Effect of atmospheric conditions and VPRM parameters on high-resolution regional CO2 simulations over East Asia

Abstract

Atmospheric CO2 concentrations are largely affected by the surface CO2 flux and atmospheric wind. To estimate atmospheric CO2 concentrations over East Asia, the effects of atmospheric conditions and the parameters of Vegetation Photosynthesis and Respiration Model (VPRM) that simulates biogenic CO2 concentrations were evaluated using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) model. The VPRM in WRF-Chem requires parameter optimization for the experimental period and region. Total six experiments with two atmospheric fields (final analysis; FNL and fifth generation of European Centre for Medium-range Weather Forecasts atmospheric reanalysis; ERA5) and three VPRM parameter tables (US, Li, and Dayalu) were conducted to investigate the appropriate atmospheric field and VPRM parameter table for East Asia. For validation, two types of wind observations (SYNOP and SONDE) and two types of CO2 observations (surface CO2 observations and OCO-2 XCO2 observations) were used. The experiments using FNL showed a lower RMSE for surface winds, whereas those using ERA5 showed a lower RMSE for upper-air winds. On average, the surface wind RMSE in the experiments using FNL was lower than that using ERA5. With respect to surface CO2 observations, the experiments using the Li table showed relatively lower RMSEs compared to those using other tables. With respect to OCO-2 XCO2 observations, the Li table with FNL showed lower RMSEs than other combinations. Overall, the combination of the Li table and FNL was the most appropriate for simulating CO2 concentrations in East Asia using WRF-Chem with VPRM.