Energy balance of forests with special consideration of advection

The present work was written as a cumulative dissertation based on peer-reviewed papers and is completed by yet unpublished results. The overall objective was to get a deeper insight into the role of the advective fluxes of sensible heat and latent heat in relation to the energy balance and its imbalance at the earth’s surface (typically the sum of the turbulent fluxes sensible and latent heat does not match the available energy). Data from two advection experiments at four coniferous sites across Europe served as the basis for the analysis. One was the advection experiment MORE II which took place in Tharandt (Germany) and the other advection experiment ADVEX was conducted at three different sites (Ritten/Renon, Italy; Wetzstein, Germany; Norunda, Sweden). An inspection of the available energy (AE) that is redistributed to the atmosphere by the sensible heat flux (H) and latent heat flux (LE) showed that the uncertainty of the available energy itself cannot explain the lack of energy balance closure for these four sites. The mean absolute uncertainty of the available energy was largest during midday and ranged from 41 W m-2 to 52 W m-2 (approx. 12 % of AE). During nighttime, the mean absolute uncertainty was smaller (20 W m-2 – 30 W m-2) but the relative uncertainty was much larger as AE itself is small. Among the investigated storage terms the heat storage change of the biomass was most important. The energy balance closure was improved for all investigated sites when storage terms were included. In principle, storage terms should not be neglected in energy balance studies. An investigation of the budget of sensible heat, not only including the vertical advection and the horizontal advection but also the horizontal turbulent flux divergence, was undertaken for the coniferous site at Tharandt. Inclusion of these fluxes resulted in an enlarged mean daily amplitude and suggests an improvement of the energy balance closure, at least during nighttime. The commonly determined budget (vertical turbulent flux plus storage change) was reduced by about 30 % when advective fluxes were included. Results suggest that the horizontal turbulent flux divergence is of minor importance but further studies are needed for an overall evaluation. First results for the inclusion of the advective fluxes of both sensible heat and latent heat indicate that the lack of energy balance closure is partly reduced but the imbalance still exists. Advective fluxes of sensible heat were also compared to advective fluxes of CO2. It became apparent that the advective fluxes of sensible heat and CO2 are, on average, of opposite sign during nighttime and both share large scatter. Both budgets (sensible heat and CO2) were considerably changed (although differently for different sites) when advective fluxes were included. Results further suggest that advective fluxes of H can be taken as an indicator concerning the presence and sign of advection of CO2. This points towards a coincident non-turbulent transport of heat and CO2. However, all investigated advective fluxes are site-specific. They are characterised by a large uncertainty due to uncertainties in the mean vertical velocity (vertical advection) and in the horizontal differences in scalar magnitude (horizontal advection). Obviously, they are influenced by the limitations of the experimental set-up (spatial resolution) and the local characteristics of the individual measurements. An overall evaluation of advective fluxes with respect to their representativeness and magnitude requires further studiesDie vorliegende Arbeit wurde als kumulative Dissertation verfasst, die auf begutachteten Publikationen beruht. Sie wird um bisher nicht veröffentlichte Daten zur Advektion latenter Wärme ergänzt. Ziel war es, vor allem die Rolle der advektiven Flüsse von sensibler und latenter Wärme in Bezug auf die Energiebilanz und das Problem der Energiebilanzschließung an der Erdoberfläche näher zu untersuchen. Unter der Energiebilanzschließungslücke wird im Allgemeinen das Phänomen verstanden, dass die Summe der gemessenen turbulenten Flüsse von sensibler und latenter Wärme zumeist nicht der gemessenen verfügbaren Energie entspricht. Als Datengrundlage für die Arbeiten dienten hierzu die Datensätze von zwei Advektionsexperimenten, die an vier verschiedenen Nadelwaldstandorten in Europa stattfanden. Das erste dieser Advektionsexperimente MORE II fand an der Ankerstation Tharandt (Deutschland) statt und das zweite (ADVEX) wurde an drei verschiedenen Standorten durchgeführt (Ritten/Renon, Italien; Wetzstein, Deutschland; Norunda, Schweden). Eine Untersuchung der verfügbaren Energie (AE), die über den sensiblen Wärmestrom (H) und den latenten Wärmestrom (LE) wieder an die Atmosphäre abgegeben wird, zeigte, dass die in der Bestimmung der verfügbaren Energie liegende Unsicherheit das Problem der Energiebilanzschließungslücke nicht ausreichend erklärt. Die mittlere absolute Unsicherheit der verfügbaren Energie war dabei mittags am größten (41 W m-2 – 52 W m-2; ca. 12 % der verfügbaren Energie). Nachts war diese kleiner (20 W m-2 – 30 W m-2). Jedoch waren dann die relativen Unsicherheiten deutlich größer, da die verfügbare Energie nachts klein ist. Von den betrachteten Speichertermen der Energiebilanz erwies sich die Speicheränderung von Wärme in der Biomasse als am wichtigsten. Für die vier untersuchten Standorte verbesserte sich die Energiebilanzschließung, wenn die Speicherterme mit einbezogen wurden. Grundsätzlich sollten alle Speicherterme bei der Bestimmung der Energiebilanz mit beachtet werden. Für den Nadelwaldstandort Tharandt wurde die Bilanz der sensiblen Wärme unter Beachtung der advektiven Flüsse und der horizontalen turbulenten Flussdivergenz erstellt. Die Einbeziehung der advektiven Flüsse und der horizontalen turbulenten Flussdivergenz führte zu einer Vergrößerung der Amplitude im mittleren Tagesgang und deutet auf eine Verbesserung der Energiebilanzschließung zumindest nachts hin. Im herkömmlichen Sinne wird die Bilanz für Energie oder Massenflüsse als Summe aus vertikalem turbulenten Fluss und Speicheränderung bestimmt. Die Gesamtsumme dieser Bilanz wurde um 30 % reduziert, wenn die advektiven Flüsse mit einbezogen wurden. Hinsichtlich der horizontalen turbulenten Flussdivergenz kann man noch keine abschließende Einschätzung geben. Die vorliegenden Ergebnisse deuten einen vernachlässigbaren Anteil an der Gesamtbilanz für diesen Term an. Erste Ergebnisse für die Bestimmung der Energiebilanz von Nadelwäldern unter Beachtung der advektiven Flüsse von sensibler und latenter Wärme zeigen eine teilweise Reduzierung der Energiebilanzschließungslücke, jedoch keine vollständige Schließung der Energiebilanz. Weiterhin wurden die advektiven Flüsse sensibler Wärme mit denen von CO2 verglichen. Die Bilanzen für den CO2-Fluss als auch für den Fluss sensibler Wärme änderten sich deutlich unter Einbeziehung der advektiven Flüsse, wenn auch unterschiedlich für verschiedene Standorte. Besonders nachts sind die advektiven Flüsse von sensibler Wärme und CO2 im Mittel durch gegensätzliche Vorzeichen gekennzeichnet. Diese Beziehung eröffnet die Möglichkeit, advektive Flüsse von CO2 auf der Basis von advektiven Flüssen sensibler Wärme hinsichtlich ihres Vorhandenseins und ihrer Richtung abzuschätzen. Dies deutet auf einen gleichzeitigen nicht-turbulenten Transport von Wärme und CO2 hin. Generell ist festzustellen, dass alle untersuchten advektiven Flüsse spezifisch für den jeweiligen Standort und durch eine große Unsicherheit gekennzeichnet sind. Diese ergibt sich zum einen aus der mittleren vertikalen Geschwindigkeit (vertikale Advektion) und zum anderen aus den horizontalen Differenzen (horizontale Advektion) der jeweiligen skalaren Größen. Die betrachteten advektiven Flüsse werden offensichtlich durch Einschränkungen, die sich aus dem experimentellen Aufbau ergeben (z.B. begrenzte räumliche Auflösung), in ähnlicher Weise beeinflusst. Eine abschließende Beurteilung der advektiven Flüsse hinsichtlich ihres Anteils an der Gesamtbilanz und ihrer Repräsentativität erfordert weitere Studien

The Perspective of Counselors on Occupational Therapy at a Residential Camp for Children with Disabilities

Introduction: By attending summer camps, children with disabilities have the opportunity to retain skills they acquire during the school year in services including occupational therapy (Marr & Dimeo, 2006); however, the perception of occupational therapy services at these camps is limited. Not all children who receive therapy services during the school year are eligible for services in the summer, which means that occupational therapy at summer camps is an opportunity to prevent deterioration of skills in those not otherwise eligible (North Dakota Department of Public Instruction, 2016). Methodology: A qualitative phenomenological research study was conducted to look at camp counselors’ perceptions of occupational therapy services for children at a summer camp for children with disabilities. Researchers interviewed six counselors from a summer camp in the Midwest using a semi-structured interview process. Data was coded and put into categories, which were then developed into three themes. This process was guided by the Person Environment Occupation (PEO) Model. Results: The counselors’ perceptions were concerned with the camper’s experience at camp and occupational therapy. Three main themes emerged that revolved around the three domains of the PEO model: the person, environment, and occupation. Conclusion: Counselors reported that campers experienced improvements in confidence, responsibility, social skills, activities of daily living, and participation in leisure activities and play. Occupational therapy services were perceived to be favorable by counselors in helping campers maintain skills, complete activities of daily living, and interact appropriately with peers in a camp setting. Significance: Children and adolescents with disabilities can benefit with improved skills by attending summer camps where therapy services are provided. The profession of occupational therapy has limited presence in summer camps, however, children could benefit from increased services provided at summer camps

Impact of CO2 storage flux sampling uncertainty on net ecosystem exchange measured by eddy covariance

Complying with several assumption and simplifications, most of the carbon budget studies based on eddy covariance (EC) measurements quantify the net ecosystem exchange (NEE) by summing the flux obtained by EC ( FC ) and the storage flux ( SC ). SC is the rate of change of a scalar, CO 2 molar fraction in this case, within the control volume underneath the EC measurement level. It is given by the difference in the quasi-instantaneous profiles of concentration at the beginning and end of the EC averaging period, divided by the averaging period. The approaches used to estimate SC largely vary, from measurements based on a single sampling point usually located at the EC measurement height, to measurements based on profile sampling. Generally a single profile is used, although multiple profiles can be positioned within the control volume. Measurement accuracy reasonably increases with the spatial sampling intensity, however limited resources often prevent more elaborated measurement systems. In this study we use the experimental dataset collected during the ADVEX campaign in which turbulent and non-turbulent fluxes were measured in three forest sites by the simultaneous use of five towers/profiles. Our main objectives are to evaluate both the uncertainty of SC that derives from an insufficient sampling of CO 2 variability, and its impact on concurrent NEE estimates.Results show that different measurement methods may produce substantially different SC flux estimates which in some cases involve a significant underestimation of the actual SC at a half-hourly time scales. A proper measuring system, that uses a single vertical profile of which the CO 2 sampled at 3 points (the two closest to the ground and the one at the lower fringe of the canopy layer) is averaged with CO 2 sampled at a certain distance and at the same height, improves the horizontal representativeness and reduces this (proportional) bias to 2–10% in such ecosystems. While the effect of this error is minor on long term NEE estimates, it can produce significant uncertainty on half-hourly NEE fluxes

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