Hygroscopic properties of the ambient aerosol in southern Sweden - a two year study
Hygroscopic properties of the ambient aerosol in southern Sweden - a two year study
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DOI：
10.5194/acp-11-8343-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Sporre, M.
中科院分区：
文献类型：
--
作者：
Fors, E. O.;Swietlicki, E.;Sporre, M.
大气气溶胶的吸湿性增长是量化人为辐射强迫的一个关键参数。到目前为止，由于仪器技术的限制，一直缺乏长期的测量。在这项工作中，基于两年多的连续测量，首次描述了大陆背景气溶胶吸湿特性的季节变化。此外，还研究了吸湿生长的日变化，以及CCN浓度的季节变化。这些气溶胶的物理性质已经用吸湿性串联差分迁移率分析仪（H-TDMA）、差分迁移率粒度仪（DMPS）和云凝结核计数器（CCNC）进行了测量。结果表明，较小颗粒的吸湿性一般小于较大颗粒，且艾特肯颗粒的吸湿性与堆积模式之间存在明显差异。所有粒径的颗粒都有季节性循环。一般来说，冬季平均吸湿性生长较低，这是由于吸湿性较差或几乎不吸湿的颗粒的相对丰度增加所致。月平均值表明，两种主要吸湿模式（一种几乎不吸湿，一种更吸湿）的吸湿生长因子相对稳定。吸湿性生长也表现为日循环，白天生长因子较高。基于H-TDMA数据的CCN预测在1%水过饱和比下低估了7%的活化CCN数浓度。低预估随着s的减小而增加，很可能是由于测量和建模不确定性的结合。研究发现，虽然气溶胶通常是外部混合的，但重新计算吸湿性为内部混合并没有显著改变CCN浓度作为过饱和的函数。
The hygroscopic growth of the atmospheric aerosol is a critical parameter for quantifying the anthropogenic radiative forcing. Until now, there has been a lack of long term measurements due to limitations in instrumental techniques. In this work, for the first time the seasonal variation of the hygroscopic properties of a continental background aerosol has been described, based on more than two years of continuous measurements. In addition to this, the diurnal variation of the hygroscopic growth has been investigated, as well as the seasonal variation in CCN concentration. These physical properties of the aerosol have been measured with a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA), a Differential Mobility Particle Sizer (DMPS), and a Cloud Condensation Nuclei Counter (CCNC). The results show that smaller particles are generally less hygroscopic than larger ones, and that there is a clear difference in the hygroscopic properties between the Aitken and the accumulation mode. A seasonal cycle was found for all particle sizes. In general, the average hygroscopic growth is lower during wintertime, due to an increase in the relative abundance of less hygroscopic or barely hygroscopic particles. Monthly averages showed that the hygroscopic growth factors of the two dominating hygroscopic modes (one barely hygroscopic and one more hygroscopic) were relatively stable. The hygroscopic growth additionally showed a diurnal cycle, with higher growth factors during day time. CCN predictions based on H-TDMA data underpredicted the activated CCN number concentration with 7% for a 1% water supersaturation ratio. The underprediction increases with decreasing s, most likely due to a combination of measurement and modeling uncertainties. It was found that although the aerosol is often externally mixed, recalculating to an internal mixture with respect to hygroscopicity did not change the CCN concentration as a function of supersaturation significantly.