The Life Cycle and Variability of Antarctic Weak Polar Vortex Events

Journal of Climate American Meteorological Society (2022) 1-63

Abstract:

<jats:title>Abstract</jats:title> <jats:p>Motivated by the strong Antarctic sudden stratospheric warming (SSW) in 2019, a survey on the similar Antarctic weak polar events (WPV) is presented, including their life cycle, dynamics, seasonality, and climatic impacts. The Antarctic WPVs have a frequency of about four events per decade, with the 2002 event being the only major SSW. They show a similar life cycle to the SSWs in the Northern Hemisphere but have a longer duration. They are primarily driven by enhanced upward-propagating wavenumber 1 in the presence of a preconditioned polar stratosphere, i.e., a weaker and more contracted Antarctic stratospheric polar vortex. Antarctic WPVs occur mainly in the austral spring. Their early occurrence is preceded by an easterly anomaly in the middle and upper equatorial stratosphere besides the preconditioned polar stratosphere. The Antarctic WPVs increase the ozone concentration in the polar region and are associated with an advanced seasonal transition of the stratospheric polar vortex by about one week. Their frequency doubles after 2000 and is closely related to the advanced Antarctic stratospheric final warming in recent decades. The WPV-resultant negative phase of the southern annular mode descends to the troposphere and persists for about three months, leading to persistent hemispheric scale temperature and precipitation anomalies.</jats:p>

SST-driven variability of the East Asian summer jet on a decadal time-scale in CMIP6 models

Quarterly Journal of the Royal Meteorological Society Wiley (2021)

Authors:

Matthew Patterson, Christopher O'Reilly, Tim Woollings, Antje Weisheimer, Bo Wu

Abstract:

The East Asian summer jet (EASJ) is an important component of the East Asian summer monsoon system and its variability is correlated with precipitation and surface temperature variations over this region. Whilst many studies have considered the interannual variability of the EASJ, less is known about variations on a decadal time-scale. This study investigates the relationship between decadal EASJ variability and sea surface temperatures (SSTs) and thus the potential predictability that SSTs may provide. Given the relatively short observational record, we make use of the long pre-industrial control simulations in the Coupled Model Intercomparison Project phase 6 (CMIP6) in addition to a large ensemble of atmosphere-only experiments, forced with random SST patterns. We then create an SST-based reconstruction of the dominant modes of EASJ variability in the CMIP6 models, finding a median EASJ–reconstruction correlation for the dominant mode of 0.43. Much of the skill in the reconstruction arises from variations in Pacific SSTs, however the tropical Atlantic also makes a significant contribution. These findings suggest the potential for multi-year predictions of the EASJ, provided that skilful SST forecasts are available.

Convection Modeling of Pure-steam Atmospheres

ASTROPHYSICAL JOURNAL LETTERS 923:1 (2021) ARTN L15

Authors:

Xianyu Tan, Maxence Lefevre, Raymond T Pierrehumbert

Inferring Shallow Surfaces on Sub-Neptune Exoplanets with JWST

ASTROPHYSICAL JOURNAL LETTERS 922:2 (2021) ARTN L27

Authors:

Shang-Min Tsai, Hamish Innes, Tim Lichtenberg, Jake Taylor, Matej Malik, Katy Chubb, Raymond Pierrehumbert

Drivers behind the summer 2010 wave train leading to Russian heat wave and Pakistan flooding

npj Climate and Atmospheric Science Springer Nature 4 (2021) 55

Authors:

Giorgia Di Capua, Sarah Sparrow, Kai Kornhuber, Efi Rousi, Scott Osprey, David Wallom, Bart van den Hurk, Dim Coumou

Abstract:

Summer 2010 saw two simultaneous extremes linked by an atmospheric wave train: a record-breaking heatwave in Russia and severe floods in Pakistan. Here, we study this wave event using a large ensemble climate model experiment. First, we show that the circulation in 2010 reflected a recurrent wave train connecting the heatwave and flooding events. Second, we show that the occurrence of the wave train is favored by three drivers: (1) 2010 sea surface temperature anomalies increase the probability of this wave train by a factor 2-to-4 relative to the model’s climatology, (2) early-summer soil moisture deficit in Russia not only increases the probability of local heatwaves, but also enhances rainfall extremes over Pakistan by forcing an atmospheric wave response, and (3) high-latitude land warming favors wave-train occurrence and therefore rainfall and heat extremes. These findings highlight the complexity and synergistic interactions between different drivers, reconciling some seemingly contradictory results from previous studies.