The results of observations and analyses made by the JMA until the end of year 2006 with regard to the atmospheric and marine greenhouse gases, the ozone layer, ultraviolet radiation, atmospheric turbidity, precipitation and dry deposition, and marine pollution are as follows.
Carbon Dioxide (CO2)
|
Yearly mean concentration in 2006
(ppm) |
The difference from previous year's concentration
(ppm) |
| Japan |
Ryori |
385.3 |
+2.8 |
| Minamitorishima |
383.7 |
+3.0 |
| Yonagunijima |
384.6 |
+2.1 |
| Global |
381.2 |
+2.0 |
| Ocean |
The area along 137°E
in winter
（7～33°N）
|
Mean concentration in 2006 (ppm) |
384.9(atmosphere)
342.0（seawater） |
| The difference from previous year's concentration (ppm) |
+3.6(atmosphere)
+2.3（seawater） |
| Mean annual growth rate（ppm/year, 1984～） |
1.7（atmosphere）
1.6（seawater） |
| Subtropical region in the western North Pacific
（130～165°E, 11～30°N）
|
Ocean net flux in 2006（Estimation, PgC/yr） |
-0.064 |
| The difference from previous year’s flux （Estimation, PgC/yr） |
0.002 |
| Equatorial Pacific（135°E～95°W, 10°S～5°N） |
Ocean net flux in 2006（Estimation, PgC/yr） |
0.52 |
| The difference from previous year’s flux （Estimation, PgC/yr） |
-0.03 |
- The all growth rates in three Japanese stations exceeded 2 ppm/year in 2006 as well as 2005. In general, CO2 growth rates are large during a El Niño event, however, the El Niño event did not occur in 2005～2006. The large growth rates in 2005 and 2006 may be ascribed to increase of CO2 emission from the biosphere due to record-breaking high temperature (the highest and the third highest record in the Northern Hemisphere in 2005 and in 2006, respectively) during 2005-2006.
- The Global mean concentration of CO2 in 2006 was 381.2 ppm from archive data in the World Data Centre for Greenhouse Gases, which has increased by 36% compared with mean concentration (280 ppm) before the industrial age (1750).
- Growth rates in atmospheric CO2 for each 30° latitude zone 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-Niño event in 1997/1998 is considered to cause this increase of growth rates. Growth rates in atmospheric CO2 in the middle and high Northern latitudes had a peak exceeding 3 ppm/year from 2002 to 2003 corresponding to the occurrence of the 2002/2003 El-Niño event. However, although the La-Niña event occurred during 2005-2006, the large growth rates were seen. The mean annual growth rates in atmospheric CO2 was 1.93 ppm/year in the last 10 years, which was larger than those in 1990s (about 1.5 ppm/year).
- The differences in the CO2 partial pressure between the sea water and the air（⊿pCO2） along 137°E were lower between 24° and 27°N in January - February and between 10° and 19°N in July 2006, and were higher at 25°N in July 2006. The oceanic CO2 concentrations in the equatorial Pacific (135°E～95°W, 10°S～5°N) were approximately 45～80 ppm hihger than atmospheric CO2 at 158～165°E in February, under the influence of the La-Niña that occurred from autumn in 2005 through spring in 2006. In July in 2006, the oceanic CO2 concentrations were nearly equal to that in the atmosphere in the almost all observation areas.
- The mean annual growth rate of the oceanic CO2 concentration averaged between 7°N-33°N along 137°E from 1984 to 2006 was 1.6±0.3 ppm/year, which was almost equal to those in the atmospheric CO2 concentration (1.7±0.1 ppm/year).
Methane (CH4)
|
Yearly mean concentration in 2006 (ppb) |
The difference from previous year's concentration
(ppb) |
| Japan |
Ryori |
1,859 |
+1 |
| Minamitorishima |
1,805 |
+6 |
| Yonagunijima |
1,824 |
+1 |
| Global |
1,782 |
-1 |
- Based on the data archived at the WDCGG, the global mean concentration of atmospheric CH4 in 2006 was 1,782 ppb, which has increased by 155% compared with mean concentration (700 ppb) before the industrial age (1750).
- 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 in 2002/2003 corresponding to the occurrence of the 2002 /2003 El-Niño event. The mean annual growth rates in atmospheric CH4 was 2.4 ppb/year in the last 10 years.
- In the western North Pacific, the subtropical and the equatorial region in January - February 2006 and the subarctic and subtropical region in June - July 2006 acted as CH4 sources. The CH4 concentrations in the atmosphere were about 1.8 ppm (1.72 - 1.89 ppm) and those in the ocean were 1.87 - 2.93 ppm.
Halocarbons
|
Yearly mean concentration in 2006 (ppt) |
| Ryori |
CFC-11 |
253 |
| CFC-12 |
544 |
| CFC-113 |
79 |
- The decreasing trends of CFC-11 and CH3CCl3 were seen in Japan (Ryori), while the increases 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.
Nitrous Oxide (N2O)
|
Yearly mean concentration in 2006 (ppb) |
| Ryori |
321.1 |
| Global |
320.1 |
- The global mean concentration of N2O is gradually increasing. The mean concentration in Japan (Ryori) in 2006 was 321.1 ppb. The mean annual growth rate in the last 10 years was 0.7 ppb/year.
- Based on the data archived at the WDCGG, the global mean concentration of N2O in 2006 was 320.1 ppb. The mean annual growth rate in atmospheric N2O was 0.76 ppb/year in the globe in the last 10 years.
Carbon Monoxide (CO)
|
Yearly mean concentration in 2006 (ppb) |
The difference from previous year's concentration (ppb) |
| Japan |
Ryori |
165 |
+7 |
| Minamitorishima |
- |
- |
| Yonagunijima |
159 |
+1 |
| Global |
about 94 |
-3 |
(Data at Minamitorishima is missing due to a trouble of instrument.）
- Based on the data archived at the WDCGG, the global mean concentration of CO in 2006 was about 94 ppb.
- 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 Niño event.
Tropospheric Ozone (O3)
|
Yearly mean concentration in 2006 (ppb) |
The difference from previous year's concentration (ppb) |
| Japan |
Ryori |
39 |
0 |
| Minamitorishima |
30 |
+1 |
| Yonagunijima |
39 |
+3 |
- A gradual increase of O3 concentration has been observed at Ryori since 1990.
- 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.
Ozone Layer
- In Tsukuba and Naha, monthly mean values were higher than normal from August to November in 2006. Especially in November, the highest monthly values in the same month since the beginning of observation were observed at both stations. In Tsukuba, the monthly value in April was also record-breaking high for the said month. Yearly variation of the total ozone over Japan is considered to be caused by the atmospheric flow fluctuations including QBO..
- The total ozone over Japan decreased mainly in the 1980s. Since the mid-1990s, although the total ozone varies year by year, no significant trends or slight increasing trends have appeared in observations.
- The ozone hole in 2006 developed to the highest levels in both its area and ozone mass deficit. The maximum ozone hole area (29,290,000 km2), which was observed on 24 September, was the second largest on record. The ozone hole size was kept largest level from the late September through November. It shrank rapidly in December and subsequently disappeared on 17 December. The total ozone observation data at Syowa station in 2006 showed far less than 220 m atm-cm from the late August through November, which is the historical lowest level for this time of the year.
- The decreasing trends are larger with increasing latitudes, while the statistically significant decreasing trends are shown in every latitudinal zone. Decreasing trends are evident in springtime in both hemispheres.
Ultraviolet Radiation
- At Sapporo, the monthly means were almost the normal or lower than the normal in the former half of the year and higher than the normal in the latter half. At Tsukuba, the monthly means were almost the normal throughout the year except in April and June when the monthly means were lower than the normal. At Naha, the monthly means were almost the normal or lower than the normal throughout the year. These observation results may be reflected mainly by weather conditions at each station.
- Increasing trends are seen in erythemal UV radiation data at all stations in Japan since the beginning of their observations in the early 1990s. Because decreasing trends are not seen in the total ozone in the same period, the cause of the above increasing trends in erythemal UV radiation may be attributable to the trends of aerosol overhead and weather.
Aerosols
- In 2006, aerosol optical depth observations using sun photometers at Ryori, Minamitorishima, and Yonagunijima showed a seasonal variation with a maximum in spring as usual. The monthly mean aerosol optical depth in April, 2006 in Ryori recorded the second largest value followed by the largest value in May, 2003. In Minamitorishima, the observation was paused in September, 2006 because of the typhoon 0612 “Ioke”.
- According to the observation of vertical distribution of aerosols by the Lidar of Ryori in 2006, 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. For the monthly mean scattering ratio, the upper layer in the troposhere shows that the appearance of the maximum tends to delay compareted with the lower layer.
Kosa (Aeolian dust)
- In 2006, the total number of days of Kosa observation was 606 day.
- From April 24 to 27 in 2006, a Kosa event was observed in the large areas from Nansei islands to Hokkaido district.
Atmospheric turbidity
- 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 aeolian dust events (Kosa).
- The Kosa event occurred relatively frequent in 2006 but the monthly mean atmospheric turbidity coeficients were almost normal.
- 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 1995, the atmospheric turbidity further falled to the level of before the eruption of Mt. Agung in February/May 1963.
Precipitation and Dry Deposition
- For precipitation chemistry, the annual mean acidity was pH 4.8 at Ryori and pH 5.5 at Minamitorishima in 2006. 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 acidity had been pH 5.5~5.8 since the beginning of the observation in 1996, but it has lagely decreased in these years.
Marine Pollution
- In 2006, the floating pollutants in the western North Pacific were an average of 5.4pieces /100km, and it was similar to 5.2pieces /100km in 2005.
- In 2006, small amount of floating tar about 0.1mg/m2 was collected at the Sea of Japan in spring and summer. Floating tar collected in the western North Pacific after 1996 has been seldom.
- In 2006, the concentrations of cadmium in surface waters were high to the southeast of Hokkaido (15-79 ng/kg). In 2006, the mean concentration of cadmium in surface waters south of 30°N was 1.6 ng/kg, which has been almost at the same level since 1997. The concentrations of mercury averaged in all stations were 3.1 ng/kg in surface waters and 2.6 ng/kg at 1000 m depth, which have been the same level since 1986.
