New particle formation in the remote marine boundary layer

Guangjie Zheng,Fan Mei,Alyssa Matthews,Jason M Tomlinson,Chongai Kuang,Maria A Zawadowicz,Luke Ziemba,Meinrat O Andreae,Robert Wood,Jian Wang,Ewan Crosbie,Richard Moore,John E Shilling,Yang Wang,Isabel L Mccoy,Michael P Jensen

doi:10.1038/s41467-020-20773-1

Abstract

Marine low clouds play an important role in the climate system, and their properties are sensitive to cloud condensation nuclei concentrations. While new particle formation represents a major source of cloud condensation nuclei globally, the prevailing view is that new particle formation rarely occurs in remote marine boundary layer over open oceans. Here we present evidence of the regular and frequent occurrence of new particle formation in the upper part of remote marine boundary layer following cold front passages. The new particle formation is facilitated by a combination of efficient removal of existing particles by precipitation, cold air temperatures, vertical transport of reactive gases from the ocean surface, and high actinic fluxes in a broken cloud field. The newly formed particles subsequently grow and contribute substantially to cloud condensation nuclei in the remote marine boundary layer and thereby impact marine low clouds.

Highlights

Marine low clouds play an important role in the climate system, and their properties are sensitive to cloud condensation nuclei concentrations
The ion signal at m/z 63 measured by a ProtonTransfer-Reaction Mass Spectrometer (PTR-MS) suggests that vertical profile of dimethyl sulfide (DMS) is similar to that of water vapor, showing elevated mixing ratio in both surface mixed layer and upper decoupled layer compared to that in the free troposphere (Fig. 1b)
While N>3nm/N>10nm is elevated in the free troposphere (FT) at ~3000 m, the absence of particles smaller than 10 nm (i.e., N>3nm/N>10nm = 1) immediately above the Marine boundary layer (MBL) suggests that the new particles present in the MBL were formed in the upper decoupled layer rather than having been entrained from the FT

Summary

Introduction

Marine low clouds play an important role in the climate system, and their properties are sensitive to cloud condensation nuclei concentrations. The vertical profile of N>3nm/N>10nm, and the aerosol size distribution measured at an altitude of 100 m indicate that the new particles formed in the upper decoupled layer were transported downwards, resulting in a N>3nm/N>10nm value of 1.2 in the surface mixed layer.

Results

Conclusion