Liquid Water: Ubiquitous Contributor to Aerosol Mass

Aerosol liquid water (ALW) is a ubiquitous component of atmospheric aerosol and influences particle chemistry, visibility, human health, and regional climate. The global abundance and spatial patterns in ALW mass concentrations and its fractional contribution to total particle mass are not routinely documented. We estimate lower-bound ALW mass concentrations at locations and time periods of aerosol mass spectrometer (AMS) field campaigns using speciated ion measurements, meteorology from the Climate Forecast System Reanalysis, and thermodynamic predictions from ISORROPIA version 2.1. The contribution of water by organic compounds is estimated using k-Kohler theory. Field campaign-specific patterns suggest that ALW mass is largest in urban and urban downwind areas, and that of growth factors is largest in rural areas. The highest average ALW mass concentration is estimated for the AMS study in Beijing and the highest mass fraction for rural Hyytiala. A more robust understanding of ALW is critical for developing and improving models that predict air quality and climate.