Singularity-sensitive gauge-based radar rainfall adjustment methods for urban hydrological applications

Gauge-based radar rainfall adjustment techniques have been widely used to improve the applicability of radar rainfall estimates to large-scale hydrological modelling. However, their use for urban hydrological applications is limited as they were mostly developed based upon Gaussian approximations and therefore tend to smooth off so-called "singularities" (features of a non-Gaussian field) that can be observed in the fine-scale rainfall structure. Overlooking the singularities could be critical, given that their distribution is highly consistent with that of local extreme magnitudes. This deficiency may cause large errors in the subsequent urban hydrological modelling. To address this limitation and improve the applicability of adjustment techniques at urban scales, a method is proposed herein which incorporates a local singularity analysis into existing adjustment techniques and allows the preservation of the singularity structures throughout the adjustment process. In this paper the proposed singularity analysis is incorporated into the Bayesian merging technique and the performance of the resulting singularity-sensitive method is compared with that of the original Bayesian (non singularity-sensitive) technique and the commonly used mean field bias adjustment. This test is conducted using as case study four storm events observed in the Portobello catchment (53 km2) (Edinburgh, UK) during 2011 and for which radar estimates, dense rain gauge and sewer flow records, as well as a recently calibrated urban drainage model were available. The results suggest that, in general, the proposed singularity-sensitive method can effectively preserve the non-normality in local rainfall structure, while retaining the ability of the original adjustment techniques to generate nearly unbiased estimates. Moreover, the ability of the singularity-sensitive technique to preserve the non-normality in rainfall estimates often leads to better reproduction of the urban drainage system's dynamics, particularly of peak runoff flows

Observation of enhanced optical spring damping in a macroscopic mechanical resonator and application for parametric instability control in advanced gravitational-wave detectors

We show that optical spring damping in an optomechanical resonator can be enhanced by injecting a phase delay in the laser frequency-locking servo to rotate the real and imaginary components of the optical spring constant. This enhances damping at the expense of optical rigidity. We demonstrate enhanced parametric damping which reduces the Q factor of a 0.1-kg-scale resonator from 1.3×10^5 to 6.5×10^3. By using this technique adequate optical spring damping can be obtained to damp parametric instability predicted for advanced laser interferometer gravitational-wave detectors

Getting integrative urban regeneration strategies done:Insights from Antwerp and Gothenburg

Integrative strategic management for urban regeneration involves reconciling conflicting demands and translating abstract concepts into concrete actions. This article examines how public-sector strategists address these dilemmas by developing a dynamic perspective that helps in understanding how they ‘strategize’. This perspective was applied to two urban regeneration projects in Gothenburg (Sweden) and Antwerp (Belgium). Our findings illustrate how actors strategize at different locations and times, putting middle-management strategists, in particular, on the horns of a dilemma. Acting quickly through establishing experimentation spaces could result in innovative outcomes, but politicians and local residents may feel bypassed; however, waiting until strategic visions are translated into detailed actions may eventually result in no action at all. This article helps us understand the disconnect between planning, implementation and performance in strategic management. Points for practitioners: Public-sector strategists have to overcome conflicting demands in urban regeneration projects and translate ambitious visions into actions. As strategists' actions can drift from the original goals, they have to regularly reflect on the contribution of actions to the vision. Middle managers, in particular, have to be careful: their leeway can lead to innovative actions but can also clash with initial goals. Finally, living labs – used to implement the strategy at a small scale – should not become detached from the broader urban regeneration project.</p

Optimal learning on climate change: why climate skeptics should reduce emissions

Climate skeptics argue that the possibility that global warming is exogenous implies that we should not take additional action towards reducing greenhouse gas emissions until we know more. However this paper shows that even climate skeptics have an incentive to reduce emissions: such a change of direction facilitates their learning process on the causes of global warming. Since the optimal policy action depends on these causes, they are valuable to know. Although an increase in emissions would also ease learning, that option is shown to be inferior because emitting greenhouse gases is irreversible. Consequently the policy implications of the different positions in the global warming debate turn out to coincide - thereby diminishing the relevance of this debate from a policy perspective. Uncertainty is no reason for inaction

Optimal learning on climate change: why climate skeptics should reduce emissions

Climate skeptics typically argue that the possibility that global warming is exogenous, implies that we should not take additional action towards reducing emissions until we know what drives warming. This paper however shows that even climate skeptics have an incentive to reduce emissions: such a directional change generates information on the causes of global warming. Since the optimal policy depends upon these causes, they are valuable to know. Although increasing emissions would also generate information, that option is inferior due its irreversibility. We show that optimality can even imply that climate skeptics should actually argue for lower emissions than believers

Overlapping-gate architecture for silicon Hall bar MOSFET devices in the low electron density regime

We report the fabrication and study of Hall bar MOSFET devices in which an overlapping-gate architecture allows four-terminal measurements of low-density 2D electron systems, while maintaining a high density at the ohmic contacts. Comparison with devices made using a standard single gate show that measurements can be performed at much lower densities and higher channel resistances, despite a reduced peak mobility. We also observe a voltage threshold shift which we attribute to negative oxide charge, injected during electron-beam lithography processing.Comment: 4 pages, 4 figures, submitted for Applied Physics Letter