A novel method to derive the aerosol hygroscopicity parameter based only on measurements from a humidified nephelometer system

Other literature type English OPEN
Kuang, Ye ; Zhao, ChunSheng ; Tao, JiangChuan ; Bian, YuXuan ; Ma, Nan ; Zhao, Gang (2017)

Aerosol hygroscopicity is crucial for understanding roles of aerosol particles in atmospheric chemistry and aerosol climate effects. Light scattering enhancement factor <i>f</i>(RH,<i>&lambda;</i>) is one of the parameters describing aerosol hygroscopicity which is defined as <i>f</i>(RH,<i>&lambda;</i>)&thinsp;=&thinsp;(<i>&sigma;<sub>sp</sub></i> (RH,<i>&lambda;</i>))/(<i>&sigma;<sub>sp</sub></i>(dry,<i>&lambda;</i>)) where <i>&sigma;<sub>sp</sub></i> (RH, <i>&lambda;</i>) or <i>&sigma;<sub>sp</sub></i> (dry, <i>&lambda;</i>) represents <i>&sigma;<sub>sp</sub></i> at wavelength <i>&lambda;</i> under certain RH or dry conditions. Traditionally, an overall hygroscopicity parameter <i>&kappa;</i> can be retrieved from measured <i>f</i>(RH, <i>&lambda;</i>), hereinafter referred to as <i>&kappa;<sub>f</sub></i>(RH), by combining concurrently measured particle number size distribution (PNSD) and mass concentration of black carbon. In this paper, a new method is proposed to directly derive <i>&kappa;<sub>f</sub></i>(RH) based only on measurements from a three-wavelength humidified nephelometer system. The advantage of this newly proposed novel approach is that it allows researchers to estimate <i>&kappa;<sub>f</sub></i>(RH) without any additional information about PNSD and black carbon. Values of <i>&kappa;<sub>f</sub></i>(RH) estimated from this new method agree very well with those retrieved by using the traditional method, the average difference between <i>&kappa;<sub>f</sub></i>(RH) derived from newly proposed method and traditional method is 0.005 and the square of correlation coefficient between them is 0.99.
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