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  Students should know and understand the reasons for the seasonal variations in climate as follows:  
 
  • the seasonal movement of the ITCZ and pressure and wind belts associated with the movement of the sun's overhead position over the year
  • temperature differences between the continental land masses and neighbouring oceans
  • the effects of the warm and cool ocean currents
  • orographic influences and prevailing winds
  
     
  "Do temperatures tend to decrease with latitude?" - Climate (from Ancient Greek klima, meaning inclination) is commonly defined as the weather averaged over a long period of time. Originally, climes were defined in Ancient Greece to describe the weather depending upon a location's latitude.
Source: http://en.wikipedia.org/wiki/Climate 		 
     
  Student Voice: Click on Pic  
     
     
  Altitude of the sun  
 

 
  As the angle of the sun in the sky decreases, the land area heated by a given ray and the depth of atmosphere through which that ray has to pass both increase. Consequently, the amount of insolation lost by absorption, scattering and reflection also increases. Places in lower latitudes are warmer than those in high latitudes. So temperatures tend to decrease with latitude.  
     
  Variations in the length of Day and Night: Places in High Latitudes have no daylight during their 'winter' because of the tilt of the earth's axis. This means they receive less insolation in that season but still lose radiation making it colder.
Places near the Equator tend to have a steadier 12 hours of daylight and 12 hours of darkness around the whole year.		  
     
  The apparent movement of the overhead sun  
 

 
  Source: Eyre and Gower p69  
     
  The overall pattern of the tricellular model is affected by the apparent movement of the overhead sun to the north and south of the Equator. This movement causes the seasonal shift of the heat Equator (thermal Equator), the ITCZ, the equatorial low pressure zone and global wind and pressure belts. Any variation in the characteristics of the ITCZ can have drastic consequences for surrounding climates, as in the Sahel droughts of the early 1970s and most of the 1080s.  
     
 

 

  
  The seasonal movement of the ITCZ (note North is on the 'right' in these diagrams)  
 

 
  Source: http://www.physicalgeography.net/fundamentals/html  
     
     
  Animation of the seasonal shift of the ITCZ (note North is on the 'right' in this gif)  
 

 
  Source: http://www.physicalgeography.net/fundamentals/chapter7.html  
     
  Seasonal shift of the ITCZ - watch the rain clouds move! Click Pic  
 

 
  Source: http://people.cas.sc.edu/carbone/modules/mods4car/africa-itcz/index.html  
     
  Temperature differences between the continental land masses and neighbouring oceans  
  Continents warm up quickly as the insolation heats the surface layer by conduction. Whereas oceans warm up slowly as the water circulates the heat throughout the whole body by convection. So continental areas are warmer than oceans in the 'high sun' season (summer). On the map below for JANUARY - you can see the red line of the THERMAL EQUATOR. Why is the thermal equator much further south over the continents of South America, Africa and even Australia than it is over the oceans in January (the southern hemisphere 'summer')?  
     
  Why do you think there is a massive high pressure over the continental landmass of eastern Asia (northern hemisphere) at this January time of year?  
     
  Comment on the distribution of High Pressure areas in the southern hemisphere in January. Can you offer an explanation for this?  
     
 

 
  Source: http://www.physicalgeography.net/fundamentals/chapter7.html  
     
  July - The Thermal Equator is over the northern hemisphere. Eastern Asia has warmed quickly and has a Low Pressure. The cool north Atlantic and north Pacific Oceans have High Pressures over them.  
     
 

 
  Source: http://www.physicalgeography.net/fundamentals/chapter7.html  
     
  Continental land areas are larger in the northern hemisphere than in the southern hemisphere. This affects global climatic patterns. The Thermal Equator extends further north overall in July than it extends south in January.  
     
  Continentality: Continental areas warm up in summer and cool down quicker in winter than coastal areas. So they have a more extreme Continental climate with a large annual range of temperature compared with coastal areas which have a maritime (equable) climate.  
 

 
     
  Continentality Game  
  Here are the figures the most extreme climate .... Orenberg (Russia) January -14*C; July +22*C  
   

Click here for full screen version

  
  Source: http://classtools.net/widgets/dustbin_7/qrLjW.htm  
  Word document labels  
  Cross-Section Draw the cross section and annotate the Jan and July temperatures for each city. Get the figures and labels from the Dustbin game.  
 

 
     
  The Monsoon  
 

 
  Source: Waugh  
 
Student Voice: Click on Pic
   
 
  Causes of the Monsoon: The major monsoon occurs in south-east Asia and results from three factors: Do the Match-Up Quiz to find them out! Click Pic below  
 

 
     
  The Summer Monsoon: Click for Hot Potato exercise giving you notes  
 

 
     
  The Winter Monsoon: Click for Hot Potato exercise giving you notes  
 

 
     
  Ocean Currents: Click on Pic  
 

 
  Source: http://www.classzone.com/books/earth_science/terc/content/visualizations/es2401/es2401page01.cfm?chapter_no=visualization  
     
 
Student Voice: Click on Pic
 
     
     
  Click on Pic for BBC notes about ocean currents.  
 

 
  http://www.bbc.co.uk/scotland/learning/bitesize/higher/geography/physical/atmosphere_rev1.shtml  
     
  Use Wikipedia and other sources to see what effect the Labrador current has on the climate of the coast of Labrador and Newfoundland. Extension - research one or two other examples.  
 

 
     
  Orographic influences and prevailing winds  
  Can you explain how and why our Monsoon work has already helped us to cover this topic.  
 

 
  The temperature of the winds is determined by its area of origin and by the characteristics of the surface over which it has blown. A wind blowing from the sea tends to be warmer in winter and colder in summer than a corresponding wind coming from the land.  
     
     
Essay Describe and explain seasonal variations in climate      KI 1.2          25 marks         (June 2010)  
  Guidance:  
   

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  Resource made with:  http://classtools.net/widgets/turningPage_8/PllHk.htm           Source: WJEC mark scheme  
     
Essay Outline the tricellular model of atmospheric circulation and discuss its applications and limitations. (20 marks)  
   

Click here for full screen version

  
  http://classtools.net/widgets/turningPage_3/FI8Jr.htm  Resource from Classtools.Net  
 

The question is about the traditional three cell model of global atmospheric circulation. This is made up of the Polar cell, the Ferrel cell in mid latitudes and the Hadley cell in the Tropics. Most standard text books will have a simple diagram of this. This model suggests that the most significant movements in the atmosphere are north-south. Where the cells meet fronts form because different air masses come into contact. The model is still of use although it is very simplified. For example, one limitation is that it doesn't take enough account of important east-west atmospheric movements such as the jet streams that exist at high altitudes. It doesn't take enough account of the Coriolis force created by the Earth's rotation. Monsoons in Asia are created by the effect of different surfaces. In summer the land heats up and air rises, this sucks in moist winds from the oceans. In winter the oceans retain more heat than the land so the wind pattern is reversed with winds blowing from the land towards the oceans. I suppose that your teacher means that this important process isn't included in the traditional model but it would be a good idea to check with her exactly what she wants you to do. I hope that this helps, though naturally it is fairly simple. Consult your textbook and have a search on the internet to find the more detailed information that your answer will need.

  
  Source: http://www.studyzones.com/questionzone/answer/23571x1137/Tri-Cellular-Model