Gas exchange responses of a desert herbaceous perennial to variable sunlight in contrasting microhabitats

Over the course of a day, aridland plants experience a range of incident photosynthetic photon flux (PPF) spanning three orders of magnitude. Rapid photosynthetic responses to changes in PPF have large effects on individual plant carbon gain and water use patterns, hence are important to plant distribution and success. We investigated the response over time of photosynthesis (A), stomatal conductance (g), and inter-cellular CO₂ concentration (C_i) to step changes in PPF in a long-lived aridland perennial that typically occurs in two contrasting microhabitats, shade under shrubs of other species and unshaded inter-shrub spaces. An initial rapid response in A and C_i for plants in both microhabitats occurred after abrupt changes in PPF. This was followed by slower changes in these parameters during the rest of the light or dark period. Stomatal conductance responded more gradually to step changes in PPF. The initial increase in A after a dark cycle was significantly greater for plants under shrubs than for plants in inter-shrub spaces, but other changes in A, g and C_i did not differ. We attribute the similar responses in plants from different microhabitats to natural variations in solar radiation and limited selection for differentiation due to population gene pools dominated by plants in the open. Our results support the hypothesis that variable light regimes select for photosynthetic gas exchange processes that closely track changes in incident PPF. Our data also support the hypothesis that gas exchange responses to variable light regimes in aridland plants minimize trade-offs between carbon gain and water loss.     

位场正则化下延在自然电位概率成像中的应用

通过位场正则化向下延拓方法,弥补自然电位法对于地下全空间信息反映不足的客观缺陷,改进仅通过地表数据成像而导致的深度不灵敏状况。在模型分析中,新方案的成像结果和真实模型非常吻合。对于实测资料解释,新方案的处理结果在横向上符合实测数据的异常反映,同时还能够准确的给出地下半空间的纵向信息。     

雷电电磁辐射的危害及安全对策

分析雷电电磁脉冲的起电机制、传播途径及其对电子设备的危害，提出对雷电电磁脉冲的防护措施。     

从宽带太阳直接辐射小时或日曝辐量反演气溶胶光学厚度研究

从宽带的太阳直接辐射1天或1小时累计量(曝辐量)气象观测资料反演气溶胶光学厚度的一个有效方法是很有用的.作者把太阳曝辐量与"等效"的瞬时太阳直接辐射关联起来,建立了一个与曝辐量"等效"的瞬时太阳直接辐射的模式;应用该模式和一个"等效"波长模式,发展了一个从太阳直接曝辐量反演气溶胶光学厚度的方法.作者还从试验上比较分析了由某时刻的宽带太阳直接辐射、每小时或1天的太阳直接辐射曝辐量反演得到的气溶胶光学厚度以及由太阳光度计探测的气溶胶光学厚度.试验结果表明,由日太阳直接辐射曝辐量反演得到的气溶胶光学厚度可理解为辐射加权的日平均光学厚度.     

p—σ混合坐标原始方程模式对地气交换的敏感性试验

在五层及九层ｐ－σ混合坐标有限区域原始方程模式中,选择几种方案对影响地气系统之间动量、热量交换的拖曳系数进行了敏感性试验,并以一次寒潮为试验个例。试验结果表明：模式结果对拖曳系数的选取是敏感的;原模式对该系统在青藏高原地区的取值偏小,增大高牟地区的ＣＤ取值能取得更好的预报效果。     

山东枣庄地区辐射逆温及其影响

本文运用1981年11月17日-12月16日共30天实地考察资料,分析了山东枣庄地区冬季辐射逆温时空变化规律。并探讨了辐射逆温的生成与云量、风速的关系。     

应用遥感图像提取煤层自燃信息时必须考虑的几个影响因素

煤层自燃是中国北方煤田中普遍存在的灾害现象,它不但烧掉了大量的煤炭资源,而且还污染了环境。实践证明,利用遥感影像判别火区位置、圈定火区范围和对火区进行动态监测,及时为灭火工程提供信息,是一项经济和社会意义很大的工作。由于受多种因素的制约,不同地区、不同波段、不同时相、不同空间分辨率的遥感图像,其影像特征（含与煤层自燃有关的热异常影像特征）都有较大的差异,因而从图像上分析和提取地物的热红外辐射特征时,需要考虑遥感图像类型、成像时间、地形条件、气象条件和岩性特征等因素的影响。本文着重讨论了地表辐射温度与上述各项因素之间的关系。     

Meteorological Aspects, Ozone, and Solar Radiation Measurements During POPCORN 1994

Meteorological data, ozone mixing ratios, and photolysis frequencies for the period August 2 to August 24, 1994, are presented and discussed in support of the field campaign POPCORN (Photochemistry of Plant Emitted Compounds and OH Radicals in Northeastern Germany). Measurements of temperature, ozone, and wind speed at different heights are used to evaluate micro-meteorological parameters. The observations provide information about local influences on the air mass composition. The analysis of radio sonde data of nearby stations provides the height of the planetary boundary layer.     

CONCENTRATION AND FLUX OF CO2, TURBULENCE FLUXES AND RADIATION BALANCE IN THE NEAR SURFACE LAYER OVER WHEAT FIELD

The gradient of CO₂ concentration, photosynthetically active radiation(PAR). net radiation.soil heat flux, profiles of wind speed, and air temperature and humidity were measured above a wheat field during May and June 1985 at Beijing Agro-Ecosystems Experimental Station. Beijing,China. Fluxes of carbon dioxide, sensible heat, latent heat and momentum were calculated by using the aerodynamic method. The observation site. equipment, calibration techniques, the errors associated with the measurement, and the computational procedures are described. The results show that the diurnal variations of amplitude of CO₂ concentrations were 103.8 to 27. 0.86. 3 to 22.8 and 69.8 to 11.6 ppm:the average CO₂ concentrations were 331.5. 339.9 and 364.6 ppm for the photosynthesis type, and 369.6. 364.0 and 375.2 ppm for the respiration type at 1. 2 and 10 m above surface, respectively, from May 14 to June 15. In the daytime, transfer direction of the CO₂ fluxes and gradients is from air to crop canopy, and at noon(1100 to 1300 BT(Beijing Time)) the transfer rate reaches negative maximum value. At night, transfer of CO₂ fluxes and gradients is in the reversed direction and reaches positive maximum in the early morning(0400 to 0600 BT). There are strong negative correlations between CO₂ flux and the net radiation(R_n),available energy(H+LE). photosynthetically active radiation(PAR) and momentum flux(τ).