Person:
Ayarzagüena Porras, Blanca

First Name

Blanca

Last Name

Ayarzagüena Porras

URI

https://hdl.handle.net/20.500.14352/75062

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Física de la Tierra y Astrofísica

Area

Física de la Tierra

Identifiers

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Now showing 1 - 10 of 11

Intraseasonal effects of El Niño–Southern oscillation on North Atlantic climate
(Journal of Climate, 2018) Ayarzagüena Porras, Blanca; Ineson, Sarah; Dunstone, Nick J.; Baldwin, Mark P.; Scaife, Adam A.
It is well established that El Niño–Southern Oscillation (ENSO) impacts the North Atlantic–European (NAE) climate, with the strongest influence in winter. In late winter, the ENSO signal travels via both tropospheric and stratospheric pathways to the NAE sector and often projects onto the North Atlantic Oscillation. However, this signal does not strengthen gradually during winter, and some studies have suggested that the ENSO signal is different between early and late winter and that the teleconnections involved in the early winter subperiod are not well understood. In this study, we investigate the ENSO teleconnection to NAE in early winter (November–December) and characterize the possible mechanisms involved in that teleconnection. To do so, observations, reanalysis data and the output of different types of model simulations have been used. We show that the intraseasonal winter shift of the NAE response to ENSO is detected for both El Niño and La Niña and is significant in both observations and initialized predictions, but it is not reproduced by free-running Coupled Model Intercomparison Project phase 5 (CMIP5) models. The teleconnection is established through the troposphere in early winter and is related to ENSO effects over the Gulf of Mexico and Caribbean Sea that appear in rainfall and reach the NAE region. CMIP5 model biases in equatorial Pacific ENSO sea surface temperature patterns and strength appear to explain the lack of signal in the Gulf of Mexico and Caribbean Sea and, hence, their inability to reproduce the intraseasonal shift of the ENSO signal over Europe.
Future Arctic sea ice loss reduces severity of cold air outbreaks in midlatitudes
(Geophysical Research Letters, 2016) Ayarzagüena Porras, Blanca; Screen, James A.
The effects of Arctic sea ice loss on cold air outbreaks (CAOs) in midlatitudes remain unclear. Previous studies have defined CAOs relative to the present‐day climate, but changes in CAOs, defined in such a way, may reflect changes in mean climate and not in weather variability, and society is more sensitive to the latter. Here we revisit this topic but applying changing temperature thresholds relating to climate conditions of the time. CAOs do not change in frequency or duration in response to projected sea ice loss. However, they become less severe, mainly due to advection of warmed polar air, since the dynamics associated with the occurrence of CAOs are largely not affected. CAOs weaken even in midlatitude regions where the winter mean temperature decreases in response to Arctic sea ice loss. These results are robustly simulated by two atmospheric models prescribed with differing future sea ice states and in transient runs where external forcings are included.
The role of climate change and ozone recovery for the future timing of major stratospheric warmings
(Geophysical Research Letters, 2013) Ayarzagüena Porras, Blanca; Langematz, Ulrike; Meul, Stefanie; Oberländer, Sophie; Abalichin, Janna; Kubin, Anne
Future changes in the occurrence rates of major stratospheric warmings (MSWs) have recently been identified in chemistry‐climate model (CCM) simulations, but without reaching a consensus, potentially due to the competition of different forcings. We examine future variations in the occurrence rates of MSWs in transient and timeslice simulations of the ECHAM/MESSy atmospheric chemistry (EMAC) CCM, with a focus on the individual effect of different external factors. Although no statistically significant variation is found in the decadal‐mean frequency of MSWs, a shift of their timing toward midwinter is detected in the future. The strengthening of the polar vortex in early winter is explained by recovering ozone levels following the future decrease in ozone‐depleting substances. In midwinter, a stronger dynamical forcing associated with changes in tropical sea surface temperatures will lead to more MSWs, through a similar mechanism that explains the stratospheric response to El Niño‐Southern Oscillation (ENSO).
No robust evidence of future changes in major stratospheric sudden warmings: a multi-model assessment from CCMI
(Atmospheric Chemistry and Physics, 2018) Ayarzagüena Porras, Blanca; Polvani, Lorenzo M.; Langematz, Ulrike; Akiyoshi, Hideharu; Bekki, Slimane; Butchart, Neal; Dameris, Martin; Deushi, Makoto; Hardiman, Steven C.; Jöckel, Patrick; Klekociuk, Andrew; Marchand, Marion; Michou, Martine; Morgenstern, Olaf; O'Connor, Fiona M.; Oman, Luke D.; Plummer, David A.; Revell, Laura; Rozanov, Eugene; Saint-Martin, David; Scinocca, John; Stenke, Andrea; Stone, Kane; Yamashita, Yousuke; Yoshida, Kohei; Zeng, Guang
Major mid-winter stratospheric sudden warmings (SSWs) are the largest instance of wintertime variability in the Arctic stratosphere. Because SSWs are able to cause significant surface weather anomalies on intra-seasonal timescales, several previous studies have focused on their potential future change, as might be induced by anthropogenic forcings. However, a wide range of results have been reported, from a future increase in the frequency of SSWs to an actual decrease. Several factors might explain these contradictory results, notably the use of different metrics for the identification of SSWs and the impact of large climatological biases in single-model studies. To bring some clarity, we here revisit the question of future SSW changes, using an identical set of metrics applied consistently across 12 different models participating in the Chemistry–Climate Model Initiative. Our analysis reveals that no statistically significant change in the frequency of SSWs will occur over the 21st century, irrespective of the metric used for the identification of the event. Changes in other SSW characteristics – such as their duration, deceleration of the polar night jet, and the tropospheric forcing – are also assessed: again, we find no evidence of future changes over the 21st century.
The relevance of the location of blocking highs for stratospheric variability in a changing climate
(Journal of Climate, 2015) Ayarzagüena Porras, Blanca; Orsolini, Yvan J; Langematz, Ulrike; Abalichin, Janna; Kubin, Anne
Previous research shows that blocking highs (BHs) influence wintertime polar stratospheric variability through the modulation of the climatological planetary waves (PWs) depending on the BH location. BHs over the Euro-Atlantic sector tend to enhance the upward PW propagation, and those over the northwestern Pacific Ocean tend to reduce it. Future changes are examined in the response of the wave activity flux to the BH location and their relationship with wintertime stratospheric variability in transient simulations of ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC). After it is verified that EMAC can reproduce qualitatively well the geographical dependence of the BH influence on PW activity injection, it is shown that this dependence does not change in the future. However, an eastward shift of the pattern of the BH influence on PW propagation over the Pacific, a farther eastward extension of the pattern over the Atlantic Ocean, and an intensification of the wavenumber-1 component of the interaction between climatological and anomalous waves are detected. Changes in the upper-tropospheric jet and an intensification of the wavenumber-1 climatological wave due to a strengthening of the Aleutian low agree with these variations. The spatial distribution of future BHs preceding extreme polar vortex events is also affected by the slight modifications in the wave activity pattern. Hence, future BHs preceding strong vortex events tend to be more concentrated over the Pacific than in the past, where BHs interfere negatively with wavenumber-1 climatological waves. Future BHs prior to major stratospheric warmings are located in a broader area than in the past, predominantly over an extended Euro-Atlantic sector.
Stratospheric connection to the abrupt end of the 2016/2017 iberian drought
(Geophysical Research Letters, 2018) Ayargüena Porras, Blanca; Barriopedro Cepero, David; Garrido Pérez, José Manuel; Ábalos Álvarez, Marta; De La Cámara Illescas, Álvaro; García Herrera, Ricardo Francisco; Calvo, N.; Ordóñez García, Carlos; Ayarzagüena Porras, Blanca
Southwestern Europe experienced extraordinary rainy and windy conditions in March 2018, leading to the end of the most severe drought since 1970 at continental scale. This anomalous weather was linked to a persistent negative North Atlantic Oscillation pattern. Two weeks earlier a sudden stratospheric warming (SSW) took place, preceded by the strongest planetary wave activity on record. In this study, we explore the connection between the SSW and the weather shift by employing a weather regime approach and flow analogues. The timing of the downward propagation of the stratospheric anomalies, the transition to and persistence of the negative North Atlantic Oscillation weather regime, and the sudden precipitation increase are all consistent with the typical tropospheric state after SSWs. Our results evidence a significant role of the 2018 SSW in the record-breaking precipitation event.
Estudio de los calentamientos estratosféricos en el hemisferio norte y su huella troposférica: pasado reciente, presente y futuro = Study of stratospheric warmings in the Northern Hemisphere and their tropospheric fingerprint: recent past, present and future
(2012) Ayarzagüena Porras, Blanca; Serrano Mendoza, Encarnación; Langematz, Ulrike
The main aim of this PhD thesis is to improve the knowledge of boreal stratospheric warmings, with a special focus on the associated tropospheric‐stratospheric feedbacks. To achieve this goal, different features of these phenomena that have not been investigated yet or that do not show a consensus among previous studies are analyzed in detail. This analysis refers to the two most relevant types of warmings, major stratospheric warmings (MSWs) and stratospheric final warmings (SFWs), in different periods of time: the recent past and present (since 1960), and the future.
The role of the stratosphere in subseasonal to seasonal prediction: 2. Predictability arising from stratosphere‐troposphere coupling
(Journal of Geophysical Research: Atmospheres, 2019) Domeisen, Daniela I. V.; Butler, Amy H.; Charlton‐Perez, Andrew J.; Ayarzagüena Porras, Blanca; Baldwin, Mark P.; Dunn‐Sigouin, Etienne; Furtado, Jason C.; Garfinkel, Chaim I.; Hitchcock, Peter; Karpechko, Alexey Yu.; Kim, Hera; Knight, Jeff; Lang, Andrea L.; Lim, Eun‐Pa; Marshall, Andrew; Roff, Greg; Schwartz, Chen; Simpson, Isla R.; Son, Seok‐Woo; Taguchi, Masakazu
The stratosphere can have a significant impact on winter surface weather on subseasonal to seasonal (S2S) timescales. This study evaluates the ability of current operational S2S prediction systems to capture two important links between the stratosphere and troposphere: (1) changes in probabilistic prediction skill in the extratropical stratosphere by precursors in the tropics and the extratropical troposphere and (2) changes in surface predictability in the extratropics after stratospheric weak and strong vortex events. Probabilistic skill exists for stratospheric events when including extratropical tropospheric precursors over the North Pacific and Eurasia, though only a limited set of models captures the Eurasian precursors. Tropical teleconnections such as the Madden‐Julian Oscillation, the Quasi‐Biennial Oscillation, and El Niño–Southern Oscillation increase the probabilistic skill of the polar vortex strength, though these are only captured by a limited set of models. At the surface, predictability is increased over the United States, Russia, and the Middle East for weak vortex events, but not for Europe, and the change in predictability is smaller for strong vortex events for all prediction systems. Prediction systems with poorly resolved stratospheric processes represent this skill to a lesser degree. Altogether, the analyses indicate that correctly simulating stratospheric variability and stratosphere‐troposphere dynamical coupling are critical elements for skillful S2S wintertime predictions.
On the representation of major stratospheric warmings in reanalyses
(Atmospheric chemistry and physics, 2019) Ayarzagüena Porras, Blanca; Palmeiro Nuñez, Froila María; Barriopedro Cepero, David; Calvo Fernández, Natalia; Langematz, Ulrike; Shibata, Kiyotaka
Major sudden stratospheric warmings (SSWs) represent one of the most abrupt phenomena of the boreal wintertime stratospheric variability, and constitute the clearest example of coupling between the stratosphere and the troposphere. A good representation of SSWs in climate models is required to reduce their biases and uncertainties in future projections of stratospheric variability. The ability of models to reproduce these phenomena is usually assessed with just one reanalysis. However, the number of reanalyses has increased in the last decade and their own biases may affect the model evaluation. Here we compare the representation of the main aspects of SSWs across reanalyses. The examination of their main characteristics in the pre- and post-satellite periods reveals that reanalyses behave very similarly in both periods. However, discrepancies are larger in the pre-satellite period compared to afterwards, particularly for the NCEP-NCAR reanalysis. All datasets reproduce similarly the specific features of wavenumber-1 and wavenumber-2 SSWs. A good agreement among reanalyses is also found for triggering mechanisms, tropospheric precursors, and surface response. In particular, differences in blocking precursor activity of SSWs across reanalyses are much smaller than between blocking definitions.
Tropospheric forcing of the stratosphere: A comparative study of the two different major stratospheric warmings in 2009 and 2010
(2011) Ayarzagüena Porras, Blanca; Langematz, Ulrike; Serrano Mendoza, Encarnación
In January 2009 and 2010, two major stratospheric warmings (MSWs) took place in the boreal polar stratosphere. Both MSWs were preceded by nearly the strongest injection of tropospheric wave activity on record since 1958 and their central date was almost coincident. However, the typical external factors that influence the occurrence of MSWs (the Quasi‐Biennial Oscillation, sunspot cycle, or El Niño) were dissimilar in the two midwinters: favorable in 2010 but unfavorable in 2009. In this study, the driving mechanisms of these two different MSWs were investigated focusing on the amplification of upward wave activity injection into the stratosphere before the MSW onset. By decomposing the total wave flux injection into contributions from the climatological planetary waves and from deviations from the latter we found clear differences in this amplification between both MSWs. The pre‐MSW period in 2009 was characterized by a peak in the 100 hPa eddy heat flux with a predominance of wave number 2 activity. This was due to strong anomalies associated with Rossby wave packets originating from a deep ridge over the eastern Pacific. In contrast, the amplification of the upward wave propagation prior to the 2010 MSW was equally due to Rossby wave packets and to the interaction between the latter and the climatological waves. This amplification enhanced wave number 1 stationary waves in January 2010, which seemed at least partially due to the 2009/2010 El Niño event. Our results show the relevance of the internal tropospheric variability in generating MSWs, particularly when the external factors do not play any role.