GAW Report No. 205 - IGAC Project

CHAPTER 3 - ASIAthe high frequency of the occurrence of acid rain, suggests there is still much research andemission control strategies needed to further improve the air quality in Shanghai.3.13 TOKYO, JAPANIntroductionTokyo is located in the southeastern part of central Japan (Tokyo Metropolitan Government:35.69°N, 159.69°E). The population of the Tokyo Metropolis was about 12.7 million, and thepopulation of the Kanto area (Tokyo Metropolis and the six surrounding prefectures) was about 41.9million in 2008. The Greater Kanto Area is one of the world’s largest megacities in terms ofpopulation [Gurjar et al., 2008].The southeastern part of the Kanto area, called the Kanto Plain (150 × 150 km 2 ), faces thePacific Ocean and to the west and north is surrounded by mountains exceeding 1000 m in height.Local meteorologyFrom late spring to mid-summer, a sea-land breeze circulation pattern driven by the heatingand cooling of the Kanto Plain during daytime and nighttime, respectively, often prevails [Kondo etal., 2006]. On clear, calm days, southerly winds typically dominate during the daytime, and air isbrought from over the ocean to the Tokyo Metropolis and further northward. From midnight to earlymorning, weak northerly winds dominate and air is transported from the northern Kanto Plain to theTokyo Metropolis.In winter, northwesterly winds associated with a strong Siberian high-pressure systemgenerally dominate over the Japanese islands. As a result, air is transported primarily from thenorthwest, over the northern part of the Kanto Plain and then to the Tokyo Metropolis. When thenorthwesterly winds dominate, sea-land breeze circulation pattern does not develop.Emissions sources and regulationsKannari et al. [2007] developed an emission inventory, called EAGrid, which estimatedhourly emissions over all of Japan with a horizontal resolution of approximately 1 km for each monthin 2000. Over the Kanto area, motor vehicles were estimated to account for 80%, 52%, 43%, 17%,and 5% of emissions of carbon monoxide (CO), particulate matter with a diameter of less than 2.5µm (PM 2.5 ), nitrogen oxides (NO X ), volatile organic compounds (VOCs), and sulphur dioxide (SO 2 ),respectively, in 2000 (Table 15). Large point sources made the largest contributions to SO 2emissions (~62%) and stationary evaporative sources were the largest contributors to VOCemissions (~63%).Table 15 - Source contributions to NOX, SO2, PM2.5, VOC, and CO emissions (Gg/year) over the Kanto areain 2000 estimated in the EAGrid inventory [Kannari et al., 2007]NOX SO2 PM2.5 VOC COLarge point sources 164 28% 95 62% 6.7 22% 5.5 1% 230 17%Other point sources 30 5% 22 14% 2.3 7% 5.8 1% 29 2%Motor vehicles 256 43% 7.2 5% 15.9 52% 144 17% 1059 80%Off-road vehicles 80 14% 1.8 1% 2.3 8% 10 1% 0 0%Other transport 60 10% 27. 18% 3.5 11% 4.2 0% 11 1%Stationaryevaporative sources535 63%Biogenic 148 17%Total 589 153 30 854 1330123