黄土高原地表能量不闭合度与垂直感热平流的关系

地表能量不平衡问题一直是陆面过程研究的一个重要科学难题.本文利用在陇中黄土高原观测的陆面过程资料,分析了气候地表能量不闭合度和短期地表能量不闭合度的分布特征,研究了地表能量不闭合度与垂直速度之间的关系,发现地表能量不闭合与垂直速度具有很好的相关性.并且,估算了近地层垂直感热平流通量,分析了考虑垂直感热平流后的地表能量平衡的特征,发现引入垂直感热平流输送对地表能量不闭合度有明显的改进. 关键词： 黄土高原 非均匀性 垂直感热平流 能量不闭合度     

黄土高原区域气候暖干化对地表能量交换特征的影响

本文将观测试验资料与陆面过程模式模拟资料相结合, 对目前4个流行的陆面过程模式的模拟资料进行了验证分析, 发现通用陆面模式(CLM)模式的模拟资料在黄土高原地区比较可靠. 在此基础上,利用近几十年CLM模式模拟资料和气象站观测资料, 分析了黄土高原地区的区域气候和地表能量交换特征的变化规律, 研究了该地区地表能量交换对降水和温度变化的响应特征, 讨论了该地区气候变化对地表能量交换特征的影响机理. 研究发现,近几十年来黄土高原区域气候表现为明显的暖干化趋势, 从而引起太阳总辐射、地表反射辐射和地表长波向上辐射的增加 及地表长波向下辐射的减小,并由此造成地表净辐射通量减少. 与之相对应,不仅地表潜热通量呈减小趋势,而且地表感热通量和土壤热通量也呈减小趋势, 但地表热量分量的分配比例基本不变.并且发现,地表感热通量的年变化主要由太阳辐射控制, 而潜热通量的年变化则受太阳辐射和降水共同影响;地表热量分量的年际变化均对降水变化响应很敏感, 而对温度变化响应不太敏感,气候干旱化对地表能量平衡的影响比气温变暖的影响更突出. 关键词： 黄土高原 区域气候暖干化 陆面过程模拟 陆面能量交换     

空气热储存、光合作用和土壤垂直水分运动对黄土高原地表能量平衡的影响

地表能量不平衡问题一直是陆面过程研究的一个重要科学难题. 本文利用黄土高原陆面过程试验(LOPEX)资料, 在将垂直感热平流项引入地表能量平衡方程的基础上, 估算了空气热储存和光合作用储存的大小, 并分别用水分守恒关系和两层土壤温度方法计算了浅层土壤水分垂直通量, 考察了空气热储存、光合作用储存和水分垂直运动热量输送对地表能量平衡的影响.结果表明: 黄土高原区自然植被下垫面的空气热储存、光合作用储存和土壤水分垂直运动热量输送平均日变化峰值分别达到1.5, 2.0和7.9 W·m^-2; 在能量平衡方程中引入这三项后, 地表能量闭合度由88.1%提高到89.6%. 空气热储存、光合作用储存和水分垂直运动热量输送对于改善黄土高原地表能量不平衡状况有一定作用, 研究区域的半干旱气候背景和植被状况是导致各热储存量与其他试验区存在差异的根本原因.     

黄土高原半干旱区露水形成的大气物理特征研究

运用2009年在黄土高原典型半干旱区定西的观测资料,分析了半干旱区露水变化特征及其大气影响因子.研究结果表明:在黄土高原半干旱区秋季,日最大凝结量可以达到0.33 mm,最小日凝结量0.09 mm,日平均凝结量为0.23 mm,这对半干旱区而言是可观的水分输入;露水凝结持续时间可以长达14 h.露水的出现频率与风速、大气相对湿度、气温、地-气温差等大气影响因子有显著关系.露水的形成机理十分复杂,是湿度因子、热力因子和动力因子综合作用的结果.在露水形成过程中,大气湿度是内因,为露水形成提供所需水汽;温度则是露水形成的关键,为露水形成提供"源动力",而风速则是重要的外部影响因素,既可以促进露水形成,也可以阻碍露水形成,是露水形成过程中不确定因子.从露水发生频率的分布特征来看,在风速0.5—2 m/s、相对湿度>80%及温度-露点差-3—6℃时、地-气温差<±2℃条件下更易形成露水. 关键词： 黄土高原半干旱区 露水形成 大气影响因子 发生频率     

黄土高原地表能量平衡分量年际变化及其对气候波动的响应

本文利用兰州大学半干旱气候与环境观测站(SACOL站)2006—2012年陆面过程观测资料和榆中站气象资料,分析了7年间榆中气温降水的气候变化背景,讨论了陆面地表能量平衡分量的年际变化,研究了波文比、能量闭合度的年际波动,探讨了地表能量平衡分量以及各陆面过程参数对黄土高原气温、降水年际波动的反馈.结果显示,地表各能量分量都对气候背景的波动做出响应,但敏感性各有不同,净辐射与气温相关性最强,感热潜热与降水相关性较好.分为冬夏半年讨论后得出,冬半年地表平衡分量与气候波动的相关性更好.冬半年中,各分量又与气温有着较高的相关,可见该地区地表能量各分量对冬半年气温波动的响应更为敏感.波文比的上升趋势与该地区降水量减少的背景响应,说明干旱程度的加深.能量闭合度的波动变化显示了在气候变化的背景下该地区陆面能量不闭合程度的加深.     

同步加速器中束流能量的修正

叙述了同步加速器中束流能量测量和修正的原理,推导出关于闭合轨道畸变和校正二极子强度的束流能量的修正公式,介绍了这些公式在北京正负电子对撞机（BEPC）上的应用,并对其结果进行了讨论．     

同步加速器中束流能量的修正

叙述了同步加速器中束流能量测量和修正的原理,推导出关于闭合轨道畸变和校正二极子强度的束流能量的修正公式,介绍了这些公式在北京正负电子对撞机(BEPC)上的应用,并对其结果进行了讨论.     

能量修正的Glauber模型对中能反应总截面的影响

叙述了对Glauber模型中的透射系数进行半经验的能量修正,并利用该修正模型计算了^12—14C,⁶Li,⁷Be,⁸B+¹²C和⁶Li,⁷Be,⁸B+⁹Be以及²⁰Ne+¹²C,¹²C+²⁷Al等系统的激发函数(能区范围10—1000MeV/u),经与实验值比较,能量修正的Glauber理论计算值能够很好地描述中能条件下的反应总截面实验测量值.     

Toward characterization of the aerosol optical properties over Loess Plateau of Northwestern China

Aerosol optical properties were obtained from a CIMEL sunphotometer of the Aerosol Robotic Network at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL). SACOL is located over the Loess Plateau of the Northwestern China. The observed data are analyzed for the period of August 2006-October 2008. We find that aerosol optical depths (AODs) have a pronounced annual cycle, with a maximum dust aerosol loading during the spring. The 2-year average values of AOD, Ångström exponent (α), and water vapor path (WVP) along with their standard deviation (in parenthesis) are 0.35 (0.21), 0.93 (0.34), and 0.77 cm (0.52 cm), respectively. The probability distributions of these quantities all have one modal value, which are 0.3, 1.1, and 0.5 cm, respectively. There is a notable feature in the relationship between daily averaged AOD and Ångström exponent: a wide range of α corresponding to moderate to low aerosol optical depths (<0.8). There is no significant correlation between daily averaged WVP and AOD. However the daily averaged Ångström exponent and WVP show a significant positive correlation, indicating that the smaller aerosol particles present when the WVP is large. Variations of the retrieved aerosol volume size distributions are mainly associated with the changes in the concentration of the coarse aerosol fraction. The geometric mean radii for the fine and coarse aerosols are 0.18 μm (±0.03 μm), and 2.53 μm (±0.25 μm), respectively. The spectral dependences of the single scattering albedos are different between the dusty and non-dusty conditions. In the presence of dust, the SSAs increase slightly with wavelength. When dust is not a major component, the corresponding values decrease with wavelength.     

云和降水扰动对黄土高原半干旱草地辐射收支及能量分配的影响

地表辐射收支和能量分配对陆-气系统的反馈是气候模式中最重要的物理过程之一. 认识半干旱地区云和降水的扰动对辐射收支和能量分配的影响规律, 是提高数值模式中评估地表辐射收支和能量平衡参数化效果的关键环节. 利用兰州大学半干旱气候与环境观测站2008年的观测资料, 研究了云和降水的扰动对辐射收支各分量的削弱作用及对地表能量平衡的影响规律. 年平均结果表明, 多云状况可以作为年平均的气候背景; 云和降水对短波辐射削弱最强, 大气向下长波辐射随天空云量的增加而增强, 地表向上长波辐射随着云量的增加而减小, 净辐射占总辐射的比率受云和降水的影响较小. 季节平均结果显示, 短波辐射日积分量在生长季和非生长季均随云量的增加而降低, 生长季云和降水对短波辐射的削弱作用明显强于非生长季. 生长季, 晴天、少云和多云时向上长波辐射差异不大, 阴天时向下和向上长波辐射明显减小. 非生长季, 地表向上长波辐射受云和降水的影响较小, 日积分量变化不大, 向下长波辐射随云量的增多而增强. 地表反照率具有明显的日变化和季节变化, 冬季大, 秋季小; 地表反照率日变化呈不对称的“V”形分布. 生长季, 感热通量和土壤热通量随云量增多而减小; 潜热通量在晴天、少云和多云状况下随云量增多而增大; 阴天时受降水影响, 净辐射的严重削弱导致了潜热通量大大降低. 非生长季, 少云时净辐射日积分量最大, 晴天时的净辐射与多云和阴天状况接近; 感热和潜热通量随云量的增多而减小, 土壤热通量日平均积分值在非生长季为负. 生长季, 多云状况的能量闭合度最好, 能量不平衡差额占净辐射的3.9%; 阴天时最差, 不平衡差额占净辐射的16.8%; 晴天和少云状况不平衡差额约占净辐射量的7%. 非生长季受积雪影响, 能量不闭合差额明显大于生长季. 关键词： 半干旱草地 云和降水的扰动 辐射收支 能量平衡     

吲哚染料的电荷转移和能量转移：应用于无金属的染料敏感太阳能电池

对于应用于无金属染料敏感太阳能电池的吲哚染料用量子化学方法进行研究．对比研究吲哚染料的基态和激发态性质,揭示了随着绕丹宁环数目的增加,HOMO和LUMO的能量差减少,吸收光谱红移,但是束缚能增加,跃迁偶极矩减少;依据电荷差分密度,电荷和能量从苯乙烯转移到吲哚环和绕丹宁;电子空穴相干性主要表现在吲哚环和绕丹宁环,对于吲哚染料系统,存在一个绕丹宁环的体系的激子数目为30个原子,带有两个绕丹宁环的体系激子数目有40个原子．理论计算结果可以应用于无金属的染料敏感太阳能电池的吲哚染料的计算机辅助设计中．     

Cenosphere formation from heavy fuel oil: a numerical analysis accounting for the balance between porous shells and internal pressure

Heavy fuel oil (HFO) as a fuel in industrial and power generation plants ensures the availability of energy at economy. Coke and cenosphere emissions from HFO combustion need to be controlled by particulate control equipment such as electrostatic precipitators, and collection effectiveness is impacted by the properties of these particulates. The cenosphere formation is a function of HFO composition, which varies depending on the source of the HFO. Numerical modelling of the cenosphere formation mechanism presented in this paper is an economical method of characterising cenosphere formation potential for HFO in comparison to experimental analysis of individual HFO samples, leading to better control and collection. In the present work, a novel numerical model is developed for understanding the global cenosphere formation mechanism. The critical diameter of the cenosphere is modelled based on the balance between two pressures developed in an HFO droplet. First is the pressure (Pr_pf) developed at the interface of the liquid surface and the inner surface of the accumulated coke due to the flow restriction of volatile components from the interior of the droplet. Second is the pressure due to the outer shell strength (Pr_C) gained from van der Walls energy of the coke layers and surface energy. In this present study it is considered that when Pr_C ≥ Pr_pf the outer shell starts to harden. The internal motion in the shell layer ceases and the outer diameter (D_SOut) of the shell is then fixed. The entire process of cenosphere formation in this study is analysed in three phases: regression, shell formation and hardening, and post shell hardening. Variations in pressures during shell formation are analysed. Shell (cenosphere) dimensions are evaluated at the completion of droplet evaporation. The rate of fuel evaporation, rate of coke formation and coke accumulation are analysed. The model predicts shell outer diameters of 650, 860 and 1040 µm, and inner diameters are 360, 410 and 430 µm respectively, for 700, 900 and 1100 µm HFO droplets. The present numerical model is validated with experimental results available from the literature. Total variation between computational and experimental results is in the range of 3–7%.     

价电子平均能级指数与镧系元素理化性质的相关性

由原子的主量子数、价电子数及价电子能级值定义一个价电子平均能级指数L,它不仅对所有的原子具有优异的选择性,达到唯一性表征,而且与镧系元素的13种理化性质呈现高度的相关性,估算值与实验值都很好吻合.     

Zero-point energy,tunnelling, and vibrational adiabaticity in the Mu + H2 reaction

Isotopic substitution of muonium for hydrogen provides an unparalleled opportunity to deepen our understanding of quantum mass effects on chemical reactions. A recent topical review in this journal of the thermal and vibrationally state-selected reaction of Mu with H₂ raises a number of issues that are addressed here. We show that some earlier quantum mechanical calculations of the Mu + H₂ reaction, which are highlighted in this review, and which have been used to benchmark approximate methods, are in error by as much as 19% in the low-temperature limit. We demonstrate that an approximate treatment of the Born–Oppenheimer diagonal correction that was used in some recent studies is not valid for treating the vibrationally state-selected reaction. We also discuss why vibrationally adiabatic potentials that neglect bend zero-point energy are not a useful analytical tool for understanding reaction rates, and why vibrationally non-adiabatic transitions cannot be understood by considering tunnelling through vibrationally adiabatic potentials. Finally, we present calculations on a hierarchical family of potential energy surfaces to assess the sensitivity of rate constants to the quality of the potential surface.