cells).

Question 13

Describe wind-flow in relation to Isobars

Answer 13

The spacing of isobars dictates the strength of wind. If isobars a close together, then there is a sharp increase/decrease of pressure over that area. High pressure will flow to low pressure, and therefore the sharp change in pressure gradient will result in strong winds.
Curvature of isobars however will dictate direction of wind flow (doesn’t just go direct from high to low pressure).

Question 14

Describe winds in relation to Anticyclones

Answer 14

High pressure systems have more spaced apart isobars, and therefore have light winds.
Wind circulation is Anticlockwise in the SH.

Question 15

Anticyclone wx characteristics

Answer 15

Fine, light winds.
Potential for showers & drizzle/low cloud & poor vis

Question 16

Describe winds in relation to Cyclones

Answer 16

In low pressure systems, Isobars are closer together and therefore have strong winds.
Wind flow in the SH is clockwise.

Question 17

Cyclone (low) wx characteristics

Answer 17

Poor & deteriorating weather - strong winds, turbulence, low cloud, poor vis & icing. Likelihood of thunderstorms.

Question 18

Describe a weather “bomb”

Answer 18

A fast forming Low where pressure drops rapidly & wx deteriorates quickly.
Associated w storm force winds, very low cloud, poor vis & storm surges.

Question 19

Describe general weather conditions associated with fronts.

Answer 19

usually associated with very poor conditions - low cloud, poor vis, turb & icing.
Cold fronts often have TS associated.

Question 20

Describe how tropical cyclones can develop

Answer 20

Birthplace is sub-tropics.
When they enter mid-latitudes, their source of energy (warm tropical air), is left behind, which can weaken the system.
However if there is enough of a temp difference between the warm core & surrounding cold air, the pressure will drop rapidly - reinvigorating the system.