Sensitivity analysis of high-resolution regional CO2 simulations over East Asia depending on meteorological fields and VPRM parameters

Abstract:

Since East Asia shows more CO₂ emissions than other regions, it is necessary to simulate the CO₂ concentrations in high resolution over East Asia. In this study, the Weather Research and Forecasting-Chemistry (WRF-Chem, v4.1.5) modeling system developed at the National Center for Atmospheric Research (NCAR) was used to simulate high-resolution regional CO₂ concentrations in East Asia. The experimental period is from 22 February to 31 March 2018. The experimental domain is East Asia, with a horizontal resolution of 9 km and 51 vertical levels.

Because the CO₂ concentration is affected by wind transport, the simulation performance of wind direction and speed in the model is important to simulate the CO₂ concentration accurately. By using the National Centers for Environmental Prediction (NCEP) Final analysis (FNL) and the European Center for Medium-range Weather Forecasts (ECMWF) 5th ECMWF ReAnalysis (ERA5) as the initial and boundary conditions of the model, the performance of simulating wind direction and speed over East Asia was examined.

In the WRF-Chem, the biospheric CO₂ was calculated by the Vegetation Photosynthesis and Respiration Model (VPRM). When calculating the gross ecosystem exchange (GEE) and Respiration (R) in the VPRM, some parameter values need to be provided and optimized for the experimental area. In this study, the US region parameter provided in the WRF-Chem and the parameters specified in Li et al. (2020) and Dayalu et al. (2018) were used to evaluate which parameter is appropriate in simulating CO₂ concentrations over East Asia.

By comparing with the observed surface CO₂ concentrations and the Orbiting Carbon Observatory-2 (OCO-2) XCO₂ concentrations, the WRF-Chem with NCEP FNL simulated the wind direction and speed more accurately then that with ERA5 in East Asia. In addition, the WRF-Chem simulated CO₂ concentrations closer to the observations when using the US parameter as the VPRM parameter, compared to the parameters suggested by Li et al. (2020) and Dayalu et al. (2018).

Acknowledgments

This study was supported by a National Research Foundation of Korea (NRF) grant funded by the South Korean government (Ministry of Science and ICT) (Grant 2017R1E1A1A03070968) and the Korea Meteorological Administration Research and Development Program under grant KMI2018-03712.