Classification of the new particle formation events observed at a tropical site, Pune, India. (October 2018) - Siingh, Devendraa
Abstract: A total number of 109 new particle formation events identified in the ion-mobility spectra measured with a Neutral Cluster and Air Ion Spectrometer in the mobility range of 3.16–0.00133 cm 2 V −1 s −1 (Diameter* range 0.36–47.1 nm) at a tropical site at Pune, (18.53 °N, 73.85 °E, 573 m amsl) India from March 08, 2010–December 31, 2012 are classified based on their shape characteristics under four categories. Most of these events occurred in the morning hours of the pre-monsoon season during the hottest months (April and May) of the year. The meteorological conditions and the changes in ion characteristics associated with some typical events are examined. Average ion-mobility spectrum for the event days shows a minimum in the negative big cluster ion (diameter, 0.85–1.6 nm) concentration and two maxima in the positive intermediate (diameter, 1.6–7.4 nm) and large ion (diameter, 7.4–47.1 nm) concentrations as compared to the average spectrum for all days. Analysis of 7-days airmass back trajectories shows that since the only source of big cluster ions is through the growth of small cluster ions (diameter, 0.36–0.85 nm) the growth of small to big cluster ions is faster when the airmass approaches our site from the land. Further, the concentrations of positive intermediate and light large (diameter, 7.4–22 nm) ions is more when the airmass approaches from the Arabian Sea. Highlights: NPF events observed at a tropical site have been classified. A new type of event, of truncated banana shape is reported. Monthly distribution of events shows that they occur in the hottest season. Backward air-mass trajectories and ion characteristics on events days were studied. Positive ion concentration on event days are more than of the negative ions.