温室内CO_2浓度的计算机控制及其在估算作物光合作用中的应用

本文介绍一个监测并控制五个玻璃试验温室内CO_2浓度的计算机自动控制系统。在计算机控制下,通过一个CO_2测定系统向每个温室输入纯CO_2气体,使其内部CO_2浓度与室外保持相等(CO_2浓度由红外气体分析仪测定)。在CO_2浓度测定的间隔期间,温室所需要的CO_2输入速率根据通风速率、未来的和现时的CO_2浓度计算确定。通过预先用N_2O气体跟踪确定的风机定位状态和风速的关系计算通风率。通过放在地面上的容器内获得的碳酸盐的重量观测土壤呼吸。在其它CO_2通量已确定后,用其剩余额估算作物净光合作用。该系统很可靠,且已在许多热带作物净光合作用的光响应特征曲线研究中得到应用。     

西欧国际天气雷达网

在过去几年里,西欧各国有很多旨在建立国家雷达网的活动。与此同时订立了一些跨国交换天气雷达资料的双边协定。欧洲经济共同体(EEC)鼓励有效的国际合作,发起了COST-72计划,它进而导致建立COST-73这一天气雷达网后续计划。本文概述COST-72的目标和已达到的程度。已经打下了建立新的COST-73计划的基础。     

K-Gill:用于大气湍流测量的双螺旋桨-风标风速表

不列颠哥伦比亚大学研制的双螺旋桨-风标风速表曾成功地用于有海洋浪花存在情况下中-高风速期间大气湍流的无人自动测量。本文介绍一种新设计的双螺旋桨-风标风速表。该仪器由安装在风标上的两个Gill风速表构成。两个螺旋桨的轴一个朝上,另一个朝下,都与水平成45°角(由此以下称K-Gill)。除了具有以前设计的一些特点外,K-Gill还具有对称性,因此,能以相同的灵敏度测量上升气流和下沉气流。机内的水平传感器可用来进行倾斜订正。为了减少气流畸变,已经从装置的底座上去掉了电子仪器外壳,而且把螺旋桨安装在远离主垂直轴的地方。本文介绍了获得风速的垂直分量和顺风水平分量的算法,讨论了各种误差源和误差的大小。     

荷电雨滴的碰撞

云滴碰撞结果对降水的演变十分重要.碰撞雨滴是并合还是分离,电荷起着决定性作用.在实验室里用以终速自由下落的荷电滴做了实验,揭示了滴碰撞的许多新特点.     

对全球变暖的一些看法

1.引言我们对全球变暖可能引起危害的适度评价主要取决于确定这种危害的真实程度如何. 最近大家才认识到对变暖这个问题是有怀疑的.但是不论真实情况如何,对这个问题也有非同寻常的极端主义观点.虽然经常获悉生态环境变化令人震惊,但是随之而来的怀疑主义并没有销声匿迹.由于承认对变     

国家强风暴预报中心(NSSFC)对1988年闪电资料的评价

一、引言美国国家气象局(NWS)已经制定了一个改进天气服务的重要现代化计划,计划将一些新的遥感技术用于90年代的业务工作。闪电定位是这些新资料源中的一个。它利用一个传感器网可以探测到云对地闪和确定闪击点的位置。在过去的十年里各个研究小组已开发了闪电定位技术。现在区域测站网     

地形降水机制

从降水量—地形高度对应关系图上可以清楚地看出山脉对水分循环的影响。图1和图2就是例子。在有些地理区城,这种对应关系是已为人们所了解,但在其它区域并非如此,许多年来关于这个问题的科学研究一直进行得很缓慢。本文回顾了目前人们对地形降水的了解。Bonacina(1945),     

The ozone,aerosol depletion and condensation nuclei events in the stratosphere

Recently, the depletion in ozone and aerosol extinctions inside Antarctic Spring westerly vortex and condensa-tion nuclei enhancement events in the mid latitudes stratosphere were related to downward transport of aerosols by subsidence and sedimentation. However, the problems associated with such hypothesis would keep a constraint on photochemical theories on ozone hole and stratospheric condensation nuclei (CN) events. Alternately, the gross fea-tures of aerosol hole are better explicable assuming a reversed residual circulation. This opens a path for combined operation on ozone by both photochemistry and dynamics in the same space domain.Independently, we relate the CN events to the growth and transport of negative ion complexes above the Peak of Junge Layer (PJL) without invoking photochemistry in order to be consistant with the observed interhemispheric dif-ferences in the planetary wave activity and CN concentration.     

SETTLING PROPERTIES OF COHESIVE AND NON-COHESIVE PARTICULATE MIXTURES IN WATER

1. INTRODUCTIONAs a wide range of size distirbution including usually a certain POrtion of cohesive material is thecommon feature of the sediment constituting hyperconcentrated flows. it is desirable to study the settling properties of mixtures of cohesive and non--cohesjve sediment particles at high concentrations.Past studies on the settling of discrete particles in a suspension of fine cohesjve sediment is scarcein the literature. The Sediment Research Laboratory of Tsinghua Universi…     

Sensitivity of medium-range weather forecasts to the use of reference atmosphere

In this paper, the authors develop the earlier work of Chen Jiabin et al. (1986). In order to reduce spectral truncation errors, the reference atmosphere has been introduced in ECMWF model, and the spectrally-represented variables, temperature, geopotential height and orography, are replaced by their deviations from the reference atmos-phere. Two modified semi- implicit schemes have been proposed to alleviate the computational instability due to the introduction of reference atmosphere. Concerning the deviation of surface geopotential height from reference atmos-phere, an exact computational formulation has been used instead of the approximate one in the earlier work. To re-duce aliasing errors in the computations of the deviation of the surface geopotential height, a spectral fit has been used slightly to modify the original Gaussian grid-point values of orography.A series of experiments has been performed in order to assess the impact of the reference atmosphere on ECMWF medium- range forecasts at the resolution T21, T42 and T63, The results we have obtained reveal that the reference atmosphere introduced in ECMWF spectral model is generally beneficial to the mean statistical scores of 1000-200 hPa height 10-day forecasts over the globe. In the Southern Hemisphere, it is a clear improvement for T21, T42 and T63 throughout the 10-day forecast period, In the Northern Hemisphere, the impact of the reference atmos-phere on anomaly correlation is positive for resolution T21, a very slightly damaging at T42 and almost neutral at T63 in the range of day 1 to day 4. Beyond the day 4 there is a clear improvement at all resolutions.