88 results on '"Hyodae Seo"'
Search Results
2. FluxSat: Measuring the Ocean–Atmosphere Turbulent Exchange of Heat and Moisture from Space
- Author
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Chelle L. Gentemann, Carol Anne Clayson, Shannon Brown, Tong Lee, Rhys Parfitt, J. Thomas Farrar, Mark Bourassa, Peter J. Minnett, Hyodae Seo, Sarah T. Gille, and Victor Zlotnicki
- Subjects
air–sea interactions ,mesoscale ,fluxes ,Science - Abstract
Recent results using wind and sea surface temperature data from satellites and high-resolution coupled models suggest that mesoscale ocean–atmosphere interactions affect the locations and evolution of storms and seasonal precipitation over continental regions such as the western US and Europe. The processes responsible for this coupling are difficult to verify due to the paucity of accurate air–sea turbulent heat and moisture flux data. These fluxes are currently derived by combining satellite measurements that are not coincident and have differing and relatively low spatial resolutions, introducing sampling errors that are largest in regions with high spatial and temporal variability. Observational errors related to sensor design also contribute to increased uncertainty. Leveraging recent advances in sensor technology, we here describe a satellite mission concept, FluxSat, that aims to simultaneously measure all variables necessary for accurate estimation of ocean–atmosphere turbulent heat and moisture fluxes and capture the effect of oceanic mesoscale forcing. Sensor design is expected to reduce observational errors of the latent and sensible heat fluxes by almost 50%. FluxSat will improve the accuracy of the fluxes at spatial scales critical to understanding the coupled ocean–atmosphere boundary layer system, providing measurements needed to improve weather forecasts and climate model simulations.
- Published
- 2020
- Full Text
- View/download PDF
3. Relative contributions of heat flux and wind stress on the spatiotemporal upper-ocean variability in the tropical Indian Ocean
- Author
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Xu Yuan, Caroline C Ummenhofer, Hyodae Seo, and Zhongbo Su
- Subjects
interannual variability ,tropical Indian Ocean ,heat flux ,wind stress ,subsurface temperature ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
High-resolution ocean general circulation model (OGCM) simulations are employed to investigate interannual variability of the upper-ocean temperature in the tropical Indian Ocean (20°S–20°N). The seasonal cycle and interannual variability in the upper-ocean temperature in the tropical Indian Ocean in the forced ocean simulation are in good agreement with available observation and reanalysis products. Two further sensitivity OGCM simulations are used to separate the relative contributions of heat flux and wind stress. The comparison of the model simulations reveals the depth-dependent influences of heat flux and wind stress on the ocean temperature variability in the tropical Indian Ocean. Generally, heat flux dominates the temperature variability in the top 30 m, while wind stress contributes most strongly to the subsurface temperature variability below 30 m. This implies that a transition depth should exist at each location, where the dominant control of the ocean temperature variability switched from heat flux to wind stress. We define the depth of this transition point as the ‘crossing depth’ and make use of this concept to better understand the depth-dependent impacts of the heat flux and wind stress on the upper-ocean temperature variability in the tropical Indian Ocean. The crossing depth tends to be shallower in the southern tropical Indian Ocean (20°S-EQ), including the Seychelles-Chagos Thermocline Ridge (SCTR) and the eastern part of the Indian Ocean Dipole (IOD), suggesting the dominance of forcing due to wind stress and the resulting ocean dynamical processes in the temperature variability in those regions. The crossing depth also shows prominent seasonal variability in the southern tropical Indian Ocean. In the SCTR, the variability of the subsurface temperature forced by the wind stress dominates largely in boreal winter and spring, resulting in the shallow crossing depth in these seasons. In contrast, the intensified subsurface temperature variability with shallow crossing depth in the eastern part of the IOD is seen during boreal autumn. Overall, our results suggest that the two regions within the tropical Indian Ocean, the SCTR and the eastern part of the IOD, are the primary locations where the ocean dynamics due to wind-stress forcing control the upper-ocean temperature variability.
- Published
- 2020
- Full Text
- View/download PDF
4. Impact of Multidecadal Variability in Atlantic SST on Winter Atmospheric Blocking
- Author
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Young-Oh Kwon, Hyodae Seo, Caroline C. Ummenhofer, and Terrence M. Joyce
- Published
- 2019
- Full Text
- View/download PDF
5. Meridional Gulf Stream Shifts Can Influence Wintertime Variability in the North Atlantic Storm Track and Greenland Blocking
- Author
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Terrence M. Joyce, Young‐Oh Kwon, Hyodae Seo, and Caroline C. Ummenhofer
- Published
- 2019
- Full Text
- View/download PDF
6. Atmospheric and Oceanic Responses to Surface Current Coupling near the Kuroshio Current
- Author
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Ajin Cho, Hajoon Song, and Hyodae Seo
- Abstract
The so-called frontal-scale air-sea interaction describing the atmospheric responses to oceanic fronts has been mainly discussed in the context of interactions between sea surface temperature and surface winds. The ocean current also influences the surface winds, which can significantly affect the atmosphere, especially in regions of energetic ocean currents and mesoscale activities as in the western boundary current systems. This study uses an atmosphere-ocean coupled model to analyze how the Kuroshio Current affects the momentum and turbulent heat fluxes and the atmospheric boundary layer and how these responses feed back to the ocean and atmosphere in this region. The ocean current coupling influences the path of Kuroshio extension and the eddy activities by mechanical and thermal current feedbacks. Mechanical current feedback reduces momentum flux and damps eddy kinetic energy (EKE) by reducing wind work as expected. On the other hand, the thermal current feedback associated with turbulent heat fluxes injects EKE by baroclinic energy conversion. Overall, the shift of Kuroshio Current and the change of eddy activities impact the region of strong turbulent heat release to the atmosphere, which can eventually trigger changes in weather systems.
- Published
- 2023
7. Ocean Mesoscale and Frontal-Scale Ocean–Atmosphere Interactions and Influence on Large-Scale Climate: A Review
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Hyodae Seo, Larry W. O’Neill, Mark A. Bourassa, Arnaud Czaja, Kyla Drushka, James B. Edson, Baylor Fox-Kemper, Ivy Frenger, Sarah T. Gille, Benjamin P. Kirtman, Shoshiro Minobe, Angeline G. Pendergrass, Lionel Renault, Malcolm J. Roberts, Niklas Schneider, R. Justin Small, Ad Stoffelen, and Qing Wang
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Atmospheric Science - Abstract
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. Significance Statement Recent high-resolution satellite observations and climate models have shown a significant impact of coupled ocean–atmosphere interactions mediated by small-scale (mesoscale) ocean processes, including ocean eddies and fronts, on Earth’s climate. Ocean mesoscale-induced spatial temperature and current variability modulate the air–sea exchanges in heat, momentum, and mass (e.g., gases such as water vapor and carbon dioxide), altering coupled boundary layer processes. Studies suggest that skillful simulations and predictions of ocean circulation, biogeochemistry, and weather events and climate variability depend on accurate representation of the eddy-mediated air–sea interaction. However, numerous challenges remain in accurately diagnosing, observing, and simulating mesoscale air–sea interaction to quantify its large-scale impacts. This article synthesizes the latest understanding of mesoscale air–sea interaction, identifies remaining gaps and uncertainties, and provides recommendations on strategies for future ocean–weather–climate research.
- Published
- 2023
8. Improving Wave‐Based Air‐Sea Momentum Flux Parameterization in Mixed Seas
- Author
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César Sauvage, James Edson, Hyodae Seo, and Carol Clayson
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Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Oceanography - Published
- 2023
9. Bay of Bengal Intraseasonal Oscillations and the 2018 Monsoon Onset
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Arnold L. Gordon, E. Creegan, Jaynise Pérez, Adam V. Rydbeck, Rashmi Sharma, Uwe Send, Maria Flatau, Verena Hormann, Craig M. Lee, Hemantha W. Wijesekera, G. S. Bhat, Michael J. McPhaden, Rajib Chattopadhyay, Luca Centurioni, Bulusu Subrahmanyam, Arachaporn Anutaliya, Simon P. de Szoeke, Ramasamy Venkatesan, Deepak Cherian, Jennifer A. MacKinnon, S. U. P. Jinadasa, Jossia Joseph, Andrew Lucas, Luc Rainville, Kaitlyn M. Woods, Harindra J. S. Fernando, Manikandan Mathur, Hyodae Seo, M. Mohapatra, Shannon M. Bohman, Gad Levy, A. K. Sahai, Matthias Lankhorst, Robert E. Todd, Lakshmi Kantha, Tamara Schlosser, E. Pattabhi Rama Rao, K. Adams, Emily L. Shroyer, Garrett S. Black, Amy F. Waterhouse, Steven R. Jayne, S. Ramsundaram, Amit Tandon, Iury T. Simoes-Sousa, Aneesh C. Subramanian, J. Thomas Farrar, Kerstin Cullen, Jeremy A. Dehart, and Debasis Sengupta
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Atmospheric Science ,Oceanography ,BENGAL ,Environmental science ,Monsoon ,Bay - Abstract
In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air–sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air–sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ∼20-day research cruise was characterized by warm sea surface temperature (SST > 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s−1). Accumulated rainfall exceeded 200 mm with 90% of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10–12 m s−1 wind and evaporation of 0.2 mm h−1. The evolving environmental state included a deepening ocean mixed layer (from ∼20 to 50 m), cooling SST (by ∼1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air–sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon.
- Published
- 2021
10. Impacts of waves and sea states on air-sea momentum flux in the Northwest Tropical Atlantic Ocean: parameterization and wave coupled climate modeling
- Author
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César Sauvage, James Edson, Hyodae Seo, and Carol Clayson
- Published
- 2022
11. Using Process Studies to Improve Climate Modeling: Strategies for Success
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Janet Sprintall, Victoria J. Coles, Kevin A. Reed, Amy H. Butler, Gregory R. Foltz, Stephen G. Penny, and Hyodae Seo
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Atmospheric Science - Published
- 2021
12. Best Practice Strategies for Process Studies Designed to Improve Climate Modeling
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Gregory R. Foltz, Janet Sprintall, Hyodae Seo, Victoria J. Coles, Amy H. Butler, Stephen G. Penny, and Kevin A. Reed
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0303 health sciences ,03 medical and health sciences ,Atmospheric Science ,Process management ,010504 meteorology & atmospheric sciences ,Computer science ,Process (engineering) ,Best practice ,Field (Bourdieu) ,Climate model ,01 natural sciences ,030304 developmental biology ,0105 earth and related environmental sciences - Abstract
Process studies are designed to improve our understanding of poorly described physical processes that are central to the behavior of the climate system. They typically include coordinated efforts of intensive field campaigns in the atmosphere and/or ocean to collect a carefully planned set of in situ observations. Ideally the observational portion of a process study is paired with numerical modeling efforts that lead to better representation of a poorly simulated or previously neglected physical process in operational and research models. This article provides a framework of best practices to help guide scientists in carrying out more productive, collaborative, and successful process studies. Topics include the planning and implementation of a process study and the associated web of logistical challenges; the development of focused science goals and testable hypotheses; and the importance of assembling an integrated and compatible team with a diversity of social identity, gender, career stage, and scientific background. Guidelines are also provided for scientific data management, dissemination, and stewardship. Above all, developing trust and continual communication within the science team during the field campaign and analysis phase are key for process studies. We consider a successful process study as one that ultimately will improve our quantitative understanding of the mechanisms responsible for climate variability and enhance our ability to represent them in climate models.
- Published
- 2020
13. Relative contributions of heat flux and wind stress on the spatiotemporal upper-ocean variability in the tropical Indian Ocean
- Author
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Zhongbo Su, Hyodae Seo, Caroline C. Ummenhofer, Xu Yuan, UT-I-ITC-WCC, Faculty of Geo-Information Science and Earth Observation, and Department of Water Resources
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Renewable Energy, Sustainability and the Environment ,Public Health, Environmental and Occupational Health ,Wind stress ,Ocean general circulation model ,Forcing (mathematics) ,Atmospheric sciences ,Ocean dynamics ,Sea surface temperature ,Heat flux ,ITC-ISI-JOURNAL-ARTICLE ,Environmental science ,Indian Ocean Dipole ,ITC-GOLD ,Thermocline ,General Environmental Science - Abstract
High-resolution ocean general circulation model (OGCM) simulations are employed to investigate interannual variability of the upper-ocean temperature in the tropical Indian Ocean (20°S–20°N). The seasonal cycle and interannual variability in the upper-ocean temperature in the tropical Indian Ocean in the forced ocean simulation are in good agreement with available observation and reanalysis products. Two further sensitivity OGCM simulations are used to separate the relative contributions of heat flux and wind stress. The comparison of the model simulations reveals the depth-dependent influences of heat flux and wind stress on the ocean temperature variability in the tropical Indian Ocean. Generally, heat flux dominates the temperature variability in the top 30 m, while wind stress contributes most strongly to the subsurface temperature variability below 30 m. This implies that a transition depth should exist at each location, where the dominant control of the ocean temperature variability switched from heat flux to wind stress. We define the depth of this transition point as the 'crossing depth' and make use of this concept to better understand the depth-dependent impacts of the heat flux and wind stress on the upper-ocean temperature variability in the tropical Indian Ocean. The crossing depth tends to be shallower in the southern tropical Indian Ocean (20°S-EQ), including the Seychelles-Chagos Thermocline Ridge (SCTR) and the eastern part of the Indian Ocean Dipole (IOD), suggesting the dominance of forcing due to wind stress and the resulting ocean dynamical processes in the temperature variability in those regions. The crossing depth also shows prominent seasonal variability in the southern tropical Indian Ocean. In the SCTR, the variability of the subsurface temperature forced by the wind stress dominates largely in boreal winter and spring, resulting in the shallow crossing depth in these seasons. In contrast, the intensified subsurface temperature variability with shallow crossing depth in the eastern part of the IOD is seen during boreal autumn. Overall, our results suggest that the two regions within the tropical Indian Ocean, the SCTR and the eastern part of the IOD, are the primary locations where the ocean dynamics due to wind-stress forcing control the upper-ocean temperature variability.
- Published
- 2020
14. Atmospheric Convection and Air–Sea Interactions over the Tropical Oceans: Scientific Progress, Challenges, and Opportunities
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Gregory R. Foltz, Charlotte A. DeMott, Kevin A. Reed, Chidong Zhang, Elizabeth J. Thompson, Hyodae Seo, Samson Hagos, Sue Chen, Alain Protat, and Antonietta Capotondi
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Atmospheric Science ,Scientific progress ,Atmospheric convection ,Earth science ,Environmental science - Published
- 2020
15. Impact of Multidecadal Variability in Atlantic SST on Winter Atmospheric Blocking
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Terrence M. Joyce, Caroline C. Ummenhofer, Hyodae Seo, and Young-Oh Kwon
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,North Atlantic oscillation ,Blocking (radio) ,Climatology ,Environmental science ,010502 geochemistry & geophysics ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
Recent studies have suggested that coherent multidecadal variability exists between North Atlantic atmospheric blocking frequency and the Atlantic multidecadal variability (AMV). However, the role of AMV in modulating blocking variability on multidecadal times scales is not fully understood. This study examines this issue primarily using the NOAA Twentieth Century Reanalysis for 1901–2010. The second mode of the empirical orthogonal function for winter (December–March) atmospheric blocking variability in the North Atlantic exhibits oppositely signed anomalies of blocking frequency over Greenland and the Azores. Furthermore, its principal component time series shows a dominant multidecadal variability lagging AMV by several years. Composite analyses show that this lag is due to the slow evolution of the AMV sea surface temperature (SST) anomalies, which is likely driven by the ocean circulation. Following the warm phase of AMV, the warm SST anomalies emerge in the western subpolar gyre over 3–7 years. The ocean–atmosphere interaction over these 3–7-yr periods is characterized by the damping of the warm SST anomalies by the surface heat flux anomalies, which in turn reduce the overall meridional gradient of the air temperature and thus weaken the meridional transient eddy heat flux in the lower troposphere. The anomalous transient eddy forcing then shifts the eddy-driven jet equatorward, resulting in enhanced Rossby wave breaking and blocking on the northern flank of the jet over Greenland. The opposite is true with the AMV cold phases but with much shorter lags, as the evolution of SST anomalies differs in the warm and cold phases.
- Published
- 2020
16. On the effect of the East/Japan Sea SST variability on the North Pacific atmospheric circulation in a regional climate model
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Hyodae Seo, Young‐Oh Kwon, and Jong‐Jin Park
- Published
- 2014
- Full Text
- View/download PDF
17. Climate Process Team: Improvement of Ocean Component of NOAA Climate Forecast System Relevant to Madden‐Julian Oscillation Simulations
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Suyang Pei, Toshiaki Shinoda, Alexander Soloviev, Hyodae Seo, Joshua X. Fu, Wanqiu Wang, and Ren-Chieh Lien
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Global and Planetary Change ,Meteorology ,Component (UML) ,Process (computing) ,Climate Forecast System ,General Earth and Planetary Sciences ,Environmental Chemistry ,Environmental science ,Madden–Julian oscillation - Published
- 2021
18. Suppressed p CO 2 in the Southern Ocean Due to the Interaction Between Current and Wind
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Hyodae Seo, Dennis J. McGillicuddy, Hajoon Song, John Marshall, and Kyungmin Kwak
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Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Co2 flux ,Biogeochemistry ,Environmental science ,Current (fluid) ,Oceanography ,Atmospheric sciences - Published
- 2021
19. Substantial Sea Surface Temperature Cooling in the Banda Sea Associated With the Madden‐Julian Oscillation in the Boreal Winter of 2015
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John Steffen, Toshiaki Shinoda, Suyang Pei, and Hyodae Seo
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Sea surface temperature ,Geophysics ,Oceanography ,Boreal ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Environmental science ,Madden–Julian oscillation - Published
- 2021
20. Impact of freshwater plumes on intraseasonal upper ocean variability in the Bay of Bengal
- Author
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J. T. Farrar, Robert A. Weller, Channing J. Prend, and Hyodae Seo
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010504 meteorology & atmospheric sciences ,0211 other engineering and technologies ,Temperature salinity diagrams ,02 engineering and technology ,Shoaling and schooling ,Oceanography ,Monsoon ,01 natural sciences ,Salinity ,Sea surface temperature ,Environmental science ,Precipitation ,Entrainment (chronobiology) ,Bay ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences - Abstract
The Monsoon Intraseasonal Oscillations (MISO) is known to be strongly coupled to the upper ocean variability in the Bay of Bengal (BoB). Here, we analyze high-resolution moored observations from the northern BoB (18 °N, in comparison with an array of moorings to the south along 90 °E (8, 12, and 15 °N) to examine the observed temperature and salinity variability during the 2015 summer monsoon season. The heat budget analysis indicates that the mixed-layer (ML) temperature tendency at 18 °N in late summer (August and September) deviated greatly from the tendency that is expected based on surface heat flux alone. Examination of moored ML salinity and satellite sea surface salinity (SSS) fields suggests that southward extension of riverine freshwater plumes to the mooring site in late summer plays an important role in modulating the heat balance. The associated shoaling of the ML results in enhanced penetrative heat loss and warming beneath the surface layer. Price-Weller-Pinkel (PWP) 1-D model simulations, which account for vertical mixing, suggest that the entrainment of this subsurface warm water under monsoon wind improves closure of the temperature balance. Long-term analysis of satellite-based sea surface temperature (SST) and rainfall data indicates that late summer ML shoaling is accompanied by amplified intraseasonal (10–60 day) SST variability and reduced MISO precipitation variability. Overall, these results demonstrate the critical importance of freshwater plumes to improved understanding of the upper-ocean heat budget and air-sea interaction in the BoB.
- Published
- 2019
21. Meridional Gulf Stream Shifts Can Influence Wintertime Variability in the North Atlantic Storm Track and Greenland Blocking
- Author
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Hyodae Seo, Young-Oh Kwon, Caroline C. Ummenhofer, and Terrence M. Joyce
- Subjects
Gulf Stream ,Geophysics ,Oceanography ,010504 meteorology & atmospheric sciences ,Blocking (radio) ,General Earth and Planetary Sciences ,Zonal and meridional ,Storm track ,Redistribution (cultural anthropology) ,010502 geochemistry & geophysics ,01 natural sciences ,Geology ,0105 earth and related environmental sciences - Abstract
Author Posting. © American Geophysical Union, 2019. 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 46(3), (2019):1702-1708. doi:10.1029/2018GL081087.
- Published
- 2019
22. The Role of Nearshore Air‐Sea Interactions for Landfalling Atmospheric Rivers on the U.S. West Coast
- Author
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Hyodae Seo, Caroline C. Ummenhofer, John Steffen, and Samuel Bartusek
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Geophysics ,Oceanography ,010504 meteorology & atmospheric sciences ,Latent heat ,General Earth and Planetary Sciences ,Environmental science ,West coast ,010502 geochemistry & geophysics ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
Research on Atmospheric Rivers (ARs) has focused primarily on AR (thermo)dynamics and hydrological impacts over land. However, the evolution and potential role of nearshore air-sea fluxes during la...
- Published
- 2021
23. The Role of Air–Sea Interactions in Atmospheric Rivers: Case Studies Using the SKRIPS Regional Coupled Model
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F. Martin Ralph, Aneesh C. Subramanian, Hyodae Seo, Arthur J. Miller, Bruce D. Cornuelle, Rui Sun, Matthew R. Mazloff, and Ibrahim Hoteit
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Atmospheric Science ,Geophysics ,Space and Planetary Science ,Earth and Planetary Sciences (miscellaneous) - Published
- 2021
24. Effects of Sea State and Small-Scale Currents on Air-Sea Fluxes in the Northwest Tropical Atlantic Ocean
- Author
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Hyodae Seo, César Sauvage, Carol Anne Clayson, and James B. Edson
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Oceanography ,Scale (ratio) ,Environmental science ,Sea state ,Tropical Atlantic ,Physics::Atmospheric and Oceanic Physics - Abstract
The Northwest Tropical Atlantic is characterized by the strong North Brazilian Current (NBC), its rings, and numerous mesoscale eddies, which ceaselessly interact with the persistent trade winds and trade cumuli. Near the coast, the ocean stratification is maintained by the Amazon and Orinoco river discharges, which control the vertical mixing and the near-shore circulation dynamics. Breaking waves and swells are ubiquitous under the trade winds, and hence, the wave-induced mixing and wave-mediated air-sea fluxes are expected to modulate the eddy variability and low-level clouds. Our study aims to enhance understanding of the air-sea fluxes mediated by the mesoscale ocean currents and surface waves and evaluate their impacts on the ocean and atmosphere.High-resolution ocean model (ROMS) and wave model (WW3) simulations are conducted for the period of the ATOMIC/EUREC4A experiments. The model surface state variables are used to compute offline the air-sea heat and momentum fluxes using the latest COARE v3.6 bulk flux algorithm under various sea state conditions induced by surface waves, ocean currents, and their interaction. The results demonstrate that considering the spatial variability in sea states via wave slope and wave age (e.g., swells and wind-seas) leads to enhanced spatial variability in drag coefficient and wind stress. Comparison to wind stress estimated using the wind-speed dependent formulation, meaning that COARE makes sea state assumptions under given wind, indicates that, at any given time, wind and wave in fact, rarely match those assumptions. The swells (wind-seas) decreases (increases) the sea surface roughness length, drag coefficient, and wind stress by 10-15%. However, we find that the sea state impact on turbulent heat flux is negligible.More importantly, we also show that considering the ocean currents in the COARE algorithm yields much stronger spatio-temporal variations in not just the wind stress but also turbulent heat fluxes. The intense and small-scale current fields in this region are associated with the NBC and its rings, smaller mesoscale eddies, and filamentary density fronts associated with the freshwater plumes. The surface currents associated with these small-scale energetic features alter the relative wind speed and thus the air-sea fluxes depending on the directional alignment between the wind and current; the increase (decrease) in both the wind and heat fluxes by ~20% is found with the current and wind are in the opposite (same) direction wind. Moreover, this relative wind effect appears to be reinforced by wave direction as well, also via the directional alignment between waves and currents, since the waves are mainly aligned with the trade wind in this region.Further analyses are underway to examining the seasonality of the modulation by the wave-current interaction, quantifying the role of the freshwater distribution, and exploring the time-mean influence on the low-level clouds. The results from the ocean and wave modeling efforts will guide our ongoing fully coupled ocean-atmosphere (and wave) model simulations to quantify their impacts on the atmosphere, including low-level clouds.
- Published
- 2021
25. Effects of spatial resolution and temporal offset of air-sea boundary-layer variables on turbulent heat flux estimates
- Author
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Hyodae Seo, Kelly Lombardo, Carol Anne Clayson, Victor Zlotnicki, Mark A. Bourassa, Tong Lee, Aneesh C. Subramanian, Tom Farrar, Shannon Brown, Rhys Parfitt, Chelle Centemann, and Sarah T. Gille
- Subjects
Boundary layer ,Offset (computer science) ,Atmospheric sciences ,Turbulent heat flux ,Image resolution ,Physics::Atmospheric and Oceanic Physics ,Geology - Abstract
Air-sea turbulent heat fluxes and their spatial gradients are important to the ocean, climate, weather, and their interactions. Satellite-based estimation of air-sea latent and sensible fluxes, providing broad coverage, require measurements of sea surface temperature, ocean-surface wind speed, and air temperature and humidity above sea surface. Because no single satellite has been able to provide simultaneous measurements of these input variables, they typically come from various satellites with different spatial resolutions and sampling times that can be offset by hours. These factors introduce errors in the estimated heat fluxes and their gradients that are not well documented. As a model-based assessment of these errors, we performed a simulation using a Weather Research and Forecasting (WRF) model forced by high-resolution blended satellite SST for the Gulf Stream extension region with a 3-km resolution and with 30-minute output. Latent and sensible heat fluxes were first computed from input variables with the original model resolutions and at coincident times. We then computed the heat fluxes by (1) decimating the input variables to various resolutions from 12.5 to 50 km, and (2) offsetting the “sampling” times of some input variables from others by 3 hours. The resultant estimations of heat fluxes and their gradients from (1) and (2) were compared with the counterparts without reducing resolution and without temporal offset of the input variables. The results show that reducing input-variable resolutions from 12.5 to 50 km weakened the magnitudes of the time-mean and instantaneous heat fluxes and their gradients substantially, for example, by a factor of two for the time-mean gradients. The temporal offset of input variables substantially impacted the instantaneous fluxes and their gradients, although not their time-mean values. The implications of these effects on scientific and operational applications of heat flux products will be discussed. Finally, we highlight a mission concept for providing simultaneous, high-resolution measurements of boundary-layer variables from a single satellite to improve air-sea turbulent heat flux estimation.
- Published
- 2021
26. The role of nearshore air-sea interactions for landfalling atmospheric rivers on the U.S. West Coast
- Author
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Samuel T Bartusek, Hyodae Seo, Caroline C Ummenhofer, and John Steffen
- Published
- 2021
27. Amplified seasonal cycle in hydroclimate over the Amazon river basin and its plume region
- Author
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Chia-Wei Lan, Hyodae Seo, Caroline C. Ummenhofer, Min-Hui Lo, Stephen Yeager, Yu-Chiao Liang, Ren-Jie Wu, and John Steffen
- Subjects
0301 basic medicine ,Science ,General Physics and Astronomy ,02 engineering and technology ,Tropical Atlantic ,Atmospheric sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,03 medical and health sciences ,Hydrology (agriculture) ,parasitic diseases ,Marine ecosystem ,Precipitation ,lcsh:Science ,Multidisciplinary ,Discharge ,Amazon rainforest ,fungi ,technology, industry, and agriculture ,food and beverages ,General Chemistry ,021001 nanoscience & nanotechnology ,Plume ,Salinity ,030104 developmental biology ,Environmental science ,lcsh:Q ,Hydrology ,0210 nano-technology ,geographic locations ,Climate sciences - Abstract
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., The hydroclimatic variations of the Amazon River basin can exert profound impacts on the marine ecosystem in the Amazon plume region. Here the authors show that an amplified seasonal cycle of Amazonia precipitation during 1979–2018 leads to enhanced seasonality in both Amazon river discharge and ocean salinity.
- Published
- 2020
28. Impact of Current‐Wind Interaction on Vertical Processes in the Southern Ocean
- Author
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Hyodae Seo, Hajoon Song, Dennis J. McGillicuddy, and John Marshall
- Subjects
Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Ekman transport ,Stratification (water) ,Eddy kinetic energy ,Oceanography ,Atmospheric sciences ,Geology - Published
- 2020
29. Distinct Mechanisms of Decadal Subsurface Heat Content Variations in the Eastern and Western Indian Ocean Modulated by Tropical Pacific SST
- Author
-
Yu Kosaka, Jonathon S. Wright, Hyodae Seo, Caroline C. Ummenhofer, Xiaolin Jin, and Young-Oh Kwon
- Subjects
Tropical pacific ,Atmospheric Science ,Indian ocean ,010504 meteorology & atmospheric sciences ,Climatology ,Environmental science ,Climate model ,Ocean heat content ,010502 geochemistry & geophysics ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
Decadal variability of the subsurface ocean heat content (OHC) in the Indian Ocean is investigated using a coupled climate model experiment, in which observed eastern tropical Pacific sea surface temperature (EPSST) anomalies are specified. This study intends to understand the contributions of external forcing relative to those of internal variability associated with EPSST, as well as the mechanisms by which the Pacific impacts Indian Ocean OHC. Internally generated variations associated with EPSST dominate decadal variations in the subsurface Indian Ocean. Consistent with ocean reanalyses, the coupled model reproduces a pronounced east–west dipole structure in the southern tropical Indian Ocean and discontinuities in westward-propagating signals in the central Indian Ocean around 100°E. This implies distinct mechanisms by which the Pacific impacts the eastern and western Indian Ocean on decadal time scales. Decadal variations of OHC in the eastern Indian Ocean are attributed to 1) western Pacific surface wind anomalies, which trigger oceanic Rossby waves propagating westward through the Indonesian Seas and influence Indonesian Throughflow transport, and 2) zonal wind anomalies over the central tropical Indian Ocean, which trigger eastward-propagating Kelvin waves. Decadal variations of OHC in the western Indian Ocean are linked to conditions in the Pacific via changes in the atmospheric Walker cell, which trigger anomalous wind stress curl and Ekman pumping in the central tropical Indian Ocean. Westward-propagating oceanic Rossby waves extend the influence of this anomalous Ekman pumping to the western Indian Ocean.
- Published
- 2018
30. A New Framework for Near‐Surface Wind Convergence Over the Kuroshio Extension and Gulf Stream in Wintertime: The Role of Atmospheric Fronts
- Author
-
Hyodae Seo and Rhys Parfitt
- Subjects
Gulf Stream ,Surface (mathematics) ,Geophysics ,010504 meteorology & atmospheric sciences ,Climatology ,Convergence (routing) ,General Earth and Planetary Sciences ,Extension (predicate logic) ,010502 geochemistry & geophysics ,01 natural sciences ,Geology ,0105 earth and related environmental sciences - Published
- 2018
31. North Atlantic winter eddy-driven jet and atmospheric blocking variability in the Community Earth System Model version 1 Large Ensemble simulations
- Author
-
Young-Oh Kwon, Alicia Camacho, Hyodae Seo, and Carlos Javier Martinez
- Subjects
Atmospheric Science ,Jet (fluid) ,010504 meteorology & atmospheric sciences ,Zonal and meridional ,010502 geochemistry & geophysics ,Blocking (statistics) ,01 natural sciences ,Latitude ,Community earth system model ,Internal variability ,Climatology ,Range (statistics) ,Climate model ,Geology ,0105 earth and related environmental sciences - Abstract
The atmospheric jet and blocking distributions, especially in the North Atlantic sector, have been challenging features for a climate model to realistically reproduce. This study examines climatological distributions of winter (December–February) daily jet latitude and blocking in the North Atlantic from the 40-member Community Earth System Model version 1 Large Ensemble (CESM1LE) simulations. This analysis aims at examining whether a broad range of internal climate variability encompassed by a large ensemble of simulations results in an improved representation of the jet latitude distributions and blocking days in CESM1LE. In the historical runs (1951–2005), the daily zonal wind at 850 hPa exhibits three distinct preferred latitudes for the eddy-driven jet position as seen in the reanalysis datasets, which represents a significant improvement from the previous version of the same model. However, the meridional separations between the three jet latitudes are much smaller than those in the reanalyses. In particular, the jet rarely migrates to the observed southernmost position around 37°N. This leads to the bias in blocking frequency that is too low over Greenland and too high over the Azores. These features are shown to be remarkably stable across the 40 ensemble members with negligible member-to-member spread. This result implies the range of internal variability of winter jet latitude and blocking frequency within the 55-year segment from each ensemble member is comparable to that represented by the full large ensemble. Comparison with 2046–2100 from the RCP8.5 future projection runs suggests that the daily jet position is projected to maintain the same three preferred latitudes, with a slightly higher frequency of occurrence over the central latitude around 50°N, instead of shifting poleward in the future as documented in some previous studies. In addition, the daily jet speed is projected not to change significantly between 1951–2005 and 2046–2100. On the other hand, the climatological mean jet is projected to become slightly more elongated and stronger on its southern flank, and the blocking frequency over the Azores is projected to decrease.
- Published
- 2018
32. On the Predominant Nonlinear Response of the Extratropical Atmosphere to Meridional Shifts of the Gulf Stream
- Author
-
Young-Oh Kwon, Hyodae Seo, Caroline C. Ummenhofer, and Terrence M. Joyce
- Subjects
Atmospheric Science ,010504 meteorology & atmospheric sciences ,Atmospheric circulation ,010502 geochemistry & geophysics ,01 natural sciences ,Gulf Stream ,Sea surface temperature ,Atlantic Equatorial mode ,Shutdown of thermohaline circulation ,North Atlantic oscillation ,Climatology ,Atlantic multidecadal oscillation ,Thermohaline circulation ,Physics::Atmospheric and Oceanic Physics ,Geology ,0105 earth and related environmental sciences - Abstract
The North Atlantic atmospheric circulation response to the meridional shifts of the Gulf Stream (GS) path is examined using a large ensemble of high-resolution hemispheric-scale Weather Research and Forecasting Model simulations. The model is forced with a broad range of wintertime sea surface temperature (SST) anomalies derived from a lag regression on a GS index. The primary result of the model experiments, supported in part by an independent analysis of a reanalysis dataset, is that the large-scale quasi-steady North Atlantic circulation response is remarkably nonlinear about the sign and amplitude of the SST anomaly chosen over a wide range of GS shift scenarios. The nonlinear response prevails over the weak linear response and resembles the negative North Atlantic Oscillation (NAO), the leading intrinsic mode of variability in the model and the observations. Further analysis of the associated dynamics reveals that the nonlinear responses are accompanied by the shift of the North Atlantic eddy-driven jet, which is reinforced, with nearly equal importance, by the high-frequency transient eddy feedback and the low-frequency wave-breaking events. Additional sensitivity simulations confirm that the nonlinearity of the circulation response is a robust feature found over the broad parameter space encompassing not only the varied SST but also the absence/presence of tropical influence, the varying lateral boundary conditions, and the initialization scheme. The result highlights the fundamental importance of the intrinsically nonlinear transient eddy dynamics and the eddy–mean flow interactions in generating the nonlinear downstream response to the meridional shifts in the Gulf Stream.
- Published
- 2017
33. Coupled ocean-atmosphere forecasting at short and medium time scales
- Author
-
Julie Pullen, Shuyi S. Chen, Rui Caldeira, Richard Allard, Philip Chu, Luciano Ponzi Pezzi, Hyodae Seo, Arthur J. Miller, Travis A. Smith, and José Matias Alves
- Subjects
Atmosphere ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Environmental science ,Oceanography ,Atmospheric sciences ,01 natural sciences ,0105 earth and related environmental sciences - Published
- 2017
34. Distinct Influence of Air–Sea Interactions Mediated by Mesoscale Sea Surface Temperature and Surface Current in the Arabian Sea
- Author
-
Hyodae Seo
- Subjects
Atmospheric Science ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Ocean current ,Mesoscale meteorology ,Wind stress ,Monsoon ,01 natural sciences ,Latitude ,Atmosphere ,Sea surface temperature ,Climatology ,Ekman transport ,Geology ,0105 earth and related environmental sciences - Abstract
During the southwest monsoons, the Arabian Sea (AS) develops highly energetic mesoscale variability associated with the Somali Current (SC), Great Whirl (GW), and cold filaments (CF). The resultant high-amplitude anomalies and gradients of sea surface temperature (SST) and surface currents modify the wind stress, triggering the so-called mesoscale coupled feedbacks. This study uses a high-resolution regional coupled model with a novel coupling procedure that separates spatial scales of the air–sea coupling to show that SST and surface currents are coupled to the atmosphere at distinct spatial scales, exerting distinct dynamic influences. The effect of mesoscale SST–wind interaction is manifested most strongly in wind work and Ekman pumping over the GW, primarily affecting the position of GW and the separation latitude of the SC. If this effect is suppressed, enhanced wind work and a weakened Ekman pumping dipole cause the GW to extend northeastward, delaying the SC separation by 1°. Current–wind interaction, in contrast, is related to the amount of wind energy input. When it is suppressed, especially as a result of background-scale currents, depth-integrated kinetic energy, both the mean and eddy, is significantly enhanced. Ekman pumping velocity over the GW is overly negative because of a lack of vorticity that offsets the wind stress curl, further invigorating the GW. Moreover, significant changes in time-mean SST and evaporation are generated in response to the current–wind interaction, accompanied by a noticeable southward shift in the Findlater Jet. The significant increase in moisture transport in the central AS implies that air–sea interaction mediated by the surface current is a potentially important process for simulation and prediction of the monsoon rainfall.
- Published
- 2017
35. Emerging European winter precipitation pattern linked to atmospheric circulation changes over the North Atlantic region in recent decades
- Author
-
Rhys Parfitt, Caroline C. Ummenhofer, Terrence M. Joyce, Hyodae Seo, Young-Oh Kwon, and Swen Brands
- Subjects
010504 meteorology & atmospheric sciences ,Atmospheric circulation ,0208 environmental biotechnology ,02 engineering and technology ,Atmospheric river ,01 natural sciences ,020801 environmental engineering ,Geophysics ,Oceanography ,Climatology ,Extratropical cyclone ,General Earth and Planetary Sciences ,Environmental science ,Storm track ,sense organs ,Precipitation ,0105 earth and related environmental sciences - Abstract
Dominant European winter precipitation patterns over the past century, along with their associated extratropical North Atlantic circulation changes, are evaluated using cluster analysis. Contrary to the four regimes traditionally identified based on daily wintertime atmospheric circulation patterns, five distinct seasonal precipitation regimes are detected here. Recurrent precipitation patterns in each regime are linked to changes in atmospheric blocking, storm track, and sea surface temperatures across the North Atlantic region. Multidecadal variability in the frequency of the precipitation patterns reveals more (fewer) winters with wet conditions in northern (southern) Europe in recent decades and an emerging distinct pattern of enhanced wintertime precipitation over the northern British Isles. This pattern has become unusually common since the 1980s and is associated with changes in moisture transport and more frequent atmospheric river events. The observed precipitation changes post-1950 coincide with changes in storm-track activity over the central/eastern North Atlantic towards the northern British Isles.
- Published
- 2017
36. Coupled ocean–atmosphere modeling and predictions
- Author
-
Luciano Ponzi Pezzi, Hyodae Seo, Yu-Heng Tseng, Vasu Misra, Tommy G. Jensen, Matthew Collins, Dian Putrasahan, Silvio Gualdi, Arthur J. Miller, and David W. Pierce
- Subjects
Atmosphere ,El Niño Southern Oscillation ,010504 meteorology & atmospheric sciences ,Fresh water ,Meteorology ,010505 oceanography ,Global warming ,Environmental science ,Climate model ,Oceanography ,01 natural sciences ,Naval research ,0105 earth and related environmental sciences - Abstract
AJMwas supported by theNSFEarth System Modeling Program (OCE1419306) and the NOAA Climate Variability and Prediction Program (NA14OAR4310276). HS thanks the Office of Naval Research for support under N00014-15-1-2588. LPP was supported by “Advanced Studies in Medium and High Latitudes Oceanography” (CAPES 23038.004304/2014-28) and “National Institute of Science andTechnology of the Cryosphere” (CNPq/PROANTAR704222/2009). VM was supported by NOAA grant NA12OAR4310078. TGJ was supported by the U. S. Naval Research Laboratory 6.2 project “Fresh Water Balance in the Coupled Ocean-Atmosphere System” (BE-435-040-62435N-6777) YHT was supported by the MOST grant 106-2111-M-002-001, Taiwan.
- Published
- 2017
37. Intraseasonal rainfall variability in the Bay of Bengal during the Summer Monsoon: coupling with the ocean and modulation by the Indian Ocean Dipole
- Author
-
Hyodae Seo, Caroline C. Ummenhofer, and Siraput Jongaramrungruang
- Subjects
Atmospheric Science ,010504 meteorology & atmospheric sciences ,Latent heating ,010502 geochemistry & geophysics ,Monsoon ,01 natural sciences ,Indian summer monsoon rainfall ,Climatology ,Latent heat ,BENGAL ,Environmental science ,Moisture convergence ,Indian Ocean Dipole ,Bay ,0105 earth and related environmental sciences - Abstract
The Indian Summer Monsoon rainfall exhibits pronounced intraseasonal variability in the Bay of Bengal (BoB). This study examines the intraseasonal rainfall variability with foci on the coupling with sea surface temperatures (SST) and its interannual modulation. The lagged composite analysis reveals that, in the northern BoB, SST warming leads the onset of intraseasonal rainfall by 5 days. Latent heat flux is reduced before the rain event but is greatly amplified during the rainfall maxima. Further analysis reveals that this intraseasonal rainfall-SST relationship through latent heating is strengthened in negative Indian Ocean Dipole (IOD) years when the bay-wide local SST is anomalously warm. Latent heat flux is further increased during the intraseasonal rainfall maxima leading to strengthened rainfall variability. The moisture budget analysis shows this is primarily due to stronger low-level moisture convergence in negative IOD years. The results provide important predictive information on the monsoon rainfall and its active/break cycles.
- Published
- 2017
38. Continental Shelf Baroclinic Instability. Part II: Oscillating Wind Forcing
- Author
-
Hyodae Seo and Kenneth H. Brink
- Subjects
Length scale ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Continental shelf ,Baroclinity ,Rossby radius of deformation ,Stratification (water) ,Mechanics ,Oceanography ,01 natural sciences ,Potential energy ,Physics::Fluid Dynamics ,Amplitude ,Downwelling ,Climatology ,Physics::Atmospheric and Oceanic Physics ,Geology ,0105 earth and related environmental sciences - Abstract
Continental shelf baroclinic instability energized by fluctuating alongshore winds is treated using idealized primitive equation numerical model experiments. A spatially uniform alongshore wind, sinusoidal in time, alternately drives upwelling and downwelling and so creates highly variable, but slowly increasing, available potential energy. For all of the 30 model runs, conducted with a wide range of parameters (varying Coriolis parameter, initial stratification, bottom friction, forcing period, wind strength, and bottom slope), a baroclinic instability and subsequent eddy field develop. Model results and scalings show that the eddy kinetic energy increases with wind amplitude, forcing period, stratification, and bottom slope. The dominant alongshore length scale of the eddy field is essentially an internal Rossby radius of deformation. The resulting depth-averaged alongshore flow field is dominated by the large-scale, periodic wind forcing, while the cross-shelf flow field is dominated by the eddy variability. The result is that correlation length scales for alongshore flow are far greater than those for cross-shelf velocity. This scale discrepancy is qualitatively consistent with midshelf observations by Kundu and Allen, among others.
- Published
- 2016
39. Eddy–Wind Interaction in the California Current System: Dynamics and Impacts
- Author
-
Arthur J. Miller, Hyodae Seo, and Joel R. Norris
- Subjects
Ekman layer ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Wind stress ,Vorticity ,Oceanography ,Atmospheric sciences ,01 natural sciences ,Ocean dynamics ,Sea surface temperature ,Climatology ,Ekman transport ,Environmental science ,Current (fluid) ,0105 earth and related environmental sciences ,Crosswind - Abstract
The summertime California Current System (CCS) is characterized by energetic mesoscale eddies, whose sea surface temperature (SST) and surface current can significantly modify the wind stress and Ekman pumping. Relative importance of the eddy–wind interactions via SST and surface current in the CCS is examined using a high-resolution (7 km) regional coupled model with a novel coupling approach to isolate the small-scale air–sea coupling by SST and surface current. Results show that when the eddy-induced surface current is allowed to modify the wind stress, the spatially averaged surface eddy kinetic energy (EKE) is reduced by 42%, and this is primarily due to enhanced surface eddy drag and reduced wind energy transfer. In contrast, the eddy-induced SST–wind coupling has no significant impact on the EKE. Furthermore, eddy-induced SST and surface current modify the Ekman pumping via their crosswind SST gradient and surface vorticity gradient, respectively. The resultant magnitudes of the Ekman pumping velocity are comparable, but the implied feedback effects on the eddy statistics are different. The surface current-induced Ekman pumping mainly attenuates the amplitude of cyclonic and anticyclonic eddies, acting to reduce the eddy activity, while the SST-induced Ekman pumping primarily affects the propagation. Time mean–rectified change in SST is determined by the altered offshore temperature advection by the mean and eddy currents, but the magnitude of the mean SST change is greater with the eddy-induced current effect. The demonstrated remarkably strong dynamical response in the CCS system to the eddy-induced current–wind coupling indicates that eddy-induced current should play an important role in the regional coupled ocean–atmosphere system.
- Published
- 2016
40. Representation of Bay of Bengal Upper-Ocean Salinity in General Circulation Models
- Author
-
T. S. Fousiya, Anant Parekh, Hyodae Seo, Jennifer A. MacKinnon, Jasti S. Chowdary, G. Srinivas, and Chellappan Gnanaseelan
- Subjects
Salinity ,Oceanography ,010504 meteorology & atmospheric sciences ,010505 oceanography ,General Circulation Model ,Climatology ,BENGAL ,01 natural sciences ,Bay ,Geology ,0105 earth and related environmental sciences - Abstract
Author Posting. © The Oceanography Society, 2016. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 29, no. 2 (2016): 38–49, doi:10.5670/oceanog.2016.37.
- Published
- 2016
41. FluxSat: Measuring the Ocean–Atmosphere Turbulent Exchange of Heat and Moisture from Space
- Author
-
Hyodae Seo, Shannon Brown, Tong Lee, Chelle L. Gentemann, Mark A. Bourassa, Carol Anne Clayson, Victor Zlotnicki, Peter J. Minnett, J. Thomas Farrar, Sarah T. Gille, and Rhys Parfitt
- Subjects
010504 meteorology & atmospheric sciences ,Classical Physics ,Science ,0211 other engineering and technologies ,Mesoscale meteorology ,02 engineering and technology ,Forcing (mathematics) ,Sensible heat ,Atmospheric sciences ,01 natural sciences ,Physical Geography and Environmental Geoscience ,Atmosphere ,Physics::Atmospheric and Oceanic Physics ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,mesoscale ,air-sea interactions ,fluxes ,Climate Action ,air–sea interactions ,Sea surface temperature ,Boundary layer ,Geomatic Engineering ,Physics::Space Physics ,General Earth and Planetary Sciences ,Environmental science ,Climate model ,Satellite - Abstract
Recent results using wind and sea surface temperature data from satellites and high-resolution coupled models suggest that mesoscale ocean–atmosphere interactions affect the locations and evolution of storms and seasonal precipitation over continental regions such as the western US and Europe. The processes responsible for this coupling are difficult to verify due to the paucity of accurate air–sea turbulent heat and moisture flux data. These fluxes are currently derived by combining satellite measurements that are not coincident and have differing and relatively low spatial resolutions, introducing sampling errors that are largest in regions with high spatial and temporal variability. Observational errors related to sensor design also contribute to increased uncertainty. Leveraging recent advances in sensor technology, we here describe a satellite mission concept, FluxSat, that aims to simultaneously measure all variables necessary for accurate estimation of ocean–atmosphere turbulent heat and moisture fluxes and capture the effect of oceanic mesoscale forcing. Sensor design is expected to reduce observational errors of the latent and sensible heat fluxes by almost 50%. FluxSat will improve the accuracy of the fluxes at spatial scales critical to understanding the coupled ocean–atmosphere boundary layer system, providing measurements needed to improve weather forecasts and climate model simulations.
- Published
- 2020
42. Estimation and prediction of the upper ocean circulation in the Bay of Bengal
- Author
-
Ganesh Gopalakrishnan, Debasis Sengupta, Aneesh C. Subramanian, Arthur J. Miller, and Hyodae Seo
- Subjects
010504 meteorology & atmospheric sciences ,010505 oceanography ,Ocean current ,Mesoscale meteorology ,Temperature salinity diagrams ,Sea-surface height ,Oceanography ,Monsoon ,01 natural sciences ,Sea surface temperature ,Climatology ,Environmental science ,Hindcast ,Argo ,0105 earth and related environmental sciences - Abstract
The upper ocean stratification and circulation in the Bay of Bengal (BoB) plays a key role in the northward propagating monsoon intraseasonal oscillation during the months of June–August. This region is highly influenced by strong, seasonal atmospheric forcing and the oceanic circulation is characterized by dominant mesoscale variability and strong horizontal gradients in salinity and temperature during the monsoon period. Given the role of the ocean in the monsoon circulation, it is important to investigate accurate ocean state estimates and forecasts of the BoB ocean circulation in preparation for coupled ocean-atmosphere modeling and predictions. Hence, we use a mesoscale-permitting regional implementation of Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint-based four-dimensional variational (4DVAR) system to assimilate satellite-derived Sea Surface Height (SSH) and Sea Surface Temperature (SST) data in the BoB for a period of one month (June 1 – 30, 2017). It is shown that the MITgcm-BoB 4DVAR assimilation system is able to significantly improve the model consistency with the assimilated observations in the BoB region, reducing the model-data misfit by 50% and provided a dynamically-consistent BoB ocean circulation for the one-month hindcast period. We performed forecasting experiments using the state estimate to initialize two forecasts for a period of 30-days (July 1 – 30, 2017) from the end of the hindcast period. These forecasts used either atmosphere reanalysis and ocean analysis forcings or monthly climatology of atmosphere reanalysis and ocean analysis forcings. They therefore do not represent a “true” regional ocean forecast, forced using actual atmosphere and ocean forecasts, but bound the performance between climatological and nearly perfect forecasts. The model forecast is a cross-validation against future observations and showed that the initial conditions from the state estimate improves the prediction of the three-dimensional circulation in the BoB. The model hindcast and forecasts were also cross-validated against independent Argo temperature and salinity observations in the BoB. Additional state estimation and forecast experiments for other periods showed similar model performance with improved hindcasts and forecasts for the BoB region.
- Published
- 2020
43. Influences of Pacific Climate Variability on Decadal Subsurface Ocean Heat Content Variations in the Indian Ocean
- Author
-
Hyodae Seo, Franziska U. Schwarzkopf, Jonathon S. Wright, Young-Oh Kwon, Arne Biastoch, Claus W. Böning, Xiaolin Jin, and Caroline C. Ummenhofer
- Subjects
Atmospheric Science ,010504 meteorology & atmospheric sciences ,Interdecadal Pacific Oscillation ,Rossby wave ,Sea-surface height ,010502 geochemistry & geophysics ,01 natural sciences ,13. Climate action ,Climatology ,Ekman transport ,Hindcast ,Common spatial pattern ,14. Life underwater ,Ocean heat content ,Thermocline ,Geology ,0105 earth and related environmental sciences - Abstract
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.
- Published
- 2018
44. Coupled Impacts of the Diurnal Cycle of Sea Surface Temperature on the Madden–Julian Oscillation
- Author
-
Arthur J. Miller, Nicholas R. Cavanaugh, Aneesh C. Subramanian, and Hyodae Seo
- Subjects
Troposphere ,Convection ,Atmospheric Science ,Sea surface temperature ,Diurnal cycle ,Climatology ,Latent heat ,Moist static energy ,Environmental science ,Madden–Julian oscillation ,Precipitation ,Atmospheric sciences - Abstract
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.
- Published
- 2014
45. Ocean Eddies and Mesoscale Variability
- Author
-
Pierre-Yves Le Traon, Lee-Lueng Fu, Rosemary Morrow, Hyodae Seo, and J. Thomas Farrar
- Subjects
Ocean dynamics ,Eddy ,Climatology ,Mesoscale meteorology ,Altimeter ,Sea-surface height ,Internal wave ,Instability ,Physics::Atmospheric and Oceanic Physics ,Mesoscale eddies ,Geology ,Physics::Geophysics - Abstract
This chapter presents a review of the advances in observing the ocean eddy field with satellite altimetry over the last 10 years and addresses the techniques being used to study the finer-scale ocean dynamics. It provides an overview of the reprocessing of along-track data, both from conventional altimetry and the new technology missions, and looks at the improvements in mapping the multi-mission data for mesoscale studies. The chapter reviews various scientific applications of the fine-scale ocean eddies. These include analyses of mesoscale eddies and jets in the global ocean and regional seas and analyses of along-track spectra from different altimetric missions and their relation with instability regimes in the ocean. The chapter covers the potential and limits of resolving higher-order dynamical processes from the mapped data and deals with the new challenges in separating the internal wave signal from the smaller mesoscale sea surface height signals.
- Published
- 2017
46. Northern Arabian Sea circulation-autonomous research (NASCar): A research initiative based on autonomous sensors
- Author
-
Eric D. Skyllingstad, Rosalind Echols, Lisa M. Beal, Verena Hormann, Patrick Conry, Luc Rainville, Ramsey R. Harcourt, Bulusu Subrahmanyam, Andrew Lucas, Hans C. Graber, Janet Sprintall, Geno Pawlak, Harindra J. S. Fernando, Andrey Y. Shcherbina, Eric Terrill, Sarah N. Giddings, Pierre F. J. Lermusiaux, Hugo N. Ulloa, Amala Mahadevan, Luca Centurioni, Craig M. Lee, Hyodae Seo, Stephen C. Riser, Steven R. Jayne, He Wang, Michael J. Caruso, Arnold L. Gordon, Robert E. Todd, Isabella B. Arzeno, Pierre L'Hégaret, Tommy G. Jensen, Julie L. McClean, Corinne B. Trott, and Lynne D. Talley
- Subjects
0106 biological sciences ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,Ocean current ,Temperature salinity diagrams ,Monsoon ,Oceanography ,01 natural sciences ,Sea surface temperature ,Ocean surface topography ,Climatology ,East Asian Monsoon ,Upwelling ,Thermohaline circulation ,Geology ,0105 earth and related environmental sciences - Abstract
The Arabian Sea circulation is forced by strong monsoonal winds and is characterized by vigorous seasonally reversing currents, extreme differences in sea surface salinity, localized substantial upwelling, and widespread submesoscale thermohaline structures. Its complicated sea surface temperature patterns are important for the onset and evolution of the Asian monsoon. This article describes a program that aims to elucidate the role of upper-ocean processes and atmospheric feedbacks in setting the sea surface temperature properties of the region. The wide range of spatial and temporal scales and the difficulty of accessing much of the region with ships due to piracy motivated a novel approach based on state-of-the-art autonomous ocean sensors and platforms. The extensive data set that is being collected, combined with numerical models and remote sensing data, confirms the role of planetary waves in the reversal of the Somali Current system. These data also document the fast response of the upper equatorial ocean to monsoon winds through changes in temperature and salinity and the connectivity of the surface currents across the northern Indian Ocean. New observations of thermohaline interleaving structures and mixing in setting the surface temperature properties of the northern Arabian Sea are also discussed.
- Published
- 2017
47. A simple diagnostic for the detection of atmospheric fronts
- Author
-
Arnaud Czaja, Hyodae Seo, and Rhys Parfitt
- Subjects
010504 meteorology & atmospheric sciences ,Threshold limit value ,atmospheric fronts ,010502 geochemistry & geophysics ,01 natural sciences ,STORM TRACKS ,objective frontal detection ,REANALYSIS ,Simple (abstract algebra) ,GULF-STREAM ,MD Multidisciplinary ,Meteorology & Atmospheric Sciences ,Geosciences, Multidisciplinary ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences ,Remote sensing ,Science & Technology ,digestive, oral, and skin physiology ,Geology ,Geophysics ,Vorticity ,PERTURBATIONS ,MODEL ,Sea surface temperature ,Temperature gradient ,RESOLUTION ,SEA-SURFACE TEMPERATURE ,Physical Sciences ,General Earth and Planetary Sciences ,Isobaric process - Abstract
In this article, a simple diagnostic to identify atmospheric fronts objectively from gridded datasets is presented. For this diagnostic, fronts are identified as regions where the normalized product of the isobaric relative vorticity and horizontal temperature gradient exceeds a threshold value. The purpose is to introduce a method that is both robust and particularly straightforward in calculation. A climatology of atmospheric fronts, as well as the identification of an individual frontal system, are computed using this diagnostic. These are subsequently compared to a more traditional frontal detection method, and the similarities and differences discussed.
- Published
- 2017
48. The skill of atmospheric linear inverse models in hindcasting the Madden–Julian Oscillation
- Author
-
Aneesh C. Subramanian, Teddy Allen, Nicholas R. Cavanaugh, Hyodae Seo, Brian E. Mapes, and Arthur J. Miller
- Subjects
Atmospheric Science ,Meteorology ,Oscillation ,Climatology ,Linear model ,Inverse ,Hindcast ,Forecast skill ,Madden–Julian oscillation ,Bivariate analysis ,Predictability ,Mathematics - Abstract
A suite of statistical atmosphere-only linear inverse models of varying complexity are used to hindcast recent MJO events from the Year of Tropical Convection and the Cooperative Indian Ocean Experiment on Intraseasonal Variability/Dynamics of the Madden–Julian Oscillation mission periods, as well as over the 2000–2009 time period. Skill exists for over two weeks, competitive with the skill of some numerical models in both bivariate correlation and root-mean-squared-error scores during both observational mission periods. Skill is higher during mature Madden–Julian Oscillation conditions, as opposed to during growth phases, suggesting that growth dynamics may be more complex or non-linear since they are not as well captured by a linear model. There is little prediction skill gained by including non-leading modes of variability.
- Published
- 2014
49. On the effect of the East/Japan Sea SST variability on the North Pacific atmospheric circulation in a regional climate model
- Author
-
Young-Oh Kwon, Hyodae Seo, and Jong Jin Park
- Subjects
Atmospheric Science ,Atmospheric circulation ,Planetary boundary layer ,Forcing (mathematics) ,Wind speed ,Sea surface temperature ,Geophysics ,Space and Planetary Science ,Climatology ,Weather Research and Forecasting Model ,Earth and Planetary Sciences (miscellaneous) ,Environmental science ,Climate model ,Storm track - Abstract
The East/Japan Sea (EJS) is a semi-enclosed marginal sea located in the upstream of the North Pacific storm track, where the leading modes of wintertime interannual variability in sea surface temperature (SST) are characterized by the basin-wide warming-cooling and the northeast-southwest dipole. Processes leading to local and remote atmospheric responses to these SST anomalies are investigated using the Weather Research and Forecast (WRF) model. The atmosphere in direct contact with anomalous diabatic forcing exhibits a linear and symmetric response with respect to the sign, pattern, and magnitude of SST anomalies, producing increased (decreased) wind speed and precipitation response over warm (cold) SSTs. This local response is due to modulation of both the vertical stability of the marine atmospheric boundary layer and the adjustment of sea level pressure, although the latter provides a better explanation of the quadrature relationship between SST and wind speed. The linearity in the local response suggests the importance of fine-scale EJS SSTs to predictability of the regional weather and climate variability. The remote circulation response, in contrast, is strongly nonlinear. An intraseasonal equivalent barotropic ridge emerges in the Gulf of Alaska as a common remote response independent of EJS SST anomalies. This downstream blocking response is reinforced by the enhanced storm track variability east of Japan via transient eddy vorticity flux convergence. Strong nonlinearity in remote response implies that detailed EJS SST patterns may not be critical to this downstream ridge response. Overall, results demonstrate a remarkably far-reaching impact of the EJS SSTs on the atmospheric circulation.
- Published
- 2014
50. Coupled effects of ocean current on wind stress in the Bay of Bengal: Eddy energetics and upper ocean stratification
- Author
-
Hajoon Song, Hyodae Seo, Aneesh C. Subramanian, and Jasti S. Chowdary
- Subjects
010504 meteorology & atmospheric sciences ,010505 oceanography ,Mixed layer ,Ocean current ,Mesoscale meteorology ,Stratification (water) ,Wind stress ,Oceanography ,Monsoon ,Atmospheric sciences ,01 natural sciences ,Ekman velocity ,Geology ,Geostrophic wind ,0105 earth and related environmental sciences - Abstract
This study examines the effect of surface current in the bulk formula for the wind stress, referred to as the relative wind (RW) effect, on the energetics of the geostrophic circulation and the upper ocean stratification in the Bay of Bengal (BoB) during the summer monsoon seasons. When the RW effect is taken into account in the high-resolution SCOAR (WRF-ROMS) regional coupled model simulation and compared to the run without such a consideration, the kinetic energy both in the mean (MKE) and eddy (EKE) is reduced by more than a factor of two. The most significant reduction in the kinetic energy is found along the path of the northward East India Coastal Current (EICC) and to the south of its separated latitude. The energetics calculations and spectral analysis reveal that this significant damping of EKE is primarily due to reduced eddy wind work principally at wavelengths close to the first baroclinic Rossby deformation radius, indicating the modulation of the wind work by geostrophic mesoscale eddy fields. Moreover, the mixed layer depth (MLD) is significantly shoaled south of the separated EICC latitude, the area dominated by anticyclonic eddy activity. The shallower mixed layer and enhanced stratification with the RW effect are attributed to doming of the isopycnals by the anomalous upward Ekman velocity, which itself is generated by the interaction of anticyclonic mesoscale surface current and the prevailing southwesterly monsoonal wind. Overall, the geostrophic circulation and upper ocean stratification along the EICC and south of its separated latitude exhibit the most significant dynamical response. This result implies that this southwestern part of the BoB is a hot spot for the momentum exchange between the surface circulation and the monsoonal winds, thus a potential area for focused field measurements for the ocean circulation energetics and air-sea interaction.
- Published
- 2019
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