Multidecadal variations of the effects of the Quasi-Biennial Oscillation on the climate system

Abstract

Abstract. Effects of the Quasi-Biennial Oscillation (QBO) on tropospheric climate are not always strong or they appear only intermittently. Studying them requires long time series of both the QBO and climate variables, which has restricted previous studies to the past 30-50 years. Here we use the benefits of an existing QBO reconstruction back to 1908. We first investigate additional, newly digitized historical observations of stratospheric winds to test the reconstruction. Then we use the QBO time series to analyse atmospheric data sets (reconstructions and reanalyses) as well as the results of coupled ocean-atmosphere-chemistry climate model simulations that were forced with the reconstructed QBO. We investigate effects related to (1) tropical-extratropical interaction in the stratosphere, wave-mean flow interaction and subsequent downward propagation, and (2) interaction between deep tropical convection and stratospheric flow. We generally find weak connections, though some are statistically significant over the 100-year period and consistent with model results. Apparent multidecadal variations in the connection between the QBO and the investigated climate responses are consistent with a small effect in the presence of large variability, with one exception: the imprint on the northern polar vortex, which is seen in recent reanalysis data, is not found in the period . Conversely, an imprint in Berlin surface air temperature is only found in but not in the recent period. Likewise, in the model simulations both links tend to appear alternatingly, suggesting a more systematic modulation due to a shift in the circulation, for example. Over the Pacific warm pool, we find increased convection during easterly QBO, mainly in boreal winter in observation-based data as well as in the model simulations, with large variability. No QBO effects were found in the Indian monsoon strength or Atlantic hurricane frequency.

Statistical Learning Methods as a Basis for Skillful Seasonal Temperature Forecasts in Europe

“…Forcing the ENSO-related SST1 component manually to be included in all random samples did not improve the results. In other studies, the ENSO has been found to affect, for example, the NAO variability (e.g., Hall et al 2017;Bell et al 2009) and the European climate in general (Brönnimann 2007). It is likely that the response to the ENSO forcing is nonlinear in Europe, and to be able to utilize SST1, linear regression models would require major modifications applied to it, as shown by Folland et al (2012) and Hall et al (2017).…”

“…reported, including sea surface temperatures (SSTs) in various basins (e.g., Kolstad and Årthun 2018;Smith et al 2016;Toniazzo and Scaife 2006;Brönnimann 2007;Rodwell and Folland 2002), continental snow cover (Allen and Zender 2011;Cohen and Jones 2011;Cohen and Entekhabi 1999), stratospheric geopotential (GPT) or winds (Jia et al 2017;Wang et al 2017;Scaife et al 2016;Brönnimann et al 2016), sea ice cover (Liptak and Strong 2014;Vihma et al 2014), and soil moisture (Orth and Seneviratne 2014;van den Hurk et al 2012). These parameters share two important properties: they vary slowly in time, and they can act as forcings for the troposphere.…”

A Moments View of Climatology and Variability of the Asian Summer Monsoon Anticyclone

“…Many studies of ASM variability and trends have focused on near-surface fields such as rainfall and low-level temperatures or winds (e.g., Kajikawa et al 2012;Preethi et al 2017;Kodera et al 2019;Brönnimann et al 2016;Wu et al 2020;and references therein), and some suggest a trend toward earlier monsoon onset in spring, with possible relationships to anthropogenic forcing (e.g., Kajikawa et al 2012;Bollasina et al 2013Bollasina et al , 2014Bombardi et al 2020). Near-surface metrics have been linked to the upper-level circulation, with, for example, westward and northward trends in the UT anticyclonic circulation associated with corresponding interannual variability in surface conditions (e.g., Preethi et al 2017), links between interannual variability in ASM precipitation onset and tropopause variations (e.g., Ravindra Babu et al 2019), and evidence of UT subtropical jet changes (weakening or latitude changes) associated with earlier monsoon onset (e.g., Samanta et al 2020;Wu et al 2020).…”

Teleconnections of the Quasi‐Biennial Oscillation in a multi‐model ensemble of QBO‐resolving models

“…The uncertainty of this reconstruction increases as the record goes further back, being particularly large prior to 1920 (Brönnimann et al, 2007). Using more recently digitized pre-1953 balloon observations to validate the reconstruction, Brönnimann et al (2016) found only 60% agreement between the reconstructed pre-1953 QBO winds and the observations, and suggested that phase onset times could be in error by 3-4 months. We neverthless include some results for the whole ERA-20C period, but with the caveat that it is unclear how much reliable information about QBO phase is available prior to 1953.…”

“…Reanalysis records extend back to the mid-twentieth century for reanalysis systems that assimilate radiosonde and satellite data, and to the late 19th century for surface-input reanalyses (Fujiwara et al, 2017). Brönnimann et al (2016) surveyed QBO teleconnections using a reconstructed QBO index going back to 1900 (Brönnimann et al, 2007) and found a weakened NAO response during the first half of the century coinciding with a strengthened European surface temperature response, but vice versa during the latter half of the century. Since the reconstructed QBO index has larger uncertainty before 1953 than afterward, apparent variations in the teleconnection strength could indicate that the state of the QBO is not well known in the earlier period.…”