Abstract
Abstract. In this study, NO2 columns from the US EPA Models-3/CMAQ model simulations carried out using the 2001 ACE-ASIA (Asia Pacific Regional Aerosol Characterization Experiment) emission inventory over East Asia were compared with the GOME-derived NO2 columns. There were large discrepancies between the CMAQ-predicted and GOME-derived NO2 columns in the fall and winter seasons. In particular, while the CMAQ-predicted NO2 columns produced larger values than the GOME-derived NO2 columns over South Korea for all four seasons, the CMAQ-predicted NO2 columns produced smaller values than the GOME-derived NO2 columns over North China for all seasons with the exception of summer (summer anomaly). It is believed that there might be some error in the NOx emission estimates as well as uncertainty in the NOx chemical loss rates over North China and South Korea. Regarding the latter, this study further focused on the biogenic VOC (BVOC) emissions that were strongly coupled with NOx chemistry during summer in East Asia. This study also investigated whether the CMAQ-modeled NO2/NOx ratios with the possibly overestimated isoprene emissions were higher than those with reduced isoprene emissions. Although changes in both the NOx chemical loss rates and NO2/NOx ratios from CMAQ-modeling with the different isoprene emissions affected the CMAQ-modeled NO2 levels, the effects were found to be limited, mainly due to the low absolute levels of NO2 in summer. Seasonal variations of the NOx emission fluxes over East Asia were further investigated by a set of sensitivity runs of the CMAQ model. Although the results still exhibited the summer anomaly possibly due to the uncertainties in both NOx-related chemistry in the CMAQ model and the GOME measurements, it is believed that consideration of both the seasonal variations in NOx emissions and the correct BVOC emissions in East Asia are critical. Overall, it is estimated that the NOx emissions are underestimated by ~57.3% in North China and overestimated by ~46.1% in South Korea over an entire year. In order to confirm the uncertainty in NOx emissions, the NOx emissions over South Korea and China were further investigated using the ACE-ASIA, REAS (Regional Emission inventory in ASia), and CAPSS (Clean Air Policy Support System) emission inventories. The comparison between the CMAQ-calculated and GOME-derived NO2 columns indicated that both the ACE-ASIA and REAS inventories have some uncertainty in NOx emissions over North China and South Korea, which can also lead to some errors in modeling the formation of ozone and secondary aerosols in South Korea and North China.
Highlights
IntroductionRecent studies using satellite measurements reported that NO2 columns (or NO2 vertical column density, VCD) have increased significantly in East Asia since 2001 (Richter et al, 2005; van der A et al, 2006; He et al, 2007)
Nitrogen oxides (NOx≡NO+NO2) emitted from anthropogenic sources, such as fossil fuel combustion and biomass burning, as well as natural sources, such as lightning and microbiological processes in soil, play important roles in Published by Copernicus Publications on behalf of the European Geosciences Union.K
In order to properly determine the contributions from North China emissions to air quality of South Korea, it is important to evaluate the accuracy of the NOx emission inventories over both regions and understand NOx-related gas-phase chemistry
Summary
Recent studies using satellite measurements reported that NO2 columns (or NO2 vertical column density, VCD) have increased significantly in East Asia since 2001 (Richter et al, 2005; van der A et al, 2006; He et al, 2007) Such increases in NOx emissions over China were confirmed partly by a bottom-up emission inventory study (Zhang et al, 2007). In order to test the accuracy of NOx emissions, several studies were carried out over East Asia comparing the 3-D model-predicted NO2 columns with satellite-derived NO2 columns (Kunhikrishnan et al, 2004; Ma et al, 2006; van Noije et al, 2006; Uno et al, 2007). The latter (biogenic emissions) could be important because they can control the levels of OH radicals, which can affect the NOx chemical loss rates
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
