Turbulent small-scale neutral and ion density fluctuations: First results of the MAC/EPSILON campaign

Abstract. In January 2005, a total of 18 rockets were launched from the Andøya Rocket Range in Northern Norway (69° N) into strong VHF radar echoes called "Polar Mesosphere Winter Echoes" (PMWE). The echoes were observed in the lower and middle mesosphere during large solar proton fluxes. In general, PMWE occur much more seldom compared to their summer counterparts PMSE (typical occurrence rates at 69° N are 1–3% vs. 80%, respectively). Our in-situ measurements by falling sphere, chaff, and instrumented payloads provide detailed information about the thermal and dynamical state of the atmosphere and therefore allow an unprecedented study of the background atmosphere during PMWE. There are a number of independent observations indicating that neutral air turbulence has caused PMWE. Ion density fluctuations show a turbulence spectrum within PMWE and no fluctuations outside. Temperature lapse rates close to the adiabatic gradient are observed in the vicinity of PMWE indicating persistent turbulent mixing. The spectral broadening of radar echoes is consistent with turbulent velocity fluctuations. Turbulence also explains the mean occurrence height of PMWE (~68–75 km): viscosity increases rapidly with altitude and destroys any small scale fluctuations in the upper mesosphere, whereas electron densities are usually too low in the lower mesosphere to cause significant backscatter. The seasonal variation of echoes in the lower mesosphere is in agreement with a turbulence climatology derived from earlier sounding rocket flights. We have performed model calculations to study the radar backscatter from plasma fluctuations caused by neutral air turbulence. We find that volume reflectivities observed during PMWE are in quantitative agreement with theory. Apart from turbulence the most crucial requirement for PMWE is a sufficiently large number of electrons, for example produced by solar proton events. We have studied the sensitivity of the radar echo strength on various parameters, most important electron number density and turbulence intensity. Our observational and theoretical considerations do not provide any evidence that charged aerosol particles are needed to explain PMWE, in contrast to the summer echoes which owe their existence to charged ice particles.

Download Full-text

Evaluating Visualisations in Voting Advice Applications

Statistics Politics and Policy ◽

10.1515/spp-2019-0009 ◽

2020 ◽

Vol 11 (1) ◽

pp. 1-21

Author(s):

Bastiaan Bruinsma

Keyword(s):

Small Scale ◽

First Results ◽

Scale Experiment ◽

Voting Advice Applications

AbstractWhile the design of voting advice applications (VAAs) is witnessing an increasing amount of attention, one aspect has until now been overlooked: its visualisations. This is remarkable, as it are those visualisations that communicate to the user the advice of the VAA. Therefore, this article aims to provide a first look at which visualisations VAAs adopt, why they adopt them, and how users comprehend them. For this, I will look at how design choices, specifically those on matching, influence the type of visualisation VAAs not only do but also have to, use. Second, I will report the results of a small-scale experiment that looked if all users comprehend similar visualisations in the same way. Here, I find that this is often not the case and that the interpretations of the users often differ. These first results suggest that VAA visualisations are wrongly underappreciated and demand closer attention of VAA designers.

Download Full-text

Small-Scale Density Fluctuations in the Adiabatic Toroidal Compressor

Physical Review Letters ◽

10.1103/physrevlett.36.792 ◽

1976 ◽

Vol 36 (14) ◽

pp. 792-794 ◽

Cited By ~ 190

Author(s):

E. Mazzucato

Keyword(s):

Density Fluctuations ◽

Small Scale

Download Full-text

On the short-term variability of turbulence and temperature in the winter mesosphere

Annales Geophysicae ◽

10.5194/angeo-36-1099-2018 ◽

2018 ◽

Vol 36 (4) ◽

pp. 1099-1116

Author(s):

Gerald A. Lehmacher ◽

Miguel F. Larsen ◽

Richard L. Collins ◽

Aroh Barjatya ◽

Boris Strelnikov

Keyword(s):

Attitude Control ◽

Large Scale ◽

Lower Thermosphere ◽

Density Fluctuations ◽

Large Temperature ◽

Small Scale ◽

Spatial And Temporal Variability ◽

Temperature Structure ◽

Wind Shears

Abstract. Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (<0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0<Ri<0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (Kp∼5).

Download Full-text

Hydrostatic Collapse Pressure and Radial Collapse Force Comparisons for Ultra-Deepwater Pipelines

Volume 6B: Pipeline and Riser Technology ◽

10.1115/omae2014-24081 ◽

2014 ◽

Cited By ~ 1

Author(s):

Marco A. P. Rosas ◽

Ana Paula F. Souza ◽

Marcos V. Rodrigues ◽

Danilo Machado L. da Silva

Keyword(s):

Numerical Models ◽

Research Work ◽

Compressive Force ◽

Quadratic Function ◽

Radial Force ◽

Small Scale ◽

Collapse Pressure ◽

First Results ◽

Specimen Test ◽

The Relationship

In this paper the behavior and the relationship between hydrostatic collapse pressure and diametrically opposed radial compressive force for pipelines were analyzed. This study presents an introduction of a research work aimed to assess the pipeline collapse pressure based on the radial collapse force. Initially the hydrostatic collapse pressure is analyzed, for pipes with different diameter to wall thickness ratio (D/t) and ovalities, using classical assessment (DNV method) and numerical models (FE). Then, the compressive radial force is also analyzed using numerical models validated by a small-scale ring specimen test. After that, the relationship between hydrostatic collapse pressure and compressive radial force is discussed. These first results show that the radial force is a quadratic function of the collapse pressure.

Download Full-text

Drivers of Change in National Disaster Governance under the Hyogo Framework for Action

Politics and Governance ◽

10.17645/pag.v8i4.3062 ◽

2020 ◽

Vol 8 (4) ◽

pp. 256-269 ◽

Cited By ~ 1

Author(s):

Maximilian S. T. Wanner

Keyword(s):

Natural Hazard ◽

National Level ◽

Development Aid ◽

Small Scale ◽

Substantial Variation ◽

Drivers Of Change ◽

Governance Capacity ◽

Systematic Assessment ◽

First Results ◽

National Disaster

Many suggestions have been made on what motivates countries to expand their measures for disaster risk reduction (DRR), including the frequency and severity of natural hazards, accountability mechanisms, and governance capacity. Despite the fact that theoretical arguments have been developed and evidence collected from small-scale case studies, few studies have attempted to explain the substantial variation in the adoption of DRR measures across countries. This study combines available data on DRR measures, natural hazard events, governance, and socioeconomic characteristics to provide a systematic assessment of the changes that have occurred in the state of DRR at the national level. In line with theoretical explanations, there are indeed associations between several measures of frequency and severity and the development of DRR status. Additionally, voice and accountability mechanisms, as well as development aid, might facilitate positive change. Although these first results of a global comparative study on change in DRR have to be taken cautiously, it is a step forward to understanding the drivers of change at the national level.

Download Full-text

A new discrete multiplicative random cascade model for downscaling intermittent rainfall fields

10.5194/hess-2019-449 ◽

2019 ◽

Author(s):

Marc Schleiss

Keyword(s):

Classical Method ◽

Mathematical Problem ◽

Grid Cell ◽

Cascade Model ◽

Small Scale ◽

Grid Cells ◽

Cascade Generator ◽

Cascade Models ◽

First Results ◽

Original Amount

Abstract. Spatial downscaling of rainfall fields is a challenging mathematical problem for which many different types of methods have been proposed. One popular solution consists in redistributing rainfall amounts over smaller and smaller scales by means of a discrete multiplicative random cascade (DMRC). This works well for slowly varying, homogeneous rainfall fields but often fails in the presence of intermittency (i.e., large amounts of zero rainfall values). The most common workaround in this case is to use two separate cascade models, one for the occurrence and another for the intensity. In this paper, a new and simpler approach based on the notion of equal-volume areas (EVAs) is proposed. Unlike classical cascades where rainfall amounts are redistributed over grid cells of equal size, the EVA cascade splits grid cells into areas of different sizes, each of them containing exactly half of the original amount of water. The relative areas of the sub-grid cells are determined by drawing random values from a logit-normal cascade generator model with scale and intensity dependent standard deviation. The process ends when the amount of water in each sub-grid cell is smaller than a fixed bucket capacity, at which point the output of the cascade can be re-sampled over a regular Cartesian mesh. The present paper describes the implementation of the EVA cascade model and gives some first results for 100 selected events in the Netherlands. Performance is assessed by comparing the outputs of the EVA model to bilinear interpolation and to a classical DMRC model based on fixed grid cell sizes. Results show that on average, the EVA cascade outperforms the classical method, producing fields with more realistic distributions, small-scale extremes and spatial structures. Improvements are mostly credited to the higher robustness of the EVA model to the presence of intermittency and to the lower variance of its generator. However, improvements are not systematic and both approaches have their advantages and weaknesses. For example, while the classical cascade tends to overestimate small-scale extremes and variability, the EVA model tends to produce fields that are slightly too smooth and blocky compared with observations.

Download Full-text

Seismostratigraphic Interpretation of Upper Cretaceous Reservoir from the Carpathian Foreland, Southern Poland

Energies ◽

10.3390/en14227776 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7776

Author(s):

Andrzej Urbaniec ◽

Anna Łaba-Biel ◽

Anna Kwietniak ◽

Imoleayo Fashagba

Keyword(s):

Late Cretaceous ◽

Upper Cretaceous ◽

Tectonic Setting ◽

Small Scale ◽

Reservoir Properties ◽

Southern Poland ◽

Seismic Sequence Stratigraphy ◽

First Results ◽

Depositional Architecture ◽

The Impact

The Upper Cretaceous complex in the central part of the Carpathian Foreland (southern Poland) is relatively poorly recognized and described. Its formations can be classified as unconventional reservoir due to poor reservoir properties as well as a low recovery factor. The main aim of the article is to expand knowledge with conclusions resulting from the analysis of the latest seismic data with the application of seismic sequence stratigraphy. Moreover, the seismic attributes analysis was utilized. The depositional architecture recognition based on both chronostratigraphic horizons and Wheeler diagram interpretations was of paramount importance. A further result was the possibility of using the chronostratigraphic image for tectonostratigraphic interpretation. Two distinguished tectonostratigraphic units corresponding to megasequences were recognized. A tectonic setting of the analyzed interval is associated with global processes noticed by other authors in other parts of the central European Late Cretaceous basin, but also locally accompanied by evidence of small-scale tectonics. This study fills the gap on the issue of paleogeography in the Late Cretaceous sedimentary basin of the Carpathian Foreland. It presents the first results of detailed reconstruction of the basin paleogeography and an attempt to determine the impact of both eustatic and tectonic factors on sedimentation processes.

Download Full-text