edu.ucar.opensky::articles:10782 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T13:39:19.892087 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7154hmz The role of relative humidity in continental new particle formation 2011-02-01T00:00:00Z publication https://n2t.org/ark:/85065/d7154hmz https://doi.org/10.1029/2010JD014186 Hamed, A. author Korhonen, H. author Sihto, S. author Joutsensaari, J. author Järvinen, H. author Petäjä, T. author Arnold, F. author Nieminen, T. author Kulmala, M. author Smith, James N. author Lehtinen, K. author Laaksonen, A. author UCAR/NCAR - Library publisher Relative humidity (RH) has been observed to be anticorrelated with continental new particle formation. Several reasons have been proposed for this rather surprising finding, but no firm conclusions have been drawn so far. Here we study several of the proposed reasons: Enhanced coagulational scavenging of sub-3 nm clusters at high RH, diminished solar radiation at high RH leading to diminished gas phase oxidation chemistry, and increased condensation sink (CS) of condensable gases due to hygroscopic growth of the preexisting particles. Our theoretical calculations indicate that the increase of coagulational scavenging plays a relatively small role in the inhibition of nucleation at high RH. On the other hand, field data show that the maximum observed gas phase sulphuric acid concentrations are limited to RHs below 60%. The field data also indicate that this is likely due to low OH concentrations at high RH. This finding is also supported by aerosol dynamics model simulations. The model was used to find out whether this is mainly due to decreased source (solar radiation) or increased sink (CS) terms at the elevated RH. The simulation results show that the decreased source term at high RH limits H₂SO₄ levels in the air, and therefore high new particle formation rates (above ~1 cm₋₃ s₋₁) rarely occur above 80% RH. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication An edited version of this paper was published by AGU. Copyright 2011 American Geophysical Union. None eng geoscientificInformation