Transport timescales and tracer properties in the extratropical UTLS

A comprehensive evaluation of seasonal backward trajectories initialized in the Northern Hemisphere lowermost stratosphere (LMS) has been performed to investigate the origin of air parcels and the main mechanisms determining characteristic structures in H2O and CO within the LMS. In particular we explain the fundamental role of the transit time since last tropopause crossing (tTST) for the chemical structure of the LMS as well as the feature of the extra-tropical tropopause transition layer (ExTL) as identified from CO profiles. The distribution of H2O in the background LMS above Θ=320 K and 340 K in northern winter and summer, respectively, is found to be governed mainly by the saturation mixing ratio, which in turn is determined by the Lagrangian Cold Point (LCP) encountered by each trajectory. Most of the backward trajectories from this region in the LMS experienced their LCP in the tropics and sub-tropics. The transit time since crossing the tropopause from the troposphere to the stratosphere (tTST) is independent of the H2O value of the air parcel. TST often occurs 20 days after trajectories have encountered their LCP. CO, on the other hand, depends strongly on tTST due to its finite lifetime. The ExTL as identified from CO measurements is then explained as a layer of air just above the tropopause, which on average encountered TST fairly recently

Relational Symplectic Groupoid Quantization for Constant Poisson Structures

As a detailed application of the BV-BFV formalism for the quantization of field theories on manifolds with boundary, this note describes a quantization of the relational symplectic groupoid for a constant Poisson structure. The presence of mixed boundary conditions and the globalization of results is also addressed. In particular, the paper includes an extension to space-times with boundary of some formal geometry considerations in the BV-BFV formalism, and specifically introduces into the BV-BFV framework a "differential" version of the classical and quantum master equations. The quantization constructed in this paper induces Kontsevich's deformation quantization on the underlying Poisson manifold, i.e., the Moyal product, which is known in full details. This allows focussing on the BV-BFV technology and testing it. For the unexperienced reader, this is also a practical and reasonably simple way to learn it.Comment: 32 pages, 15 figures, some changes (including the correction of a minor mistake) included; new appendix with the explicit computations added; to appear in Lett. Math. Phy

Individual monitoring at accelerator centres

The accurate determination of personal dose equivalent requires the proper use of appropriate radiological quantities and units, knowledge of the dose equivalent response of the personal dosemeters used and detailed information on the fluence as well as dose equivalent spectra at the workplaces. This information can then be used to select the appropriate dosemeters, to set up the optimum calibration conditions and to introduce, in case of need, normalisation factors for application in specific radiation fields. High-energy neutrons contribute significantly to the radiation fields around high-energy particle accelerators. Examples for procedures and methods to determine personal dose equivalent at accelerator centres are give

Six lectures on Geometric Quantization

These are the lecture notes for a short course on geometric quantization given by the author at the XVIII Modave Summer School on Mathematical Physics, Sep 5 - Sep 9

Run-time Variability with First-class Contexts

Software must be regularly updated to keep up with changing requirements. Unfortunately, to install an update, the system must usually be restarted, which is inconvenient and costly. In this dissertation, we aim at overcoming the need for restart by enabling run-time changes at the programming language level. We argue that the best way to achieve this goal is to improve the support for encapsulation, information hiding and late binding by contextualizing behavior. In our approach, behavioral variations are encapsulated into context objects that alter the behavior of other objects locally. We present three contextual language features that demonstrate our approach. First, we present a feature to evolve software by scoping variations to threads. This way, arbitrary objects can be substituted over time without compromising safety. Second, we present a variant of dynamic proxies that operate by delegation instead of forwarding. The proxies can be used as building blocks to implement contextualization mechanisms from within the language. Third, we contextualize the behavior of objects to intercept exchanges of references between objects. This approach scales information hiding from objects to aggregates. The three language features are supported by formalizations and case studies, showing their soundness and practicality. With these three complementary language features, developers can easily design applications that can accommodate run-time changes

Processes determining heat waves across different European climates

This study presents a comprehensive analysis of processes determining heat waves across different climates in Europe for the period 1979–2016. Heat waves are defined using a percentile‐based index and the main processes quantified along trajectories are adiabatic compression by subsidence and local and remote diabatic processes in the upper and lower troposphere. This Lagrangian analysis is complemented by an Eulerian calculation of horizontal temperature advection. During typical summers in Europe, one or two heat waves occur, with an average duration of five days. Whereas high near‐surface temperatures over Scandinavia are accompanied by omega‐like blocking structures at 500 hPa, heat waves over the Mediterranean are connected to comparably flat ridges. Tracing air masses backwards from the heat waves, we identify three trajectory clusters with coherent thermodynamic characteristics, vertical motions, and geographic origins. In all regions, horizontal temperature advection is almost negligible. In two of the three clusters, subsidence in the free atmosphere is very important in establishing high temperatures near the surface, while the air masses in the third cluster are warmed primarily due to diabatic heating near the surface. Large interregional differences occur between the British Isles and western Russia. Over the latter region, near‐surface transport and diabatic heating appear to be very important in determining the intensity of the heat waves, whereas subsidence and adiabatic warming are of first‐order importance for the British Isles. Although the large‐scale pattern is quasistationary during heat wave days, new air masses are entrained steadily into the lower troposphere during the life cycle of a heat wave. Overall, the results of the present study provide a guideline as to which processes and diagnostics weather and climate studies should focus on to understand the severity of heat waves