Microwave temperature and pressure measurements with the Odin satellite: I. Observational method

The Odin satellite is equipped with millimetre and sub-millimetre receivers for observations of several molecular lines in the middle and upper atmosphere of our planet (~25–100 km, the particular altitude range depending on the species) for studies in dynamics, chemistry, and energy transfer in these regions. The same receivers are also used to observe molecules in outer space, this being the astrophysical share of the project. Among the atmospheric lines that can be observed, we find two corresponding to molecular oxygen (118.75 GHz and 487.25 GHz). These lines can be used for retrievals of the atmospheric temperature vertical profile. In this paper, we describe the radiative-transfer modeling for O2 in the middle and upper atmosphere that we will use as a basis for the retrieval algorithms. Two different observation modes have been planned for Odin, the three-channel operational mode and a high-resolution mode. The first one will determine the temperature and pressure on an operational basis using the oxygen line at 118.75 GHz, while the latter can be used for measurements of both O2 lines, during a small fraction of the total available time for aeronomy, aimed at checking the particular details of the radiative transfer near O2 lines at very high altitudes (>70 km). The Odin temperature measurements are expected to cover the altitude range ~30–90 km

Ward's Hierarchical Clustering Method: Clustering Criterion and Agglomerative Algorithm

The Ward error sum of squares hierarchical clustering method has been very widely used since its first description by Ward in a 1963 publication. It has also been generalized in various ways. However there are different interpretations in the literature and there are different implementations of the Ward agglomerative algorithm in commonly used software systems, including differing expressions of the agglomerative criterion. Our survey work and case studies will be useful for all those involved in developing software for data analysis using Ward's hierarchical clustering method.Comment: 20 pages, 21 citations, 4 figure

Future Directions in Astronomy Visualisation

Despite the large budgets spent annually on astronomical research equipment such as telescopes, instruments and supercomputers, the general trend is to analyse and view the resulting datasets using small, two-dimensional displays. We report here on alternative advanced image displays, with an emphasis on displays that we have constructed, including stereoscopic projection, multiple projector tiled displays and a digital dome. These displays can provide astronomers with new ways of exploring the terabyte and petabyte datasets that are now regularly being produced from all-sky surveys, high-resolution computer simulations, and Virtual Observatory projects. We also present a summary of the Advanced Image Displays for Astronomy (AIDA) survey which we conducted from March-May 2005, in order to raise some issues pertitent to the current and future level of use of advanced image displays.Comment: 13 pages, 2 figures, accepted for publication in PAS

Degenerating families of dendrograms

Dendrograms used in data analysis are ultrametric spaces, hence objects of nonarchimedean geometry. It is known that there exist $p$-adic representation of dendrograms. Completed by a point at infinity, they can be viewed as subtrees of the Bruhat-Tits tree associated to the $p$-adic projective line. The implications are that certain moduli spaces known in algebraic geometry are $p$-adic parameter spaces of (families of) dendrograms, and stochastic classification can also be handled within this framework. At the end, we calculate the topology of the hidden part of a dendrogram.Comment: 13 pages, 8 figure

Decision boundaries using Bayes factors: the case of cloud masks

We assess the use of an approximation to the Bayes factor for objectively assessing spatial segmentation models. The Bayes factor allows us to automatically determine thresholds, in multidimensional feature space, for such objectives as cloud mask definition. We compare our results with a cloud map currently provided as a data product

Mumford dendrograms and discrete p-adic symmetries

In this article, we present an effective encoding of dendrograms by embedding them into the Bruhat-Tits trees associated to $p$-adic number fields. As an application, we show how strings over a finite alphabet can be encoded in cyclotomic extensions of $\mathbb{Q}_p$ and discuss $p$-adic DNA encoding. The application leads to fast $p$-adic agglomerative hierarchic algorithms similar to the ones recently used e.g. by A. Khrennikov and others. From the viewpoint of $p$-adic geometry, to encode a dendrogram $X$ in a $p$-adic field $K$ means to fix a set $S$ of $K$-rational punctures on the $p$-adic projective line $\mathbb{P}^1$. To $\mathbb{P}^1\setminus S$ is associated in a natural way a subtree inside the Bruhat-Tits tree which recovers $X$, a method first used by F. Kato in 1999 in the classification of discrete subgroups of $\textrm{PGL}_2(K)$. Next, we show how the $p$-adic moduli space $\mathfrak{M}_{0,n}$ of $\mathbb{P}^1$ with $n$ punctures can be applied to the study of time series of dendrograms and those symmetries arising from hyperbolic actions on $\mathbb{P}^1$. In this way, we can associate to certain classes of dynamical systems a Mumford curve, i.e. a $p$-adic algebraic curve with totally degenerate reduction modulo $p$. Finally, we indicate some of our results in the study of general discrete actions on $\mathbb{P}^1$, and their relation to $p$-adic Hurwitz spaces.Comment: 14 pages, 6 figure

Does the planning system in England deliver a sustainable and resilient environment? A study of the experience of town planners

The case has been made in the reports of the Intergovernmental Panel on Climate Changes for the crucial role of the built environment in mitigating the worst excesses of a warming global climate and in protecting people through adaptation. Town planners are essential actors in delivering sustainable and resilient urbanism. Given that legislation is implemented by people, the study aimed to examine how town planners experienced and thought about the changing legislation and how they understood the concepts of ‘sustainability’ and ‘resilience’ in the built environment. Semi-structured interviews were conducted with 19 planners working in England who had at least seven years’ experience. In the analysis, we explored meanings of sustainability and of resilience, and how these concepts were seen as incorporated in legislation. Sustainability was seen by the participants as embedded in regulations but its realisation varied substantially. Tensions were evident between the three pillars of environment, society and economy. ‘Resilience’ as a concept was poorly understood and legislative support was patchy at best: while flooding features extensively in local plans, wider issues of climate impact such as overheating are not comprehensively addressed. The conclusions are that planners are often frustrated in their attempts to develop a more sustainable built environment and that the current planning system is inadequate to deliver consistently sustainable and resilient outcomes. However, alignment between sustainability goals and professional identity were also noted, offering avenues to explore beyond the institutional constraints of legislation

Identities as enabling conditions of sustainability practices in urban planning: A critical realist exploration with planners in England

The case has been made in reports of the Intergovernmental Panel on Climate Change for the crucial role of the built environment in mitigating the worst excesses of a warming global climate. Urban planners are essential actors in delivering a sustainable built environment. Alongside macro influences such as policy, practices in urban planning are influenced by underlying mechanisms at the level of the individual. Adopting a Bhaskarian critical realist approach, in this study we examined enabling conditions of sustainability practices. Semi-structured interviews were conducted with 19 planners in England with at least seven years’ experience. The analysis found evidence from the planners’ experience of tensions between the three strands of sustainability, and of practices which could be understood from theoretical perspectives of collaboration/consensus, dissensus and pursuit of specific outcomes. A professional commitment towards a better environment appeared to be a generative mechanism for sustainability practices and underlying conditions included professional identity, identity as a public sector worker, organisational and team identities, and personal commitment. Constraining conditions were found to include stakeholder and political pressure and weak policy. The findings suggest points of leverage for the professional body, local authorities and planners themselves, in order to strengthen sustainability practices and potentially lead to transformation

Nitric acid in the stratosphere based on Odin observations from 2001 to 2009 – Part 2: High-altitude polar enhancements

The wintertime abundance of nitric acid (HNO<sub>3</sub>) in the polar upper stratosphere displays a strong inter-annual variability, and is known to be strongly influenced by energetic particle precipitation (EPP), primarily by protons during solar proton events (SPEs), but also by precipitating auroral or relativistic electrons. We analyse a multi-year record (August 2001 to April 2009) of middle atmospheric HNO<sub>3</sub> measurements by the Sub-Millimeter Radiometer instrument aboard the Odin satellite, with a focus on the polar upper stratosphere. SMR observations show clear evidence of two different types of polar high-altitude HNO<sub>3</sub> enhancements linked to EPP. In the first type, referred to as direct enhancements by analogy with the EPP/NO<sub>x</sub> direct effect, enhanced HNO<sub>3</sub> mixing ratios are observed for a short period (1 week) after a SPE, upwards of a level typically in the mid-stratosphere. In a second type, referred to as indirect enhancements by analogy with the EPP/NO<sub>x</sub> indirect effect, the descent of mesospheric air triggers a stronger and longer-lasting enhancement. Each of the three major SPEs that occurred during the Northern Hemisphere autumn or winter, in November 2001, October–November 2003 and January 2005, are observed to lead to both direct and indirect HNO<sub>3</sub> enhancements. On the other hand, indirect enhancements occur recurrently in winter, are stronger in the Southern Hemisphere, and are influenced by EPP at higher altitudes