Influence of vegetation on occurrence and time distributions of regional new aerosol particle formation and growth

Abstract. Occurrence frequency (fNPF) of regional atmospheric new aerosol particle formation (NPF) and consecutive growth events were studied with respect to vegetation activity, aerosol properties, air pollutants and meteorological data in Budapest over the time interval of 2008–2018. The data set evaluated contained results of in situ measurements on land surface mostly performed at the Budapest platform for Aerosol Research and Training Laboratory, of satellite-based products recorded by MODIS on Terra and of modelled vegetation emission-related properties from an advanced regional biogeochemical model. Annual mean relative occurrence frequencies were considerable (with an overall mean of 21 %), remained at a constant level (with an overall SD of 5 %) and did not exhibit tendentious change over the years. The shape of the distributions of monthly mean fNPF exhibited large variability from year to year, while the overall distribution already possessed a characteristic pattern. This structure of the NPF occurrence distributions was compared to those of environmental variables including concentrations of gas-phase H2SO4, SO2, O3, NO, NO2, CO, PM10 mass and NH3, of particle numbers in the size fractions of 6–1000, 6–100 and 100–1000 nm, condensation sink, air temperature (T), relative humidity, wind speed (WS), atmospheric pressure, global solar radiation, gross primary production of vegetation, leaf area index and stomatal conductance. There were no evident systematic similarities between fNPF on one hand and all variables on the other hand, except for H2SO4 and perhaps NH3. The spring maximum in the NPF occurrence frequency distribution often overlapped with the time intervals of positive T anomaly on vegetated territories. The link between the potential heat stress exerted on plants in sultry summer intervals and the summer fNPF minimum could not be proved. The relevance of environmental variables was assessed by their ratios on NPF event day and on non-event days. Gas-phase H2SO4 concentration showed the largest monthly ratios, followed by O3. The WS, biogenic precursor gases and SO2 can generally favour NPF events although their influence seemed to be constrained. Association between the fNPF and vegetation growth dynamics was clearly identified.