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<front>
<journal-meta>
<journal-id journal-id-type="publisher">EGUsphere</journal-id>
<journal-title-group>
<journal-title>EGUsphere</journal-title>
<abbrev-journal-title abbrev-type="publisher">EGUsphere</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">EGUsphere</abbrev-journal-title>
</journal-title-group>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/egusphere-2026-6070</article-id>
<title-group>
<article-title>Linking stratosphere&amp;ndash;troposphere coupling biases to Annular Mode predictability and midlatitude impacts in subseasonal forecast systems</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Garfinkel</surname>
<given-names>Chaim I.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lawrence</surname>
<given-names>Zachary D.</given-names>
<ext-link>https://orcid.org/0000-0003-0901-3839</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Butler</surname>
<given-names>Amy H.</given-names>
<ext-link>https://orcid.org/0000-0002-3632-0925</ext-link>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Ayarzaguena</surname>
<given-names>Blanca</given-names>
<ext-link>https://orcid.org/0000-0003-3959-5673</ext-link>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Abalos</surname>
<given-names>Marta</given-names>
<ext-link>https://orcid.org/0000-0002-1267-5115</ext-link>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Barriopedro</surname>
<given-names>David</given-names>
<ext-link>https://orcid.org/0000-0001-6476-944X</ext-link>
</name>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Calvo</surname>
<given-names>Natalia</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>de la Cámara</surname>
<given-names>Alvaro</given-names>
<ext-link>https://orcid.org/0000-0002-8831-4789</ext-link>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Charlton-Perez</surname>
<given-names>Andrew</given-names>
<ext-link>https://orcid.org/0000-0001-8179-6220</ext-link>
</name>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Cohen</surname>
<given-names>Judah</given-names>
</name>
<xref ref-type="aff" rid="aff8">
<sup>8</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Dai</surname>
<given-names>Ying</given-names>
</name>
<xref ref-type="aff" rid="aff9">
<sup>9</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Domeisen</surname>
<given-names>Daniela I. V.</given-names>
<ext-link>https://orcid.org/0000-0002-1463-929X</ext-link>
</name>
<xref ref-type="aff" rid="aff10">
<sup>10</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Dunn-Sigouin</surname>
<given-names>Etienne</given-names>
<ext-link>https://orcid.org/0000-0002-5130-064X</ext-link>
</name>
<xref ref-type="aff" rid="aff11">
<sup>11</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Erner</surname>
<given-names>Irene</given-names>
<ext-link>https://orcid.org/0000-0003-3066-1902</ext-link>
</name>
<xref ref-type="aff" rid="aff12">
<sup>12</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>García-Serrano</surname>
<given-names>Javier</given-names>
</name>
<xref ref-type="aff" rid="aff13">
<sup>13</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hindley</surname>
<given-names>Neil P.</given-names>
<ext-link>https://orcid.org/0000-0003-4377-2038</ext-link>
</name>
<xref ref-type="aff" rid="aff14">
<sup>14</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hitchcock</surname>
<given-names>Peter</given-names>
<ext-link>https://orcid.org/0000-0001-8993-3808</ext-link>
</name>
<xref ref-type="aff" rid="aff9">
<sup>9</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Jucker</surname>
<given-names>Martin</given-names>
<ext-link>https://orcid.org/0000-0002-4227-315X</ext-link>
</name>
<xref ref-type="aff" rid="aff15">
<sup>15</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Karpechko</surname>
<given-names>Alexey Yu.</given-names>
</name>
<xref ref-type="aff" rid="aff12">
<sup>12</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kim</surname>
<given-names>Hera</given-names>
<ext-link>https://orcid.org/0000-0002-8036-9443</ext-link>
</name>
<xref ref-type="aff" rid="aff16">
<sup>16</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Koren</surname>
<given-names>Gerbrand</given-names>
<ext-link>https://orcid.org/0000-0002-2275-0713</ext-link>
</name>
<xref ref-type="aff" rid="aff17">
<sup>17</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lee</surname>
<given-names>Simon H.</given-names>
<ext-link>https://orcid.org/0000-0003-0986-0093</ext-link>
</name>
<xref ref-type="aff" rid="aff18">
<sup>18</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lee</surname>
<given-names>Robert W.</given-names>
</name>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Osman</surname>
<given-names>Marisol</given-names>
<ext-link>https://orcid.org/0000-0002-6275-1454</ext-link>
</name>
<xref ref-type="aff" rid="aff19">
<sup>19</sup>
</xref>
<xref ref-type="aff" rid="aff20">
<sup>20</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Palmeiro</surname>
<given-names>Froila M.</given-names>
<ext-link>https://orcid.org/0000-0002-4120-6174</ext-link>
</name>
<xref ref-type="aff" rid="aff13">
<sup>13</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Rao</surname>
<given-names>Jian</given-names>
<ext-link>https://orcid.org/0000-0001-5030-0288</ext-link>
</name>
<xref ref-type="aff" rid="aff21">
<sup>21</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Schwartz</surname>
<given-names>Chen</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff22">
<sup>22</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Son</surname>
<given-names>Seok-Woo</given-names>
<ext-link>https://orcid.org/0000-0003-2982-9501</ext-link>
</name>
<xref ref-type="aff" rid="aff16">
<sup>16</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wright</surname>
<given-names>Corwin J.</given-names>
<ext-link>https://orcid.org/0000-0003-2496-953X</ext-link>
</name>
<xref ref-type="aff" rid="aff14">
<sup>14</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wu</surname>
<given-names>Rachel W.-Y.</given-names>
<ext-link>https://orcid.org/0000-0002-8100-2424</ext-link>
</name>
<xref ref-type="aff" rid="aff23">
<sup>23</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Fredy &amp; Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Israel</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, CO, USA</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>NOAA Physical Sciences Laboratory (PSL), Boulder, CO, USA</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>NOAA Chemical Sciences Laboratory (CSL), Boulder, CO, USA</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Department of Earth Physics and Astrophysics, Universidad Complutense de Madrid, Madrid, Spain</addr-line>
</aff>
<aff id="aff6">
<label>6</label>
<addr-line>Instituto de Geociencias (IGEO), Consejo Superior de Investigaciones Científicas– Universidad Complutense de Madrid (CSIC-UCM), Madrid, Spain</addr-line>
</aff>
<aff id="aff7">
<label>7</label>
<addr-line>Department of Meteorology, University of Reading, Reading, UK</addr-line>
</aff>
<aff id="aff8">
<label>8</label>
<addr-line>Atmospheric and Environmental Research Inc., Lexington, MA, USA</addr-line>
</aff>
<aff id="aff9">
<label>9</label>
<addr-line>Dept. Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA</addr-line>
</aff>
<aff id="aff10">
<label>10</label>
<addr-line>University of Lausanne, Lausanne, Switzerland</addr-line>
</aff>
<aff id="aff11">
<label>11</label>
<addr-line>NORCE Norwegian Research Centre and Bjerknes Centre for Climate Research, Bergen, Norway</addr-line>
</aff>
<aff id="aff12">
<label>12</label>
<addr-line>Finnish Meteorological Institute, Meteorological Research, Helsinki, Finland</addr-line>
</aff>
<aff id="aff13">
<label>13</label>
<addr-line>Group of Meteorology, Universitat de Barcelona (UB), Barcelona, Spain</addr-line>
</aff>
<aff id="aff14">
<label>14</label>
<addr-line>Centre for Climate Adaptation and Environment Research, University of Bath, Bath, UK</addr-line>
</aff>
<aff id="aff15">
<label>15</label>
<addr-line>Climate Change Research Centre and ARC Centre of Excellence for the Weather of the 21st Century, University of New South Wales, Sydney, Australia</addr-line>
</aff>
<aff id="aff16">
<label>16</label>
<addr-line>School of Earth and Environmental Sciences, Seoul National University, South Korea</addr-line>
</aff>
<aff id="aff17">
<label>17</label>
<addr-line>Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, The Netherlands</addr-line>
</aff>
<aff id="aff18">
<label>18</label>
<addr-line>School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK</addr-line>
</aff>
<aff id="aff19">
<label>19</label>
<addr-line>CONICET – Universidad de Buenos Aires, Centro de Investigaciones del Mar y la Atmósfera (CIMA), Buenos Aires, Argentina</addr-line>
</aff>
<aff id="aff20">
<label>20</label>
<addr-line>CNRS– IRD – CONICET – UBA. Instituto Franco-Argentino para el Estudio del Clima y sus Impactos (IRL 3351 IFAECI), Buenos Aires, Argentina</addr-line>
</aff>
<aff id="aff21">
<label>21</label>
<addr-line>Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters / Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China</addr-line>
</aff>
<aff id="aff22">
<label>22</label>
<addr-line>Centre for Climate Research Singapore, Singapore</addr-line>
</aff>
<aff id="aff23">
<label>23</label>
<addr-line>Department of Applied Physics and Applied Mathematics, Columbia University, New York, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>21</day>
<month>10</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>36</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Chaim I. Garfinkel et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-6070/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-6070/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-6070/egusphere-2026-6070.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-6070/egusphere-2026-6070.pdf</self-uri>
<abstract>
<p>Two-way coupling between the stratosphere and troposphere is an important source of subseasonal &amp;nbsp;predictability and can open windows of opportunity for improved forecasts. However, operational models used for subseasonal forecasting suffer from systematic biases due to insufficient resolution or poorly performing parameterizations: they underestimate the strength of upward &amp;nbsp;coupling from the troposphere to &amp;nbsp;the stratosphere, they overestimate downward coupling of the lower stratosphere to near-surface polar cap height, and the polar lower stratosphere is too cold. Using data from 22 operational subseasonal models, we explore the implications of these biases on the skill of the Northern and Southern Annular Modes (NAM and SAM) in both the troposphere and stratosphere and for regional surface impacts. Updated or upgraded model versions from nearly all modeling centers show higher skill in both the stratospheric and tropospheric NAM and SAM as compared to their earlier versions, and models with relatively higher skill for the stratospheric annular modes generally have higher skill for the tropospheric annular modes as well. Near-surface AM skill is significantly higher for initializations during strong vortex states, and to a lesser degree during weak vortex states. Models with particularly poor upward coupling strengths and with too-weak climatological heat flux at 100 hPa suffer from reduced stratospheric NAM and SAM skill. In contrast, mean state biases in the stratospheric polar vortex are relatively unimportant for stratospheric NAM and SAM skill. Even as downward coupling over the North Atlantic and Antarctica tends to be handled well by these models, they produce an overly zonal response with a &amp;nbsp;fictitious center of action in the midlatitude North Pacific, while underestimating the midlatitude near-surface temperature impacts over Eurasia, Australia, and South America. Downward coupling &amp;nbsp;in the North Pacific is particularly pronounced in models with overly strong variance in this region, and models underestimate the wave-3 pattern in Southern Hemisphere (SH) midlatitudes by a &amp;nbsp;factor of three. These biases in downward coupling mirror biases in the midlatitude structure of the tropospheric &amp;nbsp;NAM and SAM. Overall, models with finer vertical resolution near the tropopause, with a better representation of tropospheric quasi-stationary waves, and with a better representation of these coupling processes, are more skillful in both the stratosphere and troposphere. These findings have implications for future research directions of the Stratospheric Network for the Assessment of Predictability.</p>
</abstract>
<counts><page-count count="36"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>Israel Science Foundation</funding-source>
<award-id>3065/23</award-id>
</award-group>
<award-group id="gs2">
<funding-source>National Natural Science Foundation of China</funding-source>
<award-id>42361144843</award-id>
</award-group>
<award-group id="gs3">
<funding-source>United States - Israel Binational Science Foundation</funding-source>
<award-id>2021714</award-id>
</award-group>
<award-group id="gs4">
<funding-source>National Science Foundation</funding-source>
<award-id>AGS-2140909</award-id>
</award-group>
</funding-group>
</article-meta>
</front>
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<back>
</back>
</article>