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  • 1
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    Influences of Pacific Climate Variability on Decadal Subsurface Ocean Heat Content Variations in the Indian Ocean (2018)
    AMS (American Meteorological Society)
    In:  Journal of Climate, 31 (10). pp. 4157-4174.
    Details
    Publication Date: 2021-02-08
    Description: Decadal variabilities in Indian Ocean subsurface ocean heat content (OHC; 50–300 m) since the 1950s are examined using ocean reanalyses. This study elaborates on how Pacific variability modulates the Indian Ocean on decadal time scales through both oceanic and atmospheric pathways. High correlations between OHC and thermocline depth variations across the entire Indian Ocean Basin suggest that OHC variability is primarily driven by thermocline fluctuations. The spatial pattern of the leading mode of decadal Indian Ocean OHC variability closely matches the regression pattern of OHC on the interdecadal Pacific oscillation (IPO), emphasizing the role of the Pacific Ocean in determining Indian Ocean OHC decadal variability. Further analyses identify different mechanisms by which the Pacific influences the eastern and western Indian Ocean. IPO-related anomalies from the Pacific propagate mainly through oceanic pathways in the Maritime Continent to impact the eastern Indian Ocean. By contrast, in the western Indian Ocean, the IPO induces wind-driven Ekman pumping in the central Indian Ocean via the atmospheric bridge, which in turn modifies conditions in the southwestern Indian Ocean via westward-propagating Rossby waves. To confirm this, a linear Rossby wave model is forced with wind stresses and eastern boundary conditions based on reanalyses. This linear model skillfully reproduces observed sea surface height anomalies and highlights both the oceanic connection in the eastern Indian Ocean and the role of wind-driven Ekman pumping in the west. These findings are also reproduced by OGCM hindcast experiments forced by interannual atmospheric boundary conditions applied only over the Pacific and Indian Oceans, respectively.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/JCLI-D-17-0654.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Ocean Mesoscale and Frontal-Scale Ocean–Atmosphere Interactions and Influence on Large-Scale Climate: A Review (2023)
    AMS (American Meteorological Society)
    Details
    Publication Date: 2024-02-07
    Description: Two decades of high-resolution satellite observations and climate modeling studies have indicated strong ocean–atmosphere coupled feedback mediated by ocean mesoscale processes, including semipermanent and meandrous SST fronts, mesoscale eddies, and filaments. The air–sea exchanges in latent heat, sensible heat, momentum, and carbon dioxide associated with this so-called mesoscale air–sea interaction are robust near the major western boundary currents, Southern Ocean fronts, and equatorial and coastal upwelling zones, but they are also ubiquitous over the global oceans wherever ocean mesoscale processes are active. Current theories, informed by rapidly advancing observational and modeling capabilities, have established the importance of mesoscale and frontal-scale air–sea interaction processes for understanding large-scale ocean circulation, biogeochemistry, and weather and climate variability. However, numerous challenges remain to accurately diagnose, observe, and simulate mesoscale air–sea interaction to quantify its impacts on large-scale processes. This article provides a comprehensive review of key aspects pertinent to mesoscale air–sea interaction, synthesizes current understanding with remaining gaps and uncertainties, and provides recommendations on theoretical, observational, and modeling strategies for future air–sea interaction research.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    What determines the spatial pattern in summer upwelling trends on the U.S. West Coast? (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): C08012, doi:10.1029/2012JC008016.
    Description: Analysis of sea surface temperature (SST) from coastal buoys suggests that the summertime over-shelf water temperature off the U.S. West Coast has been declining during the past 30 years at an average rate of −0.19°C decade−1. This cooling trend manifests itself more strongly off south-central California than off Oregon and northern California. The variability and trend in the upwelling north of off San Francisco are positively correlated with those of the equatorward wind, indicating a role of offshore Ekman transport in the north. In contrast, Ekman pumping associated with wind stress curls better explains the stronger and statistically more significant cooling trend in the south. While the coast-wide variability and trend in SST are strongly correlated with those of large-scale modes of climate variability, they in general fail to explain the southward intensification of the trend in SST and wind stress curl. This result suggests that the local wind stress curl, often topographically forced, may have played a role in the upwelling trend pattern.
    Description: H.S. acknowledges the WHOI supports from the Coastal Research Fund in Support of Scientific Staff, the Penzance Endowed Fund in Support of Assistant Scientists, and the Andrew W. Mellon Foundation Endowed Fund for Innovative Research. K.B. and C.E. acknowledge support by the National Science Foundation through grants OCE-1059632 and OCE 1061434.
    Description: 2013-03-09
    Keywords: Coastal upwelling ; Multidecadal trend ; Wind stress curl
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 4
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    Impact of ocean warm layer thickness on the intensity of hurricane Katrina in a regional coupled model (2013)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Meteorology and Atmospheric Physics 122 (2013): 19-32, doi:10.1007/s00703-013-0275-3.
    Description: The effect of pre-storm subsurface thermal structure on the intensity of hurricane Katrina (2005) is examined using a regional coupled model. The Estimating Circulation and Climate of Ocean (ECCO) ocean state estimate is used to initialize the ocean component of the coupled model, and the source of deficiencies in the simulation of Katrina intensity is investigated in relation to the initial depth of 26°C isotherm (D26). The model underestimates the intensity of Katrina partly due to shallow D26 in ECCO. Sensitivity tests with various ECCO initial fields indicate that the correct relationship between intensity and D26 cannot be derived because D26 variability is underestimated in ECCO. A series of idealized experiments is carried out by modifying initial ECCO D26 to match the observed range. A more reasonable relationship between Katrina’s intensity and pre-storm D26 emerges: the intensity is much more sensitive to D26 than to sea surface temperature (SST). Ocean mixed layer process plays a critical role in modulating inner-core SSTs when D26 is deep, reducing mixed layer cooling and lowering the center pressure of the Katrina. Our result lends strong support to the notion that accurate initialization of pre-storm subsurface thermal structure in prediction models is critical for a skillful forecast of intensity of Katrina and likely other intense storms.
    Description: HS and SPX thank the support from NSF, NOAA, NASA and Japan Agency for Marine-Earth Science and Technology. HS acknowledges support from the Penzance Endowed Fund in Support of Assistant Scientists at WHOI.
    Description: 2014-10-01
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 5
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    ENSO’s impact on the gap wind regions of the eastern tropical Pacific Ocean (2012)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 25 (2012): 3549–3565, doi:10.1175/JCLI-D-11-00320.1.
    Description: The recently released NCEP Climate Forecast System Reanalysis (CFSR) is used to examine the response to ENSO in the northeast tropical Pacific Ocean (NETP) during 1979–2009. The normally cool Pacific sea surface temperatures (SSTs) associated with wind jets through the gaps in the Central American mountains at Tehuantepec, Papagayo, and Panama are substantially warmer (colder) than the surrounding ocean during El Niño (La Niña) events. Ocean dynamics generate the ENSO-related SST anomalies in the gap wind regions as the surface fluxes damp the SSTs anomalies, while the Ekman heat transport is generally in quadrature with the anomalies. The ENSO-driven warming is associated with large-scale deepening of the thermocline; with the cold thermocline water at greater depths during El Niño in the NETP, it is less likely to be vertically mixed to the surface, particularly in the gap wind regions where the thermocline is normally very close to the surface. The thermocline deepening is enhanced to the south of the Costa Rica Dome in the Papagayo region, which contributes to the local ENSO-driven SST anomalies. The NETP thermocline changes are due to coastal Kelvin waves that initiate westward-propagating Rossby waves, and possibly ocean eddies, rather than by local Ekman pumping. These findings were confirmed with regional ocean model experiments: only integrations that included interannually varying ocean boundary conditions were able to simulate the thermocline deepening and localized warming in the NETP during El Niño events; the simulation with variable surface fluxes, but boundary conditions that repeated the seasonal cycle, did not.
    Description: This research was supported by grants from the NOAA office of Global Programs and the NSF Climate and Global Dynamics Division.
    Description: 2012-11-15
    Keywords: North Pacific Ocean ; Atmosphere-ocean interaction ; ENSO ; Thermocline circulation ; Waves, oceanic ; Ocean models
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 6
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    The role of wave dynamics and small-scale topography for downslope wind events in southeast Greenland (2015)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric Sciences 72 (2015): 2786–2805, doi:10.1175/JAS-D-14-0257.1.
    Description: In Ammassalik, in southeast Greenland, downslope winds can reach hurricane intensity and represent a hazard for the local population and environment. They advect cold air down the ice sheet and over the Irminger Sea, where they drive large ocean–atmosphere heat fluxes over an important ocean convection region. Earlier studies have found them to be associated with a strong katabatic acceleration over the steep coastal slopes, flow convergence inside the valley of Ammassalik, and—in one instance—mountain wave breaking. Yet, for the general occurrence of strong downslope wind events, the importance of mesoscale processes is largely unknown. Here, two wind events—one weak and one strong—are simulated with the atmospheric Weather Research and Forecasting (WRF) Model with different model and topography resolutions, ranging from 1.67 to 60 km. For both events, but especially for the strong one, it is found that lower resolutions underestimate the wind speed because they misrepresent the steepness of the topography and do not account for the underlying wave dynamics. If a 5-km model instead of a 60-km model resolution in Ammassalik is used, the flow associated with the strong wind event is faster by up to 20 m s−1. The effects extend far downstream over the Irminger Sea, resulting in a diverging spatial distribution and temporal evolution of the heat fluxes. Local differences in the heat fluxes amount to 20%, with potential implications for ocean convection.
    Description: This study was supported by grants of the National Science Foundation (OCE- 0751554 and OCE-1130008) as well as the Natural Sciences and Engineering Research Council of Canada.
    Description: 2016-01-01
    Keywords: Katabatic winds ; Severe storms ; Air-sea interaction ; Mesoscale processes ; Orographic effects ; Model evaluation/performance
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 7
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    Coupled ocean-atmosphere forecasting at short and medium time scales (2018)
    Sears Foundation for Marine Research
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2017. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 75 (2017): 877-921, doi:10.1357/002224017823523991.
    Description: Recent technological advances over the past few decades have enabled the development of fully coupled atmosphere-ocean modeling prediction systems that are used today to support short-term (days to weeks) and medium-term (10–21 days) needs for both the operational and research communities. We overview the coupling framework, including model components and grid resolution considerations, as well as the coupling physics by examining heat fluxes between atmosphere and ocean, momentum transfer, and freshwater fluxes. These modeling systems can be run as fully coupled atmosphere-ocean and atmosphere-ocean-wave configurations. Examples of several modeling systems applied to complex coastal regions including Madeira Island, Adriatic Sea, Coastal California, Gulf of Mexico, Brazil, and the Maritime Continent are presented. In many of these studies, a variety of field campaigns have contributed to a better understanding of the underlying physics associated with the atmosphere-ocean feedbacks. Examples of improvements in predictive skill when run in coupled mode versus standalone are shown. Coupled model challenges such as model initialization, data assimilation, and earth system prediction are discussed.
    Description: JP acknowledges support from Office of Naval Research (ONR) grant N00014- 10-1-0300. RAA and TAS were supported through the 6.2 NRL Core Project “Coupled Ocean–Wave Prediction System” Program Element #0602435N. HS acknowledges support from ONR (N00014- 15-1-2588), NSF (OCE-f 419235), andNOAA(NA15OAR4310176). AJMwas supported by the NSF Earth System Modeling Program (OCE1419306) and the NOAA Climate Variability and Prediction Program (NA14OAR4310276). LPP is supported by CNPq’s fellowships on scientific productivity (CNPq 304009/2016-4). JA and RC were financially supported by the Oceanic Observatory of Madeira Project (M1420-01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM).
    Keywords: Coupled air-sea modeling
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    A new framework for near‐surface wind convergence over the Kuroshio Extension and Gulf Stream in wintertime : the role of atmospheric fronts (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 45 (2018): 9909-9918, doi:10.1029/2018GL080135.
    Description: It is well known that the wintertime time‐mean surface wind convergence patterns over the Kuroshio Extension and Gulf Stream show significant imprints of the underlying oceanic fronts. Previous studies have suggested that this collocation results from a time‐mean response to sea level pressure forcing from sea surface temperature gradients. However, more recent work has illustrated this phenomenon is heavily influenced by extratropical cyclones, although exact mechanisms are still debated. The purpose of this study is to introduce a new framework that explicitly distinguishes between two separate components in their contribution to the time‐mean surface wind convergence, that associated with and without atmospheric fronts. It is then argued that this distinction can help better explain the mechanisms driving the Kuroshio Extension and Gulf Stream influence on the atmosphere.
    Description: National Science Foundation (NSF); NSF Physical Oceanography program Grant Numbers: AGS‐1355339, OCE‐1419235
    Description: 2019-03-29
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
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    Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region (2020)
    Nature Research
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Liang, Y., Lo, M., Lan, C., Seo, H., Ummenhofer, C. C., Yeager, S., Wu, R., & Steffen, J. D. Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region. Nature Communications, 11(1), (2020): 4390, doi:10.1038/s41467-020-18187-0.
    Description: The Amazon river basin receives ~2000 mm of precipitation annually and contributes ~17% of global river freshwater input to the oceans; its hydroclimatic variations can exert profound impacts on the marine ecosystem in the Amazon plume region (APR) and have potential far-reaching influences on hydroclimate over the tropical Atlantic. Here, we show that an amplified seasonal cycle of Amazonia precipitation, represented by the annual difference between maximum and minimum values, during the period 1979–2018, leads to enhanced seasonalities in both Amazon river discharge and APR ocean salinity. An atmospheric moisture budget analysis shows that these enhanced seasonal cycles are associated with similar amplifications in the atmospheric vertical and horizontal moisture advections. Hierarchical sensitivity experiments using global climate models quantify the relationships of these enhanced seasonalities. The results suggest that an intensified hydroclimatological cycle may develop in the Amazonia atmosphere-land-ocean coupled system, favouring more extreme terrestrial and marine conditions.
    Description: M.-H.L., C.-W.L., and R.-J.W. are supported by the Ministry of Science and Technology in Taiwan under grant 106-2111-M-002-010-MY4. H.S. and J.D.S. are grateful for support from NOAA NA19OAR4310376 and NA17OAR4310255. C.C.U. acknowledges support from the U.S. National Science Foundation under grant OCE-1663704. The National Center for Atmospheric Research (NCAR) is a major facility sponsored by the US National Science Foundation (NSF) under Cooperative Agreement No. 1852977. We thank Dr. Young-Oh Kwon at Woods Hole Oceanographic Institution and Dr. Who Kim at NCAR for discussions about the ocean model experiment design. We thank Dr. Mehnaz Rashid at National Taiwan University and Wen-Yin Wu at the University of Texas at Austin in helping generate the high-resolution Amazon river mask. We also thank Dr. Gael Forget at Massachusetts Institue of Technology for comments on using ECCO and other ocean-state estimate products.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
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    Coupled impacts of the diurnal cycle of sea surface temperature on the Madden–Julian oscillation (2014)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2014. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 27 (2014): 8422–8443, doi:10.1175/JCLI-D-14-00141.1.
    Description: This study quantifies, from a systematic set of regional ocean–atmosphere coupled model simulations employing various coupling intervals, the effect of subdaily sea surface temperature (SST) variability on the onset and intensity of Madden–Julian oscillation (MJO) convection in the Indian Ocean. The primary effect of diurnal SST variation (dSST) is to raise time-mean SST and latent heat flux (LH) prior to deep convection. Diurnal SST variation also strengthens the diurnal moistening of the troposphere by collocating the diurnal peak in LH with those of SST. Both effects enhance the convection such that the total precipitation amount scales quasi-linearly with preconvection dSST and time-mean SST. A column-integrated moist static energy (MSE) budget analysis confirms the critical role of diurnal SST variability in the buildup of column MSE and the strength of MJO convection via stronger time-mean LH and diurnal moistening. Two complementary atmosphere-only simulations further elucidate the role of SST conditions in the predictive skill of MJO. The atmospheric model forced with the persistent initial SST, lacking enhanced preconvection warming and moistening, produces a weaker and delayed convection than the diurnally coupled run. The atmospheric model with prescribed daily-mean SST from the coupled run, while eliminating the delayed peak, continues to exhibit weaker convection due to the lack of strong moistening on a diurnal basis. The fact that time-evolving SST with a diurnal cycle strongly influences the onset and intensity of MJO convection is consistent with previous studies that identified an improved representation of diurnal SST as a potential source of MJO predictability.
    Description: The authors gratefully acknowledge support from the Office of Naval Research (N00014-13-1-0133 and N00014-13-1-0139) and National Science Foundation EaSM-3 (OCE-1419235). HS especially thanks the Penzance Endowed Fund for their support of Assistant Scientists at WHOI.
    Description: 2015-05-15
    Keywords: Deep convection ; Diurnal effects ; Madden-Julian oscillation ; Air-sea interaction ; Numerical weather prediction/forecasting ; Regional models
    Repository Name: Woods Hole Open Access Server
    Type: Article
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