Death Valley in the U.S. state of California is also an unbearably sunny place
One way to determine the sunniest place on Earth is to find out where the sun shines the longest during the day. Surprisingly, the record holder in this category is not the sunny state of Florida in the southern US, but the research stations Eureka and Alert, located much farther north – on Canada's Ellesmere Island.
There is no permanent population there – only military personnel and scientists maintain a year-round watch. In the sunniest month (May) in Eureka, the sun can shine brightly for 65.4% of the day, that is more than 15 hours. However, the average daily temperature there is –10 degrees, and in such cold it's not very conducive to sunbathing. The fact is that these research stations are among the northernmost settlements in the world and are located beyond the Arctic Circle.
This latitude in America is called the "land of the midnight sun" because in summer the sun never sets below the horizon and can shine continuously for days. This phenomenon is also known as "polar day". The polar day is followed by polar night, when the sun does not appear above the horizon at all.
Despite the fact that there is a lot of snow in the Arctic, technically it is a desert, meaning precipitation and clouds that bring it are rare in some areas. Given that the sun over Ellesmere Island can shine around the clock and is relatively rarely obscured by clouds, both Eureka and Alert receive the most hours of sunlight in the world – at least in May. But, of course, in the height of December, things are completely different there.
Each of these seasons at the poles lasts six months. Away from the poles, this phenomenon is less pronounced, but at the northern tip of Canada, there is no sun for four months.
Well then, instead, one can look for a place where the sun shines year-round – in that case, you have to travel 5,300 kilometers south. According to meteorological stations scattered across the US, the sunniest place in the world is the city of Yuma, located in the U.S. state of Arizona. The probability of sunny weather during daylight, which lasts from 11 hours in winter to 13 hours in summer, is 90%.
"In the southwestern US, high pressure dominates almost all year round, resulting in downward flows of warm air," explains climatologist Michael Crimmins from the University of Arizona in Tucson. "Therefore, there are many cloudless and warm days throughout the year."
According to Crimmins, Yuma is famous for its sunny weather because it is located in the subtropics. Due to the large-scale atmospheric circulation known as the Hadley cell, this part of the globe is hot and dry.
"At the equator, warm moist air rises, forming a tropical thunderstorm front, and then, in the belt from 30 degrees north latitude to 30 degrees south latitude, it subsides, creating high pressure at the surface," says Crimmins. "It is in this latitude belt that most of the world's major deserts are located."
However, there are other contenders for the champion title besides Yuma, since the available statistical data do not reflect the full picture.
"In the US, most of this kind of statistics is based on reliable long-term observation data, mainly at airports, so extreme values are taken from points located in cities," says Crimmins. Such observations are carried out by meteorological stations that belong to the 1st class (in terms of scope of observations and work – Ed.). According to Crimmins, "it is quite possible that somewhere these indicators are even higher, for example in Death Valley, California, but these places are not taken into account because there are no 1st-class stations there."
No scientist would be surprised if it turned out that the sunniest places on Earth are uninhabited. Humans naturally avoid constant exposure to the blazing sun, because excessive exposure to sunlight can harm them. Moreover, in deserts it is difficult to obtain accurate observational data: it is hard to get there, and the equipment installed there can easily be damaged if it gets covered with sand or, say, frost strikes at night.
In addition, there are many other countries about which we do not have such a volume of information: building weather stations is expensive, and many of the sunniest places in the world are located in developing countries. Finally, we cannot forget about the oceans and lakes: after all, 71% of the Earth's surface is under water. So in 2007, researchers at the U.S. National Aeronautics and Space Administration (NASA) decided to take a different approach and search for the sunniest places on our planet using satellites. Sensors on the satellites were able to determine whether radiation is reflected from clouds or from the earth's surface, including water bodies.
Naturally, the best places for sunbathing were found far from large populated areas. At sea, the sunniest place turned out to be a section of the Pacific Ocean south of the Hawaiian Islands and east of the island republic of Kiribati. On land, the least cloudy area was recognized as a part of the Sahara Desert in Niger, located near the ruined colonial fortress of Agadem. Scientists calculated the average daily amount of solar energy that fell on these areas for the period from 1983 to 2005. In the desert it was 6.78 kilowatt-hours per square meter, and at sea – 6.92 kilowatt-hours per square meter. This roughly corresponds to the amount of electricity used daily for heating water in an average American household.
«It was found that in these locations, the Earth's surface receives the greatest amount of solar energy. There are a couple more such areas in the African Sahara, – says Paul Stackhouse, who studies surface radiation at NASA's Langley Research Center in Hampton, Virginia. – This is due to the relatively high position of the sun at the equator and the absence of clouds due to atmospheric circulation».
Such information is not collected out of mere curiosity: it helps determine the optimal location for solar panels and is used by the solar radiation protection service in Italy.
NASA promises to publish new data in 2016, based on a 30-year observation period. It is possible that new contenders for the title of the sunniest places on Earth will appear in the list.