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Air quality assessment & management
Encircled by high mountains, Seoul has topographical conditions susceptible to lingering air pollutants.
The City of Seoul has been taking various measures to reduce air pollution: expansion of clean fuel supply, mandatory installation of car exhaust filtration devices, implementation of sulfur dioxide control measures, and the operation of environment vigilante. As a result, the amount of air pollution in Seoul in 1999 was lower than the WHO-recommended standard.
The name of Seoul comes from the ancient word 'Seorabeol' or 'Seobeol' meaning "capital." It is situated at 126 degrees east longitude and 37 degrees north latitude on the Han River. The administrative districts comprise 25 Gu with 522 Dong.
Seoul belongs to the temperate zone and has four distinct seasons: spring, summer, fall and winter. Seoul's yearly average temperature is 12.2 degrees Celsius. Temperatures in Seoul show large seasonal variation, reaching as high as 38.4 degrees Celsius in the summer and dropping as low as minus 19.2 degrees Celsius in the winter. Influenced by the North Pacific high-pressure system, Seoul has hot and humid summers with average temperatures above 20 degrees Celsius from June through September.
In the middle of summer, the city often records daily highs of over 30 degrees Celsius. In winter, Seoul is geographically influenced by the expansion of the Siberian high pressure and prevailing west wind with temperatures dropping lower than other regions at the same latitude. The rise and fall of the high-pressure system causes a typical cycle of three successive cold days followed by four warmer days, relieving people from freezing temperatures.
The annual precipitation in Seoul averages 1,344.2 millimeters , which is more than the average amount of rainfall across the peninsula. Most of the rainfall is concentrated in the rainy months (monsoon period) of June through September when downpours account for about 70 percent of the total annual precipitation. Except for those rainy spells, however, Seoul boasts fine weather throughout the year and is especially famous for its azure autumn skies.
Seoul's total area is 605.52 square kilometers , or 0.6 percent of the entire country. The Hangang (River) bisects the city into two roughly equalli sized parts of around 300 square kilometers each: the northern part (Gangbuk) and the southern part (Gangnam).
Among the 25 autonomous "gu" or wards of Seoul, the largest is Seocho-gu (47 square kilometers ) and the smallest is Jung-gu with an area only one fifth (10 square kilometers) that of Seocho-gu. The expansion of the city has been curbed since the last administrative reorganization in 1973. The lifestyles of Seoul citizens, however, have been influenced since the 1970s by the rapid growth of satellite cities around the capital area.
Seoul had a population of more than 10 million as of the end of 2005. This accounted for about a quarter of the total national population. By district, Nowon-gu had the biggest population of 625,000 In contrast, Jung-gu had the smallest population of only 134,420. Since Seoul became the capital of the nation in 1394, the population of Seoul has grown 110 times.