HR: 0800h
AN: A51D-0742    [Abstracts]
TI: Latitudinal Patterns of N2O Concentration Variations Over The Northern And Western Pacific For 1992-2006
AU: * Ishijima, K
EM: ishijima@jamstec.go.jp
AF: Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan, 3173-25 Showamachi, Kanazawa-ku, Yokohama, Kan 236-0001, Japan
AU: Nakazawa, T
EM: nakazawa@mail.tains.tohoku.ac.jp
AF: Center for Atmospheric and Oceanic Studies Graduate School of Science, Tohoku University, Aoba, Aramaki-aza, Aoba-ku, Sendai, Miy 980-8578, Japan
AU: Aoki, S
EM: aoki@mail.tains.tohoku.ac.jp
AF: Center for Atmospheric and Oceanic Studies Graduate School of Science, Tohoku University, Aoba, Aramaki-aza, Aoba-ku, Sendai, Miy 980-8578, Japan
AU: Patra, P K
EM: prabir@jamstec.go.jp
AF: Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan, 3173-25 Showamachi, Kanazawa-ku, Yokohama, Kan 236-0001, Japan
AU: Takigawa, M
EM: takigawa@jamstec.go.jp
AF: Frontier Research Center for Global Change/JAMSTEC, Yokohama, Japan, 3173-25 Showamachi, Kanazawa-ku, Yokohama, Kan 236-0001, Japan
AB: Atmospheric N₂O concentration over the Pacific have been observed by Tohoku university, using commercial ships sailing between Japan and North America and between Japan and Australia or New Zealand since 1991. The N₂O concentration showed secular increasing trend and interannual variation at all sampling positions in the Pacific observation, while the seasonal cycle was detected only at northern high latitudes. Longitudinal distributions of the annual mean N₂O concentration over the northern pacific were almost flat within 0.2 ppbv, reflecting the atmosphere well-mixed by the westerly and longitudinally even distribution of N₂O sources around the northern Pacific. The latitudinal distribution showed clear north- south gradient, in which the northern hemispheric concentration is higher by about 0.8 ppbv, implying the northern hemispheric N₂O emission is stronger mainly because of land emissions. Some characteristic patterns caused by surface N₂O emissions and by the atmospheric transport in this observation area were seen in the latitudinal distribution. One is a maximum value at 30?N due to local N₂O emissions, and the other steep concentration gradient from the equator to 20° S due to SPCZ, which seems to block smooth N₂O transport form the north to south hemisphere. The N₂O growth rate showed the interannual variation with period of about 3 years and its maximum around 1999-2000 at most positions. The growth rates also tended to present their phase propagations from west to east in the northern Pacific, and from low to high latitudes in the western Pacific. In order to investigate causes for the interannual variations in terms of surface N₂O emissions, correlation factors between climate factors and the N₂O growth rate were calculated, for the northern and southern hemisphere. As the results, soil water showed the highest correlation in each hemisphere. That is possibly thought to reflect that N₂O emission from soils is the primary factor for the interannual variation of atmospheric N₂O concentration in this observation area. The MEI (multivariate ENSO index) showed the almost complete opposite phase with the N₂O growth rate for both hemispheres, which were almost comparable with soil water in terms of the correction factor value. It is indicated that ENSO-related changes in oceanic emission and atmospheric transport also have important roles for atmospheric N₂O concentration variations in this Pacific area. These observation results were also considered, by using AGCM (Atmospheric General Circulation Model) nudged with meteorological data. Some kinds of surface flux data were used to see effects of local N₂O emissions. However, main purpose of the model simulations is to examine effects of the atmospheric transport on the N₂O concentration for long term, in order to compensate analyses of the emission effects above. We will present these model results, together with the observation results.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting