Abstract
Atmospheric ammonia (NH3) plays an important role in the formation of secondary inorganic aerosols, the neutralization of acid rain, and the deposition to ecosystems, but has not been well understood yet, especially over East Asia. Based on the GEOS-Chem model results, the IASI satellite retrievals, the in-site surface observations of a nationwide filter pack (FP) network over Japan and the long-term high resolution online NH3 measurements at Fukuoka of western Japan, the spatio-temporal distributions of atmospheric NH3 over East Asia was analyzed comprehensively. A significant seasonal variation with a summer peak was found in all datasets. Comparison between the satellite retrievals and model simulations indicated that the IASI NH3 vertical column density (VCD) showed good consistency with GEOS-Chem results over North and central China, but had large differences over South China due to the effect of clouds. Over the Japan area, GEOS-Chem simulated NH3 concentrations successfully reproduced the spatio-temporal variations compared with in-situ observations, while IASI NH3 VCD retrievals were below or near the detection limit and difficult to obtain a reasonable correlation for with model results. The comprehensive analysis indicated that there were still some differences among different datasets, and more in-situ observations, improved satellite retrievals, and high-resolution model simulations with more accurate emissions are necessary for better understanding the atmospheric NH3 over East Asia.
Highlights
Atmospheric ammonia (NH3 ) is a highly reactive gas and plays an important role in atmospheric chemical processes by reacting rapidly with sulfuric acid (H2 SO4 ) and nitric acid (HNO3 ) formed from sulfur dioxide (SO2 ) and nitrogen oxides (NOx ) and producing ammonium (NH4 + ), which is the most important ambient cation [1]
This indicated that the impact of planetary boundary layer height (PBLH) on the seasonal variation of surface NH3 concentration was much smaller compared to the impacts of emissions and gas-aerosol partitioning
Atmospheric ammonia plays an important role in the formation of secondary inorganic aerosols, the neutralization of acid rain, and the deposition to ecosystems, but has not been well understood yet, especially over East Asia
Summary
Atmospheric ammonia (NH3 ) is a highly reactive gas and plays an important role in atmospheric chemical processes by reacting rapidly with sulfuric acid (H2 SO4 ) and nitric acid (HNO3 ) formed from sulfur dioxide (SO2 ) and nitrogen oxides (NOx ) and producing ammonium (NH4 + ), which is the most important ambient cation [1]. Atmosphere 2020, 11, 900 particles or PM2.5 , especially over China, where there are large amounts of anthropogenic emissions for NH3 , SO2 , and NOx. The modelling study indicated the control of 20% NH3 emission can affect 5–11%. Via comparison of satellite retrievals and simulations using a global atmospheric chemistry transport model, it was indicated that NH3 emissions could have been significantly underestimated in the Northern Hemisphere [15]. Since the satellite retrievals may suffer large relative errors, especially in areas with low VCD, detailed evaluations are necessary, especially over East Asia where the studies are limited. In addition to the measurement of NH3 , chemical transport models (CTMs) are useful tools for studying the sources and sinks of NH3 , and the processes controlling its levels in the atmosphere. North China, more evaluations over other areas of East Asia and comparisons with satellite NH3 retrievals are necessary.
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