928 resultados para eddy covariance and meterological tower
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"This Code ... shall be known as the Southeastern New Mexico Code of Ethics." Cf. p. 6.
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"June 1983."
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CFD simulations of the 75 mm, hydrocyclone of Hsieh (1988) have been conducted using Fluent TM. The simulations used 3-dimensional body fitted grids. The simulations were two phase simulations where the air core was resolved using the mixture (Manninen et al., 1996) and VOF (Hirt and Nichols, 1981) models. Velocity predictions from large eddy simulations (LES), using the Smagorinsky-Lilly sub grid scale model (Smagorinsky, 1963; Lilly, 1966) and RANS simulations using the differential Reynolds stress turbulence model (Launder et al., 1975) were compared with Hsieh's experimental velocity data. The LES simulations gave very good agreement with Hsieh's data but required very fine grids to predict the velocities correctly in the bottom of the apex. The DRSM/RANS simulations under predicted tangential velocities, and there was little difference between the velocity predictions using the linear (Launder, 1989) and quadratic (Speziale et al., 1991) pressure strain models. Velocity predictions using the DRSM turbulence model and the linear pressure strain model could be improved by adjusting the pressure strain model constants.
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大气中CO2、CH4和其它温室气体浓度升高导致的全球气候变化引起了人们对全球碳循环和碳收支的关注,植被与大气间CO2通量的长期测定能够加深对陆地生态系统在全球碳循环作用的科学理解。本文以我国北方典型的温带植被类型长白山阔叶红松林为研究对象,利用观测塔上的涡动相关系统对长白山阔仆卜红松林进行长期的CO2通量监测,并分析CO2通量的周年动态,估算森林净生态系统生产力;同时基于测树学方法,进行群落调查,根据已有的经验公式,估算森林净生态系统生产力,综合评价长白山阔汗卜红松林碳收支,为森林碳收支的研究提供基础。主要结论有:(1)FSAM模型的分析结果表明,观测塔上40m高度的涡动相关仪器测量的信息中,76%来自于西北至西南方相对均质的阔叶红松原始林,其中footprint最大的源区在塔西南方100m-400m范围内。因此,森林群落调查选择在此区内进行,使得涡动相关法和测树学方法估算的生产力具有可比性。(2)2003-2004年碳通量季节变化趋势基本一致,从年初到4月上旬该森林生态系统保持较弱的正的碳通量(释放CO2),5月开始表现为净的碳吸收,且吸收量迅速增加,到6月达到最大值,然后又逐渐减小;9月末到10月末随着生长季的结束,净生态系统COZ交换(NEE)开始由负转为正,11-12月NEE为正,生态系统以呼吸为主。净生态系统COZ交换的年累计量表明长白山阔叶红松林为明显的碳汇,2003年和2004年净生态系统生产力NEP分别为-217±75gcm-2a-1和-190±85gcm-2a-1,相当于-2.17±0.75tCha-1a-1和-1.90±0.85tCha-1a-1。(3)根据经验公式和材积法得到阔汗卜红松林的生物量在343.9-362.3tha-l之间,应用两种方法得到2003一2004年群落的净初级生产力在10.22-10.40tCha-1a-1之间,净生态系统生产力在2.50±1.12tCha-1a-1-2.68±1.20tCha-1a-1之间。(4)测树学方法与涡动相关法测得的净生态系统生产力略有差异,但在误差有效范围内基本一致。