Effect of Altitude and Latitude on Surface Air Temperature across the Qinghai-Tibet Plateau

The correlation between mean surface air temperature and altitude is analyzed in this paper based on the annual and monthly mean surface air temperature data from 106 weather stations over the period 1961-2003 across the Qinghai-Tibet Plateau. The results show that temperature variations not only depend on altitude but also latitude, and there is a gradual decrease in temperature with the increasing altitude and latitude. The overall trend for the vertical temperature lapse rate for the whole plateau is approximately linear. Three methods, namely multivariate composite analysis, simple correlation and traditional stepwise regression, were applied to analyze these three correlations. The results assessed with the first method are well matched to those with the latter two methods. The apparent mean annual near-surface lapse rate is -4.8 ℃ /km and the latitudinal effect is -0.87 ℃ /°latitude. In summer, the altitude influences the temperature variations more significantly with a July lapse rate of -4.3℃/km and the effect of latitude is only -0.28℃ /°latitude. In winter, the reverse happens. The temperature decrease is mainly due to the increase in latitude. The mean January lapse rate is -5.0℃/km, while the effect of latitude is -1.51℃ /°latitude. Comparative analysis for pairs of adjacent stations shows that at a small spatial scale the difference in altitude is the dominant factor affecting differences in mean annual near-surface air temperature, aided to some extent bydifferences of latitude. In contrast, the lapse rate in a small area is greater than the overall mean value for the Qinghai-Tibet Plateau （5 to 13℃ /km）. An increasing trend has been detected for the surface lapse rate with increases in altitude. The temperature difference has obvious seasonal variations, and the trends for the southern group of stations （south of 33 o latitude） and for the more northerly group are opposite, mainly because of the differences in seasonal variation at low altitudes. For yearly changes, the temperature for high-altitude stations occurs earlier clearly. Temperature datasets at high altitude stations are well-correlated, and those in Nanjing were lagged for 1 year but less for contemporaneous correlations. The slope of linear trendline of temperature change for available years is clearly related to altitude, and the amplitude of temperature variation is enlarged by high altitude. The change effect in near-surface lapse rate at the varying altitude is approximately 1.0℃ /km on the rate of warming over a hundred-year period.

A Study on Parameterization of Surface Albedo over Grassland Surface in the Northern Tibetan Plateau

The relationship of surface albedo with the solar altitude angle and soil moisture is analyzed based on two-year （January 2002 to December 2003） observational data from the AWS （Automatic Weather Station） at MS3478 in the northern Tibetan Plateau during the experimental period of CEOP/CAMP-Tibet （Coordinated Enhanced Observing Period Asia-Australia Monsoon Project on the Tibetan Plateau）. As a double-variable （solar altitude angle and soil moisture） function, surface albedo varies inconspicuously with any single factor. By using the method of approximately separating the double-variable function into two, one-factor functions （product and addition）, the relationship of albedo with these two factors presents much better. The product and additional empirical formulae of albedo are then preliminarily fitted based on long-term experimental data. By comparison with observed values, it is found that the parameterization formulae fitted by using observational data are mostly reliable and their correlation coefficients are both over 0.6. The empirical formulae of albedo though, for the northern Tibetan Plateau, need to be tested by much more representative observational data with the help of numerical models and the retrieval of remote sensing data. It is practical until it is changed into effective parameterization formulae representing a grid scale in models.

Effect of electrochemical polishing time on surface topography of mild steel

The variation in altitude density function （ADF） of the surface topography of mild steel during electrochemical polishing （ECP） was investigated, and the mechanism of the variation of surface roughness with polishing time was analyzed. The results show that the variation trend of ADF with polishing time is flat-steep-flat; the variation of surface roughness results in the different distri- butions of surface current density, and there is a fine surface smoothness in the special period of ECP from 4 to 8 s.

A hybrid method of solving near-zone composite eletromagnetic scattering from targets and underlying rough surface

For composite electromagnetic(EM)scattering from rough surface and target above it in near-field condition,modified shooting and bouncing ray(SBR)method and integral equation method(IEM),which are analytic methods combined with two-scale model for rough surface,are proposed to solve the composite near-field scattering problems.And the modified method is verified in effectiveness and accuracy by comparing the simulation results with measured results.Finally,the composite near-fielding scattering characteristics of a slanted plane and rough water surface below are obtained by using the proposed methods,and the dynamic tendency of composite scattering characteristics versus near-fielding distance is analyzed,which may have practical contribution to engineering programs in need of radar targets near-field characteristics under extra-low-altitude conditions.

Observation of clouds and solar radiation over the Pacific Ocean as relation to global climate

During a research cruise over the Pacific Ocean in 1989, solar irradiance was measured with a broad-band pyranometer along the cruise track. Cloud cover was photographed with an all-sky time-lapse came ra. Cloud types were observed and recorded. The data show that both the types and the amounts of clouds affect radiation fluxes on the sea surface. For low-level and middle-level clouds, the correlations (r) between measured irradiance (in Percent of calculated maximum irradiance) and cloud amount (in fraction of sky) were significant: r=-0. 79 and - 0. 66, respectively. For high-level clouds, the correlation was not significant: r=-0. 21. The results indicate that cloud shortwave forcing is a major modifier of the earth's surface insolation and change of cloud amount may affect global climate.

叶巴滩堆石混凝土二道坝温度应力仿真分析及温控措施研究

对位于高海拔地区的叶巴滩堆石混凝土二道坝工程开展全坝段温度应力仿真分析,重点研究大坝横缝分缝措施和混凝土表面保温措施对坝体温度应力的影响。结果表明:结构分缝措施可以降低坝体内部拉应力,设置1条横缝即可有效控制坝体内部高拉应力区范围,并使应力极值降低约0.8 MPa;混凝土表面保温措施可在秋冬季节显著降低大坝表层混凝土温降幅度,减小表层温度应力水平,使应力极值降低约0.6 MPa;叶巴滩二道坝设置1条横缝并采取表面保温可满足施工期温控要求。

张家口崇礼区森林生物多样性及其垂直分布格局

选择张家口崇礼区东部山林,沿海拔高度设置样地,开展森林植被组成结构调查,分析其植被特征和生物多样性沿海拔高度的垂直分布规律.结果表明:森林植被类型以白桦为优势种的落叶阔叶林为主,随着山地海拔升高,逐渐演变为以华北落叶松为优势种的针叶林和针叶阔叶混交林.森林木本植物的物种多样性沿海拔高度呈现出先升高、后降低的变化趋势,多样性最大值区域位于海拔1900 m;森林物种丰富度主要受灌木层物种变化的影响.森林地表枯落物在海拔1500 m和1900 m样地积累较多,乔木植物对地表枯落物的贡献较大.

钛合金气门在高海拔环境中的应用优势与表面处理

在高海拔环境下,低温低压环境会导致柴油发动机的动力下降和燃烧不完全,这也会导致气门组件磨损加剧。虽然几十年来,气门制造技术已经得到了广泛探索,但是气门组件经常面临高温高压、频繁冲击和摩擦的严峻工作条件,导致摩擦磨损机制变得异常复杂,过去的气门制造优化措施并没有完全解决气门组件磨损的问题。为此,提出了一种新的解决方案,即使用铝化钛合金作为气门材料。该材料具有热强度高和重量轻的优点,非常适合用作柴油发动机气门材料。然而,由于钛铝合金的耐磨性存在短板,因此在投入实际使用之前,需要通过表面处理工艺来改善其摩擦学性能和疲劳特性。总结了多种钛铝合金表面处理方法的研究情况,包括超声表面轧制、激光表面熔覆技术、化学热处理工艺、激光表面微织构等。这些表面处理技术可以有效地改善铝化钛合金材料的摩擦学性能和疲劳特性,并消除对材料表面的负面影响。研究者们还通过使用不同的表面处理技术的复合处理来达到更好的效果。指出了未来的研究重点和方向是深入研究铝化钛合金的精确加工参数以及使用多种加工方式的可行性和作用。这将有助于更好地解决气门组件的磨损问题,提高柴油发动机的性能和可靠性。此外,还需要对铝化钛合金在其他领域的应用进行更广泛地研究和探索。

高燃压中型运载火箭发射地面低高度排导技术

综合高燃压中型运载火箭高密度发射燃气流地面排导需求及烧蚀风险分析,提出基于地面双面导流装置与高位挡流墙结合的地面低高度排导技术方案。利用火箭发射燃气动力学研究总结的燃气流膨胀特性以及导流型面设计方法,解决了地面低高度排导技术涉及的地面导流装置导流型面气动设计以及尺度控制两个关键问题。地面低高度排导技术方案设计与燃气流场瞬态仿真多轮叠代,实现了燃气流排导烧蚀范围合理控制,避免了燃气流低高度排导烧蚀反溅影响箭体。地面低高度排导技术采用专利支撑的喷水冷却防护方案实现高燃压中型运载火箭发射燃气流强烧蚀环境发射系统、发射设施综合防护。基于喷流缩比试验相似性控制方法研制了1∶10比例喷流缩比试验系统,通过喷流缩比试验验证确认高燃压中型运载火箭发射燃气流能够实现地面低高度安全、顺畅排导,同时与发射台、导流装置结构融合的阵列喷水方案能够行之有效解决高燃压中型运载火箭地面低高度排导强烧蚀难题。

高海拔多年冻土区坡向对坡面近地表水热状态的影响

高海拔多年冻土区坡向差异可引起两坡面的温度场不对称,进而造成基础设施的不均匀沉陷和纵向裂缝。目前坡向效应的研究主要围绕青藏铁路东-西两个坡面而开展的监测与模拟研究,但高原线性工程走向可能涉及不同的方向,其他走向坡面的水热差异状态研究不足。本研究在青藏高原花石峡冻土观测基地建设了一个具有八个坡向的监测实体(称:八棱台),在八个坡面和顶面近地表安装土壤温度、含水量传感器,监测研究坡向差异对坡面近地表水热状态的影响。结果表明:东-西相对坡面近地表温度差异最小,月平均温差为0.1~2.3℃,最大温差出现在5月;而南-北相对坡面近地表温度差异最大,月平均温差为1.3~7.7℃,最大温差出现在2月。其余两个相对坡面近地表温差介于东-西相对坡面和南-北相对坡面之间,其中东北-西南相对坡面温差小于西北-东南相对坡面。仅从近地表坡面温度差异来看,高海拔多年冻土区线性工程南-北走向热稳定性较好,其次是西北-东南向,坡向效应不显著而温度场对称性较好。同样八个坡面近地表土壤体积含水量总体差异为东北-西南相对坡面差异最小,融化期月平均体积含水量差最大为0.06 m^(3)·m^(-3);东-西相对坡面差最大,同期月平均体积含水量差最大为0.11 m^(3)·m^(-3)。含水量差异也引起了不同坡面冻融循环次数的显著差异,对坡面块碎石护坡材料冻融损伤破坏有重要影响。研究结果对指导未来高原线性工程规划及现役工程阴阳坡差异病害治理具有重要指导意义。

基于功率谱密度筛选的高海拔区背景噪声快速成像技术

真实且高信噪比的经验格林函数是准确提取面波频散和反演地下结构的前提,而实际噪声源分布与理论存在差异,且高海拔区噪声源数量少、能量弱,不仅需要长时间的数据采集,也难以获得高信噪比的经验格林函数。因此本文提出基于功率谱密度的背景噪声数据筛选方法,对某高海拔地区采集的92 h的背景噪声数据进行筛选,不仅大幅缩短了互相关计算时长,更有效提取了高信噪比的面波,减弱了高视速度干扰波,并获得了浅层0~140 m高分辨率的横波速度结构。本次研究为作业难度大的高海拔区开展周期短的水利水电勘察工作提供了新思路。

Numerical simulation of bistatic scattering from a target at low altitude above rough sea surface under an EM wave incidence at low grazing angle by using the finite element method

To study bistatic scattering from a target at low altitude above two- dimensional (2D) randomly rough sea surface under an electromagnetic (EM) wave incidence at low grazing angle (LGA), a numerical approach of the finite element method (FEM) is developed. The conformal perfectly matched layer (PML), as the truncation boundary of the FEM, is employed to reduce the reflection error of planar PML in conventional FEM. Numerical code of our FEM is examined by available solution of the forward backward iterative (FBM) method. Bistatic and back-scattering from composite model of a target above random rough sea surface generated by Monte Carlo realization, and functional dependence upon the sea surface wind speed, target altitude, incident and scattering angles, etc. are numerically simulated and discussed. This paper presents a numerical description of the observation principle and physical insight associated with the coupling interactions of a complex volumetric target and random rough sea surface.

An investigation of the influence of ground surface properties and shading on outdoor thermal comfort in a high-altitude residential area

Landscape elements in residential areas can effectively improve the outdoor thermal environment,with different outcomes depending on the climate conditions.This study explores how the ground surface and shading properties affect the outdoor thermal environment in a high-altitude plateau climate where few studies have been conducted.The measurements were conducted during summer and winter in a residential area in Lhasa,Tibet.Without natural shading such as trees,there is a positive correlation between Sky-view factor(SVF)and Physiological equivalent temperature(PET)during winter and a negative correlation during summer.When SVF exceeds 0.65 in summer,it may cause human discomfort.Compared to artificial shading such as a tensioned membrane,deciduous trees are superior at improving human comfort,as they can increase PET by 10.56℃ in winter and decrease it by 9.73℃ in summer.During summer,high-reflection water-permeable bricks can reduce the PET by 1.08℃,and lawns can reduce the mean rachation temperature(Tmrt)by 1.650C;however,the lawns may produce a microclimate with a high air temperature.The results from this paper can be used as a reference for landscape planning and design in residential areas in high-altitude cold-climate regions.

长江黄河上游地表水溶解氧时空分布特征研究--以四川省为例

为了解长江黄河上游地表水中溶解氧(DO)的分布特征,以四川省河流湖库作为研究对象,通过收集整理四川省237个站点(断面)的DO逐月数据,研究分析DO的时空分布特征及其与外界环境因素的相关性。结果表明,四川省河湖DO在空间上总体呈现东高西低、南北高中部低的分布特征,在时间上呈冬季>春季>秋季>夏季,其中7月最低,全年DO低于5 mg/L的月份主要出现在3—9月,以春夏季为主,发生率为0.83%。从与外界环境相关性上看,DO浓度平均值与河流海拔呈负相关,DO浓度最高值与社会经济发展呈正相关,DO浓度最低值与社会经济发展呈负相关。

基于走航观测数据的ERA5南海北部夏季短波辐射收支评估

海表短波辐射收支是海–气界面能量交换的重要物理过程。本研究利用2019年南海北部夏季科考航次的走航观测数据,评估了ERA5再分析数据的海表短波辐射通量收支。结果表明,ERA5的向下短波辐射相比观测偏小,11时和15时(北京时间)的偏差最大,可达-100 W/m^(2)。与此同时,ERA5的海表反照率整体偏低,其中高太阳高度角时段偏差较小,约为-0.03,低太阳高度角时段偏差较大,约为-0.15。向下短波辐射和反照率的偏差共同造成ERA5白天平均海表净短波辐射通量比观测偏小约25.4 W/m^(2);其中,反照率低估抵消了约50%向下短波辐射偏差的贡献。研究表明,在不同大气透射率情况下,ERA5的海表辐射收支偏差存在不同表现。ERA5海表反照率的低估可能与其采用的参数化方案在南海北部的适用性不足有关。基于观测本研究也给出了一个简单的参数优化方案。

永春县不同海拔芦柑果实日灼发生率调查分析

以永春县6个果园同一坡向、不同海拔的芦柑树作为研究对象,通过分析高温条件下果实日灼发生情况,发现果面温度、果实日灼率、日灼程度与海拔呈现极显著的负相关,即前三者是随着海拔的升高而降低。果实日灼率、日灼程度与果面温度呈极显著正相关,与光照强度的相关性差异并不显著,可知果面温度是影响芦柑日灼的主要因子,果面温度高则日灼发生率高,不同海拔主要是通过果面温度变化影响果实日灼率。

齐齐哈尔两次暴雨天气过程对比分析

利用多种资料对发生在齐齐哈尔的两次暴雨进行对比分析。结果表明:(1)这两次暴雨都发生在副热带高压位置最北期间,都是副热带高压、高空冷涡和地面低压大尺度环流造成的;“8.3”暴雨比“8.6”暴雨副热带高压位置更偏西,地面低压中心值更低。(2)“8.6”暴雨过程齐齐哈尔地区水汽输送量更大、辐合更强、低层上升运动更明显、造成暴雨范围更大。(3)“8.3”暴雨雷达回波强度更强,55 dBz以上强回波排列紧密,呈现带状;“8.6”暴雨雷达回波,甘南县境内存在“列车效应”,且径向速度场零速度线呈“S”型结构,有明显的暖平流。

抵偿面任意带投影法在高海拔地区GNSS控制网长度投影变形中的应用

在工程建设过程中,GNSS控制网的精度对施工放样和工程质量的影响至关重要。文中通过分析长度投影变形的影响因素、长度投影变形算法以及不同情况下测量坐标系的选择方法,并以贵州省某抽水蓄能电站工程GNSS控制网为例,估算测区控制网在标准带国家坐标系下的长度投影变形,通过实践证明采用抵偿面任意带投影法可有效减弱高海拔地区GNSS控制网长度投影变形值,满足测区内投影长度变形小于等于25mm/km的要求,从而满足设计和工程建设的要求,为高海拔地区大比例尺测图平面坐标系的选取提供一定的借鉴作用。

青藏高原层状地貌与高原隆升

夷平面、剥蚀面和河流阶地等层状地貌面是长周期地貌演化研究的主要对象 ,它们不仅记录了区域地貌的发育历史 ,而且可以用来反演区域构造活动、气候变化等内动力过程的演变。深入研究青藏高原上这些地貌面的特征、变形、成因和形成时代 ,是探讨青藏高原隆升年代、幅度和过程的重要途径。野外考察与室内制图表明青藏高原及其边缘山地普遍存在两级夷平面 (山顶面、主夷平面 )、一级剥蚀面和多级河流阶地。主夷平面形成于 7.0～3.6MaB .P .,形成时其高度在 1 0 0 0m以下。大约 3.6MaB .P .前主夷平面开始大规模解体 ,标志着青藏高原强烈抬升的开始。剥蚀面和河流阶地揭示 ,1 .8MaB .P .,1 .2MaB .P .,0 .8MaB .P .和 0 .1 5MaB .P .

塔里木盆地河水氢氧同位素与水化学特征分析

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