scholarly journals Heavy thunderstorms on the Polish-German lowlands in the period 1951–2008 and their circulation conditions

2012 ◽  
Vol 31 (3) ◽  
pp. 25-32
Author(s):  
Leszek Kolendowicz
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Atmospheric Pressure ◽  
Low Pressure ◽  
Pressure System ◽  
Sea Level Pressure ◽  
Air Masses ◽  
Atmospheric Fronts ◽  
Low Pressure System ◽  
The Impact

Abstract. The aim of the study was an analysis of the impact of atmospheric circulation over the territory of Europe on the frequency of occurrence of heavy thunderstorms on German Lowlands and on Polish Lowlands in the period 1951-2008. The atmospheric circulation in days with investigated phenomena was illustrated as the averaged image of the atmospheric pressure field over Europe (sea level pressure and 500 hPa geopotential heights). Heavy thunderstorm phenomena occur as a result of low pressure systems or low pressure troughs moving above investigated area and bringing cold air masses. Usually, the distribution of isobars at sea level indicates the occurrence of atmospheric fronts accompanying a low pressure system.

Low-Pressure System Component Advancements and Its Influence on Future Turbofan Engine Emissions

2009 ◽  
Author(s):  
Tomas Gro¨nstedt ◽  
Dax Au ◽  
Konstantinos Kyprianidis ◽  
Stephen Ogaji
Keyword(s):  
Power Plants ◽  
Assessment Tool ◽  
Low Pressure ◽  
System Level ◽  
Research Progress ◽  
System Component ◽  
Engine Fuel ◽  
Pressure System ◽  
Low Pressure System ◽  
The Impact

Within the European research project EnVIronmenTALly Friendly Aero Engines, VITAL, a number of low pressure system component technologies are being investigated. The emerging progress will allow the design of new power plants providing a step change in engine fuel burn and noise. As part of the VITAL project a Technoeconomic and Environmental Risk Assessment tool, the TERA2020, is being developed. Within this tool, means to assess the impact of component technology progress on the engine/aircraft system level has been implemented. Sensitivities relating parameters traditionally used to describe component performance, such as allowable shaft torque, low pressure turbine stage loading, fan blade weight and system level parameters have been established. This allows a direct assessment of the impact of component research progress on the VITAL power plant CO2 and noise emissions.

scholarly journals Interdependence of the Northern Hemisphere ice-sheets build-up during the last glaciation: the role of atmospheric circulation

2013 ◽  
Vol 9 (2) ◽  
pp. 2183-2216
Author(s):  
P. Beghin ◽  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Waves ◽  
Sea Level Pressure ◽  
Orographic Effect ◽  
Level Pressure ◽  
The Impact

Abstract. The development of large continental-scale ice sheets over Canada and Northern Europe during the last glacial cycle likely modified the track of stationary waves and influenced the location of growing ice sheets through changes in accumulation and temperature patterns. Although they are often mentioned in the literature, these feedback mechanisms are poorly constrained and have never been studied throughout an entire glacial-interglacial cycle. Using the climate model of intermediate complexity CLIMBER-2 coupled with the 3-D ice-sheet model GRISLI, we investigate the impact of stationary waves on the construction of past Northern Hemisphere ice sheets during the past glaciation. The stationary waves are not explicitly computed in the model but their effect on sea-level pressure is parameterized. Several parameterizations have been tested allowing to study separately the effect of surface temperature (thermal forcing) and topography (orographic forcing) on sea-level pressure, and therefore on atmospheric circulation and ice-sheet surface mass balance. We show that the response of ice sheets to thermal and/or orographic forcings is rather different. At the beginning of the glaciation, the orographic effect favors the growth of the Laurentide ice sheet, whereas Fennoscandia appears rather sensitive to the thermal effect. Using the ablation parameterization as a trigger to artificially modify the size of one ice sheet, the remote influence of one ice sheet on the other is also studied as a function of the stationary wave parameterizations. The sensitivity of remote ice sheets is shown to be highly sensitive to the choice of these parameterizations with a larger response when orographic effect is accounted for. Results presented in this study suggest that the various spatial distributions of ice sheets could be partly be explained by the feedbacks mechanisms occurring between ice sheets and atmospheric circulation.

Preliminary Design Assessments of Pusher Geared Counter-Rotating Open Rotors: Part II — Impact of Low Pressure System Design on Mission Fuel Burn, Certification Noise and Emissions

2015 ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Vishal Sethi
Keyword(s):  
System Design ◽  
Rotational Speed ◽  
Low Pressure ◽  
Design Parameters ◽  
Preliminary Design ◽  
Pressure System ◽  
Regulatory Constraints ◽  
Fuel Burn ◽  
Low Pressure System ◽  
The Impact

In this 2-part publication, the impact of the main low pressure system parameters of a counter rotating Geared Open Rotor (GOR) on mission fuel burn, certification noise and emissions is presented for a 160 PAX medium haul class aircraft. Due to their high propulsive efficiency, GORs have the potential to significantly reduce fuel consumption and emissions relative to conventional high bypass ratio turbofans. However, this novel engine architecture presents many design and operational challenges both at engine and aircraft level. The assessment of the impact of the main low pressure preliminary design parameters of GORs on mission fuel burn, certification noise and emissions is necessary at preliminary design stages in order to identify optimum design regions. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints. Part I of this two-part publication describes the main low pressure (LP) system design choices for a GOR as well as the preliminary design philosophy and simulation framework developed for the assessments. Part II presents the assessment studies. A fixed reference aircraft and mission were used to evaluate the different GOR engine designs. The results are presented in the form of 1-D or 2-D plots in which one or two design parameters are varied at the same time. The changes in mission fuel burn, certification noise and emissions are expressed as differences relative to a baseline design, due to the fact that preliminary design tools were used for the assessments. The main conclusions of the study are: • Increasing spacing between the propellers (from 0.65 to 1.3m) reduces noise significantly (∼6 EPNdB for each certification point) with a relatively small fuel burn penalty (∼0.3–0.5%) • Relative to unclipped designs, 20% clipped CRPs reduce flyover noise by at least 2.5 EPNdB and approach noise by at least 4.5 EPNdB. The corresponding fuel burn penalty is ∼2%. • Sideline and flyover noise can be reduced by increasing the diameter of the CRP and appropriately controlling CRP rotational speeds. Approach noise can be reduced by either reducing the diameters or the rotational speeds of the propellers. • Regardless of clipping, reducing the rotational speed of the rear propeller relative to the forward propeller reduces noise and, to a certain limit, also mission fuel burn. Further reductions in rotational speed would have an adverse effect on fuel burn. • For given rotational speeds of the propellers, the torque ratio of the gearbox is fixed within ±3%.

scholarly journals Improved Consistency of Climate Projections over Europe after Accounting for Atmospheric Circulation Variability

2017 ◽  
Vol 30 (18) ◽  
pp. 7271-7291 ◽  
Author(s):  
Claudio Saffioti ◽  
Erich M. Fischer ◽  
Reto Knutti
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Forced Response ◽  
Climate Projections ◽  
Multimodel Ensemble ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Temperature And Precipitation ◽  
The Impact ◽  
Precipitation Trends

Abstract The influence of atmospheric circulation on winter temperature and precipitation trends over Europe in the period 2006–50 is investigated in a 21-member initial condition ensemble from a fully coupled global climate model and in a multimodel framework consisting of 40 different models. Five versions of a dynamical adjustment method based on empirical orthogonal function analysis of sea level pressure are introduced, and their performance in removing the effect of atmospheric circulation on temperature and precipitation is tested. The differences in atmospheric circulation as simulated by different models in their control runs and under the historical and representative concentration pathway 8.5 (RCP8.5) forcing scenarios are investigated. Dynamical adjustment is applied to the multimodel ensemble to demonstrate that a substantial fraction of the uncertainty in projected European temperature and precipitation trends is explained by atmospheric circulation variability. A statistically significant response of sea level pressure to anthropogenic forcing is identified in the multimodel ensemble under the RCP8.5 scenario. This forced response in atmospheric circulation is associated with a dynamical contribution to the long-term multimodel mean temperature and precipitation trends. The results highlight the importance of accounting for the impact of atmospheric circulation variability on trends in regional climate projections.

Preliminary Design Assessments of Pusher Geared Counter-Rotating Open Rotors: Part I — Low Pressure System Design Choices, Engine Preliminary Design Philosophy and Modelling Methodology

2015 ◽  
Author(s):  
Pablo Bellocq ◽  
Iñaki Garmendia ◽  
Vishal Sethi
Keyword(s):  
System Design ◽  
Low Pressure ◽  
Design Parameters ◽  
Preliminary Design ◽  
Simulation Framework ◽  
Pressure System ◽  
Design Philosophy ◽  
Fuel Burn ◽  
Low Pressure System ◽  
The Impact

In this 2-part publication, the impact of the main low pressure system parameters of a pusher counter rotating Geared Open Rotor (GOR) on mission fuel burn, certification noise and emissions is presented for a 160 PAX medium haul class aircraft. Due to their high propulsive efficiency, GORs have the potential to significantly reduce fuel consumption and emissions relative to conventional high bypass ratio turbofans. However, this novel engine architecture presents many design and operational challenges both at engine and aircraft level. The assessment of the impact of the main low pressure preliminary design parameters of GORs on mission fuel burn, certification noise and emissions is necessary at preliminary design stages in order to identify optimum design regions. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints. Part I of this two-part publication describes the main low pressure (LP) system design choices for a GOR as well as the preliminary design philosophy and simulation framework developed for the assessments. Part II presents the assessment studies. The simulation framework described in this paper comprises the following models: engine and aircraft performance, engine mechanical design and weight, engine certification noise and emissions. A novel aspect of the presented simulation framework is that the design point efficiency and the design feasibility of the low pressure components are calculated for each engine design.

scholarly journals Sea level pressure response to the specification of eddy-resolving sea surface temperature in simulations of Australian east coast lows

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Christopher R S Chambers ◽  
Gary B Brassington ◽  
Jinyu Sheng ◽  
Ian Simmonds ◽  
Kevin Walsh
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Level ◽  
Time Scales ◽  
East Coast ◽  
Low Pressure ◽  
Sea Surface ◽  
Pressure System ◽  
Sea Level Pressure ◽  
Level Pressure

Four east coast lows (ECLs) were simulated with the Weather Research and Forecast model to investigate the influence of the sea surface temperature (SST) distribution on the sea level pressure (SLP). Each ECL was simulated with two different SST datasets: the Bluelink SST field and NCEP skin temperature field. The former resolved eddies in the East Australian Current while the latter did not. The simulated SLP fields in the eddy-resolving SST runs were compared with those in the non-eddy-resolving SST runs. On time-scales of about 48 hours, higher SSTs were asso-ciated with lower SLPs. The spatial scale of the SLP response was similar to that of the ocean eddies, indicative of the rapidity and robustness of the response given the rapidly evolving conditions within the storms. On shorter time-scales, the SLP response to SST change can become substantially larger. The largest reductions in SLP in the eddy-resolving SST runs were associated with regions of deep atmospheric convection that warm the tropospheric column. These areas were shown to be related to the SST distribution with the greatest SLP reductions associated with convection over strong SST gradient regions. The landfall of a damaging convective mesoscale low pressure system on 8 June 2007 was also investigated. It was found that a region of strong SST gradients on the southern flank of a large warm ocean eddy was associated with lower pressures at the time of formation of this meso-low. In addition, the only case that simulated the low pressure at the correct time (albeit at not quite the correct location) was the eddy-resolved SST run. It was hy-pothesized that the development of this meso-low that impacted the coast around Newcastle, was enhanced because of the eddy-scale SST distribution at the time.

Estimation of Design Parameters and Performance for a State-of-the-Art Turbofan

2021 ◽  
Author(s):  
Oliver Sjögren ◽  
Carlos Xisto ◽  
Tomas Grönstedt
Keyword(s):  
Performance Metrics ◽  
State Of The Art ◽  
Low Pressure ◽  
Performance Model ◽  
Cycle Performance ◽  
Civil Aviation ◽  
Design Parameters ◽  
Pressure System ◽  
Public Data ◽  
Low Pressure System

Abstract The aim of this study is to explore the possibility of matching a cycle performance model to public data on a state-of-the-art commercial aircraft engine (GEnx-1B). The study is focused on obtaining valuable information on figure of merits for the technology level of the low-pressure system and associated uncertainties. It is therefore directed more specifically towards the fan and low-pressure turbine efficiencies, the Mach number at the fan-face, the distribution of power between the core and the bypass stream as well as the fan pressure ratio. Available cycle performance data have been extracted from the engine emission databank provided by the International Civil Aviation Organization (ICAO), type certificate datasheets from the European Union Aviation Safety Agency (EASA) and the Federal Aviation Administration (FAA), as well as publicly available data from engine manufacturer. Uncertainties in the available source data are estimated and randomly sampled to generate inputs for a model matching procedure. The results show that fuel performance can be estimated with some degree of confidence. However, the study also indicates that a high degree of uncertainty is expected in the prediction of key low-pressure system performance metrics, when relying solely on publicly available data. This outcome highlights the importance of statistic-based methods as a support tool for the inverse design procedures. It also provides a better understanding on the limitations of conventional thermodynamic matching procedures, and the need to complement with methods that take into account conceptual design, cost and fuel burn.

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