Size-resolved atmospheric ice-nucleating particles during East Asian dust events

Jingchuan Chen,Yinon Rudich,Xin Fang,Naama Reicher,Min Hu,Jie Chen,Zhijun Wu

doi:10.5194/acp-21-3491-2021

Abstract

Abstract. Asian dust is an important source of atmospheric ice-nucleating particles (INPs). However, the freezing activity of airborne Asian dust, especially its sensitivity to particle size, is poorly understood. In this study we report the first INP measurement of size-resolved airborne mineral dust collected during East Asian dust events. The measured total INP concentrations in the immersion mode ranged from 10−2 to 102 L−1 in dust events at temperatures between −25 and −5 ∘C. The average contributions of heat-sensitive INPs at three temperatures, −10, −15, and −20 ∘C, were 81±12 %, 70±15 %, and 38±21 %, respectively, suggesting that proteinaceous biological materials have a substantial effect on the ice nucleation properties of Asian airborne mineral dust at high temperatures. The dust particles which originated from China's northwest deserts are more efficient INPs compared to those from northern regions. In general, there was no significant difference in the ice nucleation properties between East Asian dust particles and other regions in the world. An explicit size dependence of both INP concentration and surface ice-active-site density was observed. The nucleation efficiency of dust particles increased with increasing particle size, while the INP concentration first increased rapidly and then leveled, due to the significant decrease in the number concentration of larger particles. A new set of parameterizations for INP activity based on size-resolved nucleation properties of Asian mineral dust particles were developed over an extended temperature range (−35 to −6 ∘C). These size-dependent parameterizations require only particle size distribution as input and can be easily applied in models.

Highlights

Ice formation in tropospheric clouds significantly impacts the microphysical processes and lifetime of clouds, thereby determining radiative forcing, precipitation, and the hydrological cycle (Lohmann and Feichter, 2005; Boucher et al, 2014; Lohmann et al, 2016)
In this study we report the first ice-nucleating particles (INPs) measurement of size-resolved airborne mineral dust collected during East Asian dust events
The nucleation efficiency of dust particles increased with increasing particle size, while the INP concentration first increased rapidly and leveled, due to the significant decrease in the number concentration of larger particles

Summary

Introduction

Ice formation in tropospheric clouds significantly impacts the microphysical processes and lifetime of clouds, thereby determining radiative forcing, precipitation, and the hydrological cycle (Lohmann and Feichter, 2005; Boucher et al, 2014; Lohmann et al, 2016). Up to 2000 Tg of mineral dust is emitted from arid and semiarid areas into the troposphere annually, and its estimated atmospheric loading is the largest among different types of aerosol particles (Prospero, 1999; Textor et al, 2006). Asian dust can be transported across the Pacific Ocean, sometimes completing more than one full cycle around the globe (Sun et al, 2001; McKendry et al, 2008; Uno et al, 2009). Ground-based and aircraft cloud measurements have confirmed that dust and adsorbed biological aerosols from regions such as Asia may affect ice formation in mixed-phase clouds (Creamean et al, 2013; Pratt et al, 2009). Modeling studies suggest that Asian dust affects ice particle formation in mixedphase clouds (Wiacek et al, 2010).

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