About

Darryn Waugh's main research interests are oriented toward understanding dynamics and transport in the atmosphere and oceans. His research in the atmosphere focuses on stratospheric and upper tropospheric dynamics and transport. Improved understanding of, and ability to model, fluid motions in these regions is important for understanding the distribution of trace constituents, such as ozone, and for assessing the impact of human activities on the atmospheric environment. In recent years, he has also become interested in the transport in oceans and lakes, and the uptake of anthropogenic carbon. He holds a PhD from Cambridge University in Earth & Planetary Sciences.

Research topics

• Climatology
• Environmental science
• Geology
• Oceanography
• Atmospheric sciences
• Meteorology
• Geography
• Ecology

Selected publications

• Supplementary material to "Evaluation of stratospheric transport in three generations of Chemistry-Climate Models"

  2026-01-13

  article
  PublisherDOI

• Evaluation of stratospheric transport in three generations of Chemistry-Climate Models

  2026-01-13

  articleOpen access

  Abstract. The representation of stratospheric transport in Chemistry-Climate Models (CCMs) is key for accurately reproducing and projecting the evolution of the ozone layer and other radiatively relevant trace gases. We evaluate stratospheric transport in CCMs that have participated in three model intercomparison initiatives (CCMVal-2, CCMI-1, and CCMI-2022) over the last ~15 years using modern satellite datasets and reanalyses. Key long-standing model biases persist across generations, with some worsening in recent simulations. Transport remains overly fast in the models, with a global mean age of air young bias of ~1 year for the CCMI-2022 median. It is argued that this bias could be associated with too fast tropical upwelling in the lower stratosphere, insufficient horizontal mixing and/or excessive vertical diffusion. In the springtime southern polar stratosphere, the final warming is delayed (~3 weeks), downwelling is underestimated (~25 %), and the depth of the ozone minimum is overestimated (~10 DU) on average in the most recent models. The tropopause is too high in all generations, and the tropical cold point tropopause is too warm in the latest generation (~1–2 K). Long-term trends in transport and over 1980–1999 are consistent across model generations and highlight the crucial role of ozone depletion in contributing to accelerate the Brewer-Dobson circulation and delaying the southern polar vortex breakdown.

  PublisherOA PDFDOI

• Evaluation of stratospheric transport in three generations of Chemistry-Climate Models

  Repository KITopen (Karlsruhe Institute of Technology) · 2026-01-01

  articleOpen access

  The representation of stratospheric transport in Chemistry-Climate Models (CCMs) is key for accurately reproducing and projecting the evolution of the ozone layer and other radiatively relevant trace gases. We evaluate stratospheric transport in CCMs that have participated in three model intercomparison initiatives (CCMVal-2, CCMI-1, and CCMI-2022) over the last ∼ 15 years using modern satellite datasets and reanalyses. Key long-standing model biases persist across generations, with some worsening in recent simulations. Transport remains overly fast in the models, with a global mean age of air young bias of ∼ 1 year for the CCMI-2022 median. It is argued that this bias could be associated with too fast tropical upwelling in the lower stratosphere and possibly to excessive vertical diffusion, with mixing biases being more uncertain. In the springtime southern polar stratosphere, the final warming is delayed (∼ 3 weeks), downwelling is underestimated (∼ 25 %), and the depth of the ozone minimum is overestimated (∼ 10 DU) on average in the most recent models. The tropopause is too high in all generations, and the tropical cold point tropopause is too warm in the latest generation (∼ 1–2 K). Long-term trends in transport over 1980–1999 are consistent across model generations and highlight the crucial role of ozone depletion in contributing to accelerate the Brewer-Dobson circulation and delaying the southern polar vortex breakdown.

  PublisherDOI

• Evaluation of stratospheric transport in three generations of Chemistry-Climate Models

  Atmospheric chemistry and physics · 2026-04-21

  articleOpen access

  Abstract. The representation of stratospheric transport in Chemistry-Climate Models (CCMs) is key for accurately reproducing and projecting the evolution of the ozone layer and other radiatively relevant trace gases. We evaluate stratospheric transport in CCMs that have participated in three model intercomparison initiatives (CCMVal-2, CCMI-1, and CCMI-2022) over the last ∼ 15 years using modern satellite datasets and reanalyses. Key long-standing model biases persist across generations, with some worsening in recent simulations. Transport remains overly fast in the models, with a global mean age of air young bias of ∼ 1 year for the CCMI-2022 median. It is argued that this bias could be associated with too fast tropical upwelling in the lower stratosphere and possibly to excessive vertical diffusion, with mixing biases being more uncertain. In the springtime southern polar stratosphere, the final warming is delayed (∼ 3 weeks), downwelling is underestimated (∼ 25 %), and the depth of the ozone minimum is overestimated (∼ 10 DU) on average in the most recent models. The tropopause is too high in all generations, and the tropical cold point tropopause is too warm in the latest generation (∼ 1–2 K). Long-term trends in transport over 1980–1999 are consistent across model generations and highlight the crucial role of ozone depletion in contributing to accelerate the Brewer-Dobson circulation and delaying the southern polar vortex breakdown.

  PublisherDOI

• Impact of Southern Ocean processes on atmospheric CO2 concentration

  2025-03-15

  preprintOpen accessCorresponding

  The Southern Ocean (SO) is believed to play a pivotal role in modulating atmospheric CO2 concentrations, both across glacial/interglacial cycles and during abrupt climate shifts. Previous studies using coarse-resolution Earth system models have suggested that stronger southern hemisphere westerly winds enhance the upwelling of deep waters, which in turn increases CO2 outgassing. However, mesoscale processes have a significant impact on Southern Ocean circulation. To better capture these dynamics, we assess the effects of changes in the position and strength of the southern hemisphere westerlies through a series of numerical simulations using the eddy-rich and eddy-permitting ocean, sea-ice, and carbon cycle model, ACCESS-OM2. Our results show that a 10% increase in southern hemispheric westerly wind stress leads to a 0.13 GtC/yr increase in Southern Ocean CO2 outgassing. We also find that a poleward shift of the SH westerlies enhances CO2 outgassing, with a sensitivity of 0.08 GtC/yr for a 5-degree poleward shift. We further compare the impact and timescale of the Southern Ocean carbon cycle changes driven by dynamic wind variations with those resulting from changes in Antarctic Bottom Water transport and iron fertilisation.

  PublisherDOI

• Evolution of Titan’s Fall and Winter Polar Hood Cloud

  2025-07-09

  preprintOpen accessCorresponding

  Fall and winter on Titan are marked by the formation and persistence of a vast polar “hood” cloud, covering the cold pole and extending equatorward as far as 40° latitude [e.g., 1]. Extending from the upper troposphere into the lower stratosphere, a polar hood cloud was present in the northern hemisphere during the Voyager I flyby and then again when Cassini arrived during the next northern winter in 2004 (Ls ~ 290°) [2]. Although the full lifecycle of Titan’s polar hood cloud has not been observed, the Cassini mission provided observations of the north polar hood from mid-winter through northern spring, as well as observations of south polar clouds that started forming early in southern fall. In 2012 (Ls ~ 32°), near-infrared imagery from early southern fall revealed the formation of a vast south polar cloud near the top of the stratosphere, over 150 km higher than any previously observed cloud [3,4]. By combining observations of south polar fall with observations of north polar winter and spring, others have started to construct a story of the formation, evolution, and dissipation of Titan’s polar hood [1]. Despite the polar hood cloud’s optical thickness, details of the cloud composition remain vague. While signs of HCN, benzene, and cyanoacetylene ices have been identified in this fall south polar cloud, and radiative transfer retrievals indicate the presence of mixed ices, the abundances of less radiatively active species like methane or ethane is not as well constrained [2]. We contribute to the story of the polar hood lifecycle using a combination of cloud microphysical modeling and image analysis [5,6]. Through careful analysis of imagery, we track south polar cloud’s spatial evolution and find that it descends from an altitude of about 300 km in 2012 to below 230 km by 2016 (Ls = 79°), while expanding equatorward following the terminator [6]. We show using microphysical modeling that a pure HCN cloud with the observed characteristics [3,4] requires temperatures below 110 K at an altitude of 300 km over the pole [5]. Finally, using simulations of several additional volatile species, we trace the evolving chemical composition, and estimate the impact of condensation and precipitation on the stratospheric volatile budget.[1] Le Mouelic et al. 2018, Icarus, 311, 371–383. [2] Anderson et al. 2018, Space Sci Rev, 214, 125. [3] West et al. 2016, Icarus, 270, 399. [4] de Kok et al. 2014, Nature, 514, 65. [5] Hanson et al. 2023, Planetary Sci J, 4, 237. [6] Hanson et al. 2025, Geophys Res Lett, 52, e2024GL113415.

  PublisherDOI

• Intraurban variability of the summertime diurnal temperature range in Baltimore, Maryland

  Environmental Research Health · 2025-07-17

  articleOpen accessCorresponding

  Abstract Recent studies have shown that exposure to extreme temperature changes within one day is associated with increased morbidity and mortality. While heat and its variation spatially within cities has been well-studied, the spatial variability of the diurnal temperature range (DTR) is not well characterized. Here we use air temperature data from a network of ∼50 iButton sensors deployed in Baltimore, Maryland over multiple summers between 2016 and 2023 to characterize the spatial variations in DTR. The DTR has a distinct spatial structure compared to T max and T min , with DTR having a more complex spatial distribution with high values both within and outside the city. Additionally, while the spatial variations of T min and T max are correlated with land characteristics, such as elevation and vegetation, there are no such relationships for DTR. It is suggested that the disconnect between DTR and T max or T min occurs because DTR depends primarily on the local (∼ 5 m) rather than neighborhood scale variations in land characteristics. The measured DTR depends on placement of sensor related to forested areas and pavement and can vary as much as 3 °C–4°C between sensors. The differing spatial variation of DTR from T min and T max at the scale of the city means health studies should consider DTR as an independent risk factor from T max and T min . Further, the wide range of DTR measured within Baltimore and the sensitivity of DTR to the local environment indicates that caution is needed when using DTR from a single measurement station in health or urban planning studies, as the DTR at the station may not be representative of DTR experienced by the city population.

  PublisherDOI

• Transient and Seasonal Response of Southern Ocean Sea Surface Temperature and Antarctic Sea Ice to Stratospheric Ozone Recovery

  Journal of Climate · 2025-03-13 · 2 citations

  articleOpen accessSenior author

  Abstract This study investigates the response of the Southern Ocean sea surface temperature (SST) and Antarctic sea ice to stratospheric ozone recovery, focusing on the time scale and seasonality of the response. The response is quantified by contrasting two twenty-first-century ensemble simulations conducted with the Goddard Earth Observing System Chemistry–Climate Model: one with decreasing ozone-depleting substances (ODSs) and the other with fixed 2005 levels of ODSs. In our simulations, the response to ozone recovery has large seasonal variations, but it does not show a two-time-scale behavior. Ozone recovery causes Southern Ocean SST warming in austral summer and cooling in other seasons. Ozone recovery mitigates Antarctic sea ice decrease in the twenty-first century in austral spring, fall, and winter. However, the summer Antarctic sea ice extent is not affected by ozone recovery despite strong surface warming, because the warming occurs north of the sea ice edge. The absence of summer sea ice response likely results from the model bias of underestimating summer sea ice climatology. The summer surface warming response is associated with cooling directly below the mixed layer. Temperature tendency budget analysis shows that reduced vertical mixing plays a critical role in driving this vertical dipole temperature response. We also find that the impact of the vertical temperature advection on SST depends not only on changes in upwelling but also on changes in vertical temperature gradient. Significance Statement We study the climate impact of the projected stratospheric ozone recovery in the twenty-first century on Southern Ocean sea surface temperature and Antarctic sea ice using coupled atmosphere–ocean–chemistry model simulations. The model results show that ozone recovery causes weakening of surface winds over the Southern Ocean, which leads to warming of the Southern Ocean surface in summer and cooling in other seasons. Ozone recovery also reduces Antarctic sea ice loss in the twenty-first century. We quantify the relative importance of meridional and vertical advection and vertical mixing in determining the upper Southern Ocean temperature response to stratospheric ozone recovery. These results improve our understanding of how changes in surface winds affect the Southern Ocean temperature, circulation, and Antarctic sea ice.

  PublisherOA PDFDOI

• The Baltimore Social-Environmental Collaborative (BSEC): Equitable solutions for climate adaptation in Baltimore City

  2025-05-21

  preprintOpen accessCorresponding

  This presentation will provide an overview of the Baltimore Social-Environmental Collaborative (BSEC), a DOE-funded Urban Integrated Field Laboratory (IFL) based in Baltimore, Maryland USA. BSEC seeks a new paradigm for urban climate research. Inspired by the Urban Integrated Field Laboratory call to provide knowledge that informs equitable solutions that can strengthen community-scale resilience, we are building a people-centered, transdisciplinary IFL. BSEC begins with community priorities (human health and safety, affordable energy, transportation equity, and others) and city government priorities (clean waterways, decarbonization, functioning infrastructure) and designs observation networks and models that will deliver the climate science capable of supporting those priorities. This means that BSEC takes the form of an iterative collaborative cycle, in which an initial observation and modeling strategy is continuously updated in conversation with community partners. The guiding objective of this cycle is to produce the urban climate science needed to inform community-guided “potential equitable pathways” for climate action. In doing so, we address a number of fundamental urban science questions from across natural science and social science disciplines. This presentation will discuss BSEC principles and structure, the urban science questions been addressed, and present examples of engagement with stakeholders and decision-makers, community-driven approaches to climate mitigation and adaptation, community education and engagement, and scientific results.

  PublisherDOI

• The Titan Middle Atmosphere Intercomparison Project

  2025-07-09

  preprintOpen accessCorresponding

  The atmosphere of Titan, the largest moon of Saturn, is unique in the Solar System. Like Earth, its atmosphere is mostly composed of molecular nitrogen, though unlike Earth, there is no molecular oxygen and instead the second most abundant molecule is methane. The interactions between the products of the photodissociation of these two dominant molecules give rise to a complex suite of hydrocarbons (molecules of the form CxHy) and nitriles (CxHyNz) [1]. Continued reactions (through their collision and agglomeration) between these species ultimately lead to Titan’s characteristic orange haze, which shields Titan’s surface from most shortwave sunlight. Akin to the absorption of ultraviolet light by Earth’s stratospheric ozone, shortwave radiative heating by Titan’s haze and methane leads to the formation of Titan’s stratopause, the local thermal maximum that separates the stratosphere (about 40 to 250 km above the surface) and mesosphere (about 250 to 600 km above the surface).Across all latitudes, the zonal winds in Titan’s middle atmosphere are westerly, exclusively blowing from the west towards the east, and have been inferred to reach speeds up to ~280 m/s [2,3,4]. This is in stark contrast to the zonal winds of Earth’s stratosphere, which include both westerly and easterly blowing winds. The maintenance of Titan’s stratospheric superrotation is thought to be by the Gierasch-Rossow-Williams mechanisms [5,6]: Zonal angular momentum is delivered to the stratosphere from ascending motion from the surface and then transported to the high latitude by the meridional circulation; this transport is then balanced by the transport of zonal momentum equatorward by atmospheric eddies, likely made up of Rossby-Kelvin waves [7,8,9].Trace molecules (e.g., C2H6, C2H4, C2H2, HCN) in Titan’s stratosphere are enriched above the winter pole, in some cases by several orders of magnitude [10,11]. The enrichment is generally thought to be driven by the descending branch of Titan’s meridional overturning circulation delivering molecules from their high-altitude source region into the lower stratosphere. Once delivered to the high-latitude stratosphere, the molecules are thought to be trapped by the strong stratospheric jet. Some molecules (e.g., C2H6) exhibit ‘tongues’ extending away from the high latitude, suggestive of mixing processes transporting high latitude air into the mid latitudes [12]. This, however, has yet to be confirmed.In this presentation, we directly compare three Titan general circulation models (GCM) to determine the characteristics of Titan’s middle atmosphere that are robustly present across different model assumptions and parameterizations. Included in this intercomparison are the Titan Atmospheric Model (TAM, [13]), Titan Planetary Climate Model (Titan PCM, [14]), and TitanWRF [9]. This intercomparison of fully three-dimensional GCMs aims to provide the first multi-model resource to explain the observed seasonal-scale changes in Titan’s middle atmospheric thermal, dynamical, and compositional structure.References[1] Vuitton et al., Icarus, 2019[2] Sharkey et al., Icarus, 2021[3] Achterberg, PSJ, 2023[4] Vinatier et al., A&A, 2020[5] Gierash, JAS, 1975[6] Rossow & Williams, JAS, 1979[7] Lombardo & Lora, JGR: Planets, 2023[8] Lewis et al., PSJ, 2023[9] Lian et al., Icarus, 2025[10] Teanby et al., GRL, 2019[11] Mathe et al., Icarus, 2020[12] Shultis et al., PSJ, 2022[13] Lombardo & Lora, Icarus, 2023[14] de Batz de Trenquelléon, et al., PSJ, 2025

  PublisherDOI

Recent grants

• Multi-Model Analysis of Stratospheric Chemistry-Climate Couplings

  NSF · $364k · 2009–2013

• Collaborative Research: Global Estimates of Past and Future Uptake of Anthropogenic Carbon by the Ocean

  NSF · $243k · 2006–2011

• Impact of Stratospheric Ozone on Antarctica and the Southern Ocean

  NSF · $410k · 2011–2015

• Hadley Cell and Subtropical Jet: Dynamics and Tracer Transport

  NSF · $568k · 2019–2024

• Collaborative Research: The Dynamical Influence of the Stratosphere on the Troposphere

  NSF · $274k · 2005–2008

Frequent coauthors

• A. R. Douglass

  Goddard Space Flight Center

  111 shared

• D. E. Kinnison

  NSF National Center for Atmospheric Research

  100 shared

• David B. Considine

  85 shared

• Lawrence Coy

  Goddard Space Flight Center

  84 shared

• S. R. Kawa

  83 shared

• Michael J. Prather

  University of California, Irvine

  83 shared

• Philip J. Rasch

  Pacific Northwest National Laboratory

  82 shared

• Steven L. Baughcum

  Boeing (Australia)

  82 shared

Labs

• Waugh Research GroupPI