Annual sulfur deposition through fog, wet and dry deposition in the Kinki Region of Japan Hikari Shimadera * , Akira Kondo, Kundan Lal Shrestha, Akikazu Kaga, Yoshio Inoue Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan article info Article history: Received 17 March 2011 Received in revised form 17 August 2011 Accepted 19 August 2011 Keywords: Fog deposition Acid deposition Transboundary air pollution WRF/CMAQ Fog water deposition model abstract This study estimated annual sulfur (SO 2 þ SO 4 2 ) deposition through fog, wet and dry deposition in the Kinki Region of Japan from April 2004 to March 2005. The numerical models used in this study include the Weather Research and Forecasting model (WRF), the Community Multiscale Air Quality model (CMAQ), and a fog deposition model. WRF well predicted mountain fog at Mt. Rokko, the meteorology near the ground surface in the Kinki Region and the upper air meteorology in Japan during the simu- lation period. CMAQ well predicted the long-range atmospheric transport of aerosol SO 4 2 from the Asian Continent to Japan. The mean SO 4 2 concentration in fog water was approximately 6 times higher than that in precipitation in the Kinki Region. Ratios of fog water deposition to precipitation reached up to more than 10% in some mountainous areas in the Kinki Region. Consequently, the amount of sulfur deposition through fog water deposition was larger than that through dry deposition and comparable to that through wet deposition in some mountainous areas in the Kinki Region. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Fog is a cloud on the ground surface and reduces the horizontal visibility to less than 1000 m. Fog can be classified into several types, such as radiation fog and mountain fog, in accordance with the formation mechanism. Radiation fog occurs through radiative cool- ing of humid air masses typically from night to early in the morning on flat terrains and in valleys. Mountain fog mainly occurs through orographic lifting of humid air masses or horizontal advection of low-level cloud to mountain ranges (Klemm et al., 2005). Fog can affect forest ecosystems in mountainous areas, in which fog occurs more frequently than in other areas. Fog water deposi- tion through the interception of fog droplets by vegetation can be an important part of the hydrologic budget of forests (Vong et al., 1991; Dawson, 1998). Ionic concentrations in fog water are much higher than those in rain water (Igawa et al., 1998; Aikawa et al., 2001). Consequently, fog can contribute significantly to atmo- spheric deposition in mountainous forest areas (Baumgardner et al., 2003; Klemm and Wrzesinsky, 2007). The effects of fog may be more pronounced in Japan than in other regions because approximately two-thirds of the land area are covered with forests, most of which are located in mountainous regions. The amounts of fog water deposition have been measured using various approaches, such as the through fall measurement (e.g., Shubzda et al., 1995; Lange et al., 2003) and the eddy covariance method (e.g., Burkard et al., 2003; Klemm et al., 2005; Eugster et al., 2006). Numerical models also have been utilized to estimate fog water deposition. A one-dimensional model developed by Lovett (1984) has been widely used to predict fog water deposition in various mountain forests (e.g., Miller et al., 1993; Herckes et al., 2002a; Baumgardner et al., 2003). Katata et al. (2008) also developed a one- dimensional land surface model to better predict fog water deposi- tion, and showed the model agreed better with the measurement data by Klemm et al. (2005) than the model developed by Lovett (1984). The study of fog on a spatial scale requires numerical simulations because few fog monitoring sites exist and fog is highly variable according to regions. Mesoscale meteorological models have been employed for regional forecasting of particular fog events (e.g., Ballard et al., 1991; Pagowski et al., 2004). Shimadera et al. (2008) applied the 5th generation Mesoscale Model (MM5) (Grell et al., 1994) to fog simulation for months in the Kinki Region of Japan, and showed that the model well reproduced occurrence of fog. Shimadera et al. (2009) utilized MM5 and the Community Multiscale Air Quality model (CMAQ) (Byun and Ching, 1999) to predict concentrations of acidic compounds in fog water in the Kinki Region in March 2005. Shimadera et al. (2010) developed a two- dimensional fog water deposition model, and showed that the model was applicable to the estimate of spatial distribution of fog deposition with the meteorology and air quality modeling system. * Corresponding author. Tel./fax: þ81 06 6879 7670. E-mail addresses: shimadera@ea.see.eng.osaka-u.ac.jp, simadera@criepi.denken. or.jp (H. Shimadera). Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.08.055 Atmospheric Environment xxx (2011) 1e10 Please cite this article in press as: Shimadera, H., et al., Annual sulfur deposition through fog, wet and dry deposition in the Kinki Region of Japan, Atmospheric Environment (2011), doi:10.1016/j.atmosenv.2011.08.055