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\begin{document}

\title{Past and Future Trends in Clear-Air Turbulence over the Northern
Hemisphere}



\author[1]{Mohamed Foudad}%
\author[1]{Emilia Sanchez-Gomez}%
\author[1]{Thomas Jaravel}%
\author[1]{Mélanie C. Rochoux}%
\author[1]{Laurent Terray}%
\affil[1]{CERFACS}%


\vspace{-1em}



  
  \date{May 25, 2024}


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\begin{abstract}
Clear-Air Turbulence (CAT) is associated with wind shear in the vicinity
of jet streams in upper atmospheric levels. This turbulence occurs in
cloudless regions and causes most weather-related aircraft accidents.
Recent studies have shown that in response to climate change, CAT could
significantly increase over certain regions as a consequence of
strengthening of jet streams. In this study we use several atmospheric
reanalyses and coupled model experiments database to evaluate CAT recent
and future changes in the Northern Hemisphere. Several CAT diagnostics
are computed to assess the sensitivity of results to different
turbulence representations. A significant positive trend in CAT
frequency is found in the reanalyses in different regions in the
Northern Hemisphere over the period 1980-2021. The signal-to-noise
analysis shows that over North Africa, East Asia and Middle East the
increase of CAT occurrence in the last decades is likely attributed to
global warming. In contrast, over the North Atlantic and North Pacific
the internal climate variability is too strong to detect a response to
anthropogenic forcing in the observed trends. Future climate projections
show that over several regions in the Northern Hemisphere, CAT is
projected to increase with a high model agreement and independently of
the CAT diagnostic used. The largest increase in CAT is projected to
occur over East Asia. In the North Atlantic, large uncertainty remains
due to lack of model agreement and differences among the various CAT
diagnostics.%
\end{abstract}%



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