@article{fu_hu_zheng_mcmonigal_larson_tian_2024, title={Historical changes in wind-driven ocean circulation drive pattern of Pacific warming}, volume={15}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-024-45677-2}, abstractNote={AbstractThe tropical Pacific warming pattern since the 1950s exhibits two warming centers in the western Pacific (WP) and eastern Pacific (EP), encompassing an equatorial central Pacific (CP) cooling and a hemispheric asymmetry in the subtropical EP. The underlying mechanisms of this warming pattern remain debated. Here, we conduct ocean heat decompositions of two coupled model large ensembles to unfold the role of wind-driven ocean circulation. When wind changes are suppressed, historical radiative forcing induces a subtropical northeastern Pacific warming, thus causing a hemispheric asymmetry that extends toward the tropical WP. The tropical EP warming is instead induced by the cross-equatorial winds associated with the hemispheric asymmetry, and its driving mechanism is southward warm Ekman advection due to the off-equatorial westerly wind anomalies around 5°N, not vertical thermocline adjustment. Climate models fail to capture the observed CP cooling, suggesting an urgent need to better simulate equatorial oceanic processes and thermal structures.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Fu, Shuo and Hu, Shineng and Zheng, Xiao-Tong and Mcmonigal, Kay and Larson, Sarah and Tian, Yiqun}, year={2024}, month={Feb} }
 @article{sutton_larson_becker_2024, title={New insights on ENSO teleconnection asymmetry and ENSO forced atmospheric circulation variability over North America}, ISSN={["1432-0894"]}, DOI={10.1007/s00382-023-07058-1}, journal={CLIMATE DYNAMICS}, author={Sutton, Margaret and Larson, Sarah M. and Becker, Emily}, year={2024}, month={Jan} }
 @article{zhang_chen_hu_wang_mcmonigal_larson_2024, title={Summer Westerly Wind Intensification Weakens Southern Ocean Seasonal Cycle Under Global Warming}, volume={51}, ISSN={["1944-8007"]}, DOI={10.1029/2024GL109715}, abstractNote={Abstract Since the 1950s, observations and climate models show an amplification of sea surface temperature (SST) seasonal cycle in response to global warming over most of the global oceans except for the Southern Ocean (SO), however the cause remains poorly understood. In this study, we analyzed observations, ocean reanalysis, and a set of historical and abruptly quadrupled CO 2 simulations from the Coupled Model Intercomparison Project Phase 6 archive and found that the weakened SST seasonal cycle over the SO could be mainly attributed to the intensification of summertime westerly winds. Under the historical warming, the intensification of summertime westerly winds over the SO effectively deepens ocean mixed layer and damps surface warming, but this effect is considerably weaker in winter, thus weakening the SST seasonal cycle. This wind‐driven mechanism is further supported by our targeted coupled model experiments with the wind intensification effects being removed.}, number={14}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Zhang, Yiwen and Chen, Changlin and Hu, Shineng and Wang, Guihua and Mcmonigal, Kay and Larson, Sarah M.}, year={2024}, month={Jul} }
 @article{mcmonigal_larson_hu_kramer_2023, title={Historical Changes in Wind-Driven Ocean Circulation Can Accelerate Global Warming}, volume={50}, ISSN={["1944-8007"]}, DOI={10.1029/2023GL102846}, abstractNote={AbstractMitigation and adaptation strategies for climate change depend on accurate climate projections for the coming decades. While changes in radiative heat fluxes are known to contribute to surface warming, changes to ocean circulation can also impact the rate of surface warming. Previous studies suggest that projected changes to ocean circulation reduce the rate of global warming. However, these studies consider large greenhouse gas forcing scenarios, which induce a significant buoyancy‐driven decline of the Atlantic Meridional Overturning Circulation. Here, we use a climate model to quantify the previously unknown impact of changes to wind‐driven ocean circulation on global surface warming. Wind‐driven ocean circulation changes amplify the externally forced warming rate by 17% from 1979 to 2014. Accurately simulating changes to the atmospheric circulation is key to improving near‐term climate projections.}, number={4}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={McMonigal, Kay and Larson, Sarah and Hu, Shineng and Kramer, Ryan}, year={2023}, month={Feb} }
 @article{bellomo_meccia_d'agostino_fabiano_larson_hardenberg_corti_2023, title={Impacts of a weakened AMOC on precipitation over the Euro-Atlantic region in the EC-Earth3 climate model}, ISSN={["1432-0894"]}, DOI={10.1007/s00382-023-06754-2}, abstractNote={AbstractGiven paleoclimatic evidence that the Atlantic Meridional Overturning Circulation (AMOC) may affect the global climate system, we conduct model experiments with EC-Earth3, a state-of-the-art GCM, to specifically investigate, for the first time, mechanisms of precipitation change over the Euro-Atlantic sector induced by a weakened AMOC. We artificially weaken the strength of the AMOC in the model through the release of a freshwater anomaly into the Northern Hemisphere high latitude ocean, thereby obtaining a ~ 57% weaker AMOC with respect to its preindustrial strength for 60 model years. Similar to prior studies, we find that Northern Hemisphere precipitation decreases in response to a weakened AMOC. However, we also find that the frequency of wet days increases in some regions. By computing the atmospheric moisture budget, we find that intensified but drier storms cause less precipitation over land. Nevertheless, changes in the jet stream tend to enhance precipitation over northwestern Europe. We further investigate the association of precipitation anomalies with large-scale atmospheric circulations by computing weather regimes through clustering of geopotential height daily anomalies. We find an increase in the frequency of the positive phase of the North Atlantic Oscillation (NAO+), which is associated with an increase in the occurrence of wet days over northern Europe and drier conditions over southern Europe. Since a ~ 57% reduction in the AMOC strength is within the inter-model range of projected AMOC declines by the end of the twenty-first century, our results have implications for understanding the role of AMOC in future hydrological changes.}, journal={CLIMATE DYNAMICS}, author={Bellomo, Katinka and Meccia, Virna L. and D'Agostino, Roberta and Fabiano, Federico and Larson, Sarah M. and Hardenberg, Jost and Corti, Susanna}, year={2023}, month={Mar} }
 @article{shu_zhang_maya_larson_kosaka_yang_lin_2023, title={Role of Ocean Advections during the Evolution of the Pacific Meridional Modes}, volume={36}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-22-0296.1}, abstractNote={Abstract
The Pacific meridional modes (PMMs) are the leading ocean–atmosphere coupled modes in the subtropical northeastern (NPMM) and southeastern (SPMM) Pacific, respectively, and have been suggested to be key precursors to equatorial Pacific variability. Previous studies pointed out that both NPMM- and SPMM-related sea surface temperature (SST) anomalies are primarily driven by net surface heat flux variations during their equatorward evolution. However, whether oceanic heat advective processes would play a role during the evolution remains unclear. To address this issue, we perform an ocean mixed layer heat budget analysis based on observations and three ocean reanalysis datasets, and then reveal the effect of ocean advections on the evolution by comparing a fully coupled dynamic ocean model (DOM) to a slab ocean model (SOM). Our results suggest that for the NPMM evolution, ocean advections—primarily by anomalous meridional Ekman heat advections driven by mean and anomalous zonal wind stresses—play a damping role in the south of the NPMM. Thus, the NPMM SST anomalies appear to instead exhibit a poleward shift, although still freely propagating westward from the preceding boreal winter to the following summer. This finding challenges the traditional view that the NPMM propagates equatorward through the wind–evaporation–SST feedback. For the SPMM evolution, ocean advections play a damping role in the center of the SPMM from boreal spring to summer, as well as an intensification role in the southwest Pacific during summer. However, the effect of the intensification on the SPMM evolution is hard to determine due to the strong simulation bias of the SPMM evolution in the DOM.

Significance Statement
While it is known that both NPMM- and SPMM-associated SST anomalies are primarily driven by net surface heat flux variations during their evolution, whether ocean advections would play a role remains unknown. Here, we show that ocean advections play a role in the evolution of both PMMs. In particular, for the NPMM evolution, ocean advections play a damping role in the south of the NPMM center, causing a tendency for the NPMM to be displaced northward. The role of ocean advection challenges the prevailing notion that the NPMM simply evolves equatorward through the wind–evaporation–SST feedback.}, number={13}, journal={JOURNAL OF CLIMATE}, author={Shu, Qi and Zhang, Yu and Maya, Dillon J. A. and Larson, Sarah M. and Kosaka, Yu and Yang, Jun-chao and Lin, Xiaopei}, year={2023}, month={Jul}, pages={4327–4343} }
 @article{larson_mcdonald_2023, title={Taxation and citizen choice: The effect of a county charter on property taxes}, volume={1}, ISSN={["1540-5850"]}, url={https://doi.org/10.1111/pbaf.12336}, DOI={10.1111/pbaf.12336}, abstractNote={AbstractAs saliency of the tax burden increases, the preference for a lower burden increases, but most counties are restricted by the state from adopting new taxes or changing the existing rates. Some states allow counties to adopt a charter, freeing them from state control. Using a panel of Florida counties from 1980 to 2017, we explore whether citizens act to reduce their property tax once a charter is passed. Citizens act against their preferences not by lowering burden but rather by increasing it in the case of debt service, suggesting citizens are maximizing their optimal tax burden in exchange for services.}, journal={PUBLIC BUDGETING AND FINANCE}, author={Larson, Sarah E. and McDonald, Bruce D.}, year={2023}, month={Jan} }
 @article{larson_okumura_bellomo_breeden_2022, title={Destructive Interference of ENSO on North Pacific SST and North American Precipitation Associated with Aleutian Low Variability}, volume={35}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-21-0560.1}, abstractNote={Abstract
Identifying the origins of wintertime climate variations in the Northern Hemisphere requires careful attribution of the role of El Niño–Southern Oscillation (ENSO). For example, Aleutian low variability arises from internal atmospheric dynamics and is remotely forced mainly via ENSO. How ENSO modifies the local sea surface temperature (SST) and North American precipitation responses to Aleutian low variability remains unclear, as teasing out the ENSO signal is difficult. This study utilizes carefully designed coupled model experiments to address this issue. In the absence of ENSO, a deeper Aleutian low drives a positive Pacific decadal oscillation (PDO)-like SST response. However, unlike the observed PDO pattern, a coherent zonal band of turbulent heat flux–driven warm SST anomalies develops throughout the subtropical North Pacific. Furthermore, non-ENSO Aleutian low variability is associated with a large-scale atmospheric circulation pattern confined over the North Pacific and North America and dry precipitation anomalies across the southeastern United States. When ENSO is included in the forcing of Aleutian low variability in the experiments, the ENSO teleconnection modulates the turbulent heat fluxes and damps the subtropical SST anomalies induced by non-ENSO Aleutian low variability. Inclusion of ENSO forcing results in wet precipitation anomalies across the southeastern United States, unlike when the Aleutian low is driven by non-ENSO sources. Hence, we find that the ENSO teleconnection acts to destructively interfere with the subtropical North Pacific SST and southeastern United States precipitation signals associated with non-ENSO Aleutian low variability.}, number={11}, journal={JOURNAL OF CLIMATE}, author={Larson, Sarah M. and Okumura, Yuko and Bellomo, Katinka and Breeden, Melissa L.}, year={2022}, month={Jun}, pages={3567–3585} }
 @article{mcmonigal_larson_2022, title={ENSO Explains the Link Between Indian Ocean Dipole and Meridional Ocean Heat Transport}, volume={49}, ISSN={["1944-8007"]}, DOI={10.1029/2021GL095796}, abstractNote={AbstractIndian Ocean meridional heat transport (MHTIO) drives climate and ecosystem impacts, through changes to ocean temperature. Improved understanding of natural variability in tropical and subtropical MHTIO is needed to contextualize observations and future projections. Previous studies suggest that El Niño‐Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) can drive variability in MHTIO. However, it is unclear whether internally generated IOD can drive variability in MHTIO, or if the apparent relationship between IOD and MHTIO arises because both are modulated by ENSO. Here, we use a model experiment which dynamically removes ENSO to determine the role of internally forced IOD on MHTIO. We find that IOD is not linked to anomalies in MHTIO. Nevertheless, internal atmospheric variability drives significant MHTIO variability. There is little evidence for decadal or multidecadal variability in MHTIO, suggesting this may be a region where an anthropogenic trend rises above the level of internal variability sooner.}, number={2}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={McMonigal, K. and Larson, Sarah M.}, year={2022}, month={Jan} }
 @article{hasan_larson_mcmonigal_2022, title={Hadley Cell Edge Modulates the Role of Ekman Heat Flux in a Future Climate}, volume={49}, ISSN={["1944-8007"]}, DOI={10.1029/2022GL100401}, abstractNote={AbstractIn a future climate, the Hadley cell and associated trade easterlies are projected to expand poleward. This projected change in the atmospheric circulation is expected to impact the ocean through changes in the mean sea surface temperature (SST). We also expect implications for the large‐scale SST variability, because near‐surface wind is directly related to two drivers of the SST, that is, turbulent heat flux and anomalous wind‐driven Ekman heat flux. Previous studies show that in the subtropics, anomalous turbulent and Ekman heat fluxes oppose each other, acting to reduce SST variability, whereas, in the midlatitudes, they reinforce each other and enhance SST variability. Through analysis of reanalysis products and Coupled Model Intercomparison Project simulations, we find that the subtropical regions where the fluxes oppose each other are projected to expand poleward in a future climate, following the poleward expansion of the Hadley cell, with potential implications for the amplitude of subtropical SST variability.}, number={17}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Hasan, Mahdi and Larson, Sarah and McMonigal, Kay}, year={2022}, month={Sep} }
 @article{lee_lopez_foltz_lim_kim_larson_pujiana_volkov_chakravorty_gomez_2022, title={Java-Sumatra Ni (n)over-tilde no/Ni (n)over-tilde na and Its Impact on Regional Rainfall Variability}, volume={35}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-21-0616.1}, abstractNote={Abstract
A phenomenon referred to here as Java–Sumatra Niño/Niña (JSN or JS Niño/Niña) is characterized by the appearance of warm/cold sea surface temperature anomalies (SSTAs) in the coastal upwelling region off Java–Sumatra in the southeastern equatorial Indian Ocean. JSN develops in July–September and sometimes as a precursor to the Indian Ocean dipole, but often without corresponding SSTAs in the western equatorial Indian Ocean. Although its spatiotemporal evolution varies considerably between individual events, JSN is essentially an intrinsic mode of variability driven by local atmosphere–ocean positive feedback, and thus does not rely on remote forcing from the Pacific for its emergence. JSN is an important driver of climate variability over the tropical Indian Ocean and the surrounding continents. Notably, JS Niña events developing in July–September project onto the South and Southeast Asian summer monsoons, increasing the probability of heavy rainfall and flooding across the most heavily populated regions of the world.}, number={13}, journal={JOURNAL OF CLIMATE}, author={Lee, Sang-Ki and Lopez, Hosmay and Foltz, Gregory R. and Lim, Eun-Pa and Kim, Dongmin and Larson, Sarah M. and Pujiana, Kandaga and Volkov, Denis L. and Chakravorty, Soumi and Gomez, Fabian A.}, year={2022}, month={Jul}, pages={4291–4308} }
 @article{zhang_yu_xie_amaya_peng_kosaka_lin_yang_larson_miller_et al._2022, title={Role of ocean dynamics in equatorial Pacific decadal variability}, ISSN={["1432-0894"]}, DOI={10.1007/s00382-022-06312-2}, journal={CLIMATE DYNAMICS}, author={Zhang, Yu and Yu, Shi-Yun and Xie, Shang-Ping and Amaya, Dillon J. and Peng, Qihua and Kosaka, Yu and Lin, Xiaopei and Yang, Jun-Chao and Larson, Sarah M. and Miller, Arthur J. and et al.}, year={2022}, month={May} }
 @article{chakravorty_perez_anderson_larson_giese_pivotti_2021, title={Ocean Dynamics are Key to Extratropical Forcing of El Nino}, volume={34}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-20-0933.1}, abstractNote={AbstractEl Niño–Southern Oscillation (ENSO) has been recently linked with extratropical Pacific Ocean atmospheric variability. The two key mechanisms connecting the atmospheric variability of the extratropical Pacific with ENSO are the heat flux–driven “seasonal footprinting mechanism” (SFM) and the ocean dynamics–driven “trade wind charging” (TWC) mechanism. However, their relative contributions to ENSO are still unknown. Here we present modeling evidence that the positive phase of the SFM generates a weaker, short-lived central Pacific El Niño–like warming pattern in the autumn, whereas the TWC positive phase leads to a wintertime eastern Pacific El Niño–like warming. When both mechanisms are active, a strong, persistent El Niño develops. While both mechanisms can trigger equatorial wind anomalies that generate an El Niño, the strength and persistence of the warming depends on the subsurface heat content buildup by the TWC mechanism. These results suggest that while dynamical coupling associated with extratropical forcing is crucial to maintain an El Niño, thermodynamical coupling is an extratropical source of El Niño diversity.}, number={21}, journal={JOURNAL OF CLIMATE}, author={Chakravorty, Soumi and Perez, Renellys C. and Anderson, Bruce T. and Larson, Sarah M. and Giese, Benjamin S. and Pivotti, Valentina}, year={2021}, month={Nov}, pages={8739–8753} }
 @article{zhang_yu_amaya_kosaka_larson_wang_yang_stuecker_xie_miller_et al._2021, title={Pacific Meridional Modes without Equatorial Pacific Influence}, volume={34}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-20-0573.1}, abstractNote={AbstractInvestigating Pacific Meridional Modes (PMM) without the influence of tropical Pacific variability is technically difficult if based on observations or fully coupled model simulations due to their overlapping spatial structures. To confront this issue, the present study investigates both North (NPMM) and South PMM (SPMM) in terms of their associated atmospheric forcing and response processes based on a mechanically decoupled climate model simulation. In this experiment, the climatological wind stress is prescribed over the tropical Pacific, which effectively removes dynamically coupled tropical Pacific variability (e.g., the El Niño-Southern Oscillation). Interannual NPMM in this experiment is forced not only by the North Pacific Oscillation, but also by a North Pacific tripole (NPT) pattern of atmospheric internal variability, which primarily forces decadal NPMM variability. Interannual and decadal variability of the SPMM is partly forced by the South Pacific Oscillation. In turn, both interannual and decadal NPMM variability can excite atmospheric teleconnections over the Northern Hemisphere extratropics by influencing the meridional displacement of the climatological intertropical convergence zone throughout the whole year. Similarly, both interannual and decadal SPMM variability can also excite atmospheric teleconnections over the Southern Hemisphere extratropics by extending/shrinking the climatological South Pacific convergence zone in all seasons. Our results highlight a new poleward pathway by which both the NPMM and SPMM feed back to the extratropical climate, in addition to the equatorward influence on tropical Pacific variability.}, number={13}, journal={JOURNAL OF CLIMATE}, author={Zhang, Yu and Yu, Shiyun and Amaya, Dillon J. and Kosaka, Yu and Larson, Sarah M. and Wang, Xudong and Yang, Jun-Chao and Stuecker, Malte F. and Xie, Shang-Ping and Miller, Arthur J. and et al.}, year={2021}, month={Jul}, pages={5285–5301} }
 @article{capotondi_deser_phillips_okumura_larson_2020, title={ENSO and Pacific Decadal Variability in the Community Earth System Model Version 2}, volume={12}, ISSN={["1942-2466"]}, DOI={10.1029/2019MS002022}, abstractNote={AbstractThis study presents a description of the El Niño–Southern Oscillation (ENSO) and Pacific Decadal Variability (PDV) in a multicentury preindustrial simulation of the Community Earth System Model Version 2 (CESM2). The model simulates several aspects of ENSO relatively well, including dominant timescale, tropical and extratropical precursors, composite evolution of El Niño and La Niña events, and ENSO teleconnections. The good model representation of ENSO spectral characteristics is consistent with the spatial pattern of the anomalous equatorial zonal wind stress in the model, which results in the correct adjustment timescale of the equatorial thermocline according to the delayed/recharge oscillator paradigms, as also reflected in the realistic time evolution of the equatorial Warm Water Volume. PDV in the model exhibits a pattern that is very similar to the observed, with realistic tropical and South Pacific signatures which were much weaker in some of the CESM2 predecessor models. The tropical component of PDV also shows an association with ENSO decadal modulation which is similar to that found in observations. However, the ENSO amplitude is about 30% larger than observed in the preindustrial CESM2 simulation, and even larger in the historical ensemble, perhaps as a result of anthropogenic influences. In contrast to observations, the largest variability is found in the central Pacific rather than in the eastern Pacific, a discrepancy that somewhat hinders the model's ability to represent a full diversity in El Niño spatial patterns and appears to be associated with an unrealistic confinement of the precipitation anomalies to the western Pacific.}, number={12}, journal={JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS}, author={Capotondi, A. and Deser, C. and Phillips, A. S. and Okumura, Y. and Larson, S. M.}, year={2020}, month={Dec} }
 @article{larson_buckley_clement_2020, title={Extracting the Buoyancy-Driven Atlantic Meridional Overturning Circulation}, volume={33}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-19-0590.1}, abstractNote={AbstractVariations in the Atlantic meridional overturning circulation (AMOC) driven by buoyancy forcing are typically characterized as having a low-frequency time scale, interhemispheric structure, cross-equatorial heat transport, and linkages to the strength of Northern Hemisphere gyre circulations and the Gulf Stream. This study first tests whether these attributes ascribed to the AMOC are reproduced in a coupled model that is mechanically decoupled and, hence, is only buoyancy coupled. Overall, the mechanically decoupled model reproduces these attributes, with the exception that in the subpolar gyre, buoyancy drives AMOC variations on interannual to multidecadal time scales, yet only the multidecadal variations penetrate into the subtropics. A stronger AMOC is associated with a strengthening of the Northern Hemisphere gyre circulations, Gulf Stream, and northward oceanic heat transport throughout the basin. We then determine whether the characteristics in the mechanically decoupled model can be recovered by low-pass filtering the AMOC in a fully coupled version of the same model, a common approach used to isolate the buoyancy-driven AMOC. A major conclusion is that low-pass filtering the AMOC in the fully coupled model reproduces the buoyancy-driven AMOC pattern and most of the associated attributes, but not the statistics of the temporal variability. The strength of the AMOC–Gulf Stream connection is also not reproduced. The analyses reveal caveats that must be considered when choosing indexes and filtering techniques to estimate the buoyancy-driven AMOC. Results also provide insight on the latitudinal dependence of time scales and drivers of ocean circulation variability in coupled models, with potential implications for measurement and detection of the buoyancy-driven AMOC in the real world.}, number={11}, journal={JOURNAL OF CLIMATE}, author={Larson, Sarah M. and Buckley, Martha W. and Clement, Amy C.}, year={2020}, month={Jun}, pages={4697–4714} }
 @article{mcdonald_larson_2020, title={Implications of the Coronavirus on Sales Tax Revenue and Local Government Fiscal Health}, volume={6}, ISSN={["2381-3717"]}, url={https://doi.org/10.20899/jpna.6.3.377-400}, DOI={10.20899/jpna.6.3.377-400}, abstractNote={The outbreak of COVID—19 has raised considerable alarm about public health and safety. The response to the outbreak, however, has also brought concern regarding its impact on local governments in the United States. Local governments have been a primary respondent in the fight against the COVID—19 disease, but the response has also reduced income from a key source of revenue, sales tax. Using North Carolina counties as a case study, we explore the shock to sales and use tax revenue faced by local governments from COVID—19; we, then, estimate its impact on county fiscal health. Our results show that while many local governments were financially struggling before the outbreak, the drop in sales tax revenue severely threatens their ability to provide continued response to the virus as well as their ability to remain solvent.}, number={3}, journal={JOURNAL OF PUBLIC AND NONPROFIT AFFAIRS}, author={McDonald, Bruce D., III and Larson, Sarah E.}, year={2020}, pages={377–400} }
 @article{chakravorty_perez_anderson_giese_larson_pivotti_2020, title={Testing the Trade Wind Charging Mechanism and Its Influence on ENSO Variability}, volume={33}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-19-0727.1}, abstractNote={AbstractDuring the positive phase of the North Pacific Oscillation, westerly wind anomalies over the subtropical North Pacific substantially increase subsurface heat content along the equator by “trade wind charging” (TWC). TWC provides a direct pathway between extratropical atmospheric circulation and El Niño–Southern Oscillation (ENSO) initiation. Previous model studies of this mechanism lacked the ocean–atmospheric coupling needed for ENSO growth, so it is crucial to examine whether TWC-induced heat content anomalies develop into ENSO events in a coupled model. Here, coupled model experiments, forced with TWC favorable (+TWC) or unfavorable (−TWC) wind stress, are used to examine the ENSO response to TWC. The forcing is imposed on the ocean component of the model through the first winter and then the model evolves in a fully coupled configuration through the following winter. The +TWC (−TWC) forcing consistently charges (discharges) the equatorial Pacific in spring and generates positive (negative) subsurface temperature anomalies. These subsurface temperature anomalies advect eastward and upward along the equatorial thermocline and emerge as like-signed sea surface temperature (SST) anomalies in the eastern Pacific, creating favorable conditions upon which coupled air–sea feedback can act. During the fully coupled stage, warm SST anomalies in +TWC forced simulations are amplified by coupled feedbacks and lead to El Niño events. However, while −TWC forcing results in cool SST anomalies, pre-existing warm SST anomalies in the far eastern equatorial Pacific persist and induce local westerly wind anomalies that prevent consistent development of La Niña conditions. While the TWC mechanism provides adequate equatorial heat content to fuel ENSO development, other factors also play a role in determining whether an ENSO event develops.}, number={17}, journal={JOURNAL OF CLIMATE}, author={Chakravorty, Soumi and Perez, Renellys C. and Anderson, Bruce T. and Giese, Benjamin S. and Larson, Sarah M. and Pivotti, Valentina}, year={2020}, month={Sep}, pages={7391–7411} }
 @article{larson_pegion_2020, title={Do asymmetries in ENSO predictability arise from different recharged states?}, volume={54}, ISSN={["1432-0894"]}, DOI={10.1007/s00382-019-05069-5}, number={3-4}, journal={CLIMATE DYNAMICS}, author={Larson, Sarah M. and Pegion, Kathy}, year={2020}, month={Feb}, pages={1507–1522} }
 @article{small_bryan_bishop_larson_tomas_2020, title={What Drives Upper-Ocean Temperature Variability in Coupled Climate Models and Observations?}, volume={33}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-19-0295.1}, abstractNote={AbstractA key question in climate modeling is to what extent sea surface temperature and upper-ocean heat content are driven passively by air–sea heat fluxes, as opposed to forcing by ocean dynamics. This paper investigates the question using a climate model at different resolutions, and observations, for monthly variability. At the grid scale in a high-resolution climate model with resolved mesoscale ocean eddies, ocean dynamics (i.e., ocean heat flux convergence) dominates upper 50 m heat content variability over most of the globe. For deeper depths of integration to 400 m, the heat content variability at the grid scale is almost totally controlled by ocean heat flux convergence. However, a strong dependence on spatial scale is found—for the upper 50 m of ocean, after smoothing the data to around 7°, air–sea heat fluxes, augmented by Ekman heat transports, dominate. For deeper depths of integration to 400 m, the transition scale becomes larger and is above 10° in western boundary currents. Comparison of climate model results with observations show that the small-scale influence of ocean intrinsic variability is well captured by the high-resolution model but is missing from a comparable model with parameterized ocean-eddy effects. In the deep tropics, ocean dynamics dominates in all cases and all scales. In the subtropical gyres at large scales, air–sea heat fluxes play the biggest role. In the midlatitudes, at large scales >10°, atmosphere-driven air–sea heat fluxes and Ekman heat transport variability are the dominant processes except in the western boundary currents for the 400 m heat content.}, number={2}, journal={JOURNAL OF CLIMATE}, author={Small, R. Justin and Bryan, Frank O. and Bishop, Stuart P. and Larson, Sarah and Tomas, Robert}, year={2020}, month={Jan}, pages={577–596} }