Presentation is loading. Please wait.

Presentation is loading. Please wait.

STANDARD GRADE DEPRESSIONS John Smith Invergordon Academy.

Similar presentations


Presentation on theme: "STANDARD GRADE DEPRESSIONS John Smith Invergordon Academy."— Presentation transcript:

1 STANDARD GRADE DEPRESSIONS John Smith Invergordon Academy

2 LOW PRESSURE SYSTEMS How depressions form What happens at the warm front? What happens at the cold front? What happens in the warm sector? What happens at the occluded front?

3 Imagine an area out in the North Atlantic Ocean, to the West of the UK where the air is fairly cool. Cold air will be shown in darker blue. Warm air will be shown in red. This cool air is represented by the light blue background on the following slides. LOW PRESSURE SYSTEMS

4 1. Cold Arctic air blowing from the North East 2. Warm moist Tropical air blowing from the South West Imagine you are looking down on a large area of the North Atlantic Ocean. The air is quite cool (light blue). THE AIRMASSES OVER THE ATLANTIC In this area, different types of air masses meet. We will look at two of these.

5 Cold Arctic air blows from the North East Warm, moist Tropical air blows from the South West THE AIRMASSES MEET……

6 The two sets of air do not mix together As they blow past each other, friction causes them to swirl round ……BUT THEY DO NOT MIX

7 This means that we now have a cool area (shown by the light blue background)…. …with a wedge of very cold Arctic air (shown by the darker blue triangle)…. There is also a wedge of warm moist Tropical air. (red triangle)... Warm, moist Tropical air Cold Arctic air …this is called the COLD SECTOR. …this is called the WARM SECTOR. WARM AND COLD SECTORS

8 These systems usually move either East, or North East Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air DIRECTION OF MOVEMENT

9 The line between the cooler air and the warm sector is called the WARM FRONT. The line between the warm sector and the cold sector is called the COLD FRONT. Cool air Warm, moist Tropical air Cold Arctic air WARM AND COLD FRONTS

10 Dense cool air A SIMPLE CROSS SECTION THROUGH A DEPRESSION COLD SECTOR (cold, dense air) W A R M F R O N T C O L D F R O N T THE WARM SECTOR (warm, moist air)

11 Warm, moist Tropical air Cold Arctic air X What conditions would be felt at X? a)Cool b)Cold c)Warm CONDITIONS AT STATION X (1)

12 Warm, moist Tropical air Cold Arctic air What has passed over X? a)Warm Front b)Western Front c)Cold Front What conditions would be felt at X? a)Cool b)Cold c)Warm From which way are the winds blowing at X? a)South East b)North West c)South West Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air X CONDITIONS AT STATION X (2)

13 What has passed over X? a)Warm Front b)Western Front c)Cold Front Warm, moist Tropical air Cold Arctic air From which way are the winds blowing at X? a)North East b)North West c)South West What conditions would be felt at X? a)Cool b)Cold c)Warm Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air Warm, moist Tropical air Cold Arctic air X CONDITIONS AT STATION X (3)

14 WHAT HAVE YOU LEARNED SO FAR? Warm moist Tropical winds blow from the South West Cold Arctic winds blow from the North East The wedge of warm air is called the warm sector The wedge of cold air is called the cold sector The leading edge of the warm sector is the warm front The leading edge of the cold sector is the cold front Low pressure systems are also called depressions

15 WHAT HAPPENS AT THE WARM FRONT? Warm air begins to rise over the cooler air As this air rises, it begins to cool Cool air can hold less water vapour than warm air Water vapour begins to condense into water droplets Water droplets begin to form clouds The first – and highest – type of cloud to form along the warm front is called Cirrus

16 As the warm air rises, it cools. Dense cool air Warm air is forced to rise over denser, cool air. Water vapour condenses and forms clouds These high-level wispy clouds are called CIRRUS AIR RISING ALONG THE WARM FRONT (1)

17 CIRRUS CLOUDS

18 Dense cool air More moist air rises and cools Clouds form lower down, and give prolonged rain CIRRUS PRECIPITATION AT THE WARM FRONT These are CUMULUS

19 CUMULUS CLOUDS

20 Dense cool air More moist air rises over the cooler air. As it does so it cools. CIRRUS are very high and wispy. They are usually the first clouds we see as the warm front approaches THE WARM FRONT - SUMMARY CUMULUS clouds bring prolonged rain at the warm front Warm Front

21 AN APPROACHING WARM FRONT CIRRUS CUMULUS

22 WHAT HAPPENS AT THE COLD FRONT? The cold Arctic air moves faster than the warm air. The cold Arctic air is denser than the warm air. The cold Arctic air undercuts the warm air, forcing it up. Water vapour begins to condense into water droplets Water droplets begin to form very tall clouds The clouds along the cold front are called Cumulonimbus.

23 THE COLD FRONT The cold front rapidly undercuts the air in the warm sector, making it rise very quickly. The Warm Sector (warm, moist air)

24 Very tall clouds are formed by the rapidly rising air. These are called CUMULONIMBUS. The Warm Sector (warm, moist air) CUMULONIMBUS give very heavy showers, sometimes with thunder and lightning. PRECIPITATION AT THE COLD FRONT

25 CUMULONIMBUS CLOUDS

26 IN THE WARM SECTOR Warm, moist winds blow from the South West Air is forced to rise over cooler air Condensation occurs, and forms Stratus clouds Showers are common The sky is very overcast

27 Dense cool air THE WARM SECTOR Warm front Warm, moist air in the warm sector is rising.

28 Dense cool air CLOUD & PRECIPITATION IN THE WARM SECTOR W A R M F R O N T Warm, moist air in the warm sector is rising. The clouds formed here are mostly Stratus Stratus are flat layer clouds. They give showers. STRATUS

29 CLOUD & PRECIPITATION – SUMMARY 1 Dense cool air STRATUS CIRRUS CUMULUS CUMULONIMBUS W A R M F R O N T PERSISTENT RAINLIGHT SHOWERSHEAVY SHOWERS

30 A SATELLITE IMAGE OF A DEPRESSION

31 CLOUD PRECIPITATION TEMPERATURE WIND DIRECTION AIR PRESSURE Cumulonimbus StratusCumulusCirrus Heavy showers ShowersProlonged rain ColdWarm N.W. or NS.W.E or N.E. CROSS SECTION THROUGH A DEPRESSION Falling Low Rising Cool


Download ppt "STANDARD GRADE DEPRESSIONS John Smith Invergordon Academy."

Similar presentations


Ads by Google