Seasonal dynamics of a large, shallow lake, laguna Chascomús: The role of light limitation and other physical variables

The most conspicuous waterbodies in the Pampa region of Argentina are the so-called “lagunas”. A typical Pampean laguna may be described as a relatively large (100+ha), permanent, shallow lake. Here, we report the dynamics of laguna Chascomús, sampled weekly, from April 2001 to June 2003. During the period, the lakes experienced three consecutive floods waves that affected the concentration of major ions and the optical signature of the dissolved organic matter. Despite these hydrological alterations, laguna Chascomús was permanently limited by light. Transparency was to a great extent controlled by the incident photosynthetic available radiation irradiance. We hypothesize that wind contributes to the permanent mixing of the lake, as well as to lessen the sedimentation losses of photoautotrophs.     

空气污染抑制小雨：华南与青藏高原对比分析

以能见度作为气溶胶浓度表征物,采用1980-2011年青藏高原和华南共10个台站资料,分析空气污染对降雨的影响。结果显示:青藏高原空气质量一直维持在很好状态,而华南地区存在严重的空气污染;华南地区的南宁、北海、百色3站小雨下降趋势明显,而青藏高原5站和华南地区的梧州、桂林2站的小雨趋势变化不明显;南宁、北海、百色3站20时能见度与随后24 h(当日20时至次日20时)小雨雨量正相关显著,而青藏高原5站和梧州、桂林2站20时能见度与随后24 h小雨雨量正相关不显著,这可能表明南宁、北海、百色3站小雨下降趋势与空气污染抑制有关;定量分析显示能见度每降低1 km,南宁、北海、百色3站小雨雨量分别减少0.019、0.028和0.027 mm;南宁、北海、百色3站出现小雨时20时能见度与未来24 h内各时次归一化对流有效位能正相关显著,这一现象与空气污染抑制小雨现象吻合;归一化对流有效位能对地面能见度/气溶胶激励效应的响应时间每日有两个高值。     

轻污油储罐设闪蒸系统初探

文章针对轻污油储存现状,在轻污油进储罐前设置闪蒸系统,气相轻组分排入全厂低压瓦斯系统;液相组分经轻污油增压泵送至轻污油储罐。该闪蒸系统可以有效防止气相轻烃进入轻污油储罐,保障设备平稳运行,避免憋罐、拔顶、爆炸等事故的发生。     

Optical measurements of the Moon as a tool to study its surface

This survey is a general overview of modern optical studies of the Moon and their diagnostic meaning. It includes three united parts: phase photometry, spectrophotometry, and polarimetry. The first one is devoted to the progress in the photometry of the Moon, which includes absolute albedo determination to refine the albedo scale (e.g., to connect lunar observations and the data of lunar sample measurements) and mapping the parameters of a lunar photometric function (e.g., the phase-angle ratios method) with the aim of making qualitative estimates of regolith structure variations. This part also includes observations of the lunar opposition effect as well as photogrammetry and photoclinometry techniques. In particular, available data show that because of the low albedo of the lunar surface, the coherent backscattering enhancement hardly influences the lunar opposition spike, with the exception of the brightest lunar areas measured in the NIR. The second part is devoted to chemical/mineral mapping of the Moon's surface using spectrophotometric measurements. This section also includes analyses related to the detection of water ice or hydroxyl, prognoses of maturity, and helium-3 abundance mapping. In particular, we examine the relationship between superficial OH/H₂O compounds spectrally detected recently and bulk “water ice” found earlier by the Lunar Prospector GRS and LRO LEND, assuming that the compounds are delivered to cold traps (permanently shadowed regions) with electrostatically levitated dust saturated by solar wind hydrogen. Significant problems arise with the determination of TiO₂ content, as the correlation between this parameter and the color ratio C(750/415 nm) is very non-linear and not universal for different composition types of the lunar surface; a promising way to resolve this problem is to use color ratios in the UV spectral range. The third part is devoted to mapping of polarization parameters of the lunar surface, which enable estimates of the average size of regolith particles and their optical inhomogeneity. This includes considerations of the Umov effect and results of spectropolarimetry, negative polarization imagery, and measurements of other polarimetric parameters, including the third Stokes parameter. Although these three research divisions have not been developed equally and the numbers of proper references are very different, we try to keep a balance between them, depicting a uniform picture. It should be emphasized that many results presented in this review can be applied to other atmosphereless celestial bodies as well.     

光照周期性波动对铜绿微囊藻(Microcystis aeruginosa)和斜生栅藻(Scenedesmus obliquus)生长的抑制

利用自行研制的光生物反应器,以水库中典型的铜绿微囊藻(Microcystis aeruginosa)和斜生栅藻(Scenedesmus obliquus)为研究对象,研究了两种藻类在光照强度周期性波动条件下的抑制特性.结果表明,相对恒定时平均光照强度6100 lx而言,在光照强度周期性波动条件下,在培养至24天时,铜绿微囊藻生物量降低14%、颜色稍黄,斜生栅藻生物量降低24%、藻体严重泛黄;铜绿微囊藻的叶绿素a和类胡萝卜素含量分别降低12.7%和55.5%,斜生栅藻的叶绿素a和类胡萝卜素含量分别降低78%和74%;模拟内波的周期性波动光强下,两种藻的光合作用参数Fv/Fm、YⅡ和ETR下降,热耗散量NPQ增高,且光合作用受到抑制,生长代谢能力减弱,这为内波控藻提供了理论依据.     

气溶胶光散射数值模拟的研究现状及进展

气溶胶光散射信息是辐射传输模拟、气候学研究及大气海洋遥感等的重要前提,由于其基础性地位,气溶胶光散射数值模拟一直是大气科学领域的研究热点。本文简明扼要地对气溶胶光散射数值模拟技术的研究现状进行了综述,主要内容包括以下3个方面:(1)总结和分析了Mie散射理论在实际应用的局限性;(2)对气溶胶光散射理论进行了归类,概述了其发展历程、研究现状,重点分析了不同散射理论的基本原理、适用范围、算法复杂度及相应的优缺点;(3)总结了气溶胶光散射研究中存在的问题,扼要地概括了气溶胶光散射数值模拟的研究热点及发展方向。     

基于地面通量观测与MODIS数据估算玉米光能利用率北大核心

基于地面通量数据和中分辨率成像光谱仪(Moderate-resolution Imaging Spectroradiometer, MODIS)数据,对玉米农田生态系统光能利用率(Light Use Efficiency, LUE)进行反演和分析。通过地表碳通量资料构建了玉米农田生态系统的LUE模型,分析了LUE的变化规律;通过比较不同参照波段、不同传感器角度下计算的MOIDS光化学反射植被指数(Photochemical Reflectance Index, PRI)与LUE间的关系,构建了MOIDS PRI反演玉米LUE的模型。结果表明:(1)玉米LUE呈现出明显的季节和日尺度上的变化规律,季节变化表现为单峰形,白天的LUE呈现出“U”型变化规律;(2)相比较NDVI,PRI反演植被LUE有明显优势,利用MODIS PRIS与LUE的较好相关性,建立了PRI488、PRI551和PRI667模型进行LUE反演;(3)经比较,MODIS PRIS反演LUE时最适合的为PRI551模型,其全向散射的模型具有通用性,而如果区分出后向散射数据则采用相应的PRI551后向散射模型更好;(4)利用LUEa与全天平均LUEd拟合模型与MODIS PRI551瞬时模型联合,可实现对日尺度的光能利用率的反演,其推广应用前景值得期待。