This unit is all about rain, what makes it fall, how it influences places and how certain areas of the world have adapted to heavy rainfall. Rain is loved by billions of people all around the world because often it is the rain that brings the end to the stithling heat of the dry season. It is the rain that helps grow the crops and for this reason it is celebrated. For others, like us in Belgium it may be viewed as a nuisance. Did you know whilst most people in Belgium think it rains 50% of the time in reality it only rains 6%. In other words 1 hour and 26 minutes everyday. Check out the video below about Bergen in Norway and afterwards you will probably think Belgium is relatively dry in comparison.
Types of rain
All rain is formed by one process which is the rising and cooling of air. The trigger for air to rise can be several different things.
Relief Rain is formed by mountain barriers. Mountains force air to rise upwards and as it does the air cools and condenses.
Relief Rain is formed by mountain barriers. Mountains force air to rise upwards and as it does the air cools and condenses.
Convectional Rain is formed by the sun's heat. The sun heats the ground which in turn warms the air around it. This causes the air to expand and as it does it becomes lighter than the cooler air around it. So it is forced to rise. The sun also causes water to evaporate off the surface.
Frontal Rain forms at weather fronts. Weather fronts represent boundaries of cold and warm air. The warm air being lighter and less dense than the cold air is forced to rise above the cold air.
Humans can also create rain through cloud seeding. Check out the video and diagram to find out more about this process.
Why is it so wet in belgium?
It only rains in Belgium for 6% of the time, the other 94% of the time it's dry. So why is it that we feel it rains all the time? The main reason for this is that we don't have dry and wet seasons but instead it rais all year round. There is also not one cause of rain in Belgium, but in fact all three causes of rain are at work.
Have a look at the two maps below. Use the first map to locate the Belgium Ardennes, which are known for being very wet and then look at the second map showing relief. What type of rainfall does the Belgium Ardennes normally experience?
Have a look at the two maps below. Use the first map to locate the Belgium Ardennes, which are known for being very wet and then look at the second map showing relief. What type of rainfall does the Belgium Ardennes normally experience?
Belgium also experiences storms which can be spectacular and occur most frequently in summer. Summer storms are caused by rapid convectional processes and occur very localised. Sometimes a storm that affects Tervuren doesn't reach as far as Leuven. Convectional storms are formed by evaporation and transpiration of moisture from the surface. Another type of storm is a depression. Depressions occur all year round but affect Belgium more in winter. They are very common weather systems which also influence the UK. They are formed when different air masses collide such as cold polar air masses and warm tropical air masses. To find out more about air masses and their characteristics check out the videos below and the map on your right. |
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Climate graphs
A climate graph shows the average weather conditions ( temperature and rainfall) for a location. We are going to investigate what climate graphs look like for different wet locations; Belgium, a tropical climate and a monsoon climate.
This rainfall is called equatorial rain, as it falls along the equator creating tropical rainforests in these countries. It also extends to places in the tropics. This brings a climate, made distinct by its dry and wet seasons, which helps forms savannah grasslands.
Ironically all this tropical rain is caused by the sun and its heat.
Ironically all this tropical rain is caused by the sun and its heat.
A tropical rainforest is found in hot, humid environments in equatorial climates. They contain the most diverse range and highest volume of plant and naimal life found anywhere on earth. In general, they have hot and humid climates where it rains virtually everyday. The plants and animals have evolved characteristics which help it to survive in this unique environment.
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Rainforest development
Rainforests once covered 14% of the earth's land surface; now they cover a mere 6%. Experts estimate that the last remaining rainforests could be consumed in less than 40 years. Estimates suggest that rainforest loss is something like one third of an acre to 2.5 acres per second. This would be the equivalent of loosing an area the size of Poland every year.
Tropical Monsoon rain
The tropical monsoon is a season of very wet weather which influences Asia, Australia and West Africa. The monsoon is characterised by daily downpours of heavy rainfall caused by a seasonal shift in wind direction and irregular heating of land and sea. Some regions of the sub-contient (India) can receive up to 1000mm of rainfall in just a couple of months between June and August. To find out more click on the National Geographic link below.