How has the distribution and frequency of tropical storms changed over time?

 Tropical storms develop within the tropics (somewhere between 5° and 30° latitude north and south of the equator) but not normally on the equator. Tropical storms have different names depending on which ocean basin they are located in:
·      Cyclones in the south Pacific & Indian Oceans
·      Typhoons in the north west Pacific
·      Hurricanes in the Atlantic Ocean.

Areas where tropical storms form
Areas where tropical storms form.

What is the relationship between tropical storms and global circulation system?

Tropical storms develop in areas of low-pressure, where intense heat around the equator causes air to rise rapidly; this causes winds from higher-pressure areas 30° north (Tropic of Cancer) and 30° south (Tropic of Capricorn) of the equator to rush in. These winds are known as the trade winds. Air between 5° and 10° north and south of the equator is rising, cooling and condensing to form clouds. More and more air continues to rise and condenses rapidly, therefore clouds get denser and lower in the sky and a tropical storm will begin to develop.

Global atmospheric circulation

Air blows into the low-pressure systems from the Tropic of Cancer and Tropic of Capricorn, which are 30° north and south of the equator, this is where the high-pressure belts lie. The air moving from high to low pressure generates winds called the trade winds, these converge (come together) and meet, which along with the Coriolis effect causes the storms to spin and join together.

How might climate change affect the distribution, frequency and intensity of tropical storms?

There could be an increase in tropical storms due to climate change. Seas, which reach 26.5°C, could extend into more southerly and northerly areas than previously due to the warming climate. 

Climate modelling is unsure if the frequency (how many) will increase due to climate change but the modelling does confirm the intensity (the power) may increase as the sea surface temperatures will increase, leading to higher wind speeds (around 7% higher) and more rainfall (20%). This will result in more storms registering higher magnitudes on the saffir-simpson scale

Atlantic Storm Count
Atlantic Storm Count

Not only might the intensity of tropical storms increase so will the damage caused by storm surges increase due to the rising sea levels. This will extend areas that are damaged by tropical storms, particularly those communities on low-lying coastlines.

What might the examiner ask?

Areas where tropical storms form
Figure 1. Areas where tropical storms form.

You need to include:
+Distribution means the way something is spaced out- in this case tropical storms.
+A description of the distribution-using ocean names, tropical storm category names, compass directions and lines of latitude.
+Ensure you add the explanation and do not spend all of your time describing. E.g. Tropical storms are mainly found within the tropics region (5°-30° N & S of the equator) because tropical storms are powered by warm ocean temperatures of 26.5°C created by large concentrations of solar radiation received.

You need to include:

+Greater spread of tropical storms into ‘new’ areas due to rising sea surface temperatures.

+Tropical storm intensity due to increase due to rising sea surface temperatures.

+Greater amounts of rainfall and storm surges.

+Possibility that frequency of tropical storms may decrease.

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