scholarly journals Occurrence of Winter Stratospheric Sudden Warming Events and the Seasonal Timing of Spring Stratospheric Final Warming

2014 ◽  
Vol 71 (7) ◽  
pp. 2319-2334 ◽  
Author(s):  
Jinggao Hu ◽  
Rongcai Ren ◽  
Haiming Xu
Keyword(s):  
Significant Relationship ◽  
Planetary Wave ◽  
Early Spring ◽  
Wave Activity ◽  
Late Spring ◽  
Lower Probability ◽  
Reanalysis Dataset ◽  
Stratospheric Sudden Warming ◽  
Seasonal Timing ◽  
Stratospheric Final Warming

Abstract Based on the NCEP–NCAR reanalysis dataset covering 1958–2012, this paper demonstrates a statistically significant relationship between the occurrence of major stratospheric sudden warming events (SSWs) in midwinter and the seasonal timing of stratospheric final warming events (SFWs) in spring. Specifically, early spring SFWs that on average occur in early March tend to be preceded by non-SSW winters, while late spring SFWs that on average take place up until early May are mostly preceded by SSW events in midwinter. Though the occurrence (absence) of SSW events in midwinter may not always be followed by late (early) SFWs in spring, there is a much higher (lower) probability of late SFWs than early SFWs in spring after SSW (non-SSW) winters, particularly when the winter SSWs occur no earlier than early January or in the period from late January to early February. Diagnosis shows that, corresponding to an SSW (non-SSW) winter and the following late (early)-SFW spring, intensity of planetary wave activity in the stratosphere tends to evolve out of phase from midwinter to the following spring, being anomalously stronger (weaker) in winter and anomalously weaker (stronger) in spring. Furthermore, the strengthening of the western Eurasian high, which appears during early to mid-January in late-SFW years but does not appear until late February to mid-March in early-SFW years, always precedes the strengthening of planetary wave activity in the stratosphere and thus acts as a tropospheric precursor to the seasonal timing of SFWs.

scholarly journals Modulating Effects of Planetary Wave 3 on a Stratospheric Sudden Warming Event in 2005

2017 ◽  
Vol 74 (5) ◽  
pp. 1549-1559 ◽  
Author(s):  
Chunhua Shi ◽  
Ting Xu ◽  
Dong Guo ◽  
Zaitao Pan
Keyword(s):  
Planetary Wave ◽  
Wave Activity ◽  
Stratospheric Sudden Warming ◽  
Blocking High ◽  
Total Wave ◽  
Three Stages ◽  
Two Stages ◽  
Wave Activity Flux

Abstract The Eliassen–Palm flux (EPF) and Plumb’s wave activity flux (WAF) were computed, using ERA-Interim data, to analyze the influence of planetary wave 3 on a stratospheric sudden warming event from 17 February to 15 March 2005 (SSW05). It was found that 1) SSW05 consisted of three stages: a prior minor warming (MnW05), a late final warming (FW05), and a warming stagnation between MnW05 and FW05; 2) the wave 3 first decreased total upward EPFs by more than 30% at 100 hPa, resulting in the warming stagnation, and then increased upward EPFs by greater than 50%, leading to FW05; and 3) the anomalies of wave-3 activity fluxes were associated with the pattern of Atlantic blocking high in the latter two stages. The interactions between the wave 3 and wave 1 partitioned the zonal upward channel of total wave activity fluxes from one longitudinal region into two longitudinal regions and affected SSW05.

scholarly journals Tropospheric and Stratospheric Precursors to the January 2013 Sudden Stratospheric Warming

2016 ◽  
Vol 144 (4) ◽  
pp. 1321-1339 ◽  
Author(s):  
Hannah E. Attard ◽  
Rosimar Rios-Berrios ◽  
Corey T. Guastini ◽  
Andrea L. Lang
Keyword(s):  
Zonal Wind ◽  
Planetary Wave ◽  
Wave Activity ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Climate Forecast System ◽  
Reanalysis Dataset ◽  
Climate Forecast System Reanalysis ◽  
Eddy Heat Flux ◽  
Wave Resonance

Abstract This paper investigates the tropospheric and stratospheric precursors to a major sudden stratospheric warming (SSW) that began on 6 January 2013. Using the Climate Forecast System Reanalysis dataset, the analysis identified two distinct decelerations of the 10-hPa zonal mean zonal wind at 65°N in December in addition to the major SSW, which occurred on 6 January 2013 when the 10-hPa zonal mean zonal wind at 65°N reversed from westerly to easterly. The analysis shows that the two precursor events preconditioned the stratosphere for the SSW. Analysis of the tropospheric state in the days leading to the precursor events and the major SSW suggests that high-latitude tropospheric blocks occurred in the days prior to the two December deceleration events, but not in the days prior to the SSW. A detailed wave activity flux (WAF) analysis suggests that the tropospheric blocking prior to the two December deceleration events contributed to an anomalously positive 40-day-average 100-hPa zonal mean meridional eddy heat flux prior to the SSW. Analysis of the stratospheric structure in the days prior to the SSW reveals that the SSW was associated with enhanced WAF in the upper stratosphere, planetary wave breaking, and an upper-stratospheric/lower-mesospheric disturbance. These results suggest that preconditioning of the stratosphere occurred as a result of WAF initiated by tropospheric blocking associated with the two December deceleration events. The two December deceleration events occurred in the 40 days prior to the SSW and led to the amplification of wave activity in the upper stratosphere and wave resonance that caused the January 2013 SSW.

scholarly journals Stratospheric Final Warmings fall into two categories with different evolution over the course of the year

2022 ◽  
Vol 3 (1) ◽  
Author(s):  
Alain Hauchecorne ◽  
Chantal Claud ◽  
Philippe Keckhut ◽  
Alexis Mariaccia
Keyword(s):  
Zonal Wind ◽  
Planetary Wave ◽  
Polar Region ◽  
Polar Vortex ◽  
Reanalysis Data ◽  
Early Spring ◽  
Radiative Heating ◽  
Late Winter ◽  
Stratospheric Final Warming ◽  
Significant Difference

AbstractIn early spring the stratospheric zonal circulation reverses from westerly to easterly. The transition, called Stratospheric Final Warming (SFW), may be smooth and late, mainly controlled by the solar radiative heating of the polar region, or early and abrupt with rapid increase of polar temperature and deceleration of the zonal wind, forced by the planetary wave activity. Here we present a study, based on 71 years meteorological reanalysis data. Two composites of radiative and dynamical SFWs have been built. There is a very significant difference in the evolution during the year of polar temperature and 60°N zonal wind between the two composites. The state of the polar vortex on given month is anticorrelated with its state 2 to 3 months earlier. Early winter is anticorrelated with mid-winter and mid-winter with late winter/early spring. The summer stratosphere keeps a memory of its state in April–May after the SFW until late June.

scholarly journals Climatology and trends in the forcing of the stratospheric zonal-mean flow

2011 ◽  
Vol 11 (24) ◽  
pp. 12751-12771 ◽  
Author(s):  
E. Monier ◽  
B. C. Weare
Keyword(s):  
Planetary Wave ◽  
Polar Vortex ◽  
Early Spring ◽  
Wave Activity ◽  
Mean Flow ◽  
Flux Divergence ◽  
Temporal Shift ◽  
Long Term Changes ◽  
Environmental Prediction

Abstract. The momentum budget of the Transformed Eulerian-Mean (TEM) equation is calculated using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) and the National Centers for Environmental Prediction (NCEP) Reanalysis 2 (R-2). This study outlines the considerable contribution of unresolved waves, deduced to be gravity waves, to the forcing of the zonal-mean flow. A trend analysis, from 1980 to 2001, shows that the onset and break down of the Northern Hemisphere (NH) stratospheric polar night jet has a tendency to occur later in the season in the more recent years. This temporal shift follows long-term changes in planetary wave activity that are mainly due to synoptic waves, with a lag of one month. In the Southern Hemisphere (SH), the polar vortex shows a tendency to persist further into the SH summertime. This also follows a statistically significant decrease in the intensity of the stationary EP flux divergence over the 1980–2001 period. Ozone depletion is well known for strengthening the polar vortex through the thermal wind balance. However, the results of this work show that the SH polar vortex does not experience any significant long-term changes until the month of December, even though the intensification of the ozone hole occurs mainly between September and November. This study suggests that the decrease in planetary wave activity in November provides an important feedback to the zonal wind as it delays the breakdown of the polar vortex. In addition, the absence of strong eddy feedback before November explains the lack of significant trends in the polar vortex in the SH early spring. A long-term weakening in the Brewer-Dobson (B-D) circulation in the polar region is identified in the NH winter and early spring and during the SH late spring and is likely driven by the decrease in planetary wave activity previously mentioned. During the rest of the year, there are large discrepancies in the representation of the B-D circulation and the unresolved waves between the two reanalyses, making trend analyses unreliable.

scholarly journals Do applications of systemic herbicides when green fruit are present prevent seed production or viability of Alliaria petiolata (garlic mustard)?

2021 ◽  
pp. 1-17
Author(s):  
Leo Roth ◽  
José Luiz C. S. Dias ◽  
Christopher Evans ◽  
Kevin Rohling ◽  
Mark Renz
Keyword(s):  
Seed Production ◽  
Seed Viability ◽  
Early Spring ◽  
Alliaria Petiolata ◽  
Late Spring ◽  
Garlic Mustard ◽  
Viable Seed ◽  
Application Timing ◽  
Control Seed ◽  
Second Year

Garlic mustard [Alliaria petiolata (M. Bieb.) Cavara & Grande] is a biennial invasive plant commonly found in the northeastern and midwestern United States. Although it is not recommended to apply herbicides after flowering, land managers frequently desire to conduct management during this timing. We applied glyphosate and triclopyr (3% v/v and 1% v/v using 31.8% and 39.8% acid equivalent formulations, respectively) postemergence to established, second-year A. petiolata populations at three locations when petals were dehiscing, and evaluated control, seed production and seed viability. Postemergence glyphosate applications at this timing provided 100% control of A. petiolata by 4 weeks after treatment at all locations whereas triclopyr efficacy was variable, providing 38-62% control. Seed production was only reduced at one location, with similar results regardless of treatment. Percent seed viability was also reduced, and when combined with reductions in seed production, we found a 71-99% reduction in number of viable seed produced plant-1 regardless of treatment. While applications did not eliminate viable seed production, our findings indicate that glyphosate and triclopyr applied while petals were dehiscing is a viable alternative to cutting or hand-pulling at this timing as it substantially decreased viable A. petiolata seed production. Management Implications Postemergence glyphosate and triclopyr applications in the early spring to rosettes are standard treatments used to manage A. petiolata. However, weather and other priorities limit the window for management, forcing field practitioners to utilize more labor-intensive methods such as hand-pulling. It is not known how late in the development of A. petiolata these herbicides can be applied to prevent viable seed production. Since prevention of soil seedbank replenishment is a key management factor for effective long-term control of biennial invasive species, we hypothesized late spring foliar herbicide applications to second year A. petiolata plants when flower petals were dehiscing could be an effective management tool if seed production or viability is eliminated. Our study indicated that glyphosate applications at this timing provided 100% control of A. petiolata plants by 4 weeks after treatment at all locations, whereas triclopyr efficacy was inconsistent. Although both glyphosate and triclopyr decreased viable seed production to nearly zero at one of our three study locations, the same treatments produced significant amounts of viable seed at the other two locations. Our findings suggest late spring glyphosate and triclopyr applications should not be recommended over early spring applications to rosettes for A. petiolata management, as our late spring application timing did not prevent viable seed production, and may require multiple years of implementation to eradicate populations. Nonetheless, this application timing holds value in areas devoid of desirable understory vegetation compared to no management practices or mechanical management options including hand-pulling when fruit are present, as overall viable seed production was reduced to similar levels as these treatments.

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