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Home > Annual Report on Atmospheric and Marine Environment Monitoring No.6 Observation Results for 2004

Annual Report on Atmospheric and Marine Environment Monitoring No.6 Observation Results for 2004

Executive Summary

• The Global mean concentration of CO₂ in 2004 was 377.1 ppm from archive data in the World Data Centre for Greenhouse Gases, which has increased by 35% compared with mean concentration (280 ppm) before the industrial age (1750).
• The Global growth rates in atmospheric ₂ had the highest peak from 1997 to 1998. The increase of CO₂ emission in the tropical land area due to the global high temperature anomaly from the large El-Nino event in 1997/1998 is considered to cause this increase of growth rate. The global growth rates in atmospheric CO₂ had a peak exceeding 3 ppm/year from 2002 to 2003 in the middle and high Northern latitudes corresponding to the occurrence of the 2002/2003 El-Nino event. The mean annual growth rates in atmospheric CO₂ was 1.9 ppm/year in the last 10 years.
• The differences in the CO₂ partial pressure （�冪CO₂ ） between the sea water and the air in winter and summer, 2004 were at the same level as the means for winter and summer in the subtropical North Pacific along 137°E (10°N -30°N) .
• The mean annual growth rate of the oceanic CO₂ concentration averaged between 7oN-33oN along 137oE from 1984 to 2004 was 1.6±0.3 ppm/year, which was almost equal to that of the atmospheric CO₂ concentration, 1.7±0.1 ppm/year./li>

• The monthly flux for CO₂ estimated in the western subtropical North Pacific (11°N-30°N, 130°E-165°E) indicates that this region acts as a CO₂ sink during year because the absorption of atmospheric CO₂ in winter is larger than the CO₂ emission into the atmosphere in summer. The annual fluxes ranges between 0.025 and 0.075 PgC in 1996-2004 and the mean is 0.057 PgC.
  

• Based on the data archived at the WDCGG, the global mean concentration of atmospheric CH₄ in 2004 was 1,783 ppb, being more than 2.5 times as large as that in preindustry level (700 ppb).
• The growth rates of atmospheric CH₄ in 1990s were generally less than those in 1980s, but the growth rate in 1998 was globally large except in low latitudes. The growth rates decreased afterward, but the growth rates increased again corresponding to the occurrence of the 2002 /2003 El-Nino event. The mean annual growth rates in atmospheric CH₄ was 3.7 ppb/year in the last 10 years.
• The equatorial region, subtropical region and subarctic region in the western North Pacific acted as CH₄ sources in summer, 2004. The oceanic CH₄ concentration (partial pressure) were 2.17 ppm (1.99 - 2.70 ppm) averaged between 3°N-34°N along 137°E and 2.07 ppm (1.97 - 2.24 ppm) between 28°N-50°N along 165°E.

• The decreasing trends were seen in concentrations of CFC-11 and CH3CCl3, while the increases in the concentrations of CFC-12 and CFC-113 were almost ceased. These trends result from the regulation under the Montreal Protocol on Substances that Deplete the Ozone Layer after the Vienna Convention for the Protection of the Ozone Layer.

• The global concentration of N2O is gradually increasing. The mean concentration in Japan (Ryori) in 2004 was 319 ppb, which indicates 10 ppb increase from 1990.
• Based on the data archived at the WDCGG, the global mean concentration of N2O in 2004 was 318.6 ppb. The mean annual growth rate in atmospheric N2O was 0.8 ppb/year in the globe in the last 10 years.

• Based on the data archived at the WDCGG, the global mean concentration of CO in 2004 was 94 ppb, and the trend shows a gradual decrease.
• The enhanced CO concentrations from 1997 to 1998 were resulted from the large biomass-burning events that occurred in Southeast Asia and Siberia. The significant increase of CO growth rate in the Northern Hemisphere from 2002 to 2003 was possibly attributed to large forest fires due to high temperature anomaly from the El Nino event.

• A gradual increase was observed at Ryori after 1992, but this trend has become obscure since 2003. The concentrations in Yonagunijima are higher than those in Minamitorishima that is located in the same latitudes, and the deseasonalized concentrations are close to those in Ryori.
• The seasonal variation with low concentration in summer was obvious at Japanese three stations, being accounted for by summer dominating oceanic air mass around Japan with a low concentration of ozone. Ozone sonde observation showed a similar seasonal variation in the tropospheric O₃ concentration, but sporadic increases of concentration were found in summer in the lower troposphere at Tsukuba, which might be resulted from photochemical production of ozone.

• The amounts of global total ozone except in the tropics have shown decreasing trends, while they do not have shown significant decrease since 1990. The decreasing trends are most significant in high latitudes in spring. The amounts of total ozone maily decreased in 1980s.
• In 2004, the monthly means of total ozone were generally lower at Sapporo and Tsukuba in the former half of the year and were higher at Naha in the latter of the year. The monthly means at Minamitorishima were lower in the former half of the year. This is a result of a change in the atmospheric flow pattern in the stratosphere.
• The amounts of total ozone over Japan except at Naha have shown decreasing trends, while they do not have shown significant decrease since 1990. Particularly, the decreasing trend at Sapporo is most significant. The amounts of total ozone over Japan largely decreased in 1980s.
• In 2004, the monthly means of total ozone over the Syowa station from July to the middle of September were somewhat higher than those in the recent 15 years. Although the total ozone were lower than 220 m atm-cm (an index of ozone hole) from the middle of September to October, it increased with fluctuating largely in November to 300 m atm-cm in December.

• In 2004, monthly means of Elythmal dose daily accumulation were larger around the summer season at Tsukuba and Kagoshima. These higher values are estimated to be results of more frequent clear days in summer based on global solar radiation data and sunshine duration data.
• The increasing trends of the UV dose were detected in Japan since the beginning of 1990s, but decreasing trends of total ozone were not detected at the same period. It is thought that this increasing trends are attributed to changes of the weather and/or the amount of aerosols.

• In 2004, aerosol optical depth observations using sun photometers at Ryori, Minamitorishima, and Yonagunijima showed a seasonal variation with a maximum in spring. From July 16 to 23 at Minamitorishima, the aerosol optical depths were large and the ratio of small particles was estimated to increase. This dense aerosol event is considered due to the inflow of air pollutions from East Asia. Most of monthly aerosol optical depths at Minamitorishima were smaller than those at two other stations, while the particle size was estimated to be relatively large. This large particle in Minamitorishima is presumed to be a sea salt particle.
• According to the observation of vertical distribution of aerosols by the Lidar of Ryori in 2004, the scattering ratio in the troposphere was large compared with that in the stratosphere, indicating that aerosol concentration in the troposphere is generally high. The scattering ratio was large in the middle troposphere in spring and in the lower troposphere in summer.

• In 2004, the total number of days of Kosa observation was 497 days.
• In 2004, there were 5 Kosa events in Japan. From March 11 to 17, a Kosa event was observed in the large range from Kyushu to Hokkaido.

• Atmospheric turbidity observations using pyrheliometers at 14 stations in Japan showed seasonal variation with a maximum in summer due to water vapor increases and fluctuations in spring that may be resulted from mineral dust events (Kosa).
• While the total number of days of Kosa observation was larger, significant large atmospheric turbidity by Kosa did not appear during the spring 2004. Atmospheric turbidities in Nemuro were larger than usual year from June to October.
• The interannual variation showed impermanent increases after the large-scale volcanic eruptions. The atmospheric turbidity largely increased after the eruption of Mt. Pinatubo in June 1991, but it decreased gradually afterwards. After 1994, the atmospheric turbidity continued to be the low level that was almost the same value of the calm period before the eruption of Mt. El Chichon in March/April 1982.

• For precipitation chemistry, the annual mean acidity was pH 4.7 at Ryori and pH 5.5 at Minamitorishima in 2004. At Ryori, the annual mean acidities were higher than pH 5.0 during 1976-1977, and have varied with range pH 4.4~5.0 afterwards. At Minamitorishima, the annual mean acidities have been pH 5.5~5.8 since the beginning of the observation in 1996.

• In 2004, the mean concentration of floating pollutants was 4.3 pieces/100 km in the western North Pacific including the seas adjacent to Japan, increased than those in 2002 (2.8 pieces/100 km) and 2003 (2.9 pieces/100 km). In Japan Sea, the concentration increased from 3.6 pieces/100 km in 2003 to 10.8 pieces/100 km in 2004.
• In 2004, the maximum density of floating tar of 0.23 mg/m2 was observed east of Honshu in summer. Since 1984, floating tar collected in the seas adjacent to Japan and the western North Pacific has been at lower levels, compared with that before 1984.
• In 2004, the concentrations of cadmium in surface waters were high southeast of Hokkaido and north of 45°N along 165°E line (44-83 ng/kg). Since 1997, the concentrations south of 30°N have been at the low level of about 3 ng/kg. The concentrations of mercury averaged in all stations were below 5 ng/kg both in surface waters and at 1000 m depth with small regional variability, and have been at the same level since 1986 continuously.