FGOALS-s2 simulation of upper-level jet streams over East Asia: Mean state bias and synoptic-scale transient eddy activity

2013 ◽  
Vol 30 (3) ◽  
pp. 739-753 ◽  
Author(s):  
Fengfei Song ◽  
Tianjun Zhou
Keyword(s):  
East Asia ◽  
Transient Eddy ◽  
Synoptic Scale ◽  
Jet Streams ◽  
Eddy Activity ◽  
Upper Level ◽  
Upper Level Jet ◽  
Mean State

scholarly journals Seasonal Variations of the Synoptic-Scale Transient Eddy Activity and Polar Front Jet over East Asia

2010 ◽  
Vol 23 (12) ◽  
pp. 3222-3233 ◽  
Author(s):  
Xuejuan Ren ◽  
Xiuqun Yang ◽  
Cuijiao Chu
Keyword(s):  
East Asia ◽  
Seasonal Variations ◽  
East Asian ◽  
Polar Front ◽  
Transient Eddy ◽  
Synoptic Scale ◽  
Wind Fields ◽  
The North ◽  
Upper Level ◽  
Polar Front Jet

Abstract Seasonal variations of the synoptic-scale transient eddy activity (STEA) and the jet streams over East Asia are examined through analysis of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data. Extracted from the 6-hourly upper-level wind fields, the distribution of the jet core numbers exhibits a distinct geographical border for the East Asian subtropical jet (EASJ) and the East Asian polar front jet (EAPJ) at the latitudes of the northern Tibetan Plateau (TP). In the cool seasons, two branches of the STEA and low-level baroclinicity exist over the East Asian landmass, accompanied by the two-jet state of the EASJ and EAPJ. In the warm seasons, a single jet pattern of the EASJ along the north flank of the TP is accompanied by the weakened STEA over the mid- to high latitudes of East Asia. Further analysis shows two distinct features of the seasonal variations of the STEA over East Asia, compared with that over the North Pacific. First, during the transitional period of April–June, the main STEA band over East Asia migrates northward dramatically, in conjunction with the EAPJ shifting in the same direction. Second, both the upper-level STEA and the lower-level baroclinicity poleward of the TP are prosperous in spring. The relationship between the STEA, baroclinicity, vertical wind shear, and static stability in the EAPJ region in different seasons is further investigated. It is found that in addition to the time-mean wind fields, the rapid increase in the sensible heat flux poleward side of the TP region in spring and the associated boundary layer processes are partially responsible for the spring prosperity of the local baroclinicity and the STEA.

scholarly journals Synoptic-Scale and Mesoscale Environments Conducive to Forest Fires during the October 2003 Extreme Fire Event in Southern California

2009 ◽  
Vol 48 (3) ◽  
pp. 553-579 ◽  
Author(s):  
Chenjie Huang ◽  
Y-L. Lin ◽  
M. L. Kaplan ◽  
J. J. Charney
Keyword(s):  
Forest Fires ◽  
Wave Breaking ◽  
Southern California ◽  
Synoptic Scale ◽  
Fire Event ◽  
Dry Air ◽  
Upper Level ◽  
Upper Level Jet ◽  
Wave Induced ◽  
Jet Streak

Abstract This study has employed both observational data and numerical simulation results to diagnose the synoptic-scale and mesoscale environments conducive to forest fires during the October 2003 extreme fire event in southern California. A three-stage process is proposed to illustrate the coupling of the synoptic-scale forcing that is evident from the observations, specifically the high pressure ridge and the upper-level jet streak, which leads to meso-α-scale subsidence in its exit region, and the mesoscale forcing that is simulated by the numerical model, specifically the wave breaking and turbulence as well as the wave-induced critical level, which leads to severe downslope (Santa Ana) winds. Two surges of dry air were found to reach the surface in southern California as revealed in the numerical simulation. The first dry air surge arrived as a result of moisture divergence and isallobaric adjustments behind a surface cold front. The second dry air surge reached southern California as the meso-α- to meso-β-scale subsidence and the wave-induced critical level over the coastal ranges phased to transport the dry air from the upper-level jet streak exit region toward the surface and mix the dry air down to the planetary boundary layer on the lee side of the coastal ranges in southern California. The wave-breaking region on the lee side acted as an internal boundary to reflect the mountain wave energy back to the ground and created severe downslope winds through partial resonance with the upward-propagating mountain waves.

scholarly journals Multiscale Dynamics of the February 11-12, 2010, Deep South US Snowstorm Event

2017 ◽  
Vol 2017 ◽  
pp. 1-26
Author(s):  
Stephany M. Taylor ◽  
Michael L. Kaplan ◽  
Yuh-Lang Lin
Keyword(s):  
Surface Flux ◽  
Surface Fluxes ◽  
Deep South ◽  
Synoptic Scale ◽  
Orographic Effects ◽  
Southern Us ◽  
Multiscale Dynamics ◽  
Heating Effects ◽  
Upper Level ◽  
Upper Level Jet

This study investigates the synoptic/mesoscale dynamics responsible for an unusually heavy southern US snowstorm that occurred on February 11-12, 2010, using reanalysis, observations, and numerical simulations. This record breaking snowfall event represents an example of multiple upper level and low-level jets (LLJs) and their accompanying baroclinic zones. The analysis reveals the following synoptic scale processes as significant contributors: (1) upper level jet splitting and merging, (2) advection of cold arctic air at low levels by a large anticyclone, and (3) an incoming upper level shortwave trough. In addition to the synoptic scale processes, the following mesoscale features played a major role in this snowstorm event: coexisting potential (convective) instability and conditional symmetric instability, terrain blocking, and a double LLJ development process. Sensitivity experiments including (1) limiting the orographic effects of elevated plateau in Texas and the Sierra Madre Mountains in Mexico by reducing the terrain height to 225 meters, (2) the microphysics/latent heating effects, and (3) surface fluxes on the development and intensity of the snowstorm were also conducted by turning these options off in the numerical model. Of all three experiments, the surface flux experiment displays the least amount of influence on the developing frozen precipitation bands.

scholarly journals Evaluations of Upper-Level Turbulence Diagnostics Performance Using the Graphical Turbulence Guidance (GTG) System and Pilot Reports (PIREPs) over East Asia

2011 ◽  
Vol 50 (9) ◽  
pp. 1936-1951 ◽  
Author(s):  
Jung-Hoon Kim ◽  
Hye-Yeong Chun ◽  
Robert D. Sharman ◽  
Teddie L. Keller
Keyword(s):  
East Asia ◽  
Lead Time ◽  
Large Scale ◽  
Weather Prediction ◽  
Analysis Data ◽  
Atmospheric Conditions ◽  
Jet Streams ◽  
Forecast Lead Time ◽  
Upper Level ◽  
Nwp Model

AbstractThe forecast skill of upper-level turbulence diagnostics is evaluated using available turbulence observations [viz., pilot reports (PIREPs)] over East Asia. The six years (2003–08) of PIREPs used in this study include null, light, and moderate-or-greater intensity categories. The turbulence diagnostics used are a subset of indices in the Graphical Turbulence Guidance (GTG) system. To investigate the optimal performance of the component GTG diagnostics and GTG combinations over East Asia, various statistical evaluations and sensitivity tests are performed. To examine the dependency of the GTG system on the operational numerical weather prediction (NWP) model, the GTG system is applied to both the Regional Data Assimilation and Prediction System (RDAPS) analysis data and Global Forecasting System (GFS) analysis and forecast data with 30-km and 0.3125° (T382) horizontal grid spacings. The dependency of the temporal variation in the PIREP and GFS data and the forecast lead time of the GFS-based GTG combination are also investigated. It is found that the forecasting performance of the GTG system varies with year and season according to the annual and seasonal variations in the large-scale atmospheric conditions over the East Asia region. The wintertime GTG skill is the highest, because most GTG component diagnostics are related to jet streams and upper-level fronts. The GTG skill improves as the number of PIREP samples and the vertical resolution of the underlying NWP analysis data increase, and the GTG performance decreases as the forecast lead time increases from 0 to 12 h.

scholarly journals Analysis of the Interactions between the 200 hPa Jet and Air Pollutants in the Near-Surface Layer over East Asia in Summer

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 886
Author(s):  
Wen Wei ◽  
Bingliang Zhuang ◽  
Huijuan Lin ◽  
Yu Shu ◽  
Tijian Wang ◽  
...  
Keyword(s):  
Surface Layer ◽  
East Asia ◽  
Air Pollutants ◽  
North China Plain ◽  
East Asian ◽  
Near Surface ◽  
The North ◽  
The North China Plain ◽  
Upper Level ◽  
Upper Level Jet

The rapid economic development in East Asia has led to serious air pollution problems in the near-surface layer. Studies have shown that there is an interaction between air pollution and the East Asian upper-level jet, which is an important weather system controlling the climate in East Asia. Therefore, it is of great significance to study the relationship between the surface layer air pollutants and the upper-level jet stream in East Asia. Based on the daily wind and vertical velocity data provided by the National Centers for Environmental Prediction/National Center for Atmospheric Research as well as the surface pollutant and meteorological variable data provided by the Science Data Bank, we use statistical analysis methods to study the relationship between the East Asian upper-level jet and the high-concentration area of near-surface air pollutants in summer. Meanwhile, the mechanisms of the interaction are preliminarily discussed. The results show that the North China Plain and the Tarim Basin are the high-value areas of the particulate matter (PM) in summer during 2013–2018, and the ozone (O3) concentration in the near-surface atmospheric layer in the North China Plain is also high. The average concentrations of the PM2.5, PM10 and O3 in the North China Plain are 45.09, 70.28 and 131.27 μg·m−3, respectively, and the days with the concentration exceeding the standard reach 401, 461 and 488, respectively. During this period, there is an increasing trend in the O3 concentration and a decreasing trend in the PM concentration. The average ratio of the PM2.5 to PM10 is approximately 0.65 with a decreasing trend. The air pollutant concentration in this region has a significant relationship with the location of the East Asian upper-level jet. The low wind speed at the surface level under the control of the upper-level jet is the main reason for the high pollutant concentration besides the pollutant emission. They relate to each other through the surface humidity and the meridional and zonal wind. Meanwhile, the concentrations of the PM2.5 and PM10 are high in the near-surface layer in the Tarim Basin, and the average concentrations are 45.19 and 49.08 μg·m−3, respectively. The days with the concentration exceeding the standard are 265 and 193, respectively. The interannual variation in the PM concentration shows an increasing trend first and then a decreasing trend. The average ratio of PM2.5 to PM10 in this region reaches approximately 0.9. The ratio reaches the highest in 2013 and 2014 and then decreases to and maintains at approximately 0.85. The concentration of air pollutants in the basin has a significant relationship with the intensity of the upper-level jet in East Asia. The weakening of the upper-level jet will lead to a decrease in the surface humidity in the northern part of the basin, an increase in the surface temperature in the western part of the basin and a decrease in the surface zonal wind in the eastern part of the basin, which will result in a higher PM concentration.

scholarly journals Synoptic-Scale Environments of Predecessor Rain Events Occurring East of the Rocky Mountains in Association with Atlantic Basin Tropical Cyclones*

2013 ◽  
Vol 141 (3) ◽  
pp. 1022-1047 ◽  
Author(s):  
Benjamin J. Moore ◽  
Lance F. Bosart ◽  
Daniel Keyser ◽  
Michael L. Jurewicz
Keyword(s):  
Tropical Cyclones ◽  
Rocky Mountains ◽  
Composite Analysis ◽  
Synoptic Scale ◽  
Atlantic Basin ◽  
Upper Level ◽  
Rain Events ◽  
Upper Level Jet ◽  
Jet Streak ◽  
Baroclinic Zone

Abstract The synoptic-scale environments of predecessor rain events (PREs) occurring to the east of the Rocky Mountains in association with Atlantic basin tropical cyclones (TCs) are examined. PREs that occurred during 1988–2010 are subjectively classified based upon the synoptic-scale upper-level flow configuration within which the PRE develops, with a focus on the following: 1) the position of the jet streak relative to the TC, 2) the position of the jet streak relative to trough and ridge axes, and 3) the positions of trough and ridge axes relative to the PRE and to the TC. Three categories were identified from this classification procedure: “jet in ridge,” “southwesterly jet,” and “downstream confluence.” PRE-relative composite analysis for each category reveals that, consistent with previous studies, PREs typically occur near a low-level baroclinic zone, beneath the equatorward entrance region of an upper-level jet streak, and in the presence of a stream of water vapor from a TC. Despite these common characteristics, key differences exist among the three PRE categories related to the phasing of a TC with the synoptic-scale flow and to the interactions between a TC and its environment. Brief case studies of PREs associated with TC Rita (2005), TC Wilma (2005), and TC Ernesto (2006) are presented as specific examples of the three PRE categories.

scholarly journals Derecho and MCS Development, Evolution, and Multiscale Interactions during 3–5 July 2003

2010 ◽  
Vol 138 (8) ◽  
pp. 3048-3070 ◽  
Author(s):  
Nicholas D. Metz ◽  
Lance F. Bosart
Keyword(s):  
Gravity Wave ◽  
Cold Pool ◽  
Jet Stream ◽  
Surface Boundary ◽  
Initial Surface ◽  
Synoptic Scale ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Upper Level ◽  
Upper Level Jet

Abstract From 3 to 5 July 2003 during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX), multiple mesoscale convective systems (MCSs 1 and 2) and derechos (derechos AN, AS, A, BW, and BE) progressed across a preferred upper Midwest corridor. The derechos evolved in a favorable synoptic-scale environment. However, the environmental details associated with each derecho, such as the characteristics of the initial surface boundary, the formation position relative to the upper-level jet stream, the presence of an upper-level mesoscale disturbance, and the CAPE/shear environment varied from derecho to derecho. The MCSs and derechos composed three distinct convective episodes. Multiple mesoscale interactions between the MCSs and derechos and the environment altered the character and longevity of these episodes. The first convective episode consisted of derecho A, which formed from merging derechos AN and AS (northern and southern systems, respectively). The ∼200-hPa-deep cold pool associated with derecho A decreased surface potential temperatures by 4–8 K. MCS 1 dissipated upon entering this cold pool and an inertia–gravity wave was emitted that helped to spawn MCS 2. This inertia–gravity wave connected MCSs 1 and 2 into a compound convective episode. As derecho BW (western system) approached a strong surface boundary across Iowa created by the cold pools of derecho A and MCS 1, derecho BE (eastern system) formed. The remnants of derecho BW merged with derecho BE creating another compound convective episode. The upscale effects resulting from this active convective period directly affected subsequent convective development. Upper-level diabatic heating associated with derecho A resulted in NCEP GFS 66-h negative 1000–500-hPa thickness errors of 4–8 dam (forecast too cold) and negative 200-hPa wind errors of 10–20 m s−1 (forecast too weak). The resulting stronger than forecast 200-hPa jet stream likely increased synoptic-scale forcing for the formation and evolution of derecho BW.

Recurrent Rossby wave packets and persistent extreme weather

2021 ◽  
Author(s):  
S. Mubashshir Ali ◽  
Olivia Martius ◽  
Matthias Röthlisberger
Keyword(s):  
Southern Hemisphere ◽  
Spatial Patterns ◽  
Rossby Wave ◽  
Wave Packets ◽  
Reanalysis Data ◽  
Synoptic Scale ◽  
Background Flow ◽  
Dry Spell ◽  
Upper Level ◽  
Wet Spells

<p>Upper-level synoptic-scale Rossby wave packets are well-known to affect surface weather. When these Rossby wave packets occur repeatedly in the same phase at a specific location, they can result in persistent hot, cold, dry, and wet conditions. The repeated and in-phase occurrence of Rossby wave packets is termed as recurrent synoptic-scale Rossby wave packets (RRWPs). RRWPs result from multiple transient synoptic-scale wave packets amplifying in the same geographical region over several weeks.</p><p>Our climatological analyses using reanalysis data have shown that RRWPs can significantly modulate the persistence of hot, cold, dry, and wet spells in several regions in the Northern and the Southern Hemisphere.  RRWPs can both shorten or extend hot, cold, and dry spell durations. The spatial patterns of statistically significant links between RRWPs and spell durations are distinct for the type of the spell (hot, cold, dry, or wet) and the season (MJJASO or NDJFMA). In the Northern Hemisphere, the spatial patterns where RRWPs either extend or shorten the spell durations are wave-like. In the Southern Hemisphere, the spatial patterns are either wave-like (hot and cold spells) or latitudinally banded (dry and wet spells).</p><p>Furthermore, we explore the atmospheric drivers behind RRWP events. This includes both the background flow and potential wave-triggers such as the Madden Julian Oscillation or blocking. For 100 events of intense Rossby wave recurrence in the Atlantic, the background flow, the intensity of tropical convection, and the occurrence of blocking are studied using flow composites.</p>

scholarly journals Investigating the Local Atmospheric Response to a Realistic Shift in the Oyashio Sea Surface Temperature Front

2015 ◽  
Vol 28 (3) ◽  
pp. 1126-1147 ◽  
Author(s):  
Dimitry Smirnov ◽  
Matthew Newman ◽  
Michael A. Alexander ◽  
Young-Oh Kwon ◽  
Claude Frankignoul
Keyword(s):  
High Resolution ◽  
Surface Wind ◽  
Lower Troposphere ◽  
Vertical Motion ◽  
Atmospheric Response ◽  
Transient Eddy ◽  
Sst Front ◽  
Moisture Fluxes ◽  
Upper Level ◽  
Heat And Moisture

Abstract The local atmospheric response to a realistic shift of the Oyashio Extension SST front in the western North Pacific is analyzed using a high-resolution (HR; 0.25°) version of the global Community Atmosphere Model, version 5 (CAM5). A northward shift in the SST front causes an atmospheric response consisting of a weak surface wind anomaly but a strong vertical circulation extending throughout the troposphere. In the lower troposphere, most of the SST anomaly–induced diabatic heating is balanced by poleward transient eddy heat and moisture fluxes. Collectively, this response differs from the circulation suggested by linear dynamics, where extratropical SST forcing produces shallow anomalous heating balanced by strong equatorward cold air advection driven by an anomalous, stationary surface low to the east. This latter response, however, is obtained by repeating the same experiment except using a relatively low-resolution (LR; 1°) version of CAM5. Comparison to observations suggests that the HR response is closer to nature than the LR response. Strikingly, HR and LR experiments have almost identical vertical profiles of . However, diagnosis of the diabatic quasigeostrophic vertical pressure velocity (ω) budget reveals that HR has a substantially stronger response, which together with upper-level mean differential thermal advection balances stronger vertical motion. The results herein suggest that changes in transient eddy heat and moisture fluxes are critical to the overall local atmospheric response to Oyashio Front anomalies, which may consequently yield a stronger downstream response. These changes may require the high resolution to be fully reproduced, warranting further experiments of this type with other high-resolution atmosphere-only and fully coupled GCMs.

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