meterolgy ( chapter 5 > required skills and knowledge )

The two types of pressure systems are

1. Warm anticyclones

2. Cold anticyclones

Warm anticyclones form

From high levels convergence forcing subsidence from above which then reaches the surface and then drops

Cold level anticyclones

Form from progressive surface cooling, the subsidence is initiated from below

Warm anticyclones generally form in

Subtropical high pressure belt. They produce clear skies, warm dry surface temperatures, poor visibility and light winds.

Radiation can form fog

Cold anticyclones form from

Over the poles and over large continents in winter. They produce clear skies, very cold dry surface temperatures and poor visibility

The sky is normally sunny in

High pressure area, due to the high pressure air compressing and warms as it descends.

However has and fog may still form

Blocking anticyclones are

Large scale patterns that are nearly stationary. They intrude into typical lattitudes of thr polar front depression, effectively blocking the west to east flow

An omega block

Is an extreme version of blocking high, an area of high pressure which remains stationary for a prolonged period.

An isobaric trough

Is an extended region of relatively low atmospheric pressure, often associated with fronts. It is identified by the isobars extending away from low pressure centre

A trough line is

Is a solid black line marked on low level significant weather charts and surface pressure charts.

it signifies a line of convergence weather which might otherwise not be apparent from the isobars pattern

Three types of high pressure zones occurring at mid latitude …

1. cold temporary anticyclone

2. Warm high

3. The cold high

To identify high pressure regions in a weather chart you must find

Widely spaced isobars whose values are decreasing as you move away from the central enclosed isobars

High level convergence promotes

Subsidence ( sinking )

What is a trough

An area of relatively low atmospheric pressure

What is a ridge

An area with relatively high atmospheric pressure ~ extending from high pressure regions

Trough is

Valley of low pressure ~ weather associated with low depression e.g showery conditions and bursts of rain

Ridge is

Valley of high pressure ~ weather associated with high pressure e.g clear skies and Stratofrom clouds

Col is

High pressure area that lacks in any significant pressure area, weather includes conditions e.g very still conditions

Coriolis force acts to what direction in the northern hemisphere

Right

Coriolis force acts to what direction in the southern hemisphere

Left

Coriolis force acts at what direction at the centre

There is no force at the centre

What direction does anticyclones ( high pressure systems )

1. Northern hemisphere ~ rotate clockwise

2. Southern hemisphere ~ rotate anti-clockwise

What direction does cyclones ( low pressure )

1. Northern hemisphere ~ rotate anti clockwise

2. Southern hemisphere ~ rotate clockwise