| 摘要: |
| 粉尘是大气气溶胶的主要成分之一，对大气能量平衡起着关键作用。一般来讲，黄土高原（LP）粉尘主要来源于北方沙漠区，但有关中国东部及其周边地区粉尘来源的争论仍在继续。为此，本文对比分析了亚洲主要粉尘源区如中亚（CA）和中蒙（CM）粉尘循环对青藏高原阶段性隆升的响应，探讨了CA和CM粉尘排放对下游的贡献。利用美国大气研究中心（NCAR）最新发布的通用地球系统模式（CESM 1.0），进行了改变青藏高原海拔高度为现在10%，20%，30% …100%的9个数值试验。分析结果表明，随着青藏高原阶段性隆升中亚和中蒙干旱区冬季降水均线性减弱，与前人研究结果一致。青藏高原阶段性隆升阻塞西风环流使其减弱从而引起中亚粉尘释放减弱；而青藏高原阶段性隆升引起亚洲冬季风加强，促使中蒙粉尘释放加强，与中亚相反。模拟结果与地质记录对比进一步证实了中蒙粉尘源区对黄土高原、中国东部及临近区域粉尘沉降的贡献。 |
| 关键词: 青藏高原隆升 亚洲冬季风 粉尘排放 内陆干旱化 古气候模拟 |
| DOI：10.7515/JEE201601001 |
| CSTR： |
| 分类号: |
| 基金项目:中国科学院战略性先导科技专项（XDB03020601）；国家自然科学基金项目（41472162，41290255） |
|
| Influence of Tibetan Plateau uplift on dust cycle in arid and semi-arid region of Asia in winter |
|
LI Xinzhou1,2
|
|
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment,
Chinese Academy of Sciences, Xi’an 710061, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China
|
| Abstract: |
| Background, aim, and scope Mineral dust as one of the major atmospheric aerosols plays a role in the atmospheric energy balance. Chinese Loess is most extensive, continuous, and deepest dust deposit of the world. It recorded historical evolution of Asian monsoon and drought history was back to 22 — 25 Ma ago. Many scholars in China and abroad have analyzed the long-term evolution of the Asian monsoon and dryness of Asian inlands, using geologic records from loess, lake, desert, ice core, bios and ocean during the last several decades. While it is now generally believed that the dust source of Chinese Loess Plateau (LP) is deserts in northern China and Mongolia (CM), the source for the dust deposit in eastern China and neighboring seas are still in debate. In this paper, the responses of dust cycles over the Asian two key dust source areas such as central Asia (CA) and CM to Tibetan Plateau (TP) progressive uplift are analyzed and discussed. Materials and methods As an important driving force in the global climate and environmental changes on geological time scales, the TP uplift was one of the most significant tectonic events in Cenozoic era. Particularly, the TP uplift traced back to 50 Ma BP had profound influences on the Asian monsoon and arid central Asia. Using the Community Earth System Model version 1.0 (CESM 1.0) newly released by the National Center for Atmospheric Research, we conducted nine numerical experiments where the elevation of TP is decreased to 10%, 20%, 30%… 100%, respectively. The results of experiments are compared with the reconstructed geologic records of light eolian dust mass accumulation rate (MAR) from marine sediments from ODP 885/886, dust accumulation rate (DAR) from the Qinan loess section in the LP. Results The results show that the annual (winter) precipitation decreases about linearly with increasing TP altitude from 320 (125) mm in TP2 to 230 (90) mm in TP10 in CA. The winter precipitation also displays a linear decrease with TP rising from 55 mm in TP2 to 34 mm in TP10, whereas the response of annual shows earlier decrease (TP3—TP6) but later increase (TP6—TP10) in CM. Similar to precipitation in CA, the winter westerly index (WWI) weakens corresponding to rising TP. The uplift of TP blocks water vapor from the Atlantic carried by westerly circulation, resulting in the drought due to the lack of water in CA. However, the Asian winter monsoon index (AWMI) strengthens with the gradual uplift of TP. The strengthening of AWMI and weakening of the winter precipitation jointly promote the intensification of drought in CM. The similar responses in winter precipitation but opposite in surface winds to the TP uplift between CA and CM. Thus, the winter dust emission fluxes decrease (increase) about linearly in the CA (CM) with TP uplift. The variations with TP rising of dust aerosol depth, mass concentration, and deposition fluxes are coherent with dust emission fluxes. Furthermore, the numerical results are consistent with geologic records from Chinese Loess Plateau and northwest Pacific. Discussion This paper confirms that the geologic records deposit increase mainly results from CM that increases with TP uplift. The decreasing contribution from the CA decreases about linearly with the rising of TP altitude. However, up to now, there is no clear consensus on the history and ways in which TP was uplifted. The formation time and way of the central Asian arid zone are still uncertain. Consequently, to comprehensively understand the response characteristics of the dryness of Asian inland and dust cycle, more realistic experiments of TP uplift reconstructed based on more geologic records will be conducted in the future. Conclusions In this study, the probable effects of TP uplift on CA and CM are analyzed comparatively, using an ocean-atmosphere coupled general circulation model CESM 1.0 that to authors’ knowledge is first used in such a study. The results show that winter precipitation in CA and CM linearly decreases with the uplift of TP, in agreement with previous studies based on geologic records. As TP uplifts, the boreal winter westerly weakens, blocked by the rising TP, resulting in lower dust emission in CA. Conversely, Asian winter monsoon strengthens in responding to the uplift, giving rise to higher dust emission in CM. The variations with TP rising of dust aerosol depth, mass concentration, and deposition fluxes are coherent with dust emission fluxes. Recommendations and perspectives The results compared with geologic records confirm the contribution of CM dust emission to dust depositions over the LP, eastern China and neighboring seas. |
| Key words: Tibetan Plateau uplift Asian winter monsoon dust emission Asian interior aridification paleoclimate simulation |
