Tropical cyclonic systems are generally referred to as tropical storms. They are better known by their regional names, such as hurricanes in the Caribbean and North America, or typhoons in parts of Asia. They form near the equator over larger bodies of warm waters that evaporate from the ocean surface and fuel these emerging storm systems. Their strong winds and heavy rainfalls frequently become part of our news as they often put large numbers of human livelihoods at risk.
Recent studies show that the number of tropical cyclones (as well as tropical cyclone intensity) over the past decades has increased. Tracks of tropical storms collected over a longer period can indicate where such storms occur most frequently. The records used in this issue’s visualisation covers data from 1945 to 2008.
For this cartogram, the observed tracks of storms in that period were analysed and their frequency and intensity was plotted onto a grid which provided the basis for the map transformation.
In the larger of the two images, the land area is resized according to its storm intensity, so that the most affected areas are emphasised in this reprojection. The colours distinguish the different regions and countries of the world.
Considerable populations live in those coastal regions where tropical storms make landfall. Populations at risk are mostly to be found on the eastern coasts of the continents. Densely populated areas in the south-east of the United States, the Caribbean Islands, and large coastal populations in east China and the Bay of Bengal are therefore extremely vulnerable.
The small inset map shows how the world looks when the map transformation is applied to the whole surface of the planet, including the oceans in the actual gridded cartogram transformation.
While being even more abstract than the map over land, here it becomes visible just how concentrated the storm tracks are over sea. In general, tropical cyclonic systems slowly lose momentum after having made landfall, so that the land areas turn into much smaller proportions of this second cartogram.
This article was published in the July 2015 edition of Geographical Magazine