Sensitivity Analysis of Chemical Mechanisms in the WRF-Chem Model in Reconstructing Aerosol Concentrations and Optical Properties in the Tibetan Plateau

Abstract

To investigate the effect of gas-phase chemical schemes and aerosol mechanisms on the reconstruction of the concentrations and optical properties of aerosols in the Tibetan Plateau (TP) and adjacent regions, two simulation experiments using the mesoscale Weather Research and Forecasting (WRF) meteorological model with the chemistry module (WRF-Chem) were performed in 2013. The RADM2 gas-phase chemical mechanism and the MADE/SORGAM aerosol scheme were selected in the first configuration, whereas the CBMZ gas and MOSAIC aerosol reaction schemes were included in the second simulation. The comparison demonstrated that chemical mechanisms play a key role in affecting the evolution of gas-phase precursors and aerosol processes. Specifically, compared with RADM2, CBMZ revealed lower O 3 and higher NO 2 surface concentrations, because of more efficient O 3 -NO titration, and higher HNO 3 concentrations owing to more effective NO 2 + OH reaction. SO 2 could easily form particulate sulfate through cloud oxidation in RADM2. The MADE/SORGAM module presented higher surface PM 2.5 and PM 10 concentrations than did the MOSAIC module over the TP and in surrounding regions, because of the difference in aerosol compounds and the distribution of computed aerosol concentrations between modes and bins. The aerosol optical depth at 550 nm indicated a potential correlation with surface secondary inorganic aerosols concentrations. Higher surface sulfate and nitrate concentrations appeared to determine higher AOD values in MADE/SORGAM than in MOSAIC. Finally, the comparison with observations suggested that, the simulation performed using the CBMZ gas-phase chemical mechanism and MOSAIC aerosol module could be suitable for the efficient reconstruction of aerosols and their optical depth over the TP.

MICS-Asia III: multi-model comparison and evaluation of aerosol over East Asia

“…As one of the major components of primary aerosols, sea-salt aerosols contributes to 20 %-40 % of secondary inorganic aerosols (SIAs) over coastal regions Yang et al, 2016). These particles can provide surface areas for condensation and reaction of nitrogen and sulfur, making the simulated concentrations of SIAs more accurate (Kelly et al, 2010;Im, 2013).…”

Ground-based vertical profile observations of atmospheric composition on the Tibetan Plateau (2017–2019)

“…Previously, we have demonstrated that using the AMF calculated with MAX-DOAS-measured NO 2 vertical profiles could remarkably improve the accuracy of retrievals of NO 2 column densities (VCDs) Xing et al, 2017). On top of that, due to complex terrain and weather conditions, uncertainties in emission inventories, and imperfect model parameterization, chemical transport models face difficulties in capturing the vertical structures of atmospheric composition on the TP (Yang et al, 2018b), the uncertainties of which could be constrained through the assimilation of observations from this dataset. Section 2 describes the observation site, MAX-DOAS instrument and retrieval algorithms.…”

Long-term trends of ambient nitrate (NO<sub>3</sub><sup>−</sup>) concentrations across China based on ensemble machine-learning models

“…Wang et al, 2017). Tibetan Plateau generally showed the clean air quality due to the unique landform and scarce industrial activity (Yang et al, 2018). In addition, it was interesting to note that the Altai region and Taklimakan desert in Xinjiang autonomous region also showed some NO3hotspots, though these regions were often believed to be the remote region.…”