scholarly journals The Seasonality of Convective Events in the Labrador Sea

2014 ◽  
Vol 27 (17) ◽  
pp. 6456-6471 ◽  
Author(s):  
Hao Luo ◽  
Annalisa Bracco ◽  
Fan Zhang
Keyword(s):  
Large Scale ◽  
Current System ◽  
Horizontal Resolution ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ocean Modeling ◽  
Labrador Sea ◽  
Boundary Current ◽  
Regional Ocean Modeling System ◽  
Surface Heat Fluxes

Abstract Modeling deep convection is a key challenge for climate science. Here two simulations of the Labrador Sea circulation obtained with the Regional Ocean Modeling System (ROMS) run at a horizontal resolution of 7.5 km are used to characterize the response of convection to atmospheric forcing and its seasonal variability over the period 1980–2009. The integrations compare well with the sparse observations available. The modeled convection varies in three key aspects over the 30 years considered. First, its magnitude changes greatly at decadal scales. This aspect is supported by the in situ observations. Second, the initiation and peak of convection (i.e., initiation and maximum) shift by 2–3 weeks between strong and weak convective years. Third, the duration of convection varies by approximately one month between strong and weak years. The last two changes are associated with the variability of the time-integrated surface heat fluxes over the Labrador Sea during winter and spring, while the first results from changes in both atmospheric heat fluxes and oceanic conditions through the lateral inflow of warm Irminger Water from the boundary current system to the basin interior. Changes in surface heat fluxes over the convective region are linked to large-scale modes of variability, the North Atlantic Oscillation and Arctic Oscillation. Implications for modeling the climate variability of the Labrador basin are discussed.

scholarly journals Impacts of Atmospheric Reanalysis Uncertainty on Atlantic Overturning Estimates at 25°N

2018 ◽  
Vol 31 (21) ◽  
pp. 8719-8744 ◽  
Author(s):  
Helen R. Pillar ◽  
Helen L. Johnson ◽  
David P. Marshall ◽  
Patrick Heimbach ◽  
So Takao
Keyword(s):  
Climate Model ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Labrador Sea ◽  
Surface Heat Fluxes ◽  
Ensemble Mean ◽  
Meridional Overturning ◽  
The Impact ◽  
Average Uncertainty

Atmospheric reanalyses are commonly used to force numerical ocean models, but despite large discrepancies reported between different products, the impact of reanalysis uncertainty on the simulated ocean state is rarely assessed. In this study, the impact of uncertainty in surface fluxes of buoyancy and momentum on the modeled Atlantic meridional overturning at 25°N is quantified for the period January 1994–December 2011. By using an ocean-only climate model and its adjoint, the space and time origins of overturning uncertainty resulting from air–sea flux uncertainty are fully explored. Uncertainty in overturning induced by prior air–sea flux uncertainty can exceed 4 Sv (where 1 Sv ≡ 106 m3 s−1) within 15 yr, at times exceeding the amplitude of the ensemble-mean overturning anomaly. A key result is that, on average, uncertainty in the overturning at 25°N is dominated by uncertainty in the zonal wind at lags of up to 6.5 yr and by uncertainty in surface heat fluxes thereafter, with winter heat flux uncertainty over the Labrador Sea appearing to play a critically important role.

THE IMPACT OF SURFACE HEAT FLUXES ON THE SIMULATION OF THE BRAZIL CURRENT

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Vladimir Santos da Costa ◽  
Afonso De Moraes Paiva
Keyword(s):  
Thermal Structure ◽  
Ocean Model ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ocean Modeling ◽  
Surface Heat Fluxes ◽  
Brazil Current ◽  
Regional Ocean Model ◽  
The Impact ◽  
No Fluxes

The impact of different formulations of surface heat fluxes (no fluxes, climatological fluxes, restoring of SST towards climatology, climatological fluxes plus SST restoring, and model-computed fluxes via bulk formulas) on the modeling of the Brazil Current off southeast Brazil is investigated in numerical simulations performed with the Regional Ocean Model (ROMS). While mechanical forcing may be dominant in this region, it is shown that correct upper ocean currents and thermal structure can only be obtained when heat fluxes are implemented, even in regions of strong horizontal advection, and that some kind of feedback of the ocean state upon the fluxes is also necessary. This results are of particular importance for ocean modeling developed having operational oceanography in view.

scholarly journals The Warming of the California Current System: Dynamics and Ecosystem Implications

2005 ◽  
Vol 35 (3) ◽  
pp. 336-362 ◽  
Author(s):  
Emanuele Di Lorenzo ◽  
Arthur J. Miller ◽  
Niklas Schneider ◽  
James C. McWilliams
Keyword(s):  
Southern California ◽  
Current System ◽  
California Current ◽  
Warming Trend ◽  
Ocean Model ◽  
Surface Heat ◽  
Heat Fluxes ◽  
California Current System ◽  
Surface Heat Fluxes ◽  
The Mean

Abstract Long-term changes in the observed temperature and salinity along the southern California coast are studied using a four-dimensional space–time analysis of the 52-yr (1949–2000) California Cooperative Oceanic Fisheries Investigations (CalCOFI) hydrography combined with a sensitivity analysis of an eddy-permitting primitive equation ocean model under various forcing scenarios. An overall warming trend of 1.3°C in the ocean surface, a deepening in the depth of the mean thermocline (18 m), and increased stratification between 1950 and 1999 are found to be primarily forced by large-scale decadal fluctuations in surface heat fluxes combined with horizontal advection by the mean currents. After 1998 the surface heat fluxes suggest the beginning of a period of cooling, consistent with colder observed ocean temperatures. Salinity changes are decoupled from temperature and appear to be controlled locally in the coastal ocean by horizontal advection by anomalous currents. A cooling trend of –0.5°C in SST is driven in the ocean model by the 50-yr NCEP wind reanalysis, which contains a positive trend in upwelling-favorable winds along the southern California coast. A net warming trend of +1°C in SST occurs, however, when the effects of observed surface heat fluxes are included as forcing functions in the model. Within 50–100 km of the coast, the ocean model simulations show that increased stratification/deepening of the thermocline associated with the warming reduces the efficiency of coastal upwelling in advecting subsurface waters to the ocean surface, counteracting any effects of the increased strength of the upwelling winds. Such a reduction in upwelling efficiency leads in the model to a freshening of surface coastal waters. Because salinity and nutrients at the coast have similar distributions this must reflect a reduction of the nutrient supply at the coast, which is manifestly important in explaining the observed decline in zooplankton concentration. The increased winds also drive an intensification of the mean currents of the southern California Current System (SCCS). Model mesoscale eddy variance significantly increases in recent decades in response to both the stronger upwelling winds and the warmer upper-ocean temperatures, suggesting that the stability properties of the SCCS have also changed.

scholarly journals Deep water formation in the North Atlantic Ocean in high resolution global coupled climate models

2020 ◽  
Author(s):  
Torben Koenigk ◽  
Ramon Fuentes-Franco ◽  
Virna Meccia ◽  
Oliver Gutjahr ◽  
Laura C. Jackson ◽  
...  
Keyword(s):  
High Resolution ◽  
Climate Models ◽  
Deep Convection ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Labrador Sea ◽  
Greenland Sea ◽  
Surface Heat Fluxes ◽  
The North ◽  
Coupled Climate Models

Abstract. Simulations from seven global coupled climate models performed at high and standard resolution as part of the High Resolution Model Intercomparison Project (HighResMIP) have been analyzed to study the impact of horizontal resolution in both ocean and atmosphere on deep ocean convection in the North Atlantic and to evaluate the robustness of the signal across models. The representation of convection varies strongly among models. Compared to observations from ARGO-floats, most models substantially overestimate deep water formation in the Labrador Sea. In the Greenland Sea, some models overestimate convection while others show too weak convection. In most models, higher ocean resolution leads to increased deep convection in the Labrador Sea and reduced convection in the Greenland Sea. Increasing the atmospheric resolution has only little effect on the deep convection, except in two models, which share the same atmospheric component and show reduced convection. Simulated convection in the Labrador Sea is largely governed by the release of heat from the ocean to the atmosphere. Higher resolution models show stronger surface heat fluxes than the standard resolution models in the convection areas, which promotes the stronger convection in the Labrador Sea. In the Greenland Sea, the connection between high resolution and ocean heat release to the atmosphere is less robust and there is more variation across models in the relation between surface heat fluxes and convection. Simulated freshwater fluxes have less impact than surface heat fluxes on convection in both the Greenland and Labrador Sea and this result is insensitive to model resolution. is not robust across models. The mean strength of the Labrador Sea convection is important for the mean Atlantic Meridional Overturning Circulation (AMOC) and in around half of the models the variability of Labrador Sea convection is a significant contributor to the variability of the AMOC.

The effect of horizontal resolution on ocean surface heat fluxes in the ECMWF model

1993 ◽  
Vol 9 (1) ◽  
pp. 17-32 ◽  
Author(s):  
Peter J Gleckler ◽  
Karl E Taylor
Keyword(s):  
Ocean Surface ◽  
Horizontal Resolution ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Surface Heat Fluxes ◽  
Ecmwf Model

scholarly journals THE IMPACT OF SURFACE HEAT FLUXES ON THE SIMULATION OF THE BRAZIL CURRENT

2013 ◽  
Vol 31 (2) ◽  
pp. 307
Author(s):  
Vladimir Santos da Costa ◽  
Afonso De Moraes Paiva
Keyword(s):  
Thermal Structure ◽  
Ocean Model ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ocean Modeling ◽  
Necessary Condition ◽  
Surface Heat Fluxes ◽  
Brazil Current ◽  
Regional Ocean Model ◽  
The Impact

ABSTRACT. The impact of different formulations of surface heat fluxes (no fluxes, climatological fluxes, restoring of SST towards climatology, climatological fluxes plus SST restoring, and model-computed fluxes via bulk formulas) on the modeling of the Brazil Current is investigated in numerical simulations performed with the Regional Ocean Model (ROMS). While mechanical forcing may be dominant, it is shown that correct upper ocean currents and thermal structure can only be obtained when heat fluxes are implemented, even in regions of strong horizontal advection, and that some form of feedback of the ocean state upon the fluxes is also a necessary condition. This results are of particular importance for ocean modeling developed having operational oceanography in view.   Keywords: Brazil Current, surface heat flux, numerical modeling.  RESUMO. O impacto de diferentes formulações dos fluxos de calor em superfície (sem fluxos, fluxos climatológicos, relaxamento de TSM para climatologia, fluxos climatológicos mais relaxamento de TSM e fluxos calculados pelo modelo com “bulk formulas”) sobre a modelagem da Corrente do Brasil é investigado em simulações numéricas com o Regional Ocean Model (ROMS). Apesar da forçante mecânica ser dominante, mostra-se que uma correta representação de correntes e da estrutura térmica nas camadas superiores do oceano somente são possíveis quando fluxos de calor são implementados e que algum tipo de retroalimentação da TSM sobre os fluxos é também necessária. Estes resultados são particularmente importantes na modelagem voltada para a oceanografia operacional.   Palavras-chave: Corrente do Brasil, fluxos superficial de calor, modelagem numérica.

Modeling Equilibrium Dynamics of the Benguela Current System

2010 ◽  
Vol 40 (9) ◽  
pp. 1942-1964 ◽  
Author(s):  
Jennifer Veitch ◽  
Pierrick Penven ◽  
Frank Shillington
Keyword(s):  
Wind Stress ◽  
Large Scale ◽  
Coastal Upwelling ◽  
Current System ◽  
Ocean Modeling ◽  
Shelf Edge ◽  
Regional Ocean Modeling System ◽  
Wind Stress Curl ◽  
Benguela Current ◽  
Seasonal Signal

Abstract The Regional Ocean Modeling System (ROMS) is used to systematically investigate equilibrium conditions and seasonal variations of the Benguela system at a resolution of 9 km, including both the large-scale offshore flow regime and the economically and ecologically important coastal upwelling regime. A shelf-edge poleward flow exists in the northern Benguela region (i.e., north of ∼28°S) and is driven primarily by the wind stress curl via the Sverdrup relation. As such, it is strongly seasonal and is most intense during spring and summer, when the wind stress curl is most negative. The poleward flow deepens as it moves southward; between ∼25° and 27°S, much of it veers offshore because of the nature of the wind stress curl and its interaction with the northwestward path of the Benguela Current, which is influenced by alongshore topographical variations. The Benguela Current is driven by nonlinear interactions of passing Agulhas rings and eddies and does not have a striking seasonal signal. In the mean state, it is characterized by two streams. The more inshore stream is topographically controlled and follows the run of the shelf edge. The meandering nature of the offshore stream is a result of the preferential path of Agulhas rings. The model simulates all seven of the major upwelling cells within its domain. The three southernmost cells have the strongest seasonal signal and experience their greatest upwelling during spring and summer months, whereas the two northernmost cells have less seasonal variability but nevertheless have increased upwelling from autumn to spring (and least upwelling in summer), and the central Benguela upwelling cells experience year-round upwelling. The effect of topography on coastal upwelling was investigated by smoothing alongshore coastline and topography variations, which showed that, in all of the seven major upwelling cells, upwelling is enhanced on the downstream side of capes.

scholarly journals Large-eddy simulations of marine boundary-layer clouds associated with cold air outbreaks during the ACTIVATE campaign– part 1: Case setup and sensitivities to large-scale forcings

2021 ◽  
Author(s):  
Xiang-Yu Li ◽  
Hailong Wang ◽  
Jingyi Chen ◽  
Satoshi Endo ◽  
Geet George ◽  
...  
Keyword(s):  
Large Scale ◽  
Field Measurements ◽  
Reanalysis Data ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Liquid Water Path ◽  
Surface Heat Fluxes ◽  
Large Eddy ◽  
Turbulent Heat Fluxes

Abstract Large-eddy simulation (LES) is able to capture key boundary-layer (BL) turbulence and cloud processes. Yet, large-scale forcing and surface turbulent fluxes of sensible and latent heat are often poorly prescribed for LES simulations. We derive these quantities from measurements and reanalysis obtained for two cold air outbreak (CAO) events during Phase I of the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) in February-March 2020. We study the two contrasting CAO cases by performing LES and test the sensitivity of BL structure and clouds to large-scale forcings and turbulent heat fluxes. Profiles of atmospheric state and large-scale divergence and surface turbulent heat fluxes obtained from the reanalysis data ERA5 agree reasonablywell with those derived fromACTIVATE field measurements for both cases at the sampling time and location. Therefore, we adopt the time evolving heat fluxes, wind and advective tendencies profiles from ERA5 reanalysis data to drive the LES.We find that large-scale thermodynamic advective tendencies and wind relaxations are important for the LES to capture the evolving observed BL meteorological states characterized by the hourly ERA5 reanalysis data and validated by the observations. We show that the divergence (or vertical velocity) is important in regulating the BL growth driven by surface heat fluxes in LES simulations. The evolution of liquid water path is largely affected by the evolution of surface heat fluxes. The liquid water path simulated in LES agrees reasonably well with the ACTIVATE measurements. This study paves the path to investigate aerosol-cloud-meteorology interactions using LES informed and evaluated by ACTIVATE field measurements.

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