About

Gudrun Magnusdottir is a Professor in the Department of Earth System Science at UC Irvine. Her research group focuses on atmospheric and climate dynamics, as indicated by her role within the department and her involvement in research projects related to Earth system science. She is based at UC Irvine, with her office located in CROUL HALL, and can be contacted via email at gudrun@uci.edu. The page lists her as a key member of the research group, emphasizing her leadership position and her contributions to advancing understanding in her field.

Research topics

• Atmospheric sciences
• Political Science
• Computer Science
• Environmental science
• Climatology
• Oceanography
• Geology
• Medicine
• Public relations
• Engineering
• Data science
• Ecology
• Biology
• Earth science
• History
• Geography
• Law
• Engineering ethics
• Library science
• Epistemology

Selected publications

• Thank You to Our 2025 Peer Reviewers

  Geophysical Research Letters · 2026-03-13

  articleOpen access

  Key Points The editors thank the 2025 peer reviewers

  PublisherDOI

• Stratospheric circulation response to large Northern Hemisphere high-latitude volcanic eruptions in a global climate model

  Atmospheric chemistry and physics · 2025-04-09 · 3 citations

  articleOpen accessSenior author

  Abstract. Stratospheric aerosols after major explosive volcanic eruptions can trigger climate anomalies for up to several years following such events. Whereas the mechanisms responsible for the prolonged response to volcanic surface cooling have been extensively investigated for tropical eruptions, less is known about the dynamical response to high-latitude eruptions. Here we use global climate model simulations of an idealized 6-month-long Northern Hemisphere high-latitude eruption to investigate the stratospheric circulation response during the first three post-eruption winters. Two model configurations are used, coupled with an interactive ocean and with prescribed sea-surface temperature. Our results reveal significant differences in the response of the polar stratosphere with an interactive ocean: the surface cooling is enhanced and zonal flow anomalies are stronger in the troposphere, which impacts atmospheric waveguides and upward propagation of large-scale planetary waves. We identify two competing mechanisms contributing to the post-eruption evolution of the polar vortex: (1) a local stratospheric top-down mechanism whereby increased absorption of aerosol-induced thermal radiation yields a polar vortex strengthening via thermal wind response and (2) a bottom-up mechanism whereby anomalous surface cooling yields a wave-activity flux increase that propagates into the winter stratosphere. We detect an unusually high frequency of sudden stratospheric warmings in the simulations with interactive ocean temperatures that calls for further exploration. In the coupled runs, the top-down mechanism dominates over the bottom-up mechanism in winter 1, while the bottom-up mechanism dominates in the follow-up winters.

  PublisherOA PDFDOI

• Subseasonal forecasting and MJO teleconnections in machine learning weather prediction models

  2025-07-09 · 1 citations

  preprintOpen accessSenior author

  In recent years, machine-learning (ML) models trained on reanalysis data have equaled physics-based forecast models in terms of performance skill for global weather forecasting. With increased rollout stability, the question of how these models perform for subseasonal to seasonal (S2S, week 3 to 8) forecasting has emerged. In this study we run a large set of subseasonal hindcasts over 2004-2023 to evaluate two ML weather forecast models at the S2S time scale, SFNO-HENS (Nvidia, fully ML) and NeuralGCM (Google Research, hybrid). Corresponding hindcasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) are used as a baseline for comparison to a physics-based model. Because our focus is on predicting moisture transport over the Western United states between October and March, we evaluate the models’ prediction skill for the Madden-Julian Oscillation (MJO) and its associated teleconnections in the North Pacific. We find that both ML models are competitive with the ECWMF model, with comparable skill in predicting the North Pacific large-scale circulation and the MJO at week 3 and beyond. Even though overall the mid-latitude subseasonal prediction skill remains low, the ML models exhibit interesting behavior such as a realistic propagation of the MJO across the Maritime Continent (especially for SFNO-HENS) and realistic teleconnections when compared to ECMWF. A SFNO-HENS sensitivity experiment with altered initial conditions in the tropics demonstrates the stability of the model, and it illustrates the capability of ML models to represent important physical processes of the atmosphere at the S2S time scale.

  PublisherOA PDFDOI

• Seasonality in the Predictive Skill of Southwest United States Precipitation in the Seasonal Forecast Systems

  Geophysical Research Letters · 2025-06-19 · 2 citations

  articleOpen accessSenior author

  Abstract We examine seasonality in the skill of 8 seasonal forecast systems to predict the Southwest United States (SWUS) precipitation between October and April. The models share similarities in the large seasonality they exhibit in their prediction skill over the 1993–2016 period: from October to December, the skill is low if not non‐existent, before it gets higher in all the models, with a peak in February‐March in the model with an extended hindcast period (European Centre for Medium‐Range Weather Forecasts, ECMWF, 1981–2024 period). Using ECMWF, further analyses of daily precipitation illustrate how the model is able to better predict the SWUS precipitation over the February‐March forecast target window, versus November‐December. Higher precipitation in early February compared to early November is a contributing factor, as is the annual cycle in tropical eastern Pacific sea surface temperature, and the associated El Niño Southern Oscillation teleconnection with the extratropics.

  PublisherOA PDFDOI

• We need to simulate more northern ITCZs and less southern ITCZs over the east Pacific Ocean in coupled climate models

  2025-11-18 · 1 citations

  articleOpen access

  Tropical precipitation biases have persisted since the very first generations of climate models. These biases are highly sensitive to the region and/or season of interest, with commonalities in the east Pacific and Atlantic Ocean basins, possibly due to their similar observed climatological northern hemisphere intertropical convergence zone (ITCZ). However, the colloquial name "double ITCZ bias" comes from a time and/or zonal mean, and may be missing important information about errors at smaller time and space scales. In this study, we explore daily characteristics of the ITCZ in observations, reanalyses, and 25 Coupled Model Intercomparison Project 6 (CMIP6) models over the east Pacific Ocean. We devise and apply an algorithm that determines a region's dominant daily ITCZ configuration, its "ITCZ state," based on the daily mean precipitation field. The five ITCZ states include: northern hemisphere (nITCZ), southern hemisphere (sITCZ), double (dITCZ), equatorial (eITCZ), and absent (aITCZ). We find that nearly all CMIP6 models gravely underestimate nITCZs and overestimate sITCZs during January through May, in contrast with what "double ITCZ bias" suggests. Surprisingly, all reanalyses also underestimate nITCZs and overestimate eITCZs. Errors in ITCZ state interannual variability are consistent with mean errors in reanalyses, while sITCZ interannual variability is far too low relative to the mean in most CMIP6 models. Lastly, all reanalyses and CMIP6 models overestimate precipitation rates in the southern hemisphere ITCZ band for dITCZs and sITCZs, suggestive of errors with atmospheric origins.

  PublisherOA PDFDOI

• We need to simulate more double ITCZs and less southern ITCZs in reanalyses and coupled climate models

  2025-02-21 · 1 citations

  preprint

  Model biases in tropical precipitation have persisted for nearly 30 years. These biases are highly sensitive to the region and/or season of interest, with commonalities in the east Pacific and Atlantic Ocean basins, possibly due to their similar observed climatological northern hemisphere intertropical convergence zone (ITCZ). However, the colloquial name ”double ITCZ bias” comes from a time and/or zonal mean, and many studies do not acknowledge that these model biases are most prominent during boreal winter and spring when models overestimate a southern hemisphere ITCZ, not a double ITCZ. In this study, we explore high-resolution characteristics of the ITCZ in observations, reanalyses, and 25 Coupled Model Intercomparison Project 6 (CMIP6) models over the east Pacific Ocean. We devise and apply an algorithm that determines a region’s dominant daily ITCZ configuration, its ”ITCZ state,” based on the daily mean precipitation field. The five ITCZ states include: northern hemisphere (nITCZ), southern hemisphere (sITCZ), double (dITCZ), equatorial (eITCZ), and absent (aITCZ). We find that nearly all CMIP6 models gravely underestimate dITCZs and nITCZs and overestimate sITCZs during January through May, in contrast with what ”double ITCZ bias” suggests. Surprisingly, all reanalyses also underestimate dITCZs and overestimate sITCZs. Errors in ITCZ state interannual variability are consistent with mean errors in reanalyses, while sITCZ interannual variability is far too low relative to the mean in most CMIP6 models. Lastly, all reanalyses and the seven CMIP6 models that can produce dITCZs overestimate precipitation rates in dITCZs, while nearly all CMIP6 models overestimate precipitation rates in sITCZs.

  PublisherDOI

• We Need to Simulate More Northern ITCZs and Less Southern ITCZs Over the East Pacific Ocean in Coupled Climate Models

  Journal of Geophysical Research Atmospheres · 2025-12-17

  article

  Abstract Tropical precipitation biases have persisted since the very first generations of climate models. These biases are highly sensitive to the region and/or season of interest, with commonalities in the east Pacific and Atlantic Ocean basins, possibly due to their similar observed climatological northern hemisphere intertropical convergence zone (ITCZ). However, the colloquial name “double ITCZ bias” comes from a time and/or zonal mean, and may be missing important information about errors at smaller time and space scales. In this study, we explore daily characteristics of the ITCZ in observations, reanalyses, and 25 Coupled Model Intercomparison Project 6 (CMIP6) models over the east Pacific Ocean. We devise and apply an algorithm that determines a region's dominant daily ITCZ configuration, its “ITCZ state,” based on the daily mean precipitation field. The five ITCZ states include: northern hemisphere (nITCZ), southern hemisphere (sITCZ), double (dITCZ), equatorial (eITCZ), and absent (aITCZ). We find that nearly all CMIP6 models gravely underestimate nITCZs and overestimate sITCZs during January through May, in contrast with what “double ITCZ bias” suggests. Surprisingly, all reanalyses also underestimate nITCZs and overestimate eITCZs. Errors in ITCZ state interannual variability are consistent with mean errors in reanalyses, while sITCZ interannual variability is far too low relative to the mean in most CMIP6 models. Lastly, all reanalyses and CMIP6 models overestimate precipitation rates in the southern hemisphere ITCZ band for dITCZs and sITCZs, suggestive of errors with atmospheric origins.

  PublisherDOI

• Thank You to Our 2024 Reviewers

  Geophysical Research Letters · 2025-02-22

  articleOpen access

  Abstract On behalf of the journal, AGU, and the scientific community, the editors of Geophysical Research Letters would like to sincerely thank those who reviewed manuscripts in 2024. The hours reading and commenting on manuscripts not only improve the manuscripts but also increase the scientific rigor of future research in the field. With the advent of AGU's data policy, many reviewers have also helped immensely to evaluate the accessibility and availability of data, and many have provided insightful comments that helped to improve the data presentation and quality. We greatly appreciate the assistance of the reviewers in advancing open science, which is a key objective of AGU's data policy. We particularly appreciate the timely reviews in light of the demands imposed by the rapid review process at Geophysical Research Letters. We received 5,225 submissions in 2024, and 5,597 reviewers contributed to their evaluation by providing 9,697 reviews in total. We deeply appreciate their contributions. We would also like to acknowledge the passing of our beloved colleague, Harihar Rajaram. An AGU Fellow and longtime affiliate of AGU's Hydrology Section, Hari was the Editor‐in‐Chief of Geophysical Research Letters since 2019, a former editor on Water Resources Research, and served on the AGU Publications Committee.

  PublisherOA PDFDOI

• Decadal Variability of the MJO and Implications for Southwestern United States Wintertime Precipitation Predictability

  Geophysical Research Letters · 2025-04-02 · 2 citations

  articleOpen accessSenior author

  Abstract The Madden‐Julian Oscillation (MJO) is the dominant source of tropical convective activity on intraseasonal timescales and a significant influence on extratropical weather through remote teleconnections. Here, we investigate decadal variability of the MJO and its boreal winter teleconnections with the Southwestern United States (SWUS) using an ensemble of historical climate simulations, where tropical atmospheric variability is nudged toward reanalysis. Since the beginning of the 21st century, the MJO has been associated with a wavenumber‐5 zonal teleconnection pattern that propagates along the jet stream waveguide. This coupling is absent in the prior two decades, causing significant differences in the Southwestern United States precipitation response. These changes also result in vastly different windows of opportunity for S2S predictability during each period. This decadal variability is potentially associated with the change from a positive to negative Interdecadal Pacific Oscillation, as well as the global warming signal.

  PublisherOA PDFDOI

• Contrasting Arctic Amplification Response in the Community Earth System Model Large Ensembles and Implications for the North Atlantic Region

  Journal of Geophysical Research Atmospheres · 2025-03-22 · 3 citations

  articleOpen accessSenior author

  Abstract The response of the polar jet to climate warming and rapid Arctic change is a leading uncertainty in climate projections and critical to the future of mid‐latitude surface weather. Previous studies suggest that CMIP5‐6 model projections fall into two groups of either Arctic‐ or tropically‐driven climate change, especially in the North Atlantic. Here, we present distinct warming patterns emerging by the late 21st century between the first two generations of the Community Earth System Model Large Ensemble (CESM‐LE) and use daily diagnostics to assess associated changes in mid‐latitude circulation. We show that the subsequent versions of CESM represent categorically different storylines of North Atlantic climate change. The first version of CESM‐LE (CESM1‐LE, hereafter LENS1) exhibits severe Arctic amplification (AA) along with minor reductions in jet waviness. In contrast, CESM2‐LE (hereafter LENS2) presents subdued AA, a more pronounced North Atlantic warming hole, and a late‐century climate dominated by upper‐tropospheric tropical warming. Uniquely, in LENS2 during winter, the North Atlantic sector projects less warming in the Arctic than in the mid‐latitude mid‐troposphere. The projected North Atlantic jet is reinforced and poleward‐shifted with reduced sinuosity, blocking, and synoptic variability. The surface weather response includes greater precipitation over northern Europe, more intense drying in the eastern Mediterranean, and a lesser decline in cold extremes by late century compared to LENS1.

  PublisherOA PDFDOI

Recent grants

• CMG: Characterization of Inter-Tropical Convergence Zone (ITCZ) Dynamics and Breakdown Using Statistical Learning Methods and Satellite Data

  NSF · $618k · 2005–2010

• Extreme Weather Events in Mid-latitudes: The Role of Arctic Sea Ice, SST due to AMV and Siberian Snow Cover Through Teleconnections Involving the Stratosphere

  NSF · $701k · 2016–2020

• Variability of Tropical Elongated Convergence Zones

  NSF · $540k · 2012–2016

• Forcings and Feedbacks: Arctic Sea Ice and the Atmosphere

  NSF · $257k · 2006–2010

• Large-scale Atmospheric Circulation and Multidecadal Variability of the North Atlantic Ocean

  NSF · $680k · 2014–2017

Frequent coauthors

• Yannick Peings

  University of California, Irvine

  82 shared

• Dillon Elsbury

  25 shared

• Zachary M. Labe

  Princeton University

  15 shared

• Grzegorz Muszyński

  British Antarctic Survey

  13 shared

• Tien‐Yiao Hsu

  Scripps Institution of Oceanography

  12 shared

• Kelly Mahoney

  NOAA Physical Sciences Laboratory

  12 shared

• Ashley E. Payne

  University of Michigan–Ann Arbor

  12 shared

• François Primeau

  12 shared

Labs

• Gudrun Magnusdottir Research GroupPI

Education

• PhD, Atmospheric Science

  Colorado State University

  1989