Presentation Information
[AAS08-P28]Long-term variation analysis of isoprene column amounts over Rikubetsu
*Tomoo Nagahama1, Isamu Morino2 (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.National Institute for Environmental Studies)
Keywords:
Isoprene,Air pollutants,FTIR,GEOS-Chem,Troposphere
Most atmospheric hydrocarbons that influence the formation of air pollutants, such as tropospheric ozone, are emitted as volatile organic compounds, with approximately one-third originating from plant-derived isoprene. Therefore, understanding the distribution and variability of both isoprene and atmospheric air pollutants is essential to air pollution research. To understand temporal variations in these atmospheric concentrations, we analyzed isoprene and other air-pollutant column amounts using monitoring data on solar absorption spectra obtained from ground-based high-resolution FTIR instruments operated jointly with the National Institute for Environmental Studies in Rikubetsu, Hokkaido. This allowed us to derive long-term temporal variations. From time-series data obtained from observations since 1995, we have found that seasonal variations, in which isoprene column amounts peak in summer, and phenomena in which isoprene column amounts suddenly increase in spring, frequently occur. To elucidate the factors driving temporal variability, we conducted long-term simulations with the GEOS-Chem chemical transport model and compared them with observations. In this study, MERRA2 reanalysis data were used for the meteorological field. Calculations were performed using GEOS-Chem version 14.6 at a global horizontal resolution of 4°×5°. The values over Rikubetsu were obtained by spatial interpolation from the instantaneous values at 00:00 UT (9:00 JST) each day. Observed isoprene column amounts from 1995 to 2023 reveal not only a summer peak but also an increase in column amount during early spring, comparable to that in summer. In contrast, model calculations show a clear winter minimum and summer maximum, with no phenomenon corresponding to the rapid increase observed in spring. Furthermore, although model calculations show interannual variability, the observed annual variability remains unclear. The presentation will show details of comparisons between model calculations and observed isoprene column amounts throughout the period in Rikubetsu and will also outline plans.