New particle formation has been demonstrated to play important roles in air quality and climate change. Measurement of particle size distribution is the basis of most relevant studies. 3 nm was recognized as one critical size in terms of new particle formation. But a considerable amount of measurements on particle size distributions do not extent to 3 nm but instead start at 6 or 7 or 10 nm. Therefore, developing a convincing method to estimate the 3 nm particle formation rates from larger size is crucial to build a worldwide, comparable data set, which will be helpful to understand the mechanism of new particle formation and evaluate their roles in climate. In this study, the authors extrapolated the formation rates at 7 nm (J7) down to 3 nm (J3) at SMEAR IV station based on an approximate solution to the aerosol general dynamic equation. Data from SMEAR II station, which extend down to 3 nm, was used to evaluate the method. The manuscript is overall well written and documented. The topic fits well in the scope of ACP. I recommend this manuscript can be published after some revisions.
One general comment:
Line 201-217, authors mentioned there are one group of NPF events for which the 𝐽3, est and 𝐽3, obs are dramatically different. What's the percentage of this kind of events? Are they included in Figure 1? Are this inhomogenities mainly due to the changes of air masses? If yes, an evaluation on the stability of air masses is recommended during one event. It’s better to establish a standard method to recognize the NPF events as quantifiable or not but not based on visual observation.
Technical comments:
1. Line 230: add the bracket and stop after “Dal Maso et al., 2005”.
2. Please unify the format of units, e.g. 1/s or s-1.
3. It seems to be not necessary to show the statistical results at Puijo both in Figure 5 and Table 1. |