scholarly journals Lake-Effect Snowstorms over Southern Ontario, Canada, and Their Associated Synoptic-Scale Environment

2004 ◽  
Vol 132 (11) ◽  
pp. 2595-2609 ◽  
Author(s):  
A. Q. Liu ◽  
G. W. K. Moore
Keyword(s):  
Great Lakes ◽  
Temperature Anomaly ◽  
Low Pressure ◽  
Hudson Bay ◽  
Synoptic Scale ◽  
Pressure System ◽  
Southern Ontario ◽  
Lake Effect ◽  
Low Pressure System ◽  
Low Pressure Systems

Abstract Lake-effect snowstorms are an important source of severe winter weather over the Great Lakes region and are often triggered by the passage of synoptic-scale low pressure systems. In this paper, a climatology of lake-effect snowstorms over southern Ontario, Canada, for the period 1992–99 is developed. The distinguishing characteristics of the synoptic-scale environment associated with intense lake-effect snowstorms in the region are identified through the study of individual events and through composite analysis. In particular, it is found that a low pressure and a cold-temperature anomaly situated over Hudson Bay, north of the Great Lakes, is a favorable environment for the development of intense lake-effect snowstorms over southern Ontario. It is also found that the track of the low pressure system can have a significant impact on the development or lack thereof of lake-effect snowstorms over southern Ontario. It is found that the low pressure systems that trigger intense lake-effect snowstorms tend to have an anomalous northeastward track as compared to the eastward track of most low pressure systems that transit the region.

scholarly journals The Quasi-Biweekly Oscillation of Winter Precipitation Associated with ENSO over Southern China

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 406 ◽  
Author(s):  
Qiaoyu Tong ◽  
Suxiang Yao
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern China ◽  
Low Pressure ◽  
Winter Precipitation ◽  
Precipitation Variability ◽  
Pressure System ◽  
Vorticity Advection ◽  
Low Pressure System ◽  
Low Pressure Systems

Using ERA-interim Reanalysis data and observational data, the intraseasonal oscillation of the winter rainfall in southern China is studied. The mean square deviation of daily precipitation is used to express precipitation variability, and winter precipitation variability over southern China is determined to be highly correlated with sea surface temperature (SST) in central and eastern tropical Pacific; the dominant period of the precipitation is 10–30 days, which reflects quasi-biweekly oscillation. Examination of 1000 hPa geopotential height suggests that key low-pressure systems affecting the intraseasonal precipitation come from Lake Baikal, but with different travel paths. In El Niño years, key low-pressure systems converge with other low-pressure systems and move southeastward until reaching South China, while in La Niña years, only one low-pressure system can reach southern China. Meanwhile, the explosive development of the low-pressure system is mainly caused by the joint effects of thermal advection and vorticity advection in El Niño, and only vorticity advection accounted for the dominant status in La Niña. Multiscale analysis shows that the meridional distribution of intraseasonal circulation plays an important role on the thermal transmission and brings strong warm advection from low latitudes to high latitudes in El Niño.

scholarly journals Characteristics of high waves observed at multiple stations along the east coast of Korea

2013 ◽  
Vol 1 (4) ◽  
pp. 3373-3412
Author(s):  
S.-H. Oh ◽  
W.-M. Jeong
Keyword(s):  
Arrival Time ◽  
East Coast ◽  
Meteorological Data ◽  
Winter Season ◽  
Low Pressure ◽  
East Sea ◽  
General Mechanism ◽  
Pressure System ◽  
Low Pressure System ◽  
Low Pressure Systems

Abstract. In recent several years, extremely high waves occasionally visited the Korean coast of the East Sea and caused severe coastal disasters almost every winter season. In this paper, characteristics of such high waves are reported by analyzing wave records collected at multiple stations along the Korean east coast. Meteorological data obtained at relevant weather stations were also used in the analysis. The reason for appearance of the high waves was identified as the strong northeasters due to extra-tropical low pressure systems that had been rapidly developing in the East Sea. The general mechanism concerning the formation and spatial evolution of such strong low pressure systems was more clearly understood through the synthetic analysis of the wave and meteorological data. In particular, the influence of spatio-temporal features of the low pressure system on the resulting characteristics of the high waves was described in more detail in this study. Since the overall wave direction was northeast also, the first wave arrival time on the coastline became later for a wave station whose latitude is lower. At present, however, the arrival time of such high waves on the coast as well as their intrinsic characteristics such as wave height and period are not satisfactorily predicted by the daily weather forecast. Hence, it is necessary to enhance predictability of the high waves by investigating developmental mechanisms of the strong low pressure system in winter season more thoroughly.

A New Approach to Sizing Low Pressure Systems

2017 ◽  
Author(s):  
Nathan Keller ◽  
Monika Ivantysynova
Keyword(s):  
Hydraulic System ◽  
Low Pressure ◽  
Hydraulic Systems ◽  
Pressure System ◽  
Hydraulic Unit ◽  
Duty Cycles ◽  
Low Pressure System ◽  
Hydrostatic Transmissions ◽  
Cylinder Flow ◽  
Low Pressure Systems

Closed-circuit hydraulic systems, like hydrostatic transmissions and Displacement Controlled (DC) architecture systems, require an integrated low-pressure system. These low-pressure systems provide several important functions to the hydraulic system. They prevent cavitation, provide cooling flow through the cooler, replenish the hydraulic system with cool oil, assist in the oil filtration process, provide pressure to the hydraulic unit control systems and, in the case of DC systems with differential cylinders, balance the unequal cylinder flow. Traditionally, the sizing of low-pressure systems is accomplished using a static sizing approach. In this approach, a constant efficiency of the hydraulic units is assumed, and the system is operating at a maximum power condition. The result is often an oversized charge pump and accumulator, if one is present. A dynamic sizing method has been developed using MATLAB/Simulink® with high fidelity empirical loss models for hydraulic displacement machines. Using realistic duty cycles for hydraulic systems and measured data, the low-pressure system can be accurately sized. Dynamically sizing low-pressure systems reduce parasitic losses on the prime mover because of smaller pump sizes, thus freeing power to be used elsewhere. Another concept presented in this work is the possibility of isolating the hydraulic unit control pressure supply and the low-pressure system. Realistic examples have been simulated to demonstrate the power savings of dynamically sizing low-pressure systems.

scholarly journals Northwest Flow Snow Aspects of Hurricane Sandy

2016 ◽  
Vol 31 (1) ◽  
pp. 173-195 ◽  
Author(s):  
Steve Keighton ◽  
Douglas K. Miller ◽  
David Hotz ◽  
Patrick D. Moore ◽  
L. Baker Perry ◽  
...  
Keyword(s):  
Low Pressure ◽  
Hurricane Sandy ◽  
Synoptic Scale ◽  
Pressure System ◽  
Cold Air ◽  
Low Level ◽  
Low Pressure System ◽  
Snowfall Event ◽  
Upper Level ◽  
Forcing Mechanisms

Abstract In late October 2012, Hurricane Sandy tracked along the eastern U.S. coastline and made landfall over New Jersey after turning sharply northwest and becoming posttropical while interacting with a complex upper-level low pressure system that had brought cold air into the Appalachian region. The cold air, intensified by the extreme low pressure tracking just north of the region, combined with deep moisture and topographically enhanced ascent to produce an unusual and high-impact early season northwest flow snow (NWFS) that has no analog in recent history. This paper investigates the importance of the synoptic-scale pattern, forcing mechanisms, moisture characteristics (content, depth, and likely sources), and low-level winds, as well as the evolution of some of these features compared to more typical NWFS events in the southern Appalachian Mountains. Several other aspects of the Sandy snowfall event are investigated, including low-level stability and mountain wave formation as manifested in vertical profiles and radar observations. The importance to operational forecasters of recognizing and understanding these factors and differences from more common NWFS events is also discussed.

scholarly journals Characteristics of high waves observed at multiple stations along the east coast of Korea

2013 ◽  
Vol 13 (12) ◽  
pp. 3503-3514 ◽  
Author(s):  
S.-H. Oh ◽  
W.-M. Jeong
Keyword(s):  
Arrival Time ◽  
East Coast ◽  
Meteorological Data ◽  
Winter Season ◽  
Low Pressure ◽  
East Sea ◽  
General Mechanism ◽  
Pressure System ◽  
Low Pressure System ◽  
Low Pressure Systems

Abstract. In recent several years, extremely high waves occasionally struck the Korean coast of the East Sea and caused severe coastal disasters almost every winter season. In this paper, characteristics of such high waves are reported by analyzing wave records collected at multiple stations along the east coast of Korea. Meteorological data obtained at relevant weather stations were also used in the analysis. The reason for appearance of the high waves was identified as the strong northeasters due to extra-tropical low pressure systems that had been rapidly developing in the East Sea. The general mechanism concerning the formation and spatial evolution of such strong low pressure systems was more clearly understood through the synthetic analysis of the wave and meteorological data. In particular, the influence of spatiotemporal features of the low pressure system on the resulting characteristics of the high waves was described in more detail in this study. Since the overall wave direction was also northeast, the first wave arrival time on the coastline became later for a wave station whose latitude is lower. At present, however, the arrival time of such high waves on the coast as well as their intrinsic characteristics such as wave height and period are not satisfactorily predicted by the daily weather forecast. Hence, it is necessary to enhance predictability of the high waves by investigating developmental mechanisms of the strong low pressure system in the winter season more thoroughly.

scholarly journals The Weather Conditions for Desired Smoke Plumes at a FASMEE Burn Site

Atmosphere ◽  
2018 ◽  
Vol 9 (7) ◽  
pp. 259 ◽  
Author(s):  
Yongqiang Liu ◽  
Scott Goodrick ◽  
Gary Achtemeier
Keyword(s):  
Cold Front ◽  
Weather Conditions ◽  
Low Pressure ◽  
Pressure System ◽  
Prescribed Burns ◽  
Essential Information ◽  
Smoke Plume ◽  
Smoke Plumes ◽  
Low Pressure System ◽  
Low Pressure Systems

Weather is an important factor that determines smoke development, which is essential information for planning smoke field measurements. This study identifies the synoptic systems that would favor to produce the desired smoke plumes for the Fire and Smoke Model Evaluation Experiment (FASMEE). Daysmoke and PB-Piedmont (PB-P) models are used to simulate smoke plume evolution during the day time and smoke drainage and fog formation during the nighttime for hypothetical prescribed burns on 5–8 February 2011 at the Stewart Army Base in the southeastern United States. Daysmoke simulation is evaluated using the measured smoke plume heights of two historical prescribed burns at the Eglin Air Force Base. The simulation results of the hypothetical prescribed burns show that the smoke plume is not fully developed with low plume height during the daytime on 5 February when the burn site is under the warm, moist, and windy conditions connected to a shallow cyclonic system and a cold front. However, smoke drainage and fog are formed during the nighttime. Well-developed smoke plumes, which rise mainly vertically, extend to a majority portion of the planetary boundary layer, and have steady clear boundaries, appear on both 6 and 7 February when the air is cool but dry and calm during a transition between two low-pressure systems. The plume rises higher on the second day, mainly due to lighter winds. The smoke on 8 February shows a loose structure of large horizontal dispersion and low height after passage of a deep low-pressure system with strong cool and dry winds. Smoke drainage and fog formation are rare for the nights during 5–8 February. It is concluded that prescribed burns conducted during a period between two low-pressure systems would likely generate the desired plumes for FASMEE measurement during daytime. Meanwhile, as the fire smolders into the night, the burns would likely lead to fog formation when the burn site is located in the warm and moist section of a low-pressure system or a cold front.

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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