Aritaka Matsunami

FFT analysis of atmospheric trace concentration of N2O continuously monitored by gas chromatography and cross-correlation to climate parameters

Abstract To investigate the characteristics of N2O concentration, we applied several types of time series analyses such as fast Fourier transform (FFT), auto-correlation, and cross-correlation, to 2.5-year time series data of trace N2O concentration continuously monitored by gas chromatography and meteorological data, measured in an urban area of Nagoya. It was found that there is a positive correlation between atmospheric N2O concentration (ppbv) and, both steam pressure (hPa) and temperature (°C). In addition, negative and positive correlations in atmospheric pressure and in solar flux were also found, respectively. These findings suggest an enrichment of N2O through environmental steam during the summer season, particularly in urban areas. On the other hand, the correlation to wind direction shows a variation with amplitude of 7 ppbv, from the north-west to the south-east, and a seasonal variation up to 12 ppbv, from winter to summer. These results support the hypothesis that atmospheric steam controls the N2O concentration in urban areas. In addition, the correlation with wind direction suggests the existence of an emission source in the direction of seaside areas.

Recent Increase in Atmospheric Concentration of Nitrogen(I) Oxideat Ryori in Japan

Daily chromatographic investigation of the nitrogen(I) oxide content of the atmosphere at Ryori in Japan has shown a steep increase in concentration during the 1990s. The incremental increase was 5–9 ppbv, compared with the world-wide estimate for 1975–1985 of 1 ppbv.