Flow field within and above a forest canopy: task I, study of airflow in simulated temperate and tropical forest canopies, Fort Huachuca

CER69-70WZS-JEC-TK-6.July 1969.Includes bibliographical references (pages 32-35).For Atmospheric Sciences Laboratory U.S. Army Electronics Command Fort Monmouth, N. J.The velocity and longitudinal turbulence intensity distributions inside and above a forest canopy along its center line were investigated. For this purpose a model forest canopy was used in a meteorological wind tunnel. The results indicate that the flow may be divided into an entrance and fully developed region followed by a short adjustment distance close to canopy end. The entrance region has a decisive effect on the flow characteristics through the canopy. The velocity and turbulence inside the canopy are strongly affected by its structure. A similar qualitative variation for both velocity and turbulence was found in and above the canopy. Its influence stretches over more than 4 roughness heights above it. Generally, the results are in relatively reasonable agreement with field measurements. Investigation of the modified logarithmic law for describing the velocity profile above the canopy revealed that both flow parameters, i.e., friction velocity and roughness length, are not local constants. On the contrary, they vary drastically with height. It is suspected that this is due to the fact the assumption of constant shear stress throughout the boundary layer or significant portions of it is not satisfied

六甲山系の湖沼堆積物の粒度組成の変動と崩壊環境

金沢大学環日本海域環境研究センタ

Structure of canopy flow field, The

CER67-68TK66.August 1968.Includes bibliographical references (pages 41-43).Prepared under U.S. Army Research Grant DA-AMC-28-043-65-G20.A model study of canopy flow over high roughness elements was carried out in the Army Meteorological Wind Tunnel at Colorado State University using roughness consisting of pegs 9 cm high and 0.48 cm in diameter arranged in four patterns. The mean velocity and the turbulence intensity were measured within and above the roughness elements. Empirical expressions derived from field measurements for mean velocity profiles, turbulent velocity, and turbulence intensity were used to examine the data obtained in this model study. The logarithmic profile was adapted to analyze the data of mean velocity above the canopy. In this analysis, the friction velocity and the roughness parameter were calculated from the mean velocity profiles and related to the density of roughness elements to show the effects of roughness density on the flow field. The growth of the internal boundary layer was estimated from the mean velocity profiles and the turbulence intensity. The results of estimation were compared with semi-empirical equations. Although the coefficient of anisotropy above the canopy in this model study is larger than that in the field, the model study gave data about the turbulent flow field similar to the field data. Hence, this model was verified to be suitable for the study of diffusion.Under grant DA-AMC-28-043-65-G20

Investigation of flow over high roughness, An

CER71-72TK-WZS3.August 1971.Includes bibliographical references (pages 79-84).Prepared jointly for U.S. Army Electronics Command Contract No. DAAB07-68-C-0423 and Office of Naval Research Contract No. NO014-68-A-0493-0OO1.Circulating copy deaccessioned 2020.An experimental investigation of the atmospheric boundary-layer flow on high roughness was conducted by simulating the flow over a forest canopy in a meteorological wind tunnel. The model forest canopy used consisted of plastic simulated-evergreen trees. The measurements were carried out at constant free-stream velocity and under thermally neutral conditions. Two canopy densities were tested to explore the effects of the roughness density on the flow. One roughness density was half of the other. The results indicate that the mean velocity profiles within the fully developed flow region can be described by generalized logarithmic relationships. For the flow in the inner zone, the free-stream velocity and the roughness height are the similarity parameters for the velocity and the vertical distance, respectively. In the outer zone the freestream velocity and the momentum thickness are the scaling parameters. The roughness density has a strong influence on the momentum loss and the upward flow displacement in the transition region. The shape of the roughness element affects the mean velocity distribution inside the canopy, i.e., jetting effect. The internal boundary-layer thickness was determined based on the turbulent shear-stress distribution. It is found that the flow near the canopy leading edge has two-dimensional wake-like characteristics. The latter are due to the canopy frontal area which is a drastic step obstruction. The existence of an inertial subrange in the fully developed flow region is doubtful although local isotropy occurs for eddies smaller than 2% of the total boundary-layer thickness. The evolution of turbulent energy associated with various size eddies along the canopy can be successfully described by a discretized-energy analysis

Inter-model variability of the CMIP5 future projection of Baiu, Meiyu, and Changma precipitation

Many studies have suggested that mean precipitation associated with the East Asian Summer Monsoon (EASM) will be increased by the ongoing global warming, but its quantitative projection by climate models has large variability, with some models suggesting even decreases. We investigate the inter-model variability of projected centennial changes of the EASM separately for Baiu over Japan, Meiyu over eastern China, and Changma over Korea by using monthly-mean model outputs provided by the Coupled Model Intercomparison Project Phase 5 (CMIP5) project. Results with the Representative Concentration Pathway 4.5 and 8.5 scenarios (RCP4.5 and RCP8.5) are consolidated by normalizing with the global-mean near-surface air temperature changes. For all the three EASM land regions, inter-model differences in the mean precipitation changes are positively correlated with the southerly moisture flux changes to the south of the regions. The correlation is highest in June among the June-to-August months, whose reason may be because precipitation in early summer relies on large-scale southerly moisture transport. These changes are localized and nearly independent among the three regions where Baiu, Meiyu and Changma occur. The low-level southerly change to the south of Japan, which affects the Baiu precipitation change, is positively correlated with upper-tropospheric meridional wind to its north; it further exhibits a stationary Rossby-wave feature associated with the Silk-Road teleconnection. This study suggests that future changes in the EASM mean precipitation depend on circulation changes and more-or-less localized

Inhibition of mitochondrial complex I by the novel compound FSL0260 enhances high salinity-stress tolerance in Arabidopsis thaliana

Chemical priming is an attractive and promising approach to improve abiotic stress tolerance in a broad variety of plant species. We screened the RIKEN Natural Products Depository (NPDepo) chemical library and identified a novel compound, FSL0260, enhancing salinity-stress tolerance in Arabidopsis thaliana and rice. Through transcriptome analysis using A. thaliana seedlings, treatment of FSL0260 elevated an alternative respiration pathway in mitochondria that modulates accumulation of reactive oxygen species (ROS). From comparison analysis, we realized that the alternative respiration pathway was induced by treatment of known mitochondrial inhibitors. We confirmed that known inhibitors of mitochondrial complex I, such as rotenone and piericidin A, also enhanced salt-stress tolerance in Arabidopsis. We demonstrated that FSL0260 binds to complex I of the mitochondrial electron transport chain and inhibits its activity, suggesting that inhibition of mitochondrial complex I activates an alternative respiration pathway resulting in reduction of ROS accumulation and enhancement of tolerance to salinity in plants. Furthermore, FSL0260 preferentially inhibited plant mitochondrial complex I rather than a mammalian complex, implying that FSL0260 has a potential to be an agent for improving salt-stress tolerance in agriculture that is low toxicity to humans