EGU2020-12459
https://doi.org/10.5194/egusphere-egu2020-12459
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field

Xinghong Cheng
Xinghong Cheng
  • Chinese Academy of Meteorological Sciences, Beijing, China (cxingh@cma.gov.cn)

We carried out 14 days of Car MAX-DOAS experiments on the 6th Ring Rd of Beijing in January, September and October, 2014. The tropospheric vertical column densities (VCD) of NO2 are retrieved and used to estimate the emissions of NOx. The offline LAPS-WRF-CMAQ model system is used to simulate wind fields by assimilation of observational data and calculate the NO2 to NOx concentration ratios. The NOX emissions in Beijing for different seasons derived from Car MAX-DOAS measurements are compared with the multi-resolution emission inventory in China for 2012 (MEIC 2012), and impacts of wind field on estimated emissions and its uncertainties are also investigated. Results show that the NO2 VCD is higher in January than other two months and it is typically larger at the southern parts of the 6th Ring Road than the northern parts of it. Wind field has obvious impacts on the spatial distribution of NO2 VCD, and the mean NO2 VCD with south wind at most sampling points along the 6th Ring Rd is higher than north wind. The journey-to-journey variation pattern of estimated NOX emissions rates (ENOX) is consistent with that of the NO2 VCD, and ENOX is mainly determined by the NO2 VCD. In addition, the journey-to-journey ENOX in the same month is different and it is affected by wind speed, the ratio of NO2 and NOx concentration and the decay rate of NOX from the emission sources to measured positions under different meteorological condition. The ENOX ranges between 6.46×1025 and 50.05×1025 molec s-1. The averaged ENOX during every journey in January, September and October are respectively 35.87×1025, 20.34×1025, 8.96×1025 molec s-1. The estimated ENOX after removing the simulated error of wind speed and observed deviation of NO2 VCD are found to be mostly closer to the MEIC 2012, but sometimes ENOX is lower or higher and it indicates that the MEIC 2012 might be overestimate or underestimate the true emissions. The estimated ENOX on January 27 and September 19 are obviously higher than other journeys in the same month because the mean NO2 VCD and Leighton ratio during these two periods are larger, and corresponding wind speeds are smaller. Additionally, because south wind may affect the spatial distribution of mean NO2 VCD in Beijing which is downwind of south-central regions of Hebei province with high source emission rates, the uncertainty of the estimated ENOX with south wind will be increased.

How to cite: Cheng, X.: Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12459, https://doi.org/10.5194/egusphere-egu2020-12459, 2020