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 Synoptic perspectives on pollutant transport patterns observed by satellites over East Asia: Case studies with a conceptual model

2016 ◽  
Author(s):  
Hyun Cheol Kim ◽  
Soontae Kim ◽  
Seok-Woo Son ◽  
Pius Lee ◽  
Chun-Sil Jin ◽  
...  
Keyword(s):  
High Pressure ◽  
East Asia ◽  
Southern China ◽  
Low Pressure ◽  
Pressure System ◽  
Weather Patterns ◽  
High Pressure System ◽  
Synoptic Weather ◽  
Low Pressure System ◽  
Transport Patterns

Abstract. We demonstrate that daily pollutant transport patterns in East Asia are visible from satellite images when inspected with corresponding synoptic weather analyses. Transport pathways of air pollutants in East Asia are investigated using satellite observations, surface weather charts, and chemical-transport model simulations. It is found that during cool season (fall to spring), pollutant transports in East Asia are largely determined by synoptic weather patterns associated with high pressure system over southern China, which is extended from the Siberia High, and low pressure system over Manchuria, which is initiated by Altai-Sayan cyclogenesis. Based on the relative location and strength of these weather systems, three types of synoptic weather patterns that may contribute to pollutants transport in East Asia, especially in China and Korea, are identified: i.e., (1) a strengthening of the Siberian High and its southeastward propagation; (2) a high-pressure system over southern China followed by a frontal passage associated with a northern low-pressure system; and (3) a stagnant high-pressure system over southern China. For all three patterns, the high-pressure system in southern China is essential for the development of regional air pollution, while frontal activities associated with low-pressure system provide a forcing mechanism to transport those pollutants eastward or southeastward. Observed and simulated surface PM distributions show good agreement in both aerosol optical depth and NO2 column density further implying that anthropogenic emissions also contribute to regional events of high surface PM concentrations. It is argued that the quasi-periodic migration of synoptic weather systems in East Asia works as an efficient pump of pollutants; i.e., regional air pollutions developed under high-pressure systems are transported downstream by low-pressure systems.

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 Impacts of Pacific SSTs on Atmospheric Circulations Leading to California Winter Precipitation Variability: A Diagnostic Modeling

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 455 ◽  
Author(s):  
Boksoon Myoung ◽  
Sang-Wook Yeh ◽  
Jinwon Kim ◽  
Menas Kafatos
Keyword(s):  
Regression Model ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Winter Precipitation ◽  
Precipitation Variability ◽  
Tropical Pacific ◽  
Mirror Image ◽  
Western Tropical Pacific

One of the primary meteorological causes of the winter precipitation deficits and droughts in California (CA) is anomalous developments and maintenance of upper-tropospheric ridges over the northeastern Pacific. In order to understand and find the key factors controlling the winter precipitation variability in CA, the present study examines two dominant atmospheric modes of the 500 hPa geopotential height in the Northern Hemisphere using an Empirical Orthogonal Function (EOF) and their associated large-scale circulation patterns for the last 41 winters (1974/75–2014/15). Explaining 17.5% of variability, the second mode (EOF2) shows strong anti-cyclonic circulations in the North Pacific and cyclonic circulations in the eastern USA and mid-latitude North Atlantic, similar to the atmospheric circulation observed in the 2013/14 drought of CA. EOF2 is tightly and significantly correlated with CA winter precipitation. EOF2 is associated with warm western‒cool eastern tropical Pacific, resembling a mirror image of canonical El Niño events. In particular, it is found that, since the mid-1990s, sea surface temperatures (SSTs) in the western tropical Pacific have been more tightly correlated with EOF2 and with the variability of CA precipitation. A diagnostic regression model based on the west‒east SST difference in the tropical Pacific developed for two recent decades (1994/95–2014/15) has been found to capture the slow-moving interannual variability of the CA winter precipitation (about 50%). The regression model performs well, especially for the central and northern CA precipitation, where the impacts of El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on precipitation are indecisive. Our results emphasize the significant role of the western tropical Pacific SST forcing in the recent past, and in turn on CA droughts and potentially other precipitation extremes.

scholarly journals Inter-Seasonal Precipitation Variability over Southern China Associated with Commingling Effect of Indian Ocean Dipole and El Niño

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2023 ◽  
Author(s):  
Chaizi Heng ◽  
Sun-Kwon Yoon ◽  
Jong-Suk Kim ◽  
Lihua Xiong
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Southern Oscillation ◽  
Southern China ◽  
Kendall Test ◽  
Precipitation Variability ◽  
Spatial Sensitivity ◽  
Intensity Index

This study analyzed temporal and regional responses of precipitation to the Indian Ocean Dipole (IOD) over southern China and the differences between IOD-only and El Niño–southern oscillation–IOD cases. The Mann–Kendall test and intentionally biased bootstrapping were used. The results revealed three main phases (development and peak, decay, and aftermath) of percentage changes in seasonal total rainfall and showed the most positive sensitivity to positive IOD events in southern China. Moreover, El Niño played an essential role in intensifying the positive response to positive IOD events in the first and second phases while contributing little to the third. In terms of precipitation variability (frequency, intensity, and magnitude), seasonal maximum 1-day precipitation and maximum number of consecutive dry days were more sensitive to positive IOD events than the maximum number of consecutive wet days and simple daily precipitation intensity index. This study enhances knowledge of the temporal and spatial sensitivity of precipitation features to positive IOD events over southern China.

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 A Diagnostic-Predictive Assessment of Winter Precipitation over the Laurentian Great Lakes: Effects of ENSO and Other Teleconnections

2019 ◽  
Vol 20 (1) ◽  
pp. 117-137 ◽  
Author(s):  
Wang Fu ◽  
Scott Steinschneider
Keyword(s):  
Great Lakes ◽  
El Niño ◽  
El Nino ◽  
Winter Precipitation ◽  
Precipitation Variability ◽  
Tropical Pacific ◽  
Seasonal Forecasts ◽  
Great Lakes Basin ◽  
Atmospheric Flow ◽  
Precipitation Response

Abstract This study examines the primary atmospheric controls over winter precipitation variability in the Great Lakes basin and the potential for seasonal prediction. We employ partial least squares (PLS) regression to identify the primary modes of joint variability between winter precipitation over each of the Great Lakes and concurrent anomalies in midlevel atmospheric flow. We find that the first identified pattern (PLS1) is related to El Niño–Southern Oscillation (ENSO), while the other patterns represent unique anomalies in atmospheric flow that govern precipitation gradients over the basin, with limited seasonal predictability. Nonlinearities are found in the relationship between a sea surface temperature (SST)-based index for ENSO and PLS1 with respect to the phase, strength, and type of ENSO event. An examination of the ENSO-related propagating wave train that drives variability of PLS1 precipitation reveals that seasonally lagged tropical Pacific convection, as measured by remotely sensed outgoing longwave radiation (OLR), is more strongly and linearly related to Great Lakes winter precipitation than SST-based ENSO indices. Cross-validated linear regressions based on October OLR signals explain 20%–32% of the out-of-sample precipitation variability in the Great Lakes basin. We conclude with a deeper assessment of the underlying relationship between patterns of OLR anomalies in the western equatorial Pacific and Great Lakes winter precipitation. Results show that precipitation response to El Niño is similar regardless of OLR intensity in the tropical Pacific, but for La Niña events, the precipitation response is stronger under weak tropical OLR anomalies. The potential for further improvements in ENSO-based seasonal forecasts are discussed.

An Investigation of the Links between ENSO Flavors and Rainfall Processes in Southeastern Australia

2009 ◽  
Vol 137 (11) ◽  
pp. 3786-3795 ◽  
Author(s):  
Jaclyn N. Brown ◽  
Peter C. McIntosh ◽  
Michael J. Pook ◽  
James S. Risbey
Keyword(s):  
El Niño ◽  
Marine Boundary Layer ◽  
El Nino ◽  
Low Pressure ◽  
Moist Air ◽  
Southeastern Australia ◽  
Average Rainfall ◽  
Cutoff Low ◽  
Rainfall Variations ◽  
Low Pressure Systems

Abstract The causes of rainfall variations in southeastern Australia associated with three key El Niño years (1982, 1997, and 2002) are explored. Whereas 1982 and 2002 were exceptionally dry years, 1997 had near-average rainfall. These variations in rainfall can be explained by changes in the behavior of cutoff low pressure systems. Although each year had a similar number of cutoff low events, 1997 had higher rainfall per cutoff low event when compared with the other years. In particular, rain in 1997 is attributable to five large wet events from cutoff low pressure systems. In each of these wet events, the moist air originated from the marine boundary layer off the coast of northeastern Australia. Cutoff lows in 1982 and 2002 were much drier and did not draw in moist air from the northeastern coast. In typical classifications, 1982 and 1997 are grouped together as “canonical” El Niños whereas 2002 is a Modoki El Niño. The results presented here imply that these groupings are not definitive in explaining variations in southeastern Australian rainfall.

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.

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