Numerical investigation of inertia gravity-wave activity in the differentially heated rotating annulus: The impact of boundary conditions

2021 ◽  
Author(s):  
Felix Jochum ◽  
Fabienne Schmid ◽  
Ulrich Achatz ◽  
Costanza Rodda ◽  
Uwe Harlander
Keyword(s):  
Boundary Conditions ◽  
Gravity Wave ◽  
Heat Fluxes ◽  
Generation Mechanism ◽  
Buoyancy Frequency ◽  
Spontaneous Generation ◽  
Coriolis Parameter ◽  
Systematic Analysis ◽  
The Impact ◽  
Upper Boundary

<p>The differentially heated rotating annulus is a classic experiment used for the examination of circulation patterns and waves in the atmosphere. In particular, by choosing an atmosphere-like experimental setup that allows the buoyancy frequency to become larger than the Coriolis parameter, it provides a useful tool to study the generation mechanism of spontaneous gravity wave (GW) emission in jet-front systems. Recently, with the aim to gain better understanding about the conditions for the spontaneous generation of GWs, Rodda et al. (2020) compared experimental data with results from numerical simulations and found differences in the GW signal most likely due to the model's treatment of boundary conditions. The aim of the present study is to improve the consistency between the model and experiment and to investigate the effect of the lateral and upper boundary conditions on GW generation and propagation in an atmosphere-like configuration of the annulus. More precisely, we implement the corresponding lateral and surface heat fluxes, air-temperature variations, as well as evaporation at the upper boundary condition into the numerical model and examine the characteristics of the observed GW signals, which are identified by the horizontal divergence field. Our systematic analysis may serve as a basis for subsequent research on the spontaneous GW generation mechanism, following the overarching objective to develop a parameterization scheme for GWs emitted from jets and front.</p><p> </p><p><strong>References:</strong></p><p>Rodda, C., S. Hien, U. Achatz, and U. Harlander, 2020: A new atmospheric-like differentially heated rotating annulus configuration to study gravity wave emission from jets and fronts. Exp. Fluids <strong>61, </strong>2. https://doi.org/10.1007/s00348-019-2825-z</p>

scholarly journals Multiscale Applications of Two Online-Coupled Meteorology-Chemistry Models During Recent Field Campaigns in Australia, Part II: Comparison of WRF/Chem and WRF/Chem-ROMS and Impacts of Air-Sea Interactions and Boundary Conditions

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 210 ◽  
Author(s):  
Zhang ◽  
Wang ◽  
Jena ◽  
Paton-Walsh ◽  
Guérette ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Temporal Variations ◽  
Ocean Model ◽  
Heat Fluxes ◽  
Atmospheric Pollutants ◽  
Spatial Distributions ◽  
Surface Heat Fluxes ◽  
Regional Ocean Model System ◽  
Field Campaigns ◽  
The Impact

Air-sea interactions play an important role in atmospheric circulation and boundary layer conditions through changing convection processes and surface heat fluxes, particularly in coastal areas. These changes can affect the concentrations, distributions, and lifetimes of atmospheric pollutants. In this Part II paper, the performance of the Weather Research and Forecasting model with chemistry (WRF/Chem) and the coupled WRF/Chem with the Regional Ocean Model System (ROMS) (WRF/Chem-ROMS) are intercompared for their applications over quadruple-nested domains in Australia during the three following field campaigns: The Sydney Particle Study Stages 1 and 2 (SPS1 and SPS2) and the Measurements of Urban, Marine, and Biogenic Air (MUMBA). The results are used to evaluate the impact of air-sea interaction representation in WRF/Chem-ROMS on model predictions. At 3, 9, and 27 km resolutions, compared to WRF/Chem, the explicit air-sea interactions in WRF/Chem-ROMS lead to substantial improvements in simulated sea-surface temperature (SST), latent heat fluxes (LHF), and sensible heat fluxes (SHF) over the ocean, in terms of statistics and spatial distributions, during all three field campaigns. The use of finer grid resolutions (3 or 9 km) effectively reduces the biases in these variables during SPS1 and SPS2 by WRF/Chem-ROMS, whereas it further increases these biases for WRF/Chem during all field campaigns. The large differences in SST, LHF, and SHF between the two models lead to different radiative, cloud, meteorological, and chemical predictions. WRF/Chem-ROMS generally performs better in terms of statistics and temporal variations for temperature and relative humidity at 2 m, wind speed and direction at 10 m, and precipitation. The percentage differences in simulated surface concentrations between the two models are mostly in the range of ±10% for CO, OH, and O3, ±25% for HCHO, ±30% for NO2, ±35% for H2O2, ±50% for SO2, ±60% for isoprene and terpenes, ±15% for PM2.5, and ±12% for PM10. WRF/Chem-ROMS at 3 km resolution slightly improves the statistical performance of many surface and column concentrations. WRF/Chem simulations with satellite-constrained boundary conditions (BCONs) improve the spatial distributions and magnitudes of column CO for all field campaigns and slightly improve those of the column NO2 for SPS1 and SPS2, column HCHO for SPS1 and MUMBA, and column O3 for SPS2 at 3 km over the Greater Sydney area. The satellite-constrained chemical BCONs reduce the model biases of surface CO, NO, and O3 predictions at 3 km for all field campaigns, surface PM2.5 predictions at 3 km for SPS1 and MUMBA, and surface PM10 predictions at all grid resolutions for all field campaigns. A more important role of chemical BCONs in the Southern Hemisphere, compared to that in the Northern Hemisphere reported in this work, indicates a crucial need in developing more realistic chemical BCONs for O3 in the relatively clean SH.

Chemical Transport Facilitated by Multiphase Flow Systems1

1985 ◽  
Vol 17 (9) ◽  
pp. 1-12 ◽  
Author(s):  
Carl G. Enfield
Keyword(s):  
Organic Carbon ◽  
Boundary Conditions ◽  
Transport Equation ◽  
Fluid Phase ◽  
Chemical Transport ◽  
Facilitated Transport ◽  
Organic Fraction ◽  
Dispersive Transport ◽  
Transformation Of Variables ◽  
The Impact

Relatively immobile chemicals have been observed moving significantly faster than anticipated from hydrophobic theory. A theory is developed considering transport in three mobile fluid phases which can be used to describe this facilitated transport. The convective dispersive transport equation is solved utilizing a transformation of variables which permits utilizing existing solutions covering a wide variety of boundary conditions. The impact of the facilitated transport is demonstrated for one case where the soils organic carbon is 10%. If 2% of the fluid phase is an organic fraction, the theory developed projects that hydrophobic theory may underestimate mobility by more than 100 times. At concentrations of dissolved organic carbon normally observed in nature (5 - 10 mg/l), a measurable increased mobility is anticipated for the very immobile compounds like dioxins.

Exile, Diaspora, and Return

2017 ◽  
Author(s):  
Luis Roniger ◽  
Leonardo Senkman ◽  
Saúl Sosnowski ◽  
Mario Sznajder
Keyword(s):  
Systematic Analysis ◽  
The Arts ◽  
Scientific Disciplines ◽  
Early Twenty ◽  
Transnational Connections ◽  
Late Twentieth ◽  
Institutional Impact ◽  
Global Arena ◽  
Education Science ◽  
The Impact

This book explores how Argentina, Chile, Paraguay, and Uruguay have been affected by postexilic relocations, transnational migrant displacements, and diasporas. It provides a systematic analysis of the formation of exile communities and diaspora politics, the politics of return, and the agenda of democratization in the late twentieth and early twenty-first centuries, focusing on the impact of intellectuals, academics, activists, and public figures who had experienced exile on the reconstitution and transformation of their societies following democratization. Readers are offered a kaleidoscope of intellectual itineraries, debates, and contributions held in the public domain by individuals who confronted and fought authoritarian rule. The book covers their contributions to the restructuring and transformation of scientific disciplines and of the humanities and the arts, as well as their collective institutional impact on higher education, science and technology, and public institutions. Bringing together sociopolitical, cultural, and policy analysis with the testimonies of dozens of intellectuals, academics, political activists, and policymakers, the book addresses the impact of exile on people’s lives and on their fractured experiences, the debates and prospects of return, the challenges of dis-exile and postexilic trends, and, finally, the ways in which those who experienced exile impacted democratized institutions, public culture, and discourse. It also follows some crucial shifts in the frontiers of citizenship, moving analysis to transnational connections and permanent diasporas, including the diasporas of knowledge that increasingly changed the very meaning of being national and transnational, while connecting those countries to the global arena.

scholarly journals Characterization of the subsurface urban heat island and its sources in the Milan city area, Italy

2021 ◽  
Author(s):  
Alberto Previati ◽  
Giovanni B. Crosta
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Heat Fluxes ◽  
Shallow Aquifer ◽  
Heat Island ◽  
Groundwater Temperature ◽  
City Area ◽  
Groundwater Environment ◽  
Urban Heat ◽  
The Impact

AbstractUrban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

Self-Acceleration in the Parameterization of Orographic Gravity Wave Drag

2010 ◽  
Vol 67 (8) ◽  
pp. 2537-2546 ◽  
Author(s):  
John F. Scinocca ◽  
Bruce R. Sutherland
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Train ◽  
Leading Edge ◽  
Wave Theory ◽  
Wave Drag ◽  
Tuning Parameter ◽  
Mean Flow ◽  
Propagating Waves ◽  
The Impact

Abstract A new effect related to the evaluation of momentum deposition in conventional parameterizations of orographic gravity wave drag (GWD) is considered. The effect takes the form of an adjustment to the basic-state wind about which steady-state wave solutions are constructed. The adjustment is conservative and follows from wave–mean flow theory associated with wave transience at the leading edge of the wave train, which sets up the steady solution assumed in such parameterizations. This has been referred to as “self-acceleration” and it is shown to induce a systematic lowering of the elevation of momentum deposition, which depends quadratically on the amplitude of the wave. An expression for the leading-order impact of self-acceleration is derived in terms of a reduction of the critical inverse Froude number Fc, which determines the onset of wave breaking for upwardly propagating waves in orographic GWD schemes. In such schemes Fc is a central tuning parameter and typical values are generally smaller than anticipated from conventional wave theory. Here it is suggested that self-acceleration may provide some of the explanation for why such small values of Fc are required. The impact of Fc on present-day climate is illustrated by simulations of the Canadian Middle Atmosphere Model.

scholarly journals A numerical study of the impact perforation of sandwich panels with graded hollow sphere cores

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110094
Author(s):  
Ibrahim Elnasri ◽  
Han Zhao
Keyword(s):  
Boundary Conditions ◽  
Hollow Sphere ◽  
Sandwich Panel ◽  
Numerical Study ◽  
Sandwich Panels ◽  
Hopkinson Bar ◽  
Core Density ◽  
The Core ◽  
The Impact ◽  
Force Displacement

In this study, we numerically investigate the impact perforation of sandwich panels made of 0.8 mm 2024-T3 aluminum alloy skin sheets and graded polymeric hollow sphere cores with four different gradient profiles. A suitable numerical model was conducted using the LS-DYNA code, calibrated with an inverse perforation test, instrumented with a Hopkinson bar, and validated using experimental data from the literature. Moreover, the effects of quasi-static loading, landing rates, and boundary conditions on the perforation resistance of the studied graded core sandwich panels were discussed. The simulation results showed that the piercing force–displacement response of the graded core sandwich panels is affected by the core density gradient profiles. Besides, the energy absorption capability can be effectively enhanced by modifying the arrangement of the core layers with unclumping boundary conditions in the graded core sandwich panel, which is rather too hard to achieve with clumping boundary conditions.

scholarly journals The Effect of Atmosphere–Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 688
Author(s):  
Soline Bielli ◽  
Christelle Barthe ◽  
Olivier Bousquet ◽  
Pierre Tulet ◽  
Joris Pianezze
Keyword(s):  
Tropical Cyclone ◽  
Mixed Layer ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Ocean Mixed Layer ◽  
Surface Cooling ◽  
Southwest Indian Ocean ◽  
Left Hand ◽  
Sea Surface Cooling ◽  
The Impact

A set of numerical simulations is relied upon to evaluate the impact of air-sea interactions on the behaviour of tropical cyclone (TC) Bejisa (2014), using various configurations of the coupled ocean-atmosphere numerical system Meso-NH-NEMO. Uncoupled (SST constant) as well as 1D (use of a 1D ocean mixed layer) and 3D (full 3D ocean) coupled experiments are conducted to evaluate the impact of the oceanic response and dynamic processes, with emphasis on the simulated structure and intensity of TC Bejisa. Although the three experiments are shown to properly capture the track of the tropical cyclone, the intensity and the spatial distribution of the sea surface cooling show strong differences from one coupled experiment to another. In the 1D experiment, sea surface cooling (∼1 ∘C) is reduced by a factor 2 with respect to observations and appears restricted to the depth of the ocean mixed layer. Cooling is maximized along the right-hand side of the TC track, in apparent disagreement with satellite-derived sea surface temperature observations. In the 3D experiment, surface cooling of up to 2.5 ∘C is simulated along the left hand side of the TC track, which shows more consistency with observations both in terms of intensity and spatial structure. In-depth cooling is also shown to extend to a much deeper depth, with a secondary maximum of nearly 1.5 ∘C simulated near 250 m. With respect to the uncoupled experiment, heat fluxes are reduced from about 20% in both 1D and 3D coupling configurations. The tropical cyclone intensity in terms of occurrence of 10-m TC wind is globally reduced in both cases by about 10%. 3D-coupling tends to asymmetrize winds aloft with little impact on intensity but rather a modification of the secondary circulation, resulting in a slight change in structure.

scholarly journals University students’ representations of Europe and self-identification as Europeans: a synthesis of qualitative evidence for future policy formulation

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Esther Cores-Bilbao ◽  
María del Carmen Méndez-García ◽  
M. Carmen Fonseca-Mora
Keyword(s):  
University Students ◽  
Evidence Synthesis ◽  
Foreign Language Learning ◽  
Educational Interventions ◽  
Policy Formulation ◽  
Qualitative Evidence Synthesis ◽  
The European Union ◽  
Systematic Analysis ◽  
Qualitative Evidence ◽  
The Impact

AbstractThe current European context is characterised by the emergence of socio-political tensions that threaten to derail the cohesion objectives traditionally promoted by the authorities of the European Union. With EU citizenship in the shadow of Brexit, the fear of dismemberment of the current Europe of the 28 looms over a renewed debate on concepts like European identity, European citizenship or EU legitimacy and the involvement of its constituents in European affairs, as well as the role of education for promoting democratic awareness among young Europeans. This work aims to collect, appraise and synthesise qualitative evidence obtained in primary research exploring the perceptions of European university students about their civic and cultural identity. This systematic analysis sets out to identify predictors of positive self-identification with the EU and its institutions, focusing on the impact that different educational interventions have had on the attitudes and perceptions expressed by university students, and the importance of foreign language learning in the results obtained. The authors report their assessment of quality of the findings in a Cochrane-style qualitative evidence synthesis (QES), based on the GRADE-CERQual (Confidence in Evidence from Reviews of Qualitative research) method. The 12 informed findings described in this study support decision-making in future education policy formulation.

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