Tokyo opts to water its streets
In an effort to combat rising city temperautres, Tokyo has turned to a neglected custom called uchimizu, which is the sprinkling of water on the ground to lower air temperature.
This latest attempt to bring down summer temperatures that have been hovering in the 40s Celsius involves pumping up the water that seeps into the metro system and spraying it from the kerbside[sic] onto the road surface. A water-retentive coating stops the water from draining away, and evaporation does the rest.
At the test site, directly outside Japan’s parliament building in central Tokyo, a solar and wind-powered pump forces the subway flood water into high-pressure sprinklers that spray it over a 350-metre stretch of road. Recently, the researchers managed to cool the road surface - which often reaches up to 60 °C during the summer - by 10 °C, and the air above the road by 1 °C.
(For the Americans out there — myself included — 40°C is 104°F; 60°C is 140°F)
In recent years, the temperature of Japan’s cities has outpaced global warming by a factor of 4. Temperatures in Tokyo have increased by an average of 3°C (~6°F) compared to 100 years ago. Revisiting uchimizu has caused pavement temperatures to drop by 10°C, and the air temperature to drop by 1°C — no small feat.
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Stone buildings and pavement have a tendency to retain heat, as a result its often hotter in cities than in the surrounding country side. None the less, that is very hot, especially considering that japan is an island and is at a high lattitude.
Comment by me — August 20, 2005 @ 3:32 pm
[...] In a reverse implementation of the Tokyo pavement-watering experiments, the UK’s Transport Research Authority has buried a network of pipes which will store summer’s heat underground in insulated water pipes. In a trial of the idea, a network of polyethylene water pipes 25 millimetres in diameter has been buried below a section of private road in the UK. The pipes are laid in rows about 15 centimetres apart and at a depth of 12 centimetres, where the ground temperature is normally about 12 °C on average. In the summer this can rise to 25 °C. [...]
Pingback by polyscience.org » Storing summer heat for winter — August 21, 2005 @ 10:10 am