A method for merging flow-dependent forecast error statistics from an ensemble with static statistics for use in high resolution variational data assimilation

The background error covariance matrix, B, is often used in variational data assimilation for numerical weather prediction as a static and hence poor approximation to the fully dynamic forecast error covariance matrix, Pf. In this paper the concept of an Ensemble Reduced Rank Kalman Filter (EnRRKF) is outlined. In the EnRRKF the forecast error statistics in a subspace defined by an ensemble of states forecast by the dynamic model are found. These statistics are merged in a formal way with the static statistics, which apply in the remainder of the space. The combined statistics may then be used in a variational data assimilation setting. It is hoped that the nonlinear error growth of small-scale weather systems will be accurately captured by the EnRRKF, to produce accurate analyses and ultimately improved forecasts of extreme events.

Post War land reform and the impact on planning in Japan

One feature of Japanese urban areas in the 21st century that is bound to strike any Western visitor is the extensive spread of its suburbs with their varied mixing of land-uses. It is almost impossible to pinpoint precisely where the city begins and where it ends. During the post-War period, this characteristic pattern of land-use sprawled over the countryside, seemingly unimpeded by planning restrictions. The number of studies that highlight the problems of Japanese planning outweighs the research that explores its underlying causes. This paper aims to partly redress this imbalance by describing a case study of the failed implementation of the green belt around Tokyo and to link this with the Allied Occupation’s postwar land reforms and drafting of a new constitution in the period 1946-1951. Overall, we aim to highlight how the ostensible benefits and aims of a land reform programme can entail substantial disbenefits or unforeseen outcomes in terms of land-use planning..

State estimation using the particle filter with mode tracking

A particle filter is a data assimilation scheme that employs a fully nonlinear, non-Gaussian analysis step. Unfortunately as the size of the state grows the number of ensemble members required for the particle filter to converge to the true solution increases exponentially. To overcome this Vaswani [Vaswani N. 2008. IEEE Trans Signal Process 56:4583–97] proposed a new method known as mode tracking to improve the efficiency of the particle filter. When mode tracking, the state is split into two subspaces. One subspace is forecast using the particle filter, the other is treated so that its values are set equal to the mode of the marginal pdf. There are many ways to split the state. One hypothesis is that the best results should be obtained from the particle filter with mode tracking when we mode track the maximum number of unimodal dimensions. The aim of this paper is to test this hypothesis using the three dimensional stochastic Lorenz equations with direct observations. It is found that mode tracking the maximum number of unimodal dimensions does not always provide the best result. The best choice of states to mode track depends on the number of particles used and the accuracy and frequency of the observations.

Antarctic air over New Zealand following vortex breakdown in 1998

An ozonesonde profile over the Network for Detection of Stratospheric Change (NDSC) site at Lauder (45.0° S, 169.7° E), New Zealand, for 24 December 1998 showed atypically low ozone centered around 24 km altitude (600 K potential temperature). The origin of the anomaly is explained using reverse domain filling (RDF) calculations combined with a PV/O3 fitting technique applied to ozone measurements from the Polar Ozone and Aerosol Measurement (POAM) III instrument. The RDF calculations for two isentropic surfaces, 550 and 600 K, show that ozone-poor air from the Antarctic polar vortex reached New Zealand on 24–26 December 1998. The vortex air on the 550 K isentrope originated in the ozone hole region, unlike the air on 600 K where low ozone values were caused by dynamical effects. High-resolution ozone maps were generated, and their examination shows that a vortex remnant situated above New Zealand was the cause of the altered ozone profile on 24 December. The maps also illustrate mixing of the vortex filaments into southern midlatitudes, whereby the overall mid-latitude ozone levels were decreased.

Sharing power? Prospects for a U.S. concert-balance strategy

The Pax Americana and the grand strategy of hegemony (or “Primacy”) that underpins it may be becoming unsustainable. Particularly in the wake of exhausting wars, the Global Financial Crisis, and the shift of wealth from West to East, it may no longer be possible or prudent for the United States to act as the unipolar sheriff or guardian of a world order. But how viable are the alternatives, and what difficulties will these alternatives entail in their design and execution? This analysis offers a sympathetic but critical analysis of alternative U.S. National Security Strategies of “retrenchment” that critics of American diplomacy offer. In these strategies, the United States would anticipate the coming of a more multipolar world and organize its behavior around the dual principles of “concert” and “balance,” seeking a collaborative relationship with other great powers, while being prepared to counterbalance any hostile aggressor that threatens world order. The proponents of such strategies argue that by scaling back its global military presence and its commitments, the United States can trade prestige for security, shift burdens, and attain a more free hand. To support this theory, they often look to the 19th-century concert of Europe as a model of a successful security regime and to general theories about the natural balancing behavior of states. This monograph examines this precedent and measures its usefulness for contemporary statecraft to identify how great power concerts are sustained and how they break down. The project also applies competing theories to how states might behave if world politics are in transition: Will they balance, bandwagon, or hedge? This demonstrates the multiple possible futures that could shape and be shaped by a new strategy. viii A new strategy based on an acceptance of multipolarity and the limits of power is prudent. There is scope for such a shift. The convergence of several trends—including transnational problems needing collaborative efforts, the military advantages of defenders, the reluctance of states to engage in unbridled competition, and hegemony fatigue among the American people—means that an opportunity exists internationally and at home for a shift to a new strategy. But a Concert-Balance strategy will still need to deal with several potential dilemmas. These include the difficulty of reconciling competitive balancing with cooperative concerts, the limits of balancing without a forward-reaching onshore military capability, possible unanticipated consequences such as a rise in regional power competition or the emergence of blocs (such as a Chinese East Asia or an Iranian Gulf), and the challenge of sustaining domestic political support for a strategy that voluntarily abdicates world leadership. These difficulties can be mitigated, but they must be met with pragmatic and gradual implementation as well as elegant theorizing and the need to avoid swapping one ironclad, doctrinaire grand strategy for another.

Managing a duopolistic water market with confirmed proposals. An experiment

We report results from experimental water markets in which owners of two different sources of water supply water to households and farmers. The final water quality consumed by each type of consumer is determined through mixing of qualities from two different resources. We compare the standard duopolistic market structure with an alternative market clearing mechanism inspired by games with confirmed strategies (which have been shown to yield collusive outcomes). As in the static case, complex dynamic markets operating under a confirmed proposals protocol yield less efficient outcomes because coordination among independent suppliers has the usual effects of restricting output and increasing prices to the users. Our results suggest that, when market mechanisms are used to allocate water to its users, the rule of thumb used by competition authorities can also serve as a guide towards water market regulation.

Secondary cyclogenesis along an occluded front leading to damaging wind gusts: windstorm Kyrill, January 2007

Windstorm Kyrill affected large parts of Europe in January 2007 and caused widespread havoc and loss of life. In this study the formation of a secondary cyclone, Kyill II, along the occluded front of the mature cyclone Kyrill and the occurrence of severe wind gusts as Kyrill II passed over Germany are investigated with the help of high-resolution regional climate model simulations. Kyrill underwent an explosive cyclogenesis south of Greenland as the storm crossed polewards of an intense upper-level jet stream. Later in its life cycle secondary cyclogenesis occurred just west of the British Isles. The formation of Kyrill II along the occluded front was associated (a) with frontolytic strain and (b) with strong diabatic heating in combination with a developing upper-level shortwave trough. Sensitivity studies with reduced latent heat release feature a similar development but a weaker secondary cyclone, revealing the importance of diabatic processes during the formation of Kyrill II. Kyrill II moved further towards Europe and its development was favored by a split jet structure aloft, which maintained the cyclone’s exceptionally deep core pressure (below 965 hPa) for at least 36 hours. The occurrence of hurricane force winds related to the strong cold front over North and Central Germany is analyzed using convection-permitting simulations. The lower troposphere exhibits conditional instability, a turbulent flow and evaporative cooling. Simulation at high spatio-temporal resolution suggests that the downward mixing of high momentum (the wind speed at 875 hPa widely exceeded 45 m s-1) accounts for widespread severe surface wind gusts, which is in agreement with observed widespread losses.

The Article 51 reporting requirement for self-defense actions

This article examines one legal criterion for the exercise of the right of self-defense that has been significantly overlooked by commentators: the so-called “reporting requirement.” Article 51 of the United Nations (UN) Charter provides, inter alia, that “[m]easures taken by members in the exercise of this right of self-defense shall be immediately reported to the Security Council.” Although the requirement to report all self-defense actions to the Council is clearly set out in Article 51, the Charter offers no further guidance with regard to this obligation. Reference to the practice of states since the UN’s inception in 1945 is therefore essential to understanding the scope and nature of the reporting requirement. As such, this article is underpinned by an extensive original dataset of reporting practice covering the period from January 1, 1998 to December 31, 2013. We know from Article 51 that states “shall” report, but do they, and—if so—in what manner? What are the various implications of reporting, of failing to report, and of the way in which states report? How are reports used, and by whom? Most importantly, this article questions the ultimate value of states reporting their self-defense actions to the Security Council in modern interstate relations.

Redox- and glucose-responsive hydrogels from poly(vinyl alcohol) and 4-mercaptophenylboronic acid

Novel redox- and glucose-responsive hydrogels have been synthesized by simple mixing of poly(vinyl alcohol) (PVA) and 4-mercaptophenylboronic acid (MPBA) in aqueous solutions (pH > 9) in an oxidative aqueous media. These hydrogels are produced through the formation of disulfide linkages between MPBA molecules in an oxidative environment (oxygen dissolved in solution or hydrogen peroxide added to the reaction mixture) and complexation via dynamic covalent bonds between PVA and MPBA dimer. These hydrogels show degradation in solutions of l-glutathione and d-glucose.