Spatial distribution and occurrence probability of regional new particle formation events in eastern China

Xiaojing Shen,Huaigang Zhou,Yangmei Zhang,Lu Zhang,Niku Kivekäs,Adam Kristensson,Junying Sun,Xiaoye Zhang,Qianli Ma,Ruxia Fan,Xuefei Qi

doi:10.5194/acp-18-587-2018

Abstract

Abstract. In this work, the spatial extent of new particle formation (NPF) events and the relative probability of observing particles originating from different spatial origins around three rural sites in eastern China were investigated using the NanoMap method, using particle number size distribution (PNSD) data and air mass back trajectories. The length of the datasets used were 7, 1.5, and 3 years at rural sites Shangdianzi (SDZ) in the North China Plain (NCP), Mt. Tai (TS) in central eastern China, and Lin'an (LAN) in the Yangtze River Delta region in eastern China, respectively. Regional NPF events were observed to occur with the horizontal extent larger than 500 km at SDZ and TS, favoured by the fast transport of northwesterly air masses. At LAN, however, the spatial footprint of NPF events was mostly observed around the site within 100–200 km. Difference in the horizontal spatial distribution of new particle source areas at different sites was connected to typical meteorological conditions at the sites. Consecutive large-scale regional NPF events were observed at SDZ and TS simultaneously and were associated with a high surface pressure system dominating over this area. Simultaneous NPF events at SDZ and LAN were seldom observed. At SDZ the polluted air masses arriving over the NCP were associated with higher particle growth rate (GR) and new particle formation rate (J) than air masses from Inner Mongolia (IM). At TS the same phenomenon was observed for J, but GR was somewhat lower in air masses arriving over the NCP compared to those arriving from IM. The capability of NanoMap to capture the NPF occurrence probability depends on the length of the dataset of PNSD measurement but also on topography around the measurement site and typical air mass advection speed during NPF events. Thus the long-term measurements of PNSD in the planetary boundary layer are necessary in the further study of spatial extent and the probability of NPF events. The spatial extent, relative probability of occurrence, and typical evolution of PNSD during NPF events presented in this study provide valuable information to further understand the climate and air quality effects of new particle formation.

Highlights

Atmospheric new particle formation (NPF) from gaseous precursors is a major source of particles in the atmosphere in many regions worldwide (Kulmala et al, 2013)
With NanoMap, we evaluated the upwind locations where the particle formation took place on the NPF event days observed at the sites, and the relative probability of observable NPF events taking place around the sites was calculated
We focused on regional NPF events, in which the nucleated particles could grow to the size of potential cloud condensation nuclei (CCN)

Summary

Introduction

Atmospheric new particle formation (NPF) from gaseous precursors is a major source of particles in the atmosphere in many regions worldwide (Kulmala et al, 2013). X. Shen et al.: Spatial distribution and occurrence probability climate (Kerminen et al, 2012) and contributing to particle mass enhancement even in polluted regions for some NPF cases governed by meteorological conditions, with a minor contribution from primary emissions and regional transport (Guo et al, 2014). The continental regional NPF events can occur over a large spatial scale (Kulmala et al, 2004). The spatial scale of NPF events or the horizontal extent of the air mass in which NPF events occur can help to identify where the nucleation-mode particles possibly come from. The properties of NPF events as observed at a stationary measurement site are affected by processes and conditions present hundreds of kilometres upwind of the site (Kivekäs et al, 2016)

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Conclusion