How do they survive?

When new clusters of a few molecules are born in the atmosphere, they need to survive long enough to gain more and more mass by the addition of other molecules to become relevant for climate and health. This is what NPF-PANDA is about.

However, do we use the right tools to estimate the survival probability of those tiny particles? Typically, we measure the particle number size distribution, which means we deploy instruments which provide us with two types of information: what is the size of the particles and how many of each size do we have present? Improving our abilities to derive this particle number size distribution was described already here. However, how can we determine a probability for each individual particle to survive to larger sizes by just looking into the evolution of the ensemble of all particles?

In a recently published preprint we explore the most common methods to estimate the survival probability of particles during new particle formation. Surprisingly, we found that different methods are needed for different types of aerosol size distributions and misapplication of the conventional methods to typical new particle formation events may underestimate the survival probability. Using the correct approaches case-by-case in urban Beijing, we can demonstrate that on average the survival probability of particles in this highly polluted environment can be described by a competition of their growth and loss rates, as predicted by theory. This contrasts with the original hypothesis in NPF-PANDA that the survival of particles in highly polluted megacities might not be fully explained yet. What a major success for NPF-PANDA!

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