Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation

<p>El Niño–Southern Oscillation (ENSO) modulates severe thunderstorm activity in the US, with increased activity expected during La Niña conditions. There is also evidence that severe thunderstorm activity is influenced by the Arctic Oscillation (AO), with the positive phase being associated w...

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Main Authors: M. K. Tippett, C. Lepore, M. L. L’Heureux
Format: Article
Language:English
Published: Copernicus Publications 2022-09-01
Series:Weather and Climate Dynamics
Online Access:https://wcd.copernicus.org/articles/3/1063/2022/wcd-3-1063-2022.pdf
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author M. K. Tippett
C. Lepore
M. L. L’Heureux
author_facet M. K. Tippett
C. Lepore
M. L. L’Heureux
author_sort M. K. Tippett
collection DOAJ
description <p>El Niño–Southern Oscillation (ENSO) modulates severe thunderstorm activity in the US, with increased activity expected during La Niña conditions. There is also evidence that severe thunderstorm activity is influenced by the Arctic Oscillation (AO), with the positive phase being associated with enhanced activity. The combined ENSO–AO impact is relevant for situations such as in early 2021, when persistent, strong positive and negative AO events occurred during La Niña conditions. Here we examine the relation of a spatially resolved tornado environment index (TEI) with ENSO and the AO in climate model forecasts of February, March, and April conditions over North America. Bivariate composites on Niño 3.4 and AO indices show that TEI predictability is high (strong signals and probability shifts) when the ENSO and AO signals reinforce each other and low when they cancel each other. The largest increase in the expected value and variance of TEI occurs when Niño 3.4 is negative, and the AO is positive. Signal-to-noise ratios are higher during El Niño–negative AO than during La Niña–positive AO, but probability shifts are comparable.</p>
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spelling doaj.art-b63a269ba1824cb4952ede9390a7baf92022-12-22T04:30:51ZengCopernicus PublicationsWeather and Climate Dynamics2698-40162022-09-0131063107510.5194/wcd-3-1063-2022Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic OscillationM. K. Tippett0C. Lepore1M. L. L’Heureux2Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, USALamont–Doherty Earth Observatory, Columbia University, Palisades, New York, USAClimate Prediction Center, NCEP, NWS, NOAA, College Park, Maryland, USA<p>El Niño–Southern Oscillation (ENSO) modulates severe thunderstorm activity in the US, with increased activity expected during La Niña conditions. There is also evidence that severe thunderstorm activity is influenced by the Arctic Oscillation (AO), with the positive phase being associated with enhanced activity. The combined ENSO–AO impact is relevant for situations such as in early 2021, when persistent, strong positive and negative AO events occurred during La Niña conditions. Here we examine the relation of a spatially resolved tornado environment index (TEI) with ENSO and the AO in climate model forecasts of February, March, and April conditions over North America. Bivariate composites on Niño 3.4 and AO indices show that TEI predictability is high (strong signals and probability shifts) when the ENSO and AO signals reinforce each other and low when they cancel each other. The largest increase in the expected value and variance of TEI occurs when Niño 3.4 is negative, and the AO is positive. Signal-to-noise ratios are higher during El Niño–negative AO than during La Niña–positive AO, but probability shifts are comparable.</p>https://wcd.copernicus.org/articles/3/1063/2022/wcd-3-1063-2022.pdf
spellingShingle M. K. Tippett
C. Lepore
M. L. L’Heureux
Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation
Weather and Climate Dynamics
title Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation
title_full Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation
title_fullStr Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation
title_full_unstemmed Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation
title_short Predictability of a tornado environment index from El Niño–Southern Oscillation (ENSO) and the Arctic Oscillation
title_sort predictability of a tornado environment index from el nino southern oscillation enso and the arctic oscillation
url https://wcd.copernicus.org/articles/3/1063/2022/wcd-3-1063-2022.pdf
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