Description
Current estimates suggest that globally, about one third of cloud condensation nuclei (CCN) affecting low-levelclouds originate from new particle formation (NPF) that takes place in the free troposphere. However, the exactmechanisms of how new particles form and grow to CCN sizes, and their relative importance are not yet wellquantified.We investigate the formation of new particles and their growth to CCN-sizes in the remote marine atmosphere overthe Pacific and Atlantic basins (∼80◦N to∼86◦S). This is done using size distribution measurements (0.003-4.8μm) from the airborne-based NASA Atmospheric Tomography global survey (ATom; 2016-2018), back trajectorydata and two aerosol microphysics box models.Newly formed particles are ubiquitous at high altitudes throughout broad regions of the tropics and subtropicsunder low condensation sink conditions and are associated with upwelling in convective clouds. This pattern isobserved over four seasons and both ocean basins. NPF was also found in the free troposphere over the SouthernOcean in February 2017, however it was not observed in August 2016, indicating seasonal differences.In this study we explore processes that govern NPF and growth in the tropical and subtropical free troposphere, andover the Southern Ocean, discuss similarities and differences in NPF in these regions, examine which nucleationscheme (e.g. binary, ternary, or charged) best explain the observations, evaluate whether observed sulfur precursorsalone (SO2and DMS) can explain the NPF, and discuss the growth of these new particles to CCN sizes.| Period | 9 Apr 2019 |
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| Event title | European Geosciences Union (EGU) General Assembly 2019 |
| Event type | Conference |
| Location | Vienna, AustriaShow on map |