The formation and growth of ultrafine particles in two contrasting environments: a case study

S. Suresh Babu, K. Krishna Moorthy
2014 Annales Geophysicae  
<p><strong>Abstract.</strong> Formation of ultrafine particles and their subsequent growth have been examined during new particle formation (NPF) events in two contrasting environments under varying ambient conditions, one for a tropical semi-urban coastal station, Trivandrum, and the other for a high-altitude free-tropospheric Himalayan location, Hanle. At Trivandrum, NPF bursts took place in the late evening/night hours, whereas at Hanle the burst was a daytime event. During the nucleation
more » ... g the nucleation period, the total number concentration reached levels as high as ~ 15 900 cm<sup>−3</sup> at Trivandrum, whereas at Hanle, the total number concentration was ~ 2700 cm<sup>−3</sup>, indicating the abundant availability of precursors at Trivandrum and the pristine nature of Hanle. A sharp decrease was associated with NPF for the geometric mean diameter of the size distribution, and a large increase in the concentration of the particles in the nucleation regime (<i>D</i><sub>p</sub> < 25 nm). Once formed, these (secondary) aerosols grew from nucleation (diameter <i>D</i><sub>p</sub> < 25 nm) to Aitken (25 &amp;le; <i>D</i><sub>p</sub> &amp;le; 100 nm) regime and beyond, to the accumulation size regimes (100 &amp;le; <i>D</i><sub>p</sub> &amp;le; 1000 nm), with varying growth rates (GR) for the different size regimes at both the locations. A more rapid growth ~ 50 nm h<sup>−1</sup> was observed at Trivandrum, in contrast to Hanle where the growth rate ranged from 0.1 to 20 nm h<sup>−1</sup> for the transformation from the nucleation to accumulation – a size regime that can potentially act as cloud condensation nuclei (CCN). The faster coagulation led to lifetimes of < 1 h for nucleation mode particles.</p>
doi:10.5194/angeo-32-817-2014 fatcat:jx7ylwnu2neatfmeryrlqvk54e