Sensitivities of NO<sub>x</sub> transformation and the effects on surface ozone and nitrate

Abstract

Abstract. As precursors to tropospheric ozone and nitrate, nitrogen oxide (NO x ) in the present atmosphere and its transformation in response to emission and climate perturbations are studied by using the CAM-Chem model and air quality measurements from the National Emissions Inventory (NEI), Clean Air Status and Trends Network (CASTNET), and Environmental Protection Agency Air Quality System (EPA AQS). It is found that NO x transformations in present atmospheric conditions show different sensitivities over industrial and non-industrial regions. As a result, the surface ozone and nitrate formations can be divided into several regimes associated with the dominant emission types and relative levels of NO x and volatile organic compounds (VOC). Ozone production in industrial regions (the main NO x emission source areas) increases in warmer conditions and slightly decreases following an increase in NO x emissions due to NO x titration, which is opposite to the response in non-industrial regions. The ozone decrease following a temperature increase in non-industrial regions indicates that ozone production in regions that lack NO x emission sources may be sensitive to NO x transformation in remote source regions. The increase in NO 2 from NO x titration over industrial regions results in an increase rate of total nitrate that remains higher than the increase rate of NO x emissions. The presented findings indicate that a change in the ozone concentration is more directly affected by changes in climate and precursor emissions, while a change in the nitrate concentration is affected by local ozone production types and their seasonal transfer. The sensitivity to temperature perturbations shows that a warmer climate accelerates the decomposition of odd nitrogen (NO y ) during the night. As a result, the transformation rate of NO x to nitrate decreases. Examinations of the historical emissions and air quality records of a typical NO xlimited area, such as Atlanta and a VOC-limited area, such as Los Angeles further confirm the conclusions drawn from the modeling experiments.

Extensive spatiotemporal analyses of surface ozone and related meteorological variables in South Korea for the period 1999–2010

“…In the model experiments by Lin et al (2008), both averaged O 3 concentrations and frequencies of high O 3 episodes were predicted to increase in future over the United States and East Asia. Recent global climate-chemistry model experiments by Lei and Wang (2014) also implied the future O 3 increases in industrial regions due to more O 3 production by photochemical reactions and less O 3 removal by nocturnal odd nitrogen (NO y ) chemistry in warmer conditions.…”

Modeling tropospheric ozone and particulate matter in Tunis, Tunisia using generalized additive model

“…In fact, a minimum of O 3 concentration is observed at around 8:00 and a maximum at around 19:00 when traffic is an important source of emissions and the vertical mixing is reduced. Influenced by transport of O 3 from other regions and local NO X concentrations at night, the increase of the surface O 3 concentration during the night time was larger than that during the daytime (Lei and Wang, 2014). Day of the week at Gazela and Mannouba (Table 3) was found to have little influence on ozone, (F=3.81, F=3.27.…”

Sensitivities of NO<sub>x</sub> transformation and the effects on surface ozone and nitrate

“…Emissions of ozone precursors are based on the present-day inventory (for the year 2000) as described by Emmons et al (2010). The meteorology data that drive the CAM-Chem model are derived from the National Centers for Environmental Prediction (NCEP) reanalysis II 1 • × 1 • fields from 1999 to 2002(Kanamitsu et al, 2002. The sixhour interval data are re-gridded to a horizontal resolution of 1.9 • latitude by 2.5 • longitude and 26 vertical levels extending up to 0.01 hPa.…”