[A-CG37] Global Carbon Cycle Observation and Analysis

[ACG37-03] CO₂ simulation over Kanto region using WRF-GHG high-resolution model

*Jagat Bisht¹, Masahiro Yamaguchi¹, Masayuki Takigawa¹, Prabir Patra¹, Yugo Kanaya¹ (1.Japan Agency for Marine-Earth Science and Technology )

Keywords:WRF-GHG, CO2, NO2

Carbon dioxide (CO₂) is a well-mixed and major greenhouse gas (GHG) in the Earth’s atmosphere which consists of both anthropogenic and natural sources. The high-resolution modeling frameworks better represent the topographic complexity, synoptic weather condition, and sub-grid scale transport that affect atmospheric CO₂ distribution. This study simulates CO₂ using Weather Research and Forecasting coupled with GHG modules over the Kanto region in Japan with a 1 km spatial resolution using a 4-level two-way nested setting starting from a 27-km resolution (27 km, 9 km, 3 km, and 1 km). We compared the WRF-GHG simulation results with hourly in-situ observations at Kisai and Mt. Dodaira in Saitama Prefecture, and found reasonable agreement between model simulations and observations (correlation coefficient > 0.50). Our analysis suggests the anthropogenic CO₂ emission dominance over the in-situ observations sites in the Kanto region, particularly in the winter months. We have also shown the NO₂ simulation from WRF-chem for short-lived species with a similar model configuration as our WRF-GHG simulation. NO₂ has a lifetime on the order of hours which co-emits with CO₂ when fossil fuels are combusted at high temperatures. Covariation analysis of NO₂ and CO₂ is suitable to identify freshly emitted CO₂. We found a very strong correlation (correlation coefficient > 0.75) between observed CO₂ and NO₂, and also between observed CO₂ and simulated NO₂ concentrations. The lower correlation between model and observed CO₂, compared to observed CO₂ and NO₂, suggests that the sources of anthropogenic CO₂ require improvements.

Acknowledgements
We thank the Center for Environmental Science in Saitama for collecting and sharing continuous CO₂ measurements via WDCGG. The NO2 data are from the AEROS (Atmospheric Environmental Regional Observation System) of Ministry of the Environment of Japan shared via NIES (National Institute for Environmental studies).