火山活动对热带高空温度变化的影响

本文利用序列回归分析、对比分析和个例分析法分析了火山活动对热带高空大气的温度效应. 主要结论为：火山活动影响最显著的高度是平流层70 hPa约22 km高空,由此高度向上或向下,火山活动的影响都逐渐减小;火山活动将引起平流层大气升温、对流层大气降温,其分界线大致位于对流层顶300 hPa附近;火山活动对于热带70 hPa高空温度距平变化的影响超过了总方差的45.7%;单独考察几次强火山活动（如阿贡火山、皮纳图博火山和厄尔奇冲火山等）的温度效应表明,在热带地区强火山爆发后的20个月内,对热带高空温度的影响超过了其距平变化的80%！成为该时段高空温度变化的决定性因素.     

平流层准两年变化对南海夏季风影响机制的探讨

利用美国大气研究中心(the National Center for Atmospheric Research, NCAR)的中层大气模式模拟了平流层准两年振荡(Quasi-Biennial Oscillation, QBO)过程对对流层顶和对流层上层的影响, 并结合NCEP(the National Centers for Environmental Prediction)/NCAR、欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)月平均的风场资料和实际的探空观测资料, 分析了平流层QBO对南海夏季风的影响作用. 结果表明: 平流层QBO会引起平流层的异常经向环流并向下传播, 在QBO位相的中后期和位相转换期影响到对流层顶和对流层上层, 使热带和低纬度的对流层上层形成异常的经向气压梯度, 最终在夏季的对流层热带地区激发出不同类型的异常环流—西风位相时, 激发出与南海夏季风环流相反的异常环流, 在南海地区有显著的异常下沉运动, 对南海夏季风有削弱作用; 东风位相时, 激发出反Hadley环流型的异常环流, 在南海地区有明显的异常上升气流, 对南海夏季风有加强的效果. 虽然QBO对南海夏季风经向环流有影响, 但它并不是决定南海夏季风准两年变化的唯一因子.     

北半球平流层极涡崩溃过程的动力诊断分析

极地气候变化研究, 特别是极地在气候变化中作用的研究, 现在已经成为国际重要的研究领域, 是2007~2008年开展的“国际气候年”的核心研究问题. 针对以前研究中北半球平流层极涡崩溃时间的分歧, 首先确定了北半球平流层极涡在春季的崩溃时间, 并分析了在平流层极涡崩溃过程中的环流演变和波动活动特征. 分析表明北半球平流层极涡的平均崩溃时间为4月10日左右, 极涡崩溃时间的年际变化比较大, 最早和最晚的崩溃时间跨度达到两个月. 长期趋势表明20世纪90年代以来极涡持续时间增长. 对极涡崩溃异常早年和异常晚年的合成分析显示极涡崩溃过程在早晚年有不同的特征. 极涡崩溃早年, 平流层极涡在3月中旬只有一次快速的衰减过程, 这次过程主要与对流层上传的行星尺度波动异常有关; 而极涡崩溃异常晚年一般有两次衰减过程, 第一次衰减为一次快速过程, 对应有异常的波动活动, 和平流层的爆发性增温有关. 第二次过程则是一次慢过程, 此次过程不伴随异常的波动活动, 主要是非绝热过程起作用. 进一步对极涡崩溃异常早晚年大气低层环流异常的研究表明, 极涡崩溃早晚年低层温度场和位势高度场的异常上有明显不同, 这表明平流层极涡的崩溃伴随有上下层的动力耦合过程.     

青藏高原地面加热场强度对北半球大气环流和中国天气气候异常的影响研究

选取拉萨、玉树和伍道梁分别作为青藏高原南部、东部和中北部地面加热场强度的代表站, 对青藏高原地面加热场强度的基本气候特征以及异常变化趋势作了分析; 对高原地面加热场强度异常对北半球大气环流和中国气候异常的影响进行了统计诊断研究.     

北半球春季平流层最后增温过程及其年际和年代际变化特征

利用1979～2010年NCEP-DOE 2逐日再分析资料,以北半球春季平流层极夜急流核心纬带(65°～75°N)纬向平均纬向风最后一次转为东风的日期定义为春季平流层最后增温事件(SFW)的爆发日期,研究发现,SFW事件平均在4月中下旬发生,且由平流层高层向低层依次滞后,10 hPa的SFW爆发平均超前50 hPa约13天;爆发当日伴随纬向风场时间变率和行星波辐合的最大值,平流层环流实现由冬向夏的季节转换;过去32年以来SFW的爆发早晚具有显著的年际变化,最早的SFW事件发生在3月中旬,最晚的SFW事件在5月下旬才出现.合成分析表明,SFW爆发偏早(晚)年的春季,纬向风场由西风向东风的转变更为快速(缓慢),爆发前5天至爆发后5天,30 hPa纬向风减小约20 m s-1(5 m s-1),伴随的平流层行星波活动也相对较强(弱);表现在环流异常场上,SFW爆发前后平流层极区环流异常呈反(同)位相分布,表明发生较早的SFW事件主要受波强迫驱动而伴随爆发性增温,而发生较晚的SFW事件则更反映了极涡的季节变化特征.无论SFW偏早还是偏晚年,爆发后极区平流层与对流层温度异常之间均呈反位相关系,反映了SFW爆发事件中的平流层-对流层动力耦合特征.另外,在20世纪90年代中期前后,SFW爆发日期还存在明显的年代际转折,90年代中期之前SFW平均发生日期较之后约偏早11天;与之相联系的是冬末、春初行星波活动在90年代中期之前偏强,而在90年代中期之后有偏弱趋势.     

ENSO对平流层气溶胶分布的影响

本文采用ONI(Oceanic Nino Index)和HALOE(Halogen Occultation Experiment)气溶胶面积密度资料,从其滞后相关性入手分析了ENSO循环对平流层气溶胶的影响,通过对滞后于El Nino和La Nina时气溶胶含量的比较探讨了ENSO强迫的影响程度,并用剩余环流及其输送量解释了平流层气溶胶变化的动力机制.结果表明:ENSO对平流层气溶胶的分布有明显影响,在赤道和低纬度上空尤为显著,El Nino发生后半年内热带平流层低层的气溶胶面积密度较平均值偏大,平流层中层的面积密度则偏小,而La Nina反之.El Nino和La Nina影响的差异显著,在分别滞后于El Nino和La Nina事件2~8个月间的60 hPa气溶胶含量差异甚至高达45%,海表温度变化1 K则在滞后半年内气溶胶面积密度的变化可达到16%.ENSO的强烈影响能够维持大约半年,两年后基本消退.热带的变化幅度明显强于中高纬度,南北半球的变化特征也有所不同.ENSO通过影响剩余环流导致气溶胶输送量发生变化,进而引起气溶胶分布出现上述差异.     

平流层爆发性增温期间赤道电集流中太阴潮汐的经度变化统计学研究

本文利用地磁台站和卫星磁场数据,对平流层爆发性增温(Sudden Stratospheric Warming,SSW)期间赤道电集流(Equatorial Electrojet,EEJ)中太阴半日潮汐的经度变化进行了统计学分析.结果显示,SSW期间秘鲁和印度扇区的EEJ中太阴半日潮汐明显增强,且存在显著的经度差异.秘鲁扇区的EEJ中太阴半日潮汐达到峰值的时间要早于印度扇区,进一步分析发现峰值时间的经度差异与太阳活动和准两年振荡相位有关.此外,SSW期间秘鲁扇区EEJ的太阴半日潮汐峰值强度比印度扇区高.对比不同经度带背景磁场的强度与太阴半日潮汐的峰值幅度的关系,可以看出SSW期间EEJ太阴半日潮汐峰值幅度的经度差异与背景磁场强度有关,但也存在其他物理过程的影响.     

亚洲夏季平流层-对流层水汽交换年际变化与亚洲夏季风的联系

亚洲地区是物质由对流层向平流层输送的主要通道,在平流层-对流层交换中扮演着积极的角色. 本文主要利用卫星资料和欧洲中心ERA40再分析资料,借助Wei诊断模式研究亚洲地区夏季上对流层-下平流层(UTLS)水汽分布和平流层-对流层水汽交换特征,重点着眼于水汽交换的年际变化,并探讨其与亚洲夏季风的联系. 结果表明,季风区UTLS水汽较赤道地区偏多,且通过磁带记录信号的传播,可穿越对流层顶影响下平流层水汽的多寡. 夏季平流层-对流层水汽交换表现出明显的年际特征,其年际变化与亚洲季风强弱变化有密切联系,尤其与南亚夏季风的关系更为显著. 在亚洲夏季风影响下,亚洲地区出现异常的大气环流和垂直运动,从而影响平流层-对流层之间水汽的交换. 这些结果对认识其它大气成分的输送过程也具有重要的指示意义.     

琼州海峡裂谷成因的火山活动标志

根据雷琼地区存在大规模火山活动以及新生界明显地由断陷的南、北侧向海峡急剧增厚的事实，结合近年来海峡地区的物探成果，论证了琼州海峡的裂谷成因，是上地幔物质上涌的结果。该地区的高热流值、高地热增温率和强震活动都说明，琼州海峡是现今仍具有一定活动性的裂谷构造。     

副热带急流强度和赤道QBO对平流层突然增温的影响

使用一个全球原始方程半谱模式模拟了副热带急流强度和赤道准两年振荡（ＱＢＯ）对平流层突然增温（ＳＳＷ）的影响．结果指出：副热带急流强度对ＳＳＷ有明显影响,副热带急流越强,ＳＳＷ发展越快,极区最大增温区的高度越低;赤道ＱＢＯ不同相位零风线的南北位移对ＳＳＷ没有明显影响;ＱＢＯ东风相位时副热带急流更强,而ＱＢＯ西风相位时副热带急流较弱的观测事实,可能是大的中冬ＳＳＷ更容易发生在ＱＢＯ东风相位的主要原因．     

高空大气涛动现象与太阳活动的联系

本文根据全球高空10 hPa位势高度距平场EOF分析得知,存在于地面层大气中的南北向涛动现象~北极高空大气涛动和南极涛动,在高空大气中更为清楚,而且这种高空南北向涛动现象是波及全球的;存在于地面层大气中著名的纬向涛动现象~南方涛动(Southern Oscillation,SO)和北方涛动(North Oscillation,NO),在高空大气中则变得不甚清楚.表征北极高空大气涛动的第一模态与表征南极涛动的第二模态的方差贡献率分别为41.47%和27.04%,二者累积方差贡献率达到68.51%,构成了平流层高空大气年代际振荡的主要形式;另外还存在两半球对称性中高纬度南极涛动模态和两半球不对称性中高纬度南极涛动模态,是高空大气中出现概率比较小的振荡形式.谱分析表明,无论北极高空大气涛动模态、南极涛动模态还是中高纬度纬向涛动模态,都存在与太阳磁场磁性指数相一致的22年准周期变化以及与太阳黑子相对数相一致的11年准周期变化;采用逐次滤波法的滤波分析和对比分析表明,高空大气涛动现象的重要影响因子乃太阳活动,其中太阳磁场的大幅度涨落及其磁性变化是主要因素,太阳黑子相对数的变化为次要因素.     

姑咱台SS-Y伸缩仪数字化观测数据异常分析

以姑咱地震台SS-Y伸缩仪2007年至2013年12月的日均值资料作为研究对象,分析日均值资料的年变特征;对2007年以来甘孜藏族自治州及邻区发生的几次中强地震前SS-Y仪的异常变化进行了分析研究,对该观测项数字化资料的映震能力获得了初步认识,有利于挖掘数字化资料中的地震前兆异常信息。     

理塘毛垭温泉水温异常研究

1975-2005年间，四川省理塘毛垭温泉水温变化与地震有一定的对应.地热变化异常与地震的密切关系已被较多震例所证实. 2005年2月25日（温泉水温53 ℃）～3月14日（温泉水温26.9 ℃），毛垭温泉水温下降了26.1 ℃，2月水温月均值54.1 ℃、3月水温月均值30.7 ℃，下降了23.4 ℃，这一现象引起了地震系统各级领导和专家的高度重视.2005年3月中国地震局监测预报司在成都主持召开了南北地震带紧急震情会商会.根据会议决定，四川省地震局预报研究所组织了“毛垭温泉水温异常专题研讨会”，针对毛垭温泉水温下降异常，将30年来的资料进行了系统全面的分析，对于毛垭温泉的地震地质背景、温泉的热源、水温异常与强地震的关系作了较深入的研究，并且重点研究了水温下降异常特征与川滇两省强震的关系，对于毛垭温泉未来水温的三种动态变化趋势和近期川滇两省的强震趋势进行了探讨。     

Horizontal eddy diffusivities in the northern hemispheric stratosphere and lower mesosphere

Meterological rocket soundings, launched between 1969–74 at six locations representative of low, middle, and high altitudes, are employed with the use of the statistical theory of diffusion, to determine the zonal and meridional component of eddy diffusivity between 30 and 55 km as a function of season, latitude, and altitude. A comparison is also made between annually-averaged eddy diffusivities above and below 30 km.It is shown that the zonal component of eddy diffusivity is approximately three to five times as large as the meridional component, in most cases. Both components of eddy diffusivity vary greatly with season, latitude, and altitude. Highest eddy diffusivities, found in the vicinity of the winter westerly jet, are approximately one order of magnitude higher than those present during the summer. Tropical eddy diffusivities, however, remain relatively small throughout the year. Annually, a minimum is indicated near 25 km between maximums located at the stratopause and tropopause.     

The 11-year solar cycle, the Sun's rotation, and the middle stratosphere in winter. Part II: Response of planetary waves

The effect of the 11-year solar cycle on the response of planetary wavenumbers 1 and 2 at 10 and 30 hPa in winter to solar activity oscillations on the time scale of the Sun's rotation (27.2 day) is discussed in terms of statistical spectral analysis. The three oscillations studied are the 27.2 d (period of the Sun's rotation), 25.3 d (periodicity caused by modulation of the 27.2 d stratospheric response by annual atmospheric variation), and 54.4 d (doubled period of the solar rotation). A significant effect of the 11-year solar cycle is found for the 54.4 d periodicity in planetary wavenumber 1, and for the 27.2 and 25.3 d periodicities in planetary wavenumber 2. The effect of the 11-year solar cycle is expressed in the evident differences between the amplitudes of responses of planetary waves at maximum and minimum of the solar cycle: the amplitudes are much larger at high than at low solar activity. The 11-year modulation of planetary wave activity is most pronounced at mid-latitudes, mainly at 40–60°N, where the observed variability of planetary waves is large. The results obtained are in good agreement with results of the recent modeling study by Shindell et al. (Science 284 (1999) 305).     

Modelling the effects of land use and climate changes on hydrology in the Ursern Valley,Switzerland

While many studies have been conducted in mountainous catchments to examine the impact of climate change on hydrology, the interactions between climate changes and land use components have largely unknown impacts on hydrology in alpine regions. They need to be given special attention in order to devise possible strategies concerning general development in these regions. Thus, the main aim was to examine the impact of land use (i.e. bushland expansion) and climate changes (i.e. increase of temperature) on hydrology by model simulations. For this purpose, the physically based WaSiM‐ETH model was applied to the catchment of Ursern Valley in the central Alps (191 km²) over the period of 1983?2005. Modelling results showed that the reduction of the mean monthly discharge during the summer period is due primarily to the retreat of snow discharge in time and secondarily to the reduction in the glacier surface area together with its retreat in time, rather than the increase in the evapotranspiration due to the expansion of the “green alder” on the expense of grassland. The significant decrease in summer discharge during July, August and September shows a change in the regime from b‐glacio‐nival to nivo‐glacial. These changes are confirmed by the modeling results that attest to a temporal shift in snowmelt and glacier discharge towards earlier in the year: March, April and May for snowmelt and May and June for glacier discharge. It is expected that the yearly total discharge due to the land use changes will be reduced by 0.6% in the near future, whereas, it will be reduced by about 5% if climate change is also taken into account. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of climate changes and water‐related human activities on annual stream flows of the Shiyang river basin in arid north‐west China

The change of annual stream flow in the Shiyang river basin, a typical arid‐inland basin in north‐west China, was investigated using hydrological, meteorological and water‐related human activities' data of the past 50 years. The long‐term trends of the hydrological time series were examined by non‐parametric techniques, including the Pettitt and Mann–Kendall tests. Double cumulative curves and multi‐regression methods were used to separate and quantify the effects of climate changes and human activities on the stream flows. The results show that the study area has been experiencing a significant upward warming trend since 1986 and precipitation shows a decreasing trend in the mountainous region but an increasing trend in the plains region. All stream flows in the upper reach and lower reaches of the Shiyang river exhibit decreasing tendencies. Since 1970, human activities, such as irrigation, have had a significant effect on the upstream flow, and account for 60% of total flow decreases in the 1970s. However, climate changes are the main reason for the observed flow decreases in the 1980s and 1990s, with contributions to total flow decrease of 68% and 63%, respectively. Before 1975, flow decreases in the upper reaches were the main factor causing reduced flows in the lower reaches of the Shiyang river. After 1975, the effect of human activities became more pronounced, with contributions of 63%, 68% and 56% to total flow decreases in the lower reaches of the Shiyang river in the periods 1975 to 1980, 1980s and 1990s, respectively. As a result, climate change is responsible for a large proportion of the flow decreases in the upstream section of the catchment during the 1980s and 1990s, while human activities have caused flow decreases downstream during the same period. Copyright © 2007 John Wiley & Sons, Ltd.     

Homogenization of climate series:The basis for assessing climate changes

Long-term meteorological observation series are fundamental for reflecting climate changes.However,almost all meteorological stations inevitably undergo relocation or changes in observation instruments,rules,and methods,which can result in systematic biases in the observation series for corresponding periods.Homogenization is a technique for adjusting these biases in order to assess the true trends in the time series.In recent years,homogenization has shifted its focus from the adjustments to climate mean status to the adjustments to information about climate extremes or extreme weather.Using case analyses of ideal and actual climate series,here we demonstrate the basic idea of homogenization,introduce new understanding obtained from recent studies of homogenization of climate series in China,and raise issues for further studies in this field,especially with regards to climate extremes,uncertainty of the statistical adjustments,and biased physical relationships among different climate variables due to adjustments in single variable series.     

Response of grain size of Quaternary gravels to climate and tectonics in the northern Tibetan Plateau

The widely distributed thick gravel deposits along the rim of the Tibetan Plateau have been long thought to be the product of rapid tectonic uplift of the plateau. However, this has been challenged by recent works that suggest these thick gravels may be the result of climate change. In this paper we carried out a detailed field measurement of gravel grain sizes from the Jiuquan and Gobi Gravel Beds in the top of the Laojunmiao section in the Jiuxi Basin in the northern margin of Qilian Mts. (northern Tibetan Plateau). The results suggest that the grain sizes of the Jiuquan and Gobi Gravel Beds over the last 0.8 Ma are characterized by nine coarse-fine cycles having strong 100-ka and 41-ka periodicities that correlate well with the loess-paleosol monsoon record and isotopic global climatic record from deep sea sediments as well as by a long trend of coarsening in gravel grain size. The coarse gravel layers were formed during the warm-humid interglaciations while the fine layers correspond to the cold-dry glaciations. Because the paleoclimate in NW China began to get dramatically drier after the mid-Pleistocene, we think the persistent coarsening of gravel grain size was most probably caused by the rapid uplift of the northern Tibetan Plateau, and that the orbital scale cyclic variations in gravel grain size were driven by orbital forcing factors that were superimposed on the tectonically-forced long-term coarsening trend in gravel size. These findings also shed new light on the interaction results of climate and tectonics in relation to the uplift of the Tibetan Plateau.     

Assessing the results of scenarios of climate and land use changes on the hydrology of an Italian catchment: modelling study

Hydrological models are recognized as valid scientific tools to study water quantity and quality and provide support for the integrated management and planning of water resources at different scales. In common with many catchments in the Mediterranean, the study catchment has many problems such as the increasing gap between water demand and supply, water quality deterioration, scarcity of available data, lack of measurements and specific information. The application of hydrological models to investigate hydrological processes in this type of catchments is of particular relevance for water planning strategies to address the possible impact of climate and land use changes on water resources. The distributed catchment scale model (DiCaSM) was selected to study the impact of climate and land use changes on the hydrological cycle and the water balance components in the Apulia region, southern Italy, specifically in the Candelaro catchment (1780 km²). The results obtained from this investigation proved the ability of DiCaSM to quantify the different components of the catchment water balance and to successfully simulate the stream flows. In addition, the model was run with the climate change scenarios for southern Italy, i.e. reduced winter rainfall by 5–10%, reduced summer rainfall by 15–20%, winter temperature rise by 1·25–1·5 °C and summer temperature rise by 1·5–1·75 °C. The results indicated that by 2050, groundwater recharge in the Candelaro catchment would decrease by 21–31% and stream flows by 16–23%. The model results also showed that the projected durum wheat yield up to 2050 is likely to decrease between 2·2% and 10·4% due to the future reduction in rainfall and increase in temperature. In the current study, the reliability of the DiCaSM was assessed when applied to the Candelaro catchment; those parameters that may cause uncertainty in model output were investigated using a generalized likelihood uncertainty estimation (GLUE) methodology. The results showed that DiCaSM provided a small level of uncertainty and subsequently, a higher confidence level. Copyright © 2010 John Wiley & Sons, Ltd.