Last few lessons...

Long overdue - sorry! A reminder of the last few lessons....

Global Atmospheric Circulation

The tri-cellular model shown below goes some way to explain the global patterns of pressure, precipitation and winds... There is a nice, straightforward explanation of the tri-cellular model, along with Rossby waves and jet streams on the S-Cool site (click on the picture...).

Cool Temperate Western Maritime Climate...

(ie the type of climate we have...)

- located 40o to 60o N and S, mainly on western edges of continents

Make sure that your climate graph (blue bars for precipitation and red line for temperature... Bahrain!) is completed and that you can describe the characteristics of the climate... The data you used to plot your graph was for Sheffield... Remember that there is variation within the British Isles as illustrated by the rather nice maps in this Met Office Factsheet.


Air Masses

5 of them affecting the British Isles - Polar Continental (Pc), Arctic Maritime (Am), Polar Maritime (Pm), Tropical Maritime (Tm) and Tropical Continental (Tc).

The temperature of an air mass and its moisture content are dependent on the source region (hot or cold) and the path (over land or sea) of the air mass.


Types of rainfall

Three main types - orographic (relief), frontal and convectional. In all cases, warm moist air is rising and cooling, water vapour is condensing, clouds are forming and rain is falling. The key difference is what makes the warm air rise in the first place.

For the moment, we need to concentrate on frontal rainfall - where warm and cold air meet...

Depressions

Mid-latitude depressions, or low pressure systems, are the most common weather system to affect the UK. Depressions can affect the UK at any time of the year and bring wet and windy weather.

Three main stages - embryo, maturity and decay - nicely summarised on the S-Cool site.

You need to be able to describe the changes in the weather patterns that occur with the passage of a depression, as well as being able to identify depressions on satellite images and synoptic charts.

A reminder here from the Met Office about station plots and what they mean...

And Postman Pat (courtesy of Tony Cassidy), should you want to watch again, is here!!


Next, anticyclones...