Numerical impacts on tracer transport: Diagnosing the influence of dynamical core formulation and resolution on stratospheric transport

Accurate representation of stratospheric trace gas transport is important for ozone modeling and climate projection. Intermodel spread can arise from differences in the representation of transport by the diabatic (overturning) circulation vs. comparatively faster adiabatic mixing by breaking waves, or through numerical errors, primarily diffusion. This study investigates the impact of these processes on transport using an idealised tracer, the age-of-air. Transport is assessed in two state-of-the-art dynamical cores based on fundamentally different numerical formulations: finite volume and spectral element. Integrating the models in free-running and nudged tropical wind configurations reveals the crucial impact of tropical dynamics on stratospheric transport. Using age-budget theory, vertical and horizontal gradients of age allow comparison of the roles of the diabatic circulation, adiabatic mixing, and the numerical diffusive flux. Their respective contribution is quantified by connecting the full 3-d model to the tropical leaky pipe framework of Neu and Plumb (1999). Transport by the two cores varies significantly in the free-running integrations, with the age in the middle stratosphere differing by about 2 years primarily due to differences in adiabatic mixing. When winds in the tropics are constrained, the difference in age drops to about 0.5 years; in this configuration, more than half the difference is due to the representation of the diabatic circulation. Numerical diffusion is very sensitive to the resolution of the core, but does not play a significant role in differences between the cores when they are run at comparable resolution. It is concluded that fundamental differences rooted in dynamical core formulation can account for a substantial fraction of transport bias between climate models.

Symbiosis increases population size and buffers environmental fluctuations in a physiologically-structured model parameterized for thyasirid bivalves

Symbioses whereby one partner provisions a nutritional resource to the other may alter energy allocation towards reproduction and survival in the recipient partner, potentially impacting population dynamics. Asymbiotic thyasirid bivalves feed predominantly on free-living bacteria, which fluctuate in abundance due to seasonality-driven temperature variations. Symbiotic thyasirids are mixotrophs, gaining nutrients from free-living bacteria and symbiotic bacteria that they host on their enlarged gills. Symbiotic bacteria may function as an additional energy reserve for thyasirids, allowing the hosts to allocate more energy to reproduction. We hypothesize that, for symbiotic thyasirids, the symbionts are a nutritional source that mitigates resource limitation. Using Dynamic Energy Budget theory, we built a physiologically-structured population model assuming equal mortality rates in both species. We find that without seasonal fluctuations, symbiotic thyasirids have higher abundances than asymbiotic thyasirids since the symbionts increase reproduction. Both species have similar population sizes in fluctuating environments, suggesting different adaptations to seasonality: asymbiotic thyasirids have adapted their physiology, while symbiotic thyasirids have adapted through mixotrophy. Our results highlight the significance of linking individual energetics and life-history traits to population dynamics and are the first step towards understanding the role of symbioses in population and community dynamics.

A Dynamic Energy Budget Model of Ornate Box Turtle Shell Growth

Many aspects of box turtle development may depend on size rather than age. Notable examples include sexual maturity and the development of the fully closing hinge in the shell that allows box turtles to completely hide in their shells. Thus, it is important to understand how turtles grow in order to have a complete understanding of turtle biology. Previous studies show that turtle shell growth behaves in a logistic manner. These studies use functional models that fit the data well but do little to explain mechanisms. In this work we use the ideas found in dynamic energy budget theory to build a model of box turtle shell growth. We show this model fits the data as well as previous models for ornate box turtles Terrapene ornata ornata, but also offers explanations for observed phenomena, such as maximum sizes and the appearance of biphasic growth.

Examining the implications of classical budget theories in the local government budgeting process: Union Councils in Bangladesh

Background: In many countries, local governments are neither well equipped nor properly accountable for performing their functions smoothly. They have also failed to become effective strategic partners of the national government and other levels of subnational governments. They have neither sufficient tax-base and local resource-entitlement nor full-bodied intergovernmental support. But the demands for services and goods continue to exceed the supply at local-government level in Bangladesh and elsewhere. As a result, the local government planning and budgeting issues become centrally positioned in the debate on the subnational level decentralisation, especially concerning fiscal decentralisation and political economics of local governments.Aim: Keeping this fact in mind, the study examined the implications of classical budget theories in the local government budgeting process, particularly in the budgetary process and decisions of local government union councils in Bangladesh.Setting: The data collection period was January 2018 to February 2018. The units of analysis of this study are ‘the classical budget theories’ and the lowest tier of the rural local government institutions in Bangladesh – that is, ‘the union. councils’.Methods: The study followed ‘focused synthesis’ and ‘qualitative case research’ methods for data collection and used the epistemological view ‘positivism’ for data analysis.Results: The study contributed to the literature stream of local government studies, public budget theory, subnational finance and budgeting, and the political economics of the local government.Conclusion: This research reveals that ‘budgetary incrementalism’ and ‘high conditionality’ to inter-governmental transfers undermine the essence of community stakeholders’ consultations and spirit of local governance. It also unveils that central limitation towards effective functioning of a local government union council in Bangladesh is more related to the crisis of ownership and competence of the elected council rather than just to the external influences that somewhat affect their autonomy in the budgeting process and decisions.