Study of relationship between daily maxima in ozone and temperature in an urban site in India

he relationship between surface-level observations of daily maxima in ozone (O3max) volume mixing ratio and ambient air temperature (Tmax) has been studied at an urban site, i.e. Pune (18.4°N, 73.8°E), India during 2003-04. The mixing ratios of O3max were found to be highest during winter to pre-monsoon period and lowest in the monsoon season. The dependence of O3max levels on Tmax has been quantified using the linear regression fit for the different seasons. However, except for the monsoon season, reasonably good correlations between O3max and Tmax were noticed. The correlation between daily O3max concentration and minimum NOx (NOxmin) concentration was also studied to assess the importance of photochemical mechanism mainly reduction in the loss due to titration. Overall, the strong dependencies of O3max on Tmax and NOxmin signify the role of both meteorological and photochemical processes during most months of a year. The positive slopes of ΔO3max/ΔTmax and ΔO3max/ΔNOxmin clearly indicate the role of significant production and accumulation of O3 under high temperature and low NOx conditions respectively, during winter and premonsoon seasons. The statistical analysis of O3 in relation with the key meteorological and chemical parameters is important to understand the sensitivity of secondary pollutants on various controlling factors

Global organic and inorganic aerosol hygroscopicity and its effect on radiative forcing

The climate effects of atmospheric aerosol particles serving as cloud condensation nuclei (CCN) depend on chemical composition and hygroscopicity, which are highly variable on spatial and temporal scales. Here we present global CCN measurements, covering diverse environments from pristine to highly polluted conditions. We show that the effective aerosol hygroscopicity, κ , can be derived accurately from the fine aerosol mass fractions of organic particulate matter ( ϵ org ) and inorganic ions ( ϵ inorg ) through a linear combination, κ  =  ϵ org  ⋅  κ org  +  ϵ inorg  ⋅  κ inorg . In spite of the chemical complexity of organic matter, its hygroscopicity is well captured and represented by a global average value of κ org  = 0.12 ± 0.02 with κ inorg  = 0.63 ± 0.01 as the corresponding value for inorganic ions. By showing that the sensitivity of global climate forcing to changes in κ org and κ inorg is small, we constrain a critically important aspect of global climate modelling. The effective hygroscopicity of organic matter and inorganic ions in atmospheric aerosols can be efficiently and accurately parameterized by global average values to constrain a critically important aspect in climate and Earth system model

An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08)

The Amazon Basin provides an excellent environment for studying the sources, transformations, and properties of natural aerosol particles and the resulting links between biological processes and climate. With this framework in mind, the Amazonian Aerosol Characterization Experiment (AMAZE-08), carried out from 7 February to 14 March 2008 during the wet season in the central Amazon Basin, sought to understand the formation, transformations, and cloud-forming properties of fine- and coarse-mode biogenic aerosol particles, especially as related to their effects on cloud activation and regional climate. Special foci included (1) the production mechanisms of secondary organic components at a pristine continental site, including the factors regulating their temporal variability, and (2) predicting and understanding the cloud-forming properties of biogenic particles at such a site. In this overview paper, the field site and the instrumentation employed during the campaign are introduced. Observations and findings are reported, including the large-scale context for the campaign, especially as provided by satellite observations. New findings presented include: (i) a particle number-diameter distribution from 10 nm to 10 Î1/4m that is representative of the pristine tropical rain forest and recommended for model use; (ii) the absence of substantial quantities of primary biological particles in the submicron mode as evidenced by mass spectral characterization; (iii) the large-scale production of secondary organic material; (iv) insights into the chemical and physical properties of the particles as revealed by thermodenuder-induced changes in the particle number-diameter distributions and mass spectra; and (v) comparisons of ground-based predictions and satellite-based observations of hydrometeor phase in clouds. A main finding of AMAZE-08 is the dominance of secondary organic material as particle components. The results presented here provide mechanistic insight and quantitative parameters that can serve to increase the accuracy of models of the formation, transformations, and cloud-forming properties of biogenic natural aerosol particles, especially as related to their effects on cloud activation and regional climate. © 2010 Author(s)

Erratum: An overview of the amazonian aerosol characterization experiment 2008 (AMAZE-08) (Atmospheric Chemistry and Physics (2010) 10 (11415-11438))

No abstract available