Infl uence of Tibetan Plateau uplift on dust cycle in arid and semi-arid region of Asia in winter

2016-03-06 11:55LIXinzhou
地球环境学报 2016年1期
关键词:中蒙源区阶段性

LI Xinzhou

(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)

Infl uence 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)

Background, aim, and scopeMineral 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 methodsAs an important driving force in the global climate and environmental changes on geological time scales, the TP uplift was one of the most signi fi cant tectonic events in Cenozoic era. Particularly, the TP uplift traced back to 50 Ma BP had profound in fl uences 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.ResultsThe 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 intensi fi cation 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 fl uxes decrease (increase) about linearly in the CA (CM) with TP uplift. The variations with TP rising of dust aerosol depth, mass concentration, and deposition fl uxes are coherent with dust emission fl uxes. Furthermore, the numerical results are consistent with geologic records from Chinese Loess Plateau and northwest Pacific.DiscussionThis 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.ConclusionsIn this study, the probable effects of TP uplift on CA and CM are analyzed comparatively, using an oceanatmosphere coupled general circulation model CESM 1.0 that to authors’ knowledge is fi rst 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 fl uxes are coherent with dust emission fl uxes.Recommendations and perspectivesThe results compared with geologic records con fi rm the contribution of CM dust emission to dust depositions over the LP, eastern China and neighboring seas.

Tibetan Plateau uplift; Asian winter monsoon; dust emission; Asian interior aridi fi cation; paleoclimate simulation

1 Introduction

As an important driving force for the global climate and environmental changes on geological time scales, the Tibetan Plateau (TP) uplift was one of the most significant tectonic events in Cenozoic era (Molnar et al, 1993; Yin and Harrison, 2000).Particularly, TP uplift traced back to 50 Ma BP (Molnar et al, 2010) had profound influences on the Asian monsoon and arid central Asia (Liu and Dong, 2013). The TP lifting is believed not only to enhance the Asian Monsoon circulation but also to altered global energy and water cycles (Prell and Kutzbach, 1992; Liu and Yin, 2002; Jiang et al, 2008) by reshaping the processes of drought over arid central Asia (Manabe and Broccoli, 1990).

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 (Liu and Ding, 1998; Sun et al, 1998; Ding et al, 1999; An, 2000; Sun et al, 2006; Gupta, 2010; Sun et al, 2010). They attempted to explain these geological records based on the TP uplift hypothesis (Wang, 1990; Liu et al, 1998; Liu and Yin, 2002; Molnar, 2005; An et al, 2006; Zhang and Liu, 2010). Climatic shifts contained geologic records in Asian indicated by some continental and marine deposits were commonly considered the result of TP uplift (Harrison et al, 1992; Burbank et al, 1993; Rea et al, 1998; An et al, 2001; Qiang et al, 2001; Molnar, 2005). For example, the loess in Chinese Loess Plateau “documents” the long-term evolution history of the Asian monsoon and the process of aridi fi cation in inland Asian. It has been found that in northern China the oldest eolian loess had appeared during late Oligocene to early Miocene (22—25 Ma BP) (Guo et al, 2002; Sun et al, 2010; Qiang et al, 2011), which is a critical period for the environmental transform from a planetary westerly into a monsoon-dominated flow system (Wang, 1990; Liu et al, 1998; Guo et al, 2008).

In recent years, considerable progress in the environmental effects of TP uplift has been made through geologic records and numerical simulations (Huber and Goldner, 2012; Liu and Dong, 2013). Especially, numerical experiments confirmed the potential impacts of TP uplift on the Asian monsoon (Liu and Yin, 2002; Liu et al, 2003; Boos and Kuang, 2010; Wu et al, 2012). It has been widely recognized that TP uplift has been an important driving force for the Asian monsoon and the aridi fi cation in inland Asia (An et al, 2001; Guo et al, 2002). Generally, the loess over Chinese Loess Plateau is believed to be mainly carried by Asian winter monsoon, although the longdistance transport by the westerly or northwesterly circulations from further upstream in central Asia is likely. However, whether eolian dust deposit over the oceans and ice cores further downstream were transported by winter northwesterly monsoon or the winter planetary westerly is still to be determined. Recent research on the Qinghai Lake indicated the importance of the westerly circulation (An et al, 2012), in constrast to earlier studies stressed the role of Asian winter monsoon as the major transport dynamic of dust deposits on the LP (An et al, 2001; Sun et al, 2008). In this paper, we will contrast relative roles of different sources and transport means contributing to the dust deposition in eastern Asia and northern Paci fi c as TP progressively uplifts.

2 Numerical model and experimental design

The Community Earth System Model version 1.0 (CESM 1.0), developed by the National Center for Atmospheric Research, is used in this study. CESM 1.0 is a fully coupled global climate model that consists of multi-components: atmosphere, land, ocean, sea ice and land ice based on the Community Climate System Model (CCSM 3/4) (Collins et al, 2006; Gent et al, 2011). CCSM has been widely used for past, present, and future climate simulations (e.g., Meehl et al, 2006; Neale et al, 2010; Levis et al, 2012), although the coupled CESM is relatively new and has not been used for TP uplift (to authors knowledge). A dust module accounting for emission, transport, and deposition is included in atmospheric component in CESM 1.0, allowing analyzing the response of dust activity to TP uplift. In the present study, CESM is configured to have the horizontal resolution of 1.9°× 2.5° with the vertical resolutions of 26 atmosphere and 40 ocean levels.

We performed nine experiments in which the TP elevation (60°—110°E, 20°—40°N) was changed into 100%, 90%, 80% … 20% of the presentday value, denoted TP10 (100%), TP9, TP8 … TP2 (20%), respectively. This design is similar to Liu andYin (2002), the difference is using the latest CESM containing dust cycle module in the present paper.

The TP10 experiment represents the presentday topography with an average height of more than 4000 m over TP. The average altitude is 800 m in the experiment of TP2 and it is about 2000 m in TP5. In order to highlight the role of the TP topography, all other lower boundary conditions including land use types and initial atmospheric fi elds except for the TP topography in all experiments remain the same as the present-day condition. For each experiment, 12-yr continuous integration was conducted and the output from the last 10-yr average was used in the analysis. Fig.1 shows sea level pressures in summer (June—August or JJA) and winter (December—February or DJF) averaged over 1979—2008 based on the NCEPDOE Reanalysis 2 (NCEP Ⅱ; Fig.1a and 1b), as compared with mean simulated summer and winter sea level pressure for TP10 (Fig.1c and 1d). The simulated sea level pressure distribution patterns, such as summer Asian low (AL) and winter Siberia high (SH) centers, matched well with the NCEP II climatology. In this study, two focus regions are chosen to represent the dust source areas and TP uplifting effect: central Asia (CA, 50°—70°E, 35°—50°N) and northern China-Mongolia (CM, 95°—115°E, 35°—50°N), delineated by the box in Fig.2b. The choice of the analysis regions are based partly on our previous studies that demonstrated the regions are of reprehensive of dust sources and also of sensitivity to the TP uplifting (Li et al, 2013).

Fig.1 Distributions of contemporary sea level pressures (unit: hPa) in summer (June—August or JJA, left) and winter (December—February or DJF, right) averaged over 1979—2008 based on the NCEP—DOE Reanalysis Ⅱ (NCEP Ⅱ; top) and 10-year averages simulated by CESM 1.0 (bottom). The box labeled AL in Fig.1c) delineates Asian Low region (20°— 80°E, 10°—30°N) and the box labeled SH is the Siberian High region (70°—110°E, 40°—60°N)

3 In fl uences of the uplift of TP on the winter climate in Asian inland

3.1 Precipitation

Precipitation is one of the most important variables affecting dust activity in arid Asian inland, especially in winter (and spring) when dust activity is strongest. In CA, one third (32.2%) of the annual total precipitation occurs in winter based on observation (Xie and Arkin, 1997). Our previous work withCCSM 3, the predecessor of CESM 1.0, simulated a winter portion of 49.2% for CA (Li et al, 2013). The current CESM 1.0 simulations produced similar portion to CCSM 3 (not shown). Fig.3 shows the simulated winter and annual precipitation averaged in CA and CM for the nine experiments. In CA, annual precipitation decreases about linearly with increasing TP altitude from 320 mm in TP2 to 230 mm in TP10. The winter precipitation also shows a general decrease with TP uplifting although the decreasing rate tends to be less linear. In CM, the winter precipitation displays a linear decrease with TP rising from 55 mm in TP2 to 34 mm in TP10, whereas the response of annual precipitation showed earlier decrease (T3—T6) but later increase (TP6—TP10). This nonlinear response features of precipitation in CM mainly relates to altitude of the TP, especially for over 50% of the TP in which the enhanced summer monsoon increased signi fi cantly the precipitation (Liu and Yin, 2002). The winter precipitation decrease from TP2—TP10 in CA and CM are 25% and 38%, respectively. These results confirm an earlier suggestion that TP blocks the westerly, resulting in less precipitation in CA, as indicated Fig.3c. It is worth mentioning that precipitation in eastern Asia tends to increase linearly with rising TP at a faster increasing rate in summer. The eastern Asian summer monsoon strengthens and moves northwards, giving rise to more precipitation in EA as TP uplifts (not shown). These results are consistent with geologic records (An et al, 2001; Ding et al, 2002) and numerical simulations (Liu and Yin, 2002; Liu and Dong, 2013).

Fig.2 Differences in dust emission (a, unit: kg·m-2) and surface wind (b, unit: m·s-1) between TP10 and TP5 in DJF The two red boxes in (b) indicate the central Asia (CA) and central Mongolia (CM), respectively. The blacken area represents regions 2000 m above sea level round TP.

3.2 Winter westerly circulation and Asian winter monsoon

An obvious feature is the change in atmospheric circulation in northern mid-latitudes due to the TP uplift, when the environment fl ow transformed from a planetary westerly into a monsoon-dominated fl ow (Wang, 1990; Liu et al, 1998; Guo et al, 2008; Liu and Dong, 2013). The latest finding indicates that the Lake Qinghai (100°E, 37°N) formed at 5.1 Ma BP as a result of strengthening of the eastern Asian summer monsoon transforming the region from arid to moist area (Fu et al, 2013; Han et al, 2014), which is closely associated with TP uplift. Fig.3 plots two wind indices: the winter westerly index (WWI) and Asian winter monsoon index (AWMI) for the nine experiments (TP2—TP10). The WWI is defined as the global average of sea level pressure differences between 35°N and 55°N (Li et al, 2013), according to the zonal index proposed by Rossby et al (1939). The AWMI is defined as the averaged sea level pressure for the Siberian High region (70°— 110°E, 40°— 60°N; the box in Fig.1d) in boreal winter (Li and Liu, 2012). Similar to precipitation in CA, the WWI weakens corresponding to rising TP. The uplift of TP blocks water vapor from the Atlantic carried by westerly circulation (Li et al, 2013), resulting in the drought due to the lack of water in CA. On the other hand, the AWMI (Fig.3d) strengthens with the gradual uplift of TP as demonstrated by Liu and Yin (2002). The strengthening of AWMI and weakening of the winter precipitation jointly promote the intensi fi cation of drought in CM.

Fig.3 The changes of precipitation in central Asia (CA: 50☒—70☒E, 35☒—50☒N, (a)) and northern China-Mongolia (CM: 95°—115°E, 35°—50°N, (b)), winter westerly index (WWI, (c)), and winter Asian monsoon index (WAMI, (d)) in response to the gradual uplifting of TP

4 Effects of the TP uplift on Asian dust emission, transport, and deposition

4.1 Dust emission

About half of dust from the arid and semi-arid Asia is transported downstream to Chinese Loess Plateau, northern Paci fi c, northern American and even Arctic (Andreae, 1995; Li and Liu, 2007). Past studies had con fi rmed that the Asian winter monsoon increases continuously with the gradual uplift of the TP, whereas the westerly circulation decreases, which could cause abnormally changes in dust emission from the source. The dust emission is determined largely by the surface precipitation,wind speed and temperature (Zhang, 2001). The surface wind speed dominates the intensityof dust emissions if other factors such as precipitation, temperature, etc. remain constant (Zender et al, 2003). Fig.2 shows the differences in dust emission fluxes and surface wind fields between TP10 and TP5 in winter. The dust emission fluxes in TP10 compared with TP5 in winter shows a significant decrease in CA and increase in CM as TP lifts. These contrasting responses of dust emission to TP uplift prompt us to think that the CA and CM should be separately discussed correspondingly, especially in the tectonic movement scale. With TP uplift, winter precipitation decreases linearly in CA and CM, but WWI and AWMI response reversely, causing dust emission response in opposite directions. The differences in surface wind fields among different experiments indicate that there is an easterly winds in CA caused by TP blocking and a northwesterly wind anomaly in CM caused by enhanced Siberia high pressure center (Fig.2b). With the increase of TP altitude, the winter dust emission fluxes (Fig.4a) decreased (increased) monotonically in CA (CM). Overall, precipitation is an important factor of Asian arid region of drought, but the wind fields finally determine dust emission intensity.

Fig.4 Changes in dust emission fl uxes (a, unit: g·m-2) and dust aerosol optical depth (b) responding to the uplifting of TP in winter and difference in dust mass concentration in CA (c) and CM (d) between TP10 and TP5 for winter (unit: μg·kg-1) The dust emission fl uxes are scaled 8 times in CM in order to match that of CA.

4.2 Dust transport

Dust aerosol optical depth in CM shows a gradual increases as TP uplifts (Fig.4b), likely due to the stronger winter dust emission fluxes. On the other hand, the dust aerosol optical depth over CA does not show a similar increase and actually it decreases almost across TP6 through TP10. The dust mass concentration in CA decreases sharply as TP uplifts, while mainly concentrated near the ground surface (Fig.4c). This mainly re fl ects the decrease in the emission. The mass concentration in CM shows an increase under 550 hPa (Fig.4d), likely due to large particles concentrated in the lower troposphere. But dust mass concentration decreases above 550 hPaup to about 200 hPa. This decrease in dust mass concentration in spite of increase in emission indicates that the decrease was ventilated by stronger westerly winds. Since the dust particles are smaller in general in the upper troposphere, the long-distance transport of fi ne dust increases after TP uplifts, which agrees with earlier results that the coarse loess in Chinese Loess Plateau is short-distance transported by the near ground airflow dominated by Asian winter monsoon (An et al, 1991. Recently, the fi ne silt and clay fractions are also suggested to be transported from short-distance by winter monsoon (Sun et al, 2008).

4.3 Dust deposition

After all, dust deposition is perhaps the only quantity that can at least be indirectly compared with geologic records. As one of available paleoenvironmental archives, Chinese Loess accurately records the evolution history of the Asian monsoon. Since 1960s, many scholars examined geologic records including loess (Gallet et al, 1998; Zhang, 2001; Qin et al, 2009), lakes (Fu et al, 2013), marine sediments (Duce et al, 1980; Zhuang et al, 1992; Rea, 1994) and glaciers (Biscaye et al, 1997) and recognized Asian dust source as the main contributor to the Loess Plateau. For this comparison we computed winter dust deposition fl uxes (Fig.5a) over the Chinese Loess Plateau (100°—115°E, 30°—45°N) and the whole eastern Asia (100°— 140°E, 20°— 50°N). For both regions, winter dust deposition fl uxes increase linearly responding to TP uplift. The dust mass concentration in the whole troposphere over eastern Asia and northwest Paci fi c also has an increasing trend responding to the TP uplift (not shown). Comparatively, the records of dust deposition in eastern Asia and even in the northwestern Pacific Ocean are scarce. Here two widely used geological proxies for dust deposition rate variations covering past 22 Ma are chosen for comparison: one is from the Qinan loess section in the Chinese Loess Plateau (Guo et al, 2002) and the other is from marine sediments from ODP 885/886 (Rea et al, 1998). Fig.5b schematically shows the growth process of the TP (An et al, 2006) compared with documented record. The simulated deposition is quite reasonable compared with the dust deposition record. The sudden jump in deposition rate after about 3 Ma BP recorded at the ocean station 885/886 matches well the stepwise uplifting. Interestingly simulated dust deposition fluxes in the Chinese Loess Plateau and eastern Asia also show a dip from TP7 to TP9, which is roughly corresponds to 5—6 Ma BP.

Fig.5 (a) Simulated winter dust deposition fluxes in Chinese Loess Plateau (LP, 100°—115°E, 30°—45°N) and eastern Asian (EA, 100°—140°E, 20°—50°N). (b) Reconstructed geological records of light eolian dust mass accumulation rate (MAR) (ODP 885/886, Rea et al, 1998), dust accumulation rate (DAR) (Qinan, Guo et al, 2002) and schematic TP height (black, An et al, 2006)

Dust emission fl ux depends both on precipitation and winds and thus the DMC’s response to the TP rising is rather nonlinear. The DMC is largest in TP9 and TP6 is larger than TP7. In fact, precipitation response to the TP uplift is not strictly monatomic, likely associated with complex response with response.Furthermore, it is clearly shown that the emission in TP9 is largest, 20% larger than TP10 (Fig.5a).

5 Discussions and conclusions

In this study, the potential effects of TP uplift on central Asia (CA) and northern China-Mongolia (CM) are analyzed comparatively, using an oceanatmosphere coupled general circulation model CESM 1.0 that to authors’ knowledge is first used in such a study. To highlighting the TP uplift effects on dust cycle, we use the modern dust source region distribution, without considering the expansion and shrinkage of the dust source region from the geological records. We found similar responses in winter precipitation but opposite in surface winds to the TP uplift between CA and CM. Precipitation is an important factor of Asian arid region of drought, but surface wind fields largely determine dust emission intensity. As documented by numerous studies, the TP uplift enhances the Asian winter monsoon and thus increases dust emission from the CM, promoting dust accumulation in Chinese Loess Plateau. However, our simulations indicate that the winter westerly fl ow is weakened, bringing the aridi fi cation in CA. Furthermore, the winter dust emission fl uxes 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 fl uxes. Numerical results in this paper are consistent with geologic records from Chinese Loess Plateau and northwest Pacific. The decreasing contribution from the CA with TP uplift suggests that the recorded deposit increase mainly results from CM that increases with TP uplift.

Presently two main broad views exist about the formation mechanism of Asian interior aridification (Ge et al, 2013). One view points out that global cooling with less water vapor from Pacific is the most important driving force for arid central Asia and TP uplift followed the global cooling. The other view believes that the Asian interior aridification is controlled by TP uplift that reduced the atmospheric CO2concentration through weathering and erosion (Raymo et al, 1992), consistent with geologic record about TP uplift and environment evolution (Ruddiman and Kutzback, 1990). From previous geologic records and modeling results, the Himalayan uplift may have a large effect in the establishment and development of the South Asian monsoon (Boos and Kuang, 2010; Wu et al, 2012; Zhang et al, 2012). However, the formation and evolution of the monsoon in northern East Asia, the intensi fi ed dryness north of the TP, and enhanced Asian dust cycle may be closely related to the uplift of TP main body, especially the northern part of the TP (Liu and Dong, 2013). Up to now, there is no clear consensus on the history and ways in which TP was uplifted (Liu and Dong, 2013). In addition, the experiments in this paper mainly focused on geologic record (Sun et al, 2006; An et al, 2012) that mainly reflected the changes of boreal westerly and Asian winter monsoon while the dust storms largely occur in Spring (Liu et al, 2004; Roe, 2009). 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 are needed in the future.

Our results showed that the TP uplift effects on CM annual precipitation, winds, and dust activity are rather nonlinear, compared to the CA situation. i) Annual precipitation was minimum for intermediate TP elevation (TP6, Fig.3b). ii) The zonal wind at 850 hPa was also weakest in TP6 and strongest in TP8 (figure slightly). iii) The maximum AOD and mass concentration does not occur in TP10, rather in TP9. The AOD and mass concentration in TP9 are 25%— 30% larger than TP10 (Fig.6), suggesting that the highest TP elevation may even cause less dust deposition than slightly lower TP elevation. If we were to extrapolate to an experiment where the elevation even exceeds the present one, the dust deposition might be reduced compared to present day. Apparently, further experiments are needed to con fi rm this extrapolation.

Fig.6 Vertical distribution of dust concentration (unit: μg·kg-1)over CM in difference experiments during winter

Acknowledgements:I wish to thank Prof. Pan Zaitao and Liu Xiaodong for their valuable help in design of experiment and manuscript preparation.

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青藏高原阶段性隆升对亚洲干旱半干旱区冬季粉尘循环的影响

李新周1,2
(1.中国科学院地球环境研究所 黄土与第四纪地质国家重点实验室,西安 710061;2.中国科学院青藏高原地球科学卓越创新中心,北京 100101)

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。

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

2015-11-05;录用日期:2016-01-05

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)

李新周,E-mail: lixz@ieecas.cn

10.7515/JEE201601001

Received Date:2015-11-05;Accepted Date:2016-01-05

Foundation Item:Strategic Priority Research Program of Chinese Academy of Sciences (XDB03020601); National Natural Science Foundation of China (41472162, 41290255)

LI Xinzhou, E-mail: lixz@ieecas.cn

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