Suppression of precipitation by dust particles originated in the Tibetan Plateau Yongxiang Han a, b, * , Xiaomin Fang a , Tianliang Zhao c , Huzhi Bai b , Shichang Kang a , Lianchun Song b a Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Shuangqing Street 18, Beijing 100085, China b Lanzhou Arid Meteorological Institute, China Meteorological Administration & Gansu Key Laboratory of Arid Climatic Change and Reducing Disaster, Lanzhou 730020, China c Air Quality Research Branch, Environment Canada, Toronto, Ontario m3H 5T4, Canada article info Article history: Received 19 April 2008 Received in revised form 14 September 2008 Accepted 8 October 2008 Keywords: Tibetan Plateau Dust aerosol Precipitation CALIPSO abstract Dust aerosols play an important role in modulating the hydrologic cycle. The Tibetan Plateau (TP) is little polluted by human activities as an ideal site to study the effect of dust aerosol on precipitation. In this study, observational data of dust storms and precipitation in the TP and its vicinities as well as CALIPSO satellite data were used to analyze the distributions and vertical structure of dust storms on the plateau. The results showed that dust storms occur with high frequency and raise dust particles into the troposphere from ground level to a height of 5–9 km to modulate the hydrologic cycle in the TP. There are significant negative correlations between dust aerosol and precipitation in the dust source regions during the period of both 40 and 200 years. It is found that the role of precipitation in suppressing dust storms could be unimportant, while dust aerosol may play an important role in suppressing precipitation in the hinterland of the TP. Our study provides a potential approach to better understand the climate changes in the TP. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction The Tibetan Plateau (TP) is lofty in the midlatitude westerly zone in the Northern Hemisphere and plays an important role in modulating the regional and global climate (Li and Fang, 1999; Nie et al., 2008). It is a ‘‘water tower’’ for Asia. The Mekong, the Yellow River, the Yangtze, the Yarlung Tsampo (Brahmaputra), the Indus, and the Karnali all originate from the TP and support hundreds of millions of people downstream. Even tiny changes in the TP’s hydrologic cycle will have important implications for the climate, ecosystem, and economy for the TP itself and the surrounding regions. For example, the variations of snow cover over the TP affect not only the hydrologic cycle in the TP itself but also the precipi- tation pattern, such as flooding in South China and drought in north China (Liu and Yanai, 2002; Zhu and Ding, 2007). Recent studies (Jacobson, 2002; Nober et al., 2003) suggested that aerosols can substantially alter the energy balance of the atmosphere and the earth’s surface, thereby modulating the hydrologic cycle. Dust aerosol is the most important constituent of aerosols, accounting for nearly half of the total aerosols in the troposphere (Lohmann and Feichter, 2005). Because of the limitation in observation data for the interaction of cloud and aerosols, the research on the condensation nuclear effect now depends mainly on hypothesis and numeral simulation (Teller and Levin, 2006). Many recent studies showed aerosols tend to invigorate convection and to intensify ice processes (Khain et al., 2005, 2008; Lynn et al., 2005a,b), and aerosols can both increase or decrease precipitation depending on environmental conditions. However, under comparatively dry atmospheric conditions, the experiment per- formed by Rosenfeld et al. (2001) in the Sahara area indicated that desert dust can suppress precipitation. Central Asia is one of the most important source regions of dust storms, inferior only to the Sahara Desert, supplying dust particles to modulate the regional hydrologic cycle (Zhao et al., 2006). Using a two-dimensional spectral resolving cloud model, the effects of mineral dust particles on development of cloud microphysical and precipitation were simulated in North China (Chen et al., 2007; Yin and Chen, 2007). The results showed that when dust particles are involved in cloud development as CCN (cloud condensation nuclei) and IN (ice nuclei) at the same time, the increased dust aerosol will suppress the precipitation because the enhancing effect of GCCN is almost suppressed by the stronger suppressing effect of IN (Chen et al., 2007; Yin and Chen, 2007). Furthermore, Han et al. (2008a) found that the role of precipitation in suppressing dust storm occurrence is unimportant and that dust aerosol may play a more important role in suppressing the precipitation in the arid and extra-arid regions. However, the constituents of aerosols are complex because of dense population, industry, and severe pollution caused by human activities in northern China. * Corresponding author. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Shuangqing Street 18, Beijing 100085, China. E-mail address: han-yx66@126.com (Y. Han). Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2008.10.018 Atmospheric Environment 43 (2009) 568–574