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1.
We examine the impact of the Atmospheric Brown Clouds on the direct radiative forcing of the Himalayan foothills and the Indo-Gangetic Plains (IGP) regions, home for over 500 million S. Asians. The NASA-Terra MODIS satellite data reveal an extensive layer of aerosols covering the entire IGP and Himalayan foothills region with seasonal mean AODs of about 0.4 to 0.5 in the visible wavelengths (0.55 micron), which fall among the largest seasonal mean dry season AODs for the tropics. We show new surface data which reveal the presence of strongly absorbing aerosols that lead to a large reduction in solar radiation fluxes at the surface during the October to May period. The three-year mean (2001 to 2003) October to May seasonal and diurnal average reduction in surface solar radiation for the IGP region is about 32 (±5) W m−2 (about 10% of TOA insolation or 20% of surface insolation). The forcing efficiency (forcing per unit optical depth) is as large as −27% (note that the forcing is negative) of top-of-atmosphere (TOA) solar insolation, and exceeds the forcing efficiency that has been observed for other polluted regions in America, Africa, East Asia, and Europe. General circulation model sensitivity studies suggest that both the local and remote influence of the aerosol induced radiative forcing is to strengthen the lower atmosphere inversion, stabilize the boundary layer, amplify the climatological tendency for a drier troposphere, and decrease evaporation. These aerosol-induced changes could potentially increase the life times of aerosols, make them more persistent, and decrease their single scattering albedos, thus potentially leading to a detrimental positive feedback between aerosol concentrations, aerosol forcing, and aerosol persistence. In addition, both the model studies and observations of pan evaporation suggest that the reduction in surface solar radiation may have led to a reduction in surface evaporation of moisture. These results suggest the vulnerability of this vital region to air pollution related direct and indirect (through climate changes) impacts on agricultural productivity of the region. 相似文献
2.
Regional variability in dust‐on‐snow processes and impacts in the Upper Colorado River Basin 
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下载免费PDF全文 S. McKenzie Skiles Thomas H. Painter Jayne Belnap Lacey Holland Richard L. Reynolds Harland L. Goldstein John Lin 《水文研究》2015,29(26):5397-5413
Dust deposition onto mountain snow cover in the Upper Colorado River Basin frequently occurs in the spring when wind speeds and dust emission peaks on the nearby Colorado Plateau. Dust loading has increased since the intensive settlement in the western USA in the mid 1880s. The effects of dust‐on‐snow have been well studied at Senator Beck Basin Study Area (SBBSA) in the San Juan Mountains, CO, the first high‐altitude area of contact for predominantly southwesterly winds transporting dust from the southern Colorado Plateau. To capture variability in dust transport from the broader Colorado Plateau and dust deposition across a larger area of the Colorado River water sources, an additional study plot was established in 2009 on Grand Mesa, 150 km to the north of SBBSA in west central, CO. Here, we compare the 4‐year (2010–2013) dust source, deposition, and radiative forcing records at Grand Mesa Study Plot (GMSP) and Swamp Angel Study Plot (SASP), SBBSA's subalpine study plot. The study plots have similar site elevations/environments and differ mainly in the amount of dust deposited and ensuing impacts. At SASP, end of year dust concentrations ranged from 0.83 mg g?1 to 4.80 mg g?1, and daily mean spring dust radiative forcing ranged from 50–65 W m?2, advancing melt by 24–49 days. At GMSP, which received 1.0 mg g?1 less dust per season on average, spring radiative forcings of 32–50 W m?2 advanced melt by 15–30 days. Remote sensing imagery showed that observed dust events were frequently associated with dust emission from the southern Colorado Plateau. Dust from these sources generally passed south of GMSP, and back trajectory footprints modelled for observed dust events were commonly more westerly and northerly for GMSP relative to SASP. These factors suggest that although the southern Colorado Plateau contains important dust sources, dust contributions from other dust sources contribute to dust loading in this region, and likely account for the majority of dust loading at GMSP. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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为研究东亚地区矿物尘气溶胶的直接辐射效应,在区域气候模式RegCM3中加入起尘方案、建立矿物尘气溶胶输送模式,并将其辐射过程加入区域气候模式的辐射方案.通过对2001年3月～2002年3月的模拟发现：中国西北和蒙古国年平均地表起尘率在1μg/(m2·s)以上,最大达到90μg/(m2·s)是东亚地区最主要的矿物尘气溶胶源地;东亚地区矿物尘气溶胶柱含量最大值达5g/m2,出现在塔克拉玛干沙漠和秦岭地区;气溶胶大气顶直接辐射强迫基本呈现大陆上为正、海洋上正负均有的分布特征,区域平均辐射强迫在春夏秋冬分别为108, 088, 037,040W/m2,短波辐射强迫在陆上为正、海上正负均有,长波辐射强迫均为正值;四季的地表辐射强迫分别为-564, -225, -137, -187W/m2;辐射强迫数值对矿物尘气溶胶单次散射反照率的变化较敏感. 相似文献
5.
With a radiative transfer model, assessments are made of the radiative forcing in northern mid-latitudes due to aircraft emissions up to 1990. Considered are the direct climate effects from the major combustion products carbon dioxide, nitrogen dioxide, water vapor and sulphur dioxide, as well as the indirect effect of ozone production from NOx emissions. Our study indicates a local radiative forcing at the tropopause which should be negative in summer (-0.5 to 0.0 W/m2) and either negative or positive in winter (-0.3 to 0.2 W/m2). To these values the indirect effect of contrails has to be added, which for the North Atlantic Flight Corridor covers the range -0.2 to 0.3 W/m2 in summer and 0.0 to 0.3 W/m2 in winter. Apart from optically dense non-aged contrails during summer, negative forcings are due to solar screening by sulphate aerosols. The major positive contributions come from contrails, stratospheric water vapor in winter and ozone in summer. The direct effect of NO2 is negligible and the contribution of CO2 is relatively small. 相似文献
6.
本文应用欧洲中期预报中心（ECMWF,European Centre for Medium\|Range Weather Forecasts—ERA\|40）资料和美国国家环境预测中心和国家大气研究中心(NCEP/NCAR, National Centers for Environmental Prediction/National Center for Atmospheric Research)资料,研究了青藏高原雪深变化对南海夏季风爆发的影响和ENSO对青藏高原降雪的影响.结果表明：（1）ECMWF的雪深资料是可信的,可以用来研究青藏高原雪深变化对南海夏季风爆发的影响;（2）青藏高原的积雪异常影响到500 hPa以上的温度异常和印度洋与大陆间的气温对比,一方面使上层的南亚高压移动速度发生变化,另一方面也影响到低层大气的运动和东西向风异常,在青藏高原少雪年,东印度洋产生西风异常和一个气旋对,而在青藏高原多雪年,东印度洋产生东风异常和一个反气旋对;（3）ENSO与青藏高原春季积雪关系密切.东太平洋SST正异常时,东印度洋和南海气压偏高,从而导致该区海陆经向压强梯度增强和西风异常.另外,此时青藏高原北部气压偏高,北风偏强,副热带锋面增强,同时,印度洋的SST偏高,为青藏高原降雪提供了水汽保障,这些都有利于青藏高原的降雪. 相似文献
7.
观测资料的分析极为清楚地表明,江淮流域的夏季降水有着极为明显的低频变化,周期为30-60d和近20d的振荡是其最基本的特征,尤其是在多雨的年份.对应江淮夏季多雨(涝)年和少雨(旱)年,大气环流的分析表明其大气季节内振荡(IS0)的形势有着显著的差异.例如在多雨(少雨)年,在长江以南的850hPa上为一个低频(IS0)反气旋(气旋)性环流控制,而中国北部和日本一带为气旋(反气旋)性环流,从而在江淮流域形成较强的低频辐合(辐散)气流;在200hPa的青藏高原上却为一个低频气旋(反气旋)性环流所控制.分析还表明,对应多雨年,在江淮流域有明显的由中高讳度向南传播和由低玮度向北传播的大气低频振荡的汇合情况;而对应于少雨年,由中高纬度向南传播的低频系统较不明显,在江淮流域低频系统的汇合也较为不清楚. 相似文献
8.
《Journal of Atmospheric and Solar》2008,70(5):820-834
Extensive and collocated measurements of several aerosol parameters were made over the eastern Arabian Sea, during the inter-monsoon and summer monsoon seasons of 2003 as a part of the Arabian Sea Monsoon Experiment (ARMEX). Associated with the seasonal changes in the synoptic wind fields from northeasterly/easterly to westerly/northwesterly, the aerosol characteristics and columnar optical depth show large variations. Consequently, the atmospheric forcing is found to increase from March to April and then to decrease consistently towards June. However, the magnitude of the forcing efficiency of aerosols continuously decreases from winter to summer. Such temporal changes in radiative forcing need to be accounted for in reducing the uncertainty in aerosol climate impact. 相似文献
9.
R. Meerkötter U. Schumann D. R. Doelling P. Minnis T. Nakajima Y. Tsushima 《Annales Geophysicae》1999,17(8):1080-1094
A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres. Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere, a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 Wm−2 daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude. The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover. 相似文献
10.
The effect of present-day and future NOx emissions from aircraft on the NOx and ozone concentrations in the atmosphere and the corresponding radiative forcing were studied using a three-dimensional chemistry transport model (CTM) and a radiative model. The effects of the aircraft emissions were compared with the effects of the three most important anthropogenic NOx surface sources: road traffic, electricity generation and industrial combustion. From the model results, NOx emissions from aircraft are seen to cause an increase in the NOx and ozone concentrations in the upper troposphere and lower stratosphere, and a positive radiative forcing. For the reference year 1990, the aircraft emissions result in an increase in the NOx concentration at 250 hPa of about 20 ppt in January and 50 ppt in July over the eastern USA, the North Atlantic Flight Corridor and Western Europe, corresponding to a relative increase of about 50%. The maximum increase in the ozone concentrations due to the aircraft emissions is about 3-4 ppb in July over the northern mid-latitudes, corresponding to a relative increase of about 3-4%. The aircraft-induced ozone changes cause a global average radiative forcing of 0.025 W/m2 in July. According to the ANCAT projection for the year 2015, the aircraft NOx emissions in that year will be 90% higher than in the year 1990. As a consequence of this, the calculated NOx perturbation by aircraft emissions increases by about 90% between 1990 and 2015, and the ozone perturbation by about 50-70%. The global average radiative forcing due to the aircraft-induced ozone changes increases by about 50% between 1990 and 2015. In the year 2015, the effects of the aircraft emissions on the ozone burden and radiative forcing are clearly larger than the individual effects of the NOx surface sources. Taking chemical conversion in the aircraft plume into account in the CTM explicitly, by means of modified aircraft NOx emissions, a significant reduction of the aircraft-induced NOx and ozone perturbations is realised. The NOx perturbation decreases by about 40% and the ozone perturbation by about 30% in July over Western Europe, the eastern USA and the North Atlantic Flight Corridor. 相似文献
11.
Snow and ice present interesting challenges to hydrologists. Simulating the radiative balance over snow, which is an important part of surface–atmosphere interactions, is particularly challenging because of the decay in albedo over time and the difficulty in estimating surface temperature and incoming long-wave radiation fluxes. Few models are available that include a comprehensive energy and water balance for cold season conditions. The simultaneous heat and water model (SHAW) is a detailed, physical process model of a vertical, one-dimensional canopy–snow–residue–soil system which integrates the detailed physics of heat and water transfer through a plant canopy, snow, residue and soil into one simultaneous solution. Detailed provisions for metamorphosis of the snowpack are included. The SHAW model was applied to data for one winter/spring season (November to May) on a ploughed field in Minnesota without prior calibration to test the performance of the radiation components. Maximum snow depth during this period was 30 cm. For the nearly 100 days of snowcover, the model accounted for 69% of the variation in net solar radiation, 66% of the variation in incoming long-wave radiation, 87% of the variation in emitted long-wave radiation, 26% of the variation in net long-wave radiation and 55% of the variation in net radiation balance. Mean absolute error in simulated values ranged from 10 W m−2 for emitted long-wave radiation to 27 W m−2 for the entire net radiation balance. Mean bias error ranged from 8 W m−2 for emitted long-wave radiation to −16 W m−2 for the entire net radiation balance. When the entire 170 days of simulation, which included periods without snowcover, were included in the analysis, the variation in observed values increased greatly. As a result, the variation in observed values accounted for by the model increased to 97, 71, 93, 56 and 94%, respectively, while the mean absolute and mean bias errors in simulated values remained nearly the same. Model modifications and parameter adjustments necessary to improve winter-time simulation were investigated. Simulation results suggest that the SHAW model may be a useful tool in simulating the interactive influences of radiative transfer at the surface–atmosphere interface. 相似文献
12.
Since 2000, 18 High Asia glaciers have been surveyed for black carbon (BC) deposition 22 times, and numerous snow samples and ice cores have been collected by researchers. However, most of the results were interpreted individually in papers. Here, we assemble the data and discuss the distribution of BC deposition and its impacts on the melting of the glaciers through radiative forcing. We find that BC distribution on the surfaces of High Asia glaciers primarily depends upon their elevations (i.e., higher sites have lower concentrations) and then upon regional BC emissions and surface melting conditions. BC concentrations in High Asia glaciers are similar to the Arctic and western American mountains but are significantly less than heavy industrialized areas such as northern China. Although Himalayan glaciers, which are important due to their water resources, are directly facing the strong emissions from South Asia, their mean BC is the lowest due to high elevations. A new finding indicated by ice core records suggested that great valleys in the eastern Himalayan section are effective pathways for BC entering the Tibetan Plateau and make increasing BC trends in the local glaciers. On average, BC deposition causes a mean forcing of ∼6 W m−2 (roughly estimated 5% of the total forcing) in High Asia glaciers and therefore may not be a major factor impacting the melting of most glaciers. 相似文献
13.
Z.N. Begum 《Journal of Atmospheric and Solar》1998,60(18):1751-1754
A theoretical model based on some physical assumptions has been integrated to study the scattering of solar radiation by aerosol particulates of any size present in the atmosphere. Using this model, which incorporates multiple scattering, scattered fluxes of radiation with varying optical depths and also the optical depth versus wavelengths are computed. The present results are found to be in close agreement with the observations of the Pre-Indian Ocean Experiment (INDOEX) 1996. This provides evidence of the direct effect of aerosol particulates on the radiative forcing of the atmosphere. 相似文献
14.
An algorithm based on simulated satellite signal calculated by the 6S radiative transfer model has been developed in order to retrieve the aerosol optical thickness of dust over the Atlantic ocean. The algorithm is applied to the visible channel of Geostationary Operational Environmental Satellite (GOES 8) images. The inversion uses a look-up table giving the satellite signal intensity as a function of surface albedo, viewing geometry, solar illumination and the optical properties of the aerosols. The study consists of assessing the feasibility of monitoring and mapping the transport of suspended particles across the Atlantic from the Sahara to the Caribbean. The study area is between 10 and 25 N and 30 and 65 W. The optical thickness of aerosols has been calculated over a period of 11 days between 10th and 20th of June 1997 for the 14:15 UT GOES image acquisition. The calculated aerosol optical thickness ranges from 0.0 to 0.81 with an important event of dust presence occurring between 13th and 16th of June. The retrieved aerosol optical thickness is in good agreement with the values obtained between 14h UT and 15h UT from ground based sun photometer measurements on the island of Guadeloupe, and a coefficient correlation (R2) of 0.88 has been found between the data sets. 相似文献
15.
本文利用大气环流模式及大气化学模式所得气溶胶资料,估算了相对1850s时期硫酸盐和黑碳气溶胶引起的全球及东亚区域人为辐射强迫,重点分析其在东亚区域的季节和长期变化特征.结果表明,就当前全球年平均全天空而言,人为硫酸盐气溶胶对大气顶的直接和云反照率强迫分别为-0.37和-0.98 W·m-2,黑碳气溶胶对大气顶和整层大气的辐射强迫值为0.16和0.47 W·m-2;中国东部区域是目前上述气溶胶辐射强迫最强的区域,硫酸盐的直接和间接辐射强迫分别超过-2.0和-4.0 W·m-2,黑碳对大气顶和整层大气的直接辐射强迫分别可达2.0和5.0W·m-2;估算的东亚区域上述气溶胶辐射强迫仍在不断增强,峰值预计出现在2010s时段,而且中国东部较强的辐射强迫还可能维持至2030s左右;在未来中、高排放情景下,东亚区域以上两种气溶胶预计对全球气溶胶辐射强迫有更大的贡献.分析还表明,夏季东亚区域较强的水汽会增强吸湿性硫酸盐气溶胶的光学厚度和晴空直接辐射强迫;云的作用一方面会强化东亚区域全天空条件下大气顶黑碳的辐射强迫,另一方面会影响硫酸盐气溶胶间接云反照率强迫的季节变化;上述气候特征的差异使得东亚区域的气溶胶辐射强迫表现出与欧美区域有所不同的特征.本文所用的气溶胶资料与模式气象场的偏差会给气溶胶辐射强迫计算带来一些不确定性,进一步改进气候模式中气溶胶过程、水汽和云等气象场的模拟将有助于获得更为合理的区域气溶胶辐射强迫估算结果. 相似文献
16.
K.V.S. Badarinath Shailesh Kumar Kharol Anu Rani Sharma 《Journal of Atmospheric and Solar》2009,71(1):112-120
Agriculture crop residue burning in tropics is an important source of atmospheric aerosols and monitoring their long-range transport is an important element in climate change studies. Synchronous measurements using micro-pulsed lidar, MICROTOPS-II sun photometer, multi-filter rotating shadow band radiometer (MFRSR) on aerosol optical depth and ground reaching solar irradiance were carried at an urban location in central region of India. Aerosol backscatter profiles obtained from micro-pulse lidar showed elevated aerosol layers up to ～3 km on certain days during October 2007. Satellite data observations on aerosol properties suggested transport of particles from agriculture crop residue burning in Indo-Gangetic Plains over large regions. Radiative forcing of aerosols estimated from SBDART model with input information on aerosol chemical properties, aerosol optical depth and single scattering albedo and broadband solar irradiance measurements using MFRSR showed good correlation (R=0.98). 相似文献
17.
C. O. Oluwafemi 《Pure and Applied Geophysics》1983,121(5-6):1065-1076
Solar, sky, and aureole radiance data from Kensington, Australia, and Lagos, Nigeria, are analysed. The values of the aerosol
optical thickness at Lagos are comparable to measured values elsewhere in the subregion (Abidjan) under light haze. The values
at Kensington are close to those of the “background aerosol.” Identical and anomalous values of aerosol optical thickness
occurred at 1.67 μm at both stations as less than 15% of the values can be accounted for by aerosols. The high optical depths
are therefore explained in terms of absorption, possibly mainly by CO2 (59–65%) and, to a lesser extent, by H2O (20–26%). Following correction for molecular multiple scattering, the aerosol scattering phase function increases substantially
at 0.5 μm in Kensington and decreases considerably at 0.76 μm in Lagos when compared to the uncorrected function, confirming
the relative fineness of the Kensington aerosol. The Lagos aerosol size distribution for moderately dusty air is reasonably
bimodally log-normal with modal radiusr
m=0.49 μm (1.36 μm) for the moder≤1 μm (r>1 μm). The Kensington aerosol resembles one withr
m=0.05 μm forr<1 μm. There the Born approximation appears appropriate, and the weighted mean square radiusp
2=0.13 μm2. In the near forward direction the aerosol scattering phase funciton for Lagos resembles Deirmendjian’s simulations for a
silicate-L haze and, for Kensington, a silicate-H haze. 相似文献
18.
《Journal of Atmospheric and Solar》1999,61(1-2):25-36
From the coldest period of the Little Ice Age to the present time, the surface temperature of the Earth increased by perhaps 0.8°C. Solar variability may account for part of this warming which, during the past 350 years, generally tracks fluctuating solar activity levels. While increases in greenhouse gas concentrations are widely assumed to be the primary cause of recent climate change, surface temperatures nevertheless varied significantly during pre-industrial periods, under minimal levels of greenhouse gas variations. A climate forcing of 0.3 W m−2 arising from a speculated 0.13% solar irradiance increase can account for the 0.3°C surface warming evident in the paleoclimate record from 1650 to 1790, assuming that climate sensitivity is 1°C W−1 m−2 (which is within the IPCC range). The empirical Sun–climate relationship defined by these pre-industrial data suggests that solar variability may have contributed 0.25°C of the 0.6°C subsequent warming from 1900 to 1990, a scenario which time dependent GCM simulations replicate when forced with reconstructed solar irradiance. Thus, while solar variability likely played a dominant role in modulating climate during the Little Ice Age prior to 1850, its influence since 1900 has become an increasingly less significant component of climate change in the industrial epoch. It is unlikely that Sun–climate relationships can account for much of the warming since 1970, not withstanding recent attempts to deduce long term solar irradiance fluctuations from the observational data base, which has notable occurrences of instrumental drifts. Empirical evidence suggests that Sun–climate relationships exist on decadal as well as centennial time scales, but present sensitivities of the climate system are insufficient to explain these short-term relationships. Still to be simulated over the time scale of the Little Ice Age to the present is the combined effect of direct radiative forcing, indirect forcing via solar-induced ozone changes in the atmosphere, and speculated charged particle mechanisms whose pathways and sensitivities are not yet specified. 相似文献
19.
《Journal of Atmospheric and Solar》1999,61(6):425-446
Measurements of both broadband and spectral UV radiation have been carried out at Lhasa (29°40′N, 91°08′E, 3648 m above sea level) on the Tibetan Plateau, using a moderate bandwidth filter instrument (NILUV) and a Fixed Imaging Compact Spectrometer (FICS). In this paper, the erythemal UV dose rates deduced from broadband measurements during the period from 1 July 1996 to 10 December 1997 are presented. The observed highest erythemal UV dose rate is 500 (or 458) mW/m2 in July 1996 (or 1997), and the corresponding daily erythemal UV dose can reach up to 7.60 (or 7.00) kJ/m2 and 9.18 (or 8.96) kJ/m2, respectively, for the monthly mean and the monthly maximum. Comparisons with the UV levels at other locations at similar latitudes show that both the monthly mean and monthly maximum erythemal UV doses at Lhasa can be higher by a factor of 1.3–1.5 than those at San Diego (32°05′N, 117°1′W) in summer (from May to August), and exceed the corresponding values at Perth (32°0′S, 115°8′E) in the southern hemisphere summer (from November to February) by a factor of 1.2–1.4. Comparisons of both the broadband measurements and spectral measurements with the outputs of a discrete ordinate method (DOM) radiative transfer model have also been conducted. The results from the comparisons of broadband measurements with model outputs show that a 15, 11 and 10% agreement may be achieved around solar noon (with solar zenith angle smaller than 60°), respectively, for global irradiances in the 305, 320 and 340 mm channels, whilst the corresponding agreements are about 8 and 4% for the erythemal UV dose rate and the 340–305 nm ratio, respectively. The comparisons of the measured spectral irradiance with model calculations indicate that large discrepancies may appear at wavelengths shorter than 310 nm and longer than 380 nm. However, a 10% agreement may be generally achieved in UVA for solar zenith angle lower than 55°C. The corresponding agreement is about 20 and 5%, respectively, for UVB and the erythemal UV dose rate. 相似文献
20.
The fundamental mode Love and Rayleigh waves generated by ten earthquakes and recorded across the Tibet Plateau, at QUE, LAH, NDI, NIL, KBL, SHL, CHG, SNG and HKG are analysed. Love- and Rayleigh-wave attenuation coefficients are obtained at time periods of 5–120 s using the spectral amplitudes of these waves for 23 different paths. Love wave attenuation coefficient varies from 0.0021 km?1, at a period of 10 s, to 0.0002 km?1 at a period of 90 s, attaining two maxima at time periods of 10 and 115 s, and two minima at time periods of 25 and 90 s. The Rayleigh-wave attenuation coefficient also shows a similar trend. The very low value for the dissipation factor, Qβ, obtained in this study suggests high dissipation across the Tibetan paths. Backus-Gilbert inversion theory is applied to these surface wave attenuation data to obtain average Qβ?1 models for the crust and uppermost mantle beneath the Tibetan Plateau. Independent inversion of Love- and Rayleigh-wave attenuation data shows very high attenuation at a depth of ～50–120 km (). The simultaneous inversion of the Love and Rayleigh wave data yields a model which includes alternating regions of high and low Qβ?1 values. This model also shows a zone of high attenuating material at a depth of ～40–120 km. The very high inferred attenuation at a depth of ～40–120 km supports the hypothesis that the Tibetan Plateau was formed by horizontal compression, and that thickening occurred after the collision of the Indian and Eurasian plates. 相似文献