scholarly journals Quantitative evaluation of ozone and selected climate parameters in a set of EMAC simulations

2015 ◽  
Vol 8 (3) ◽  
pp. 733-768 ◽  
Author(s):  
M. Righi ◽  
V. Eyring ◽  
K.-D. Gottschaldt ◽  
C. Klinger ◽  
F. Frank ◽  
...  
Keyword(s):  
Water Vapor ◽  
Boundary Conditions ◽  
Tropospheric Ozone ◽  
Strong Dependence ◽  
Transport Sector ◽  
Climate Projections ◽  
Data Sets ◽  
Different Boundary Conditions ◽  
Climate Parameters ◽  
Free Running

Abstract. Four simulations with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model have been evaluated with the Earth System Model Validation Tool (ESMValTool) to identify differences in simulated ozone and selected climate parameters that resulted from (i) different setups of the EMAC model (nudged vs. free-running) and (ii) different boundary conditions (emissions, sea surface temperatures (SSTs) and sea ice concentrations (SICs)). To assess the relative performance of the simulations, quantitative performance metrics are calculated consistently for the climate parameters and ozone. This is important for the interpretation of the evaluation results since biases in climate can impact on biases in chemistry and vice versa. The observational data sets used for the evaluation include ozonesonde and aircraft data, meteorological reanalyses and satellite measurements. The results from a previous EMAC evaluation of a model simulation with nudging towards realistic meteorology in the troposphere have been compared to new simulations with different model setups and updated emission data sets in free-running time slice and nudged quasi chemistry-transport model (QCTM) mode. The latter two configurations are particularly important for chemistry-climate projections and for the quantification of individual sources (e.g., the transport sector) that lead to small chemical perturbations of the climate system, respectively. With the exception of some specific features which are detailed in this study, no large differences that could be related to the different setups (nudged vs. free-running) of the EMAC simulations were found, which offers the possibility to evaluate and improve the overall model with the help of shorter nudged simulations. The main differences between the two setups is a better representation of the tropospheric and stratospheric temperature in the nudged simulations, which also better reproduce stratospheric water vapor concentrations, due to the improved simulation of the temperature in the tropical tropopause layer. Ozone and ozone precursor concentrations, on the other hand, are very similar in the different model setups, if similar boundary conditions are used. Different boundary conditions however lead to relevant differences in the four simulations. Biases which are common to all simulations are the underestimation of the ozone hole and the overestimation of tropospheric column ozone, the latter being significantly reduced when lower lightning emissions of nitrogen oxides are used. To further investigate possible other reasons for such bias, two sensitivity simulations with an updated scavenging routine and the addition of a newly proposed HNO3-forming channel of the HO2+NO reaction were performed. The update in the scavenging routine resulted in a slightly better representation of ozone compared to the reference simulation. The introduction of the new HNO3-forming channel significantly reduces the overestimation of tropospheric ozone. Therefore, including the new reaction rate could potentially be important for a realistic simulation of tropospheric ozone, although laboratory experiments and other model studies need to confirm this hypothesis and some modifications to the rate, which has a strong dependence on water vapor, might also still be needed.

scholarly journals Quantitative evaluation of ozone and selected climate parameters in a set of EMAC simulations

2014 ◽  
Vol 7 (5) ◽  
pp. 6549-6627
Author(s):  
M. Righi ◽  
V. Eyring ◽  
K.-D. Gottschaldt ◽  
C. Klinger ◽  
F. Frank ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Water Vapour ◽  
Atmospheric Chemistry ◽  
Performance Metrics ◽  
Strong Dependence ◽  
Transport Sector ◽  
Climate Projections ◽  
Different Boundary Conditions ◽  
Climate Parameters ◽  
Free Running

Abstract. Four simulations with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model have been evaluated with the Earth System Model Validation Tool (ESMValTool) to identify differences in simulated ozone and selected climate parameters that resulted from (i) different setups of the EMAC model (nudged vs. free-running) and (ii) different boundary conditions (emissions, sea surface temperatures (SSTs) and sea-ice concentrations (SICs)). To assess the relative performance of the simulations, quantitative performance metrics are calculated consistently for the climate parameters and ozone. This is important for the interpretation of the evaluation results since biases in climate can impact on biases in chemistry and vice versa. The observational datasets used for the evaluation include ozonesonde and aircraft data, meteorological reanalyses and satellite measurements. The results from a previous EMAC evaluation of a model simulation with weak nudging towards realistic meteorology in the troposphere have been compared to new simulations with different model setups and updated emission datasets in free-running timeslice and nudged Quasi Chemistry-Transport Model (QCTM) mode. The latter two configurations are particularly important for chemistry-climate projections and for the quantification of individual sources (e.g. transport sector) that lead to small chemical perturbations of the climate system, respectively. With the exception of some specific features which are detailed in this study, no large differences that could be related to the different setups of the EMAC simulations (nudged vs. free-running) were found, which offers the possibility to evaluate and improve the overall model with the help of shorter nudged simulations. The main differences between the two setups is a better representation of the tropospheric and stratospheric temperature in the nudged simulations, which also better reproduce stratospheric water vapour concentrations, due to the improved simulation of the temperature in the tropical tropopause layer. Ozone and ozone precursor concentrations on the other hand are very similar in the different model setups, if similar boundary conditions are used. Different boundary conditions however lead to relevant differences in the four simulations. SSTs and SICs, which are prescribed in all simulations, play a key role in the representation of the ozone hole, which is significantly underestimated in some experiments. A bias that is present in all simulations is an overestimation of tropospheric column ozone, which is significantly reduced when lower lightning emissions of nitrogen oxides are used. To further investigate possible other reasons for such bias, two sensitivity simulations with an updated scavenging routine and the addition of a newly proposed HNO3-forming channel of the HO2+ NO reaction were performed. The update in the scavenging routine resulted in a slightly better representation of ozone compared to the reference simulation. The introduction of the new HNO3-forming channel significantly reduces this bias. Therefore, including the new reaction rate could potentially be important for a realistic simulation of tropospheric ozone, although laboratory experiments and other models studies need to confirm this hypothesis and some modifications to the rate, which has a strong dependence on water vapour, might also still be needed.

scholarly journals Mechanics of tubular helical assemblies: ensemble response to axial compression and extension

2021 ◽  
Author(s):  
Jacopo Quaglierini ◽  
Alessandro Lucantonio ◽  
Antonio DeSimone
Keyword(s):  
Boundary Conditions ◽  
Elastic Properties ◽  
Central Region ◽  
Mechanical Response ◽  
Different Boundary Conditions ◽  
Kirchhoff Rods ◽  
Model Versus ◽  
The Individual ◽  
Opposite Chirality

Abstract Nature and technology often adopt structures that can be described as tubular helical assemblies. However, the role and mechanisms of these structures remain elusive. In this paper, we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods, arranged in pairs with opposite chirality and connected by pin joints, both analytically and numerically. We first focus on compression and find that, whereas a single helical rod would buckle, the rods of the assembly deform coherently as stable helical shapes wound around a common axis. Moreover, we investigate the response of the assembly under different boundary conditions, highlighting the emergence of a central region where rods remain circular helices. Secondly, we study the effects of different hypotheses on the elastic properties of rods, i.e., stress-free rods when straight versus when circular helices, Kirchhoff’s rod model versus Sadowsky’s ribbon model. Summing up, our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods, as well as some interesting features, and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology. Graphic Abstract We study the mechanical response under compression/extension of an assembly composed of 8 helical rods, pin-jointed and arranged in pairs with opposite chirality. In compression we find that, whereas a single rod buckles (a), the rods of the assembly deform as stable helical shapes (b). We investigate the effect of different boundary conditions and elastic properties on the mechanical response, and find that the deformed geometries exhibit a common central region where rods remain circular helices. Our findings highlight the key role of mutual interactions in the ensemble response and shed some light on the reasons why tubular helical assemblies are so common and persistent.

scholarly journals Assessment of Sampling Effects on Various Satellite-Derived Integrated Water Vapor Datasets Using GPS Measurements in Germany as Reference

2020 ◽  
Vol 12 (7) ◽  
pp. 1170 ◽  
Author(s):  
Cintia Carbajal Henken ◽  
Lisa Dirks ◽  
Sandra Steinke ◽  
Hannes Diedrich ◽  
Thomas August ◽  
...  
Keyword(s):  
Water Vapor ◽  
Pairwise Comparison ◽  
Weather Conditions ◽  
Satellite System ◽  
High Temporal Resolution ◽  
Data Sets ◽  
Frequency Distributions ◽  
Temporal Sampling ◽  
Global Navigation Satellite ◽  
Satellite Instruments

Passive imagers on polar-orbiting satellites provide long-term, accurate integrated water vapor (IWV) data sets. However, these climatologies are affected by sampling biases. In Germany, a dense Global Navigation Satellite System network provides accurate IWV measurements not limited by weather conditions and with high temporal resolution. Therefore, they serve as a reference to assess the quality and sampling issues of IWV products from multiple satellite instruments that show different orbital and instrument characteristics. A direct pairwise comparison between one year of IWV data from GPS and satellite instruments reveals overall biases (in kg/m 2 ) of 1.77, 1.36, 1.11, and −0.31 for IASI, MIRS, MODIS, and MODIS-FUB, respectively. Computed monthly means show similar behaviors. No significant impact of averaging time and the low temporal sampling on aggregated satellite IWV data is found, mostly related to the noisy weather conditions in the German domain. In combination with SEVIRI cloud coverage, a change of shape of IWV frequency distributions towards a bi-modal distribution and loss of high IWV values are observed when limiting cases to daytime and clear sky. Overall, sampling affects mean IWV values only marginally, which are rather dominated by the overall retrieval bias, but can lead to significant changes in IWV frequency distributions.

Thermal phase transition behaviours of the blue phase of bent-core nematogen and chiral dopant mixtures under different boundary conditions

Soft Matter ◽  
2014 ◽  
Vol 10 (41) ◽  
pp. 8224-8228 ◽  
Author(s):  
Min-Jun Gim ◽  
Gohyun Han ◽  
Suk-Won Choi ◽  
Dong Ki Yoon
Keyword(s):  
Phase Transition ◽  
Boundary Conditions ◽  
Liquid Crystalline ◽  
Isotropic Phase ◽  
Different Boundary Conditions ◽  
Various Boundary Conditions ◽  
Thermal Phase Transition ◽  
Thermal Phase ◽  
Blue Phase ◽  
Chiral Dopants

We have investigated dramatic changes in the thermal phase transition of a liquid-crystalline (LC) blue phase (BP) consisting of bent-core nematogen and chiral dopants under various boundary conditions during cooling from the isotropic phase.

Experimental Validation and Numerical Simulation of Shape Memory Flat Wire Actuators

2014 ◽  
Author(s):  
Alexander Czechowicz ◽  
Sven Langbein
Keyword(s):  
Shape Memory Alloy ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Smart Materials ◽  
Empirical Data ◽  
Dynamic Properties ◽  
Fatigue Behavior ◽  
Different Boundary Conditions ◽  
Heating And Cooling ◽  
Actual Shape

Shape memory alloys (SMA) are thermally activated smart materials. Due to their ability to change into a previously imprinted actual shape through the means of thermal activation, they are suitable as actuators for mechatronical systems. Despite of the advantages shape memory alloy actuators provide, these elements are only seldom integrated by engineers into mechatronical systems. Reasons are the complex characteristics, especially at different boundary conditions and the missing simulation- and design tools. Also the lack of knowledge and empirical data are a reason why development projects with shape memory actuators often lead to failures. This paper deals with the dynamic properties of SMA-actuators (Shape Memory Alloy) — characterized by their rate of heating and cooling procedures — that today can only be described insufficiently for different boundary conditions. Based on an analysis of energy fluxes into and out of the actuator, a numerical model of flat-wire used in a bow-like structure, implemented in MATLAB/SIMULINK, is presented. Different actuation parameters, depending on the actuator-geometry and temperature are considered in the simulation in real time. Additionally this publication sums up the needed empirical data (e.g. fatigue behavior) in order to validate the numerical two dimensional model and presents empirical data on SMA flat wire material.

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