The roles of the Quasi-Biennial Oscillation and El Nino for entry stratospheric water vapour in observations and coupled chemistry-ocean CCMI and CMIP6 models

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.

Assessing the consequences of including aerosol absorption in potential Stratospheric Aerosol Injection Climate Intervention Strategies

Theoretical Stratospheric Aerosol Intervention (SAI) strategies model the deliberate injection of aerosols or their precursors into the stratosphere thereby reflecting incident sunlight back to space and counterbalancing a fraction of the warming due to increased concentrations of greenhouse gases. This cooling mechanism is known to be relatively robust through analogues from explosive volcanic eruptions which have been documented to cool the climate of the Earth. However, a practical difficulty of SAI strategies is how to deliver the injection high enough to ensure dispersal of the aerosol within the stratosphere on a global scale. Recently, it has been suggested that including a small amount of absorbing material in a dedicated 10-day intensive deployment might enable aerosols or precursor gases to be injected at significantly lower, more technologically-feasible altitudes. The material then absorbs sunlight causing a localised heating and ‘lofting’ of the particles, enabling them to penetrate into the stratosphere. Such self-lofting has recently been observed following the intensive wildfires in 2019–2020 in south east Australia, where the resulting absorbing aerosol penetrated into the stratosphere and was monitored by satellite instrumentation for many months subsequent to emission. This study uses the fully coupled UKESM1 climate model simulations performed for the Geoengineering Model Intercomparison Project (GeoMIP) and new simulations where the aerosol optical properties have been adjusted to include a moderate degree of absorption. The results indicate that partially absorbing aerosols i) reduce the cooling efficiency per unit mass of aerosol injected, ii) increase deficits in global precipitation iii) delay the recovery of the stratospheric ozone hole, iv) disrupt the Quasi Biennial Oscillation when global mean temperatures are reduced by as little as 0.1 K, v) enhance the positive phase of the wintertime North Atlantic Oscillation which is associated with floods in Northern Europe and droughts in Southern Europe. While these results are dependent upon the exact details of the injection strategies and our simulations use ten times the ratio of black carbon to sulfate that is considered in the recent intensive deployment studies, they demonstrate some of the potential pitfalls of injecting an absorbing aerosol into the stratosphere to combat the global warming problem.

Characteristics of quasi-biennial oscillation over Kenya and their predictability potential for the seasonal rainfall

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.

Prediction of terrestrial and extraterrestrial parameters by modelling and extrapolating their natural regularities

Extrapolation of dominant modes of fluctuations after fitting suitable mathematical function to the observed long period time series is one of the approaches to long-term weather or short-term climate prediction. Experiences suggest that reliable predictions can be made from such approaches provided the time series being modeled possesses adequate regularity. Choice of the suitable function is also an important task of the time series modelling-extrapolation-prediction, or TS-MEP, process. Perhaps equally important component of this method is the development of effective filtering module. The filtering mechanism should be such that it effectively suppresses the high frequency, or unpredictable, variations and carves out the low frequency mode, or predictable, variation of the given series. By incorporating a possible solution to these propositions a new TS-MEP method has been developed in this paper. A Variable Harmonic Analysis (VHA) has been developed to decompose the time series into sine and cosine waveforms for any desired wavelength resolution within the data length (or fundamental period). In the Classical Harmonic Analysis (CHA) the wavelength is strictly an integer multiple of the fundamental period. For smoothing the singular spectrum analysis (SSA) has been applied. The SSA provides the mechanism to decompose the series into certain number of principal components (PCs) and then recombine the first few PCs, representing the dominant modes of variation, to get the smoothed version of the actual series. Twenty-four time series of terrestrial and extraterrestrial parameters, which visibly show strong regularity, are considered in the study. They can be broadly grouped into five categories: (i) inter-annual series of number of storms/depressions over the Indian region, seasonal and annual mean northern hemisphere land-area surface air temperature and the annual mean sunspot number (chosen cases of long term/short term trends or oscillation); (ii) monthly sequence of zonal wind at 50- hPa, 30-hPa levels over Balboa (representative of quasi-biennial oscillation); (iii) monthly sequence of surface air temperature (SAT) over the India region (strongly dominated by seasonality); (iv) monthly sequence of sea surface temperature (SST) of tropical Indian and Pacific Oceans (aperiodic oscillations related to El Nino/La Nina); and (v) sequence of monthly sea level pressure (SLP) of selected places over ENSO region (seasonality and oscillation). Best predictions are obtained for the SLP followed by SAT and SST due to strong domination of seasonality and/or aperiodic oscillations. The predictions are found satisfactory for the lower stratospheric zonal wind over Balboa, which displays quasi-periodic oscillations. Because of a steep declining trend a reliable prediction of number of storms/depressions over India is possible by the method. Prediction of northern hemisphere surface air temperature anomaly is not found satisfactory.

Climatic variability of the stratosphere-troposphere coupling during the last decades

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.

Einfluss der Madden-Julian-Oszillation auf die mittlere Atmosphäre in Beobachtungen des MLS-Satelliteninstruments

<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>

Trends and periodicities of rainfall over north Africa

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.

Spectral characteristics of the quasi-biennial oscillation of total Ozone

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.