Local and Non‐local Impacts of Gaps on Submerged Canopy Flow

Abstract Inland freshwater bodies form the largest natural source of carbon to the atmosphere. To study this contribution to the atmospheric carbon cycle, eddy-covariance flux measurements at lake sites have become increasingly popular. The eddy-covariance method is derived for solely local processes from the surface (lake). Non-local processes, such as entrainment or advection, would add erroneous contributions to the eddy-covariance flux estimations. Here, we use four years of eddy-covariance measurements of carbon dioxide from Lake Erken, a freshwater lake in mid-Sweden. When the lake is covered with ice, unexpected lake fluxes were still observed. A statistical approach using only surface-layer data reveals that non-local processes produce these erroneous fluxes. The occurrence and strength of non-local processes depend on a combination of wind speed and distance between the instrumented tower and upwind shore (fetch), which we here define as the time over water. The greater the wind speed and the shorter the fetch, the higher the contribution of non-local processes to the eddy-covariance fluxes. A correction approach for the measured scalar fluxes due to the non-local processes is proposed and also applied to open-water time periods. The gas transfer velocity determined from the corrected fluxes is close to commonly used wind-speed based parametrizations.

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Incorporating a Global Perspective Into Future-Oriented Forest Management Scenarios

International Journal of Agricultural and Environmental Information Systems ◽

10.4018/ijaeis.2019010102 ◽

2019 ◽

Vol 10 (1) ◽

pp. 21-39 ◽

Cited By ~ 2

Author(s):

Panagiotis P. Koulelis ◽

Constance L. McDermott

Keyword(s):

Forest Management ◽

Global Perspective ◽

Management Scenarios ◽

Forest Protection ◽

Potential Increase ◽

Footprint Analysis ◽

Non Local ◽

Local Impacts ◽

Political Economic ◽

The Eu

This research serves to integrate the concept of an “ecological footprint” into future-oriented forest management scenarios. Scenarios are commonly used to explore stakeholder perceptions of possible forest futures, and are typically focused on the local impacts of different management choices. This article illustrates how global footprint analysis can be incorporated into scenarios to enable local forest stakeholders in the EU to consider the impacts of their local decisions at national and global levels. This illustration could be helpful to the construction of a forest decision support system that includes wood trade information and social processes (simulation of management decisions under changing political/economic conditions). It finds that different future forest management scenarios involving a potential increase or decrease of the harvested timber, or potential increase or decrease of subsidies for forest protection, combined with various possible changes in local consumption patterns, might have impact on both “internal” (local) and “external” (non-local) forest footprints.

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Local and non-local climatic impacts of land use across scales

10.5194/egusphere-egu21-10471 ◽

2021 ◽

Author(s):

Liang Chen

Keyword(s):

Land Use ◽

Spatial Scales ◽

Climate Extremes ◽

Land Use Land Cover ◽

Land Use Impacts ◽

Community Earth System Model ◽

Climatic Impacts ◽

Non Local ◽

Local Impacts ◽

Climate Studies

<p>It has been widely recognized that land use/land cover changes have great potential to influence climate at different scales. However, their local and non-local impacts have not been well understood. First, previous studies are limited by the assumption that the local impacts of land use do not modify the atmospheric background states. Second, land-use impacts may vary if simulations are conducted at a different spatial scale. In this study, we investigate the local and non-local impacts of historical land use using the Community Earth System Model version 2, and explore the possible influence of model resolutions on the local and non-local impacts. The local and non-local impacts of land use are separated using atmospheric nudging, in which the horizontal winds in the upper atmosphere are forced to follow the ERA-Interim reanalysis, whereas the nudging strength is zero at the surface. The multi-resolution experiments suggest that the local impacts of land use are consistent at different spatial scales, but the non-local impacts are influenced by the model resolution. We will also discuss the local and non-local impacts of land use on climate extremes across scales. This study presents a new way to distinguish the local and non-local impacts and highlights the uncertainty in simulated land-use impact in climate studies.&#160;</p>

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Toward High-Resolution Low-Voltage SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103152 ◽

1988 ◽

Vol 46 ◽

pp. 218-219

Author(s):

Zhifeng Shao

Keyword(s):

Low Voltage ◽

Spherical Aberration ◽

Chromatic Aberration ◽

Limiting Factor ◽

Operating Voltage ◽

Probe Radius ◽

Non Local ◽

Electron Microscopes ◽

Image Position ◽

Scanning Electron Microscopes

Recently, low voltage (≤5kV) scanning electron microscopes have become popular because of their unprecedented advantages, such as minimized charging effects and smaller specimen damage, etc. Perhaps the most important advantage of LVSEM is that they may be able to provide ultrahigh resolution since the interaction volume decreases when electron energy is reduced. It is obvious that no matter how low the operating voltage is, the resolution is always poorer than the probe radius. To achieve 10Å resolution at 5kV (including non-local effects), we would require a probe radius of 5∽6 Å. At low voltages, we can no longer ignore the effects of chromatic aberration because of the increased ratio δV/V. The 3rd order spherical aberration is another major limiting factor. The optimized aperture should be calculated as

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Chromatic aberration and low-voltage SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127293 ◽

1987 ◽

Vol 45 ◽

pp. 546-547

Author(s):

Zhifeng Shao ◽

A.V. Crewe

Keyword(s):

Electron Energy ◽

Low Voltage ◽

Spherical Aberration ◽

Chromatic Aberration ◽

Primary Electron ◽

Probe Size ◽

Non Local ◽

Optical Treatment ◽

Electron Microscopes ◽

Scanning Electron Microscopes

For scanning electron microscopes, it is plausible that by lowering the primary electron energy, one can decrease the volume of interaction and improve resolution. As shown by Crewe /1/, at V0 =5kV a 10Å resolution (including non-local effects) is possible. To achieve this, we would need a probe size about 5Å. However, at low voltages, the chromatic aberration becomes the major concern even for field emission sources. In this case, δV/V = 0.1 V/5kV = 2x10-5. As a rough estimate, it has been shown that /2/ the chromatic aberration δC should be less than ⅓ of δ0 the probe size determined by diffraction and spherical aberration in order to neglect its effect. But this did not take into account the distribution of electron energy. We will show that by using a wave optical treatment, the tolerance on the chromatic aberration is much larger than we expected.

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