Biennial Oscillation
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2022 ◽  
Author(s):  
Shlomi Ziskin Ziv ◽  
Chaim I. Garfinkel ◽  
Sean Davis ◽  
Antara Banerjee

Abstract. The relative importance of two processes that help control the concentrations of stratospheric water vapor, the Quasi-Biennial Oscillation (QBO) and El Nino-Southern Oscillation (ENSO), are evaluated in observations and in comprehensive coupled ocean-atmosphere-chemistry models. The possibility of nonlinear interactions between these two is evaluated both using Multiple Linear Regression (MLR) and three additional advanced machine learning techniques. The QBO is found to be more important than ENSO, however nonlinear interactions are non-negligible, and even when ENSO, the QBO, and potential nonlinearities are included the fraction of entry water vapor variability explained is still substantially less than what is accounted for by cold point temperatures. While the advanced machine learning techniques perform better than an MLR in which nonlinearities are suppressed, adding nonlinear predictors to the MLR mostly closes the gap in performance with the advanced machine learning techniques. Comprehensive models suffer from too weak a connection between entry water and the QBO, however a notable improvement is found relative to previous generations of comprehensive models. Models with a stronger QBO in the lower stratosphere systematically simulate a more realistic connection with entry water.


MAUSAM ◽  
2022 ◽  
Vol 45 (1) ◽  
pp. 57-62
Author(s):  
L.J . OGALLO ◽  
R. E. OKOOLA ◽  
D. N. WANJOHI

investigated using monthly zo.ta l wind com ponents from Nairob i (Kenya ) within the period1966-1987. RelatiHn.;;hips between the stra tospher ic eas terl y and westerly wino phases and t he seasona l ra infallanomalics were also iO\t,"..')t igatN.Res ults Irom spec tra l a nalysis indicated tho d ominance (If a 28 mon th s' period in the IllOal w ind comnoncn.The \'Crtical ra te of propagar ioa of both westerly and easterly wind phases was about - · 1.2 kmmonth.Results from statist ical analysis indicated signitica nr (at 5 '~~ level) association between rainfall anomalyclass (above normal. normal. a mi below normal) and east erly and westerl y wind phas...es.


2021 ◽  
pp. 1-54
Author(s):  
Wen Chen ◽  
Kaiming Hu ◽  
Shangfeng Chen

Abstract The tropospheric biennial oscillation (TBO) of East Asian summer monsoon (EASM) has major impacts on East Asian climate. Here it is shown that, since the late-1970s, the TBO signal of EASM has strengthened significantly. The EASM TBO in wind anomalies undergoes a transition from a cyclone over the western North Pacific (WNPC) in preceding summer to an anticyclone over the western North Pacific (WNPAC) in following summer, with the anomalies strengthening remarkably after the late-1970s. Correspondingly, the biennial component of precipitation anomalies in eastern China show different distributions. Both observational and numerical simulation analyses demonstrate that these changes are caused by the westward shift of El Niño warming and enhanced Indo-Pacific and Atlantic-Pacific coupling. The positive sea surface temperature (SST) anomalies associated with the TBO of EASM shift toward the central Pacific after the late-1970s, which favor the strengthening of the WNPC and cause a weakened EASM. In following summer, both the north Indian Ocean and tropical north Atlantic SST warming are closely coupled with El Niño since the late-1970s, which favor the strengthening of WNPAC and cause an intensified EASM. Together, these changes provide more favorable background state for the transition of circulation anomalies over the western North Pacific, giving rise to enhanced biennial variability in EASM in the late-1970s.


Author(s):  
К.А. Диденко ◽  
Т.С. Ермакова ◽  
А.И. Погорельцев ◽  
Е.В. Ракушина

В данной работе показано, как изменялось взаимодействие между тропосферой и стратосферой в последние десятилетия. Также оценено влияние таких явлений, как квазидвухлетнее колебание (КДК) на данное взаимодействие. Для этого было проанализировано распространение планетарных волн в атмосфере с использованием трехмерных потоков волновой активности, показана временная изменчивость потоков и линейный тренд. Кроме того, была оценена реакция тропосферы над Сибирью и Восточной Азией на КДК. The study of the variability of stratosphere-troposphere coupling during the last decades is considered. The influence of such phenomena as quasi-biennial oscillation (QBO) on this interaction was also estimated. For this, the propagation of planetary waves in the atmosphere was analyzed using three-dimensional wave activity fluxes. The temporal variability of fluxes and a linear trend was shown. In addition, the response of the troposphere over Siberia and East Asia to the QBO was assessed.


2021 ◽  
Author(s):  
Christoph G. Hoffmann ◽  
Lena Buth ◽  
Christian von Savigny

<p>Die Madden-Julian-Oszillation (MJO) ist die dominierende Komponente intrasaisonaler Variabilität in der tropischen Troposphäre. Sie tritt durch ein periodisch auftretendes Zentrum anormal starker Konvektion in Erscheinung, das vom indischen Ozean ostwärts über den maritimen Kontinent hinweg zum Pazifik zieht und sich dort auflöst. Durch die vielfältigen Einflüsse auf das Wettergeschehen in der Region und durch die (Quasi-)Periodizität von 30 bis 90 Tagen ist das Auftreten der MJO von direktem Interesse für die Entwicklung einer möglichen subsaisonalen Wettervorhersage und deswegen seit längerem Gegenstand intensiver Forschung. Dabei verspricht man sich eine Verbesserung von Vorhersagen sowohl für die direkt betroffenen tropischen Regionen, als auch für andere Teile der Erde, da die MJO Bestandteil einiger Televerbindungen ist.</p> <p>In der Forschung zur Variabilität der mittleren Atmosphäre hat die MJO bisher dagegen nur eine kleinere Rolle gespielt. Es gibt allerdings Gründe, die Wechselwirkungen von MJO und mittlerer Atmosphäre genauer zu untersuchen: Zum einen wird ein Teil der oben genannten Televerbindungen vermutlich über die Stratosphäre vermittelt, so dass der stratosphärische Einfluss wieder auf die Troposphäre zurückwirkt. Zum anderen ist man zum besseren Verständnis der mittleren Atmosphäre selbst daran interessiert, Quellen für die dort beobachtete Variabilität zu identifizieren. Auf der Zeitskala von einigen Wochen stand hier bisher der solare 27-Tage-Zyklus im Vordergrund. Die MJO hat jedoch das Potential auf einer ähnlichen Zeitskala zu Variabilität zu führen. Für beide genannten Gründe, sich mit dem Einfluss der MJO auf die mittlere Atmosphäre zu befassen, gibt es in der Literatur schon deutliche Hinweise, die allerdings häufig auf Modell- oder reanalysierten Daten beruhen.</p> <p>Dies haben wir zum Anlass genommen, reine Beobachtungen von verschiedenen Parametern der mittleren Atmosphäre auf Einflüsse der MJO hin zu prüfen. Konkret stützen wir uns auf Beobachtungen des Satelliteninstruments MLS an Bord des NASA-Satelliten Aura. Mit einem einfachen statistischen Ansatz, der Komposit-Analyse, konnten wir Einflüsse der MJO auf verschiedene Parameter wie Temperatur, Ozon und Wasserdampf identifizieren. Diese Einflüsse erstrecken sich von der Tropopause teils bis in die Mesosphäre und zeigen teils von Wellen-Interaktionen in der mittleren Atmosphäre bekannte räumliche Strukturen. Der Einfluss der MJO wird dabei von weiteren Randbedingungen wie den Jahreszeiten oder dem Status der „Quasi-Biennial Oscillation (QBO)“ beeinflusst. In der Präsentation werden wir diese Ergebnisse vorstellen und uns dafür hauptsächlich auf die Temperatur als einen der zentralen Parameter stützen.</p>


MAUSAM ◽  
2021 ◽  
Vol 51 (2) ◽  
pp. 155-162
Author(s):  
FAWZIA I. MOURSY

Trends and periodicities in the annual rainfall of north Africa are studied using data for 45 stations having record lengths of over 60 year. Increasing or decreasing rainfall tendencies are found over large continuous areas in north Africa. These trends, however, are not significant over all the stations in the areas but only at a few places distributed at random. Wherever a trend is significant, It has persistence or a periodicity of more than 40 year. Quasi- Biennial Oscillation (QBO) is exhibited at several stations in the areas of increasing or decreasing trend. Similarly, the 11-year cycle (solar cycle) is also exhibited in both areas. The QBO and the solar cycle are both present at only six stations.


MAUSAM ◽  
2021 ◽  
Vol 50 (2) ◽  
pp. 187-196
Author(s):  
R. P. KANE

The 12-month running means of the 50 hPa low latitude zonal wind and total ozone values for the latitude zones NP (North Polar), NT (North Temperate), TRO (Tropical), ST (South Temperate), SP (South Polar) were subjected to special analysis, separately over the two successive 18 year intervals, 1958-1975 and 1976-1993. In the interval 1958-1975, the wind had a prominent peak at 2.45 years and two smaller but significant peaks at 1.98 and 3.05 years. For ozone only NP. NT and ST had roughly similar peaks (2.37, 2.41, 2.48 years), while TRO and SP had different peaks (2.27 and 2.12 years). All ozone series had significant peaks at 20-21 months, barely significant in the wind series. Ozone peaks were noticed in the 3-5 years band also. In the interval 1976-1993, the patterns were different. The wind had only one prominent peak at 2.51 years. For ozone, NP, NT, ST had roughly similar peaks (2.41, 2.45, 2.45 years) while TRO. Speed different peaks (2.32 and 2.29 years). All ozone series had significant peaks at 20-22 months and in the 3-5 year band; but these were absent in the wind series. The 3-5 year band probably indicates ENSO effects. A cross-correlation analysis between wind and ozone showed that TRO maxima coincided with westerly wind maxima. while NT, ST and NT, NP were phase shifted by 4 and 6 seasons.


2021 ◽  
Vol 13 (23) ◽  
pp. 4923
Author(s):  
Michal Kozubek ◽  
Jan Laštovička ◽  
Radek Zajicek

This study analyses long-term trends in temperature and wind climatology based on ERA5 data. We study climatology and trends separately for every decade from 1980 to 2020 and their changes during this period. This study is focused on the pressure levels between 100–1 hPa, which essentially covers the whole stratosphere. We also analyze the impact of the sudden stratospheric warmings (SSW), North Atlantic Oscillation (NAO), El Nino Southern Oscillation (ENSO) and Quasi-biennial oscillation (QBO). This helps us to find details of climatology and trend behavior in the stratosphere in connection to these phenomena. ERA5 is one of the newest reanalysis, which is widely used for the middle atmosphere. We identify the largest differences which occur between 1990–2000 and 2000–2010 in both temperature climatology and trends. We suggest that these differences could relate to the different occurrence frequency of SSWs in 1990–2000 versus 2000–2010.


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