Simulation of CO2 concentration over east Asia using the regional transport model WRF- CO2

Abstract

The Weather Research and Forecasting (WRF) model is used for regional transport simulations of atmospheric carbon dioxide (referred to as WRF-CO2) for the East Asia region at the horizontal resolution of 27 × 27 km. The domain extends from 18°N to 51°N in latitude and 101°E to 165°E in longitude, including the islands of Japan, South Korea, North Korea and a part of China. The simulation period is limited to the year 2002. To understand the role of surface fluxes and transport, we have simulated atmospheric CO2 using 5 different CO2 fluxes from ocean, fossil fuel and terrestrial biospheres at various horizontal resolutions, and at hourly to monthly time intervals. The model simulations are compared with observed time series at 9 stations, which are located under different ecological and climate conditions. The model simulations are evaluated at different seasonal, synoptic and diurnal time scales for CO2 and meteorological parameters, such as air temperature, relative humidity, wind speed and direction. The performance of WRF-CO2 model is found to be satisfactory in all aspects when compared to global model simulated results obtained under the TransCom (Transport Model Intercomparison Project) continuous experiment. The WRF-CO2 model is shown to have the ability to resolve distinct concentration variations, both diurnal and synoptic, at two closely spaced stations within 25 km. The diurnal cycles of terrestrial biospheric fluxes and the planetary boundary layer are found to be most dominant controls for CO2 diurnal variations, whereas the surface fluxes horizontal distributions and wind directions are identified as the dominant controls for CO2 synoptic variations. Further increase in horizontal resolution of biospheric fluxes and meteorology in WRF-CO2 simulation is required for improving the model-observation agreement. © 2012, Meteorological Society of Japan.