Reducing model complexity for explanation and prediction

Numerical models can be useful for explaining poorly understood phenomena or for reliable quantitative predictions. When modeling a multi-scale system, a ‘top-down’ approach—basing models on emergent variables and interactions, rather than explicitly on the much faster and smaller scale processes that give rise to them—facilitates both goals. Parameterizations representing emergent interactions range from highly simplified and abstracted to more quantitatively accurate. Empirically based large-scale parameterizations lead more reliably to accurate large-scale behavior than do parameterizations of much smaller scale processes. Conversely, purposefully simplified representations of model interactions can enhance a model's utility for explanation, clarifying the key feedbacks leading to an enigmatic behavior. For such potential insights to be relevant, the interactions in the model need to correspond to those in the ‘real’ system in some straightforward way. Such a correspondence usually holds for models constructed for predictive purposes, although this is not a requirement. The goals motivating a modeling endeavor help determine the most appropriate modeling strategies, as well as the most appropriate criteria for judging model usefulness.     

Dilemmas of development in Oceania: the political economy of the Tongan agro-export sector

This article critically engages with the recent diffusion of the orthodox development model in Oceania and highlights some evolving dilemmas. In particular, it explores the social, economic and ecological tensions arising from economic reforms that are exacerbating the fragility of already vulnerable nation-states and communities. In order to illustrate its arguments, a case study of the impacts of agro-export growth in Tonga is presented. Attention is drawn to the socially inequitable and ecologically unsustainable outcomes of rapid growth in this sector. In analyzing the political economy of the squash pumpkin sector, the authors point to the important role that culture plays in mediating and conditioning development outcomes. Reflecting on the Tongan case, it is argued that to better understand the implications of orthodox developmental reform in the region, research must seek to more explicitly incorporate distributional and ethical analysis.     

Propagation of solar flare-associated interplanetary shock waves in the heliospheric meridional plane

We have analyzed 149 flare-associated shock wave events based on interplanetary scintillation (IPS) observational data. All of the flare-associated shock waves tend to propagate toward the low latitude region near the solar equator for flares that are located in both the solar northern and southern hemispheres. Also, the fastest propagation directions tend toward the heliospheric current sheet near 1 AU. We suggest that this tendency is caused by the dynamic action of near-Sun magnetic forces on the ejected coronal plasma that traverses the helmet-like magnetic topologies near the Sun outward to the classical topology that is essentially parallel to the heliospheric current sheet.