A Solar World

British people are said to have an obsession for the weather. Therefore it is not surprising that weather stories have a common place in the media. A recent article in the Guardian’s Weatherwatch series (read more in Weatherwatch: Forget the Balearics – come to Bognor) was searching for the sunniest place in Britain. People living across the Channel may be quite surprised to hear that the concept of sunshine is known (or at least, does exist) in Britain, but it does. British holidaymakers may have actually been much better off staying on the island, rather than heading towards the European continent, as it turned out to be a quite wet summer 2011 there (but the records claim that it wasn’t much better on the British Isles either…).
Globally seen, and with a slightly more scientific twist, there is of course quite a lot sunshine in the northern hemisphere during the (northern) summer months. NASA Earth Obersavations regularly releases data of the solar insolation (the intensity of the sunlight that reaches the earth surface) on a monthly basis (see here for the data source and further details). The original NASA image (included in the below map as an inset) shows “where and how much sunlight fell on Earth’s surface during the time period indicated. Scientists call this measure solar insolation. Knowing how much of the Sun’s energy reaches the surface helps scientists understand weather and climate patterns as well as patterns of plant growth around our world. Solar insolation maps are also useful to engineers who design solar panels and batteries designed to convert energy from the Sun into electricity to power appliances in our homes and work places. […] The colors in these maps show how much sunlight (in Watts per square meter) fell on the Earth’s surface during the given time period” (quoted from NEO).
I used their data for a more experimental approach to visualise the most recent solar insolation (showing data for July 2011) using a gridded cartogram transformation. Instead of transforming people, the following cartogram resizes each grid cell according to the total energy of incoming sunlight reaching the land surface during the month July 2011. The cartogram shows the dominance of sunlight in the northern hemisphere during the northern summer season in the month just after the summer solstice. The seasonal variation of sunshine and the different distribution of sunlight between the northern and southern half of the planet become visible in their quantitative distribution. The northern landmasses are oddly bulging out of the map, while Antarctica disappears in the dark of the polar winter:

Map / Gridded Population Cartogram of Solar Insolation in July 2011
(click for larger map)


Data credits: Reference image (see map inset) by Jesse Allen, NASA Earth Observatory, based on FLASHFlux data. FLASHFlux data are produced using CERES observations convolved with MODIS measurements from both the Terra and Aqua satellite. Data provided by the FLASHFlux team, NASA Langley Research Center. The data has been edited and modified to be suitable for a cartogram transformation.

The map is a conceptual map that gives a first idea of the suitability of gridded cartogram transformations for other quantitative dimensions than only population. For the topic of solar insolation, it may now for example be interesting to collect annual data and do a corresponding transformation that takes the changes of the seasons into account. While this map here may at a first glance be quite surprising with a considerable size being existent on the northern hemisphere, this distribution will change towards the land areas around the equator. For the moment, this map gives a snapshot-view of the (northern) summer 2011, and those who felt it wasn’t that much of a summer should see that there was still some sunshine around in most places. Our perception of weather is as much a part of the weather stories as the weather itself.
Talking about the weather…more weather stories can be seen (and heard) in my presentation during the delegate’s session at the SoC 2011. Some of the material can now be found here.
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