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.

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.

The Impact of Outer-Core Surface Heat Fluxes on the Convective Activities and Rapid Intensification of Tropical Cyclones

2020 ◽  
Vol 77 (11) ◽  
pp. 3907-3927
Author(s):  
Chin-Hsuan Peng ◽  
Chun-Chieh Wu
Keyword(s):  
Inner Core ◽  
Surface Wind ◽  
Outer Core ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Intensity Change ◽  
Rapid Intensification ◽  
Core Surface ◽  
Surface Heat Fluxes ◽  
The Impact

AbstractThe rapid intensification (RI) of Typhoon Soudelor (2015) is simulated using a full-physics model. To investigate how the outer-core surface heat fluxes affect tropical cyclone (TC) structure and RI processes, a series of numerical experiments are performed by suppressing surface heat fluxes between various radii. It is found that a TC would become quite weaker when the surface heat fluxes are suppressed outside the radius of 60 or 90 km [the radius of maximum surface wind in the control experiment (CTRL) at the onset of RI is roughly 60 km]. However, interestingly, the TC would experience stronger RI when the surface heat fluxes are suppressed outside the radius of 150 km. For those sensitivity experiments with capped surface heat fluxes, the members with greater intensification rate show stronger inner-core mid- to upper-level updrafts and higher heating efficiency prior to the RI periods. Although the outer-core surface heat fluxes in these members are suppressed, the inner-core winds become stronger, extracting more ocean energy from the inner core. Greater outer-core low-level stability in these members results in aggregation of deep convection and subsequent generation and concentration of potential vorticity inside the inner core, thus confining the strongest winds therein. The abovementioned findings are also supported by partial-correlation analyses, which reveal the positive correlation between the inner-core convection and subsequent 6-h intensity change, and the competition between the inner-core and outer-core convections (i.e., eyewall and outer rainbands).

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.

scholarly journals Multiscale Applications of Two Online-Coupled Meteorology-Chemistry Models During Recent Field Campaigns in Australia, Part II: Comparison of WRF/Chem and WRF/Chem-ROMS and Impacts of Air-Sea Interactions and Boundary Conditions

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 210 ◽  
Author(s):  
Zhang ◽  
Wang ◽  
Jena ◽  
Paton-Walsh ◽  
Guérette ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Temporal Variations ◽  
Ocean Model ◽  
Heat Fluxes ◽  
Atmospheric Pollutants ◽  
Spatial Distributions ◽  
Surface Heat Fluxes ◽  
Regional Ocean Model System ◽  
Field Campaigns ◽  
The Impact

Air-sea interactions play an important role in atmospheric circulation and boundary layer conditions through changing convection processes and surface heat fluxes, particularly in coastal areas. These changes can affect the concentrations, distributions, and lifetimes of atmospheric pollutants. In this Part II paper, the performance of the Weather Research and Forecasting model with chemistry (WRF/Chem) and the coupled WRF/Chem with the Regional Ocean Model System (ROMS) (WRF/Chem-ROMS) are intercompared for their applications over quadruple-nested domains in Australia during the three following field campaigns: The Sydney Particle Study Stages 1 and 2 (SPS1 and SPS2) and the Measurements of Urban, Marine, and Biogenic Air (MUMBA). The results are used to evaluate the impact of air-sea interaction representation in WRF/Chem-ROMS on model predictions. At 3, 9, and 27 km resolutions, compared to WRF/Chem, the explicit air-sea interactions in WRF/Chem-ROMS lead to substantial improvements in simulated sea-surface temperature (SST), latent heat fluxes (LHF), and sensible heat fluxes (SHF) over the ocean, in terms of statistics and spatial distributions, during all three field campaigns. The use of finer grid resolutions (3 or 9 km) effectively reduces the biases in these variables during SPS1 and SPS2 by WRF/Chem-ROMS, whereas it further increases these biases for WRF/Chem during all field campaigns. The large differences in SST, LHF, and SHF between the two models lead to different radiative, cloud, meteorological, and chemical predictions. WRF/Chem-ROMS generally performs better in terms of statistics and temporal variations for temperature and relative humidity at 2 m, wind speed and direction at 10 m, and precipitation. The percentage differences in simulated surface concentrations between the two models are mostly in the range of ±10% for CO, OH, and O3, ±25% for HCHO, ±30% for NO2, ±35% for H2O2, ±50% for SO2, ±60% for isoprene and terpenes, ±15% for PM2.5, and ±12% for PM10. WRF/Chem-ROMS at 3 km resolution slightly improves the statistical performance of many surface and column concentrations. WRF/Chem simulations with satellite-constrained boundary conditions (BCONs) improve the spatial distributions and magnitudes of column CO for all field campaigns and slightly improve those of the column NO2 for SPS1 and SPS2, column HCHO for SPS1 and MUMBA, and column O3 for SPS2 at 3 km over the Greater Sydney area. The satellite-constrained chemical BCONs reduce the model biases of surface CO, NO, and O3 predictions at 3 km for all field campaigns, surface PM2.5 predictions at 3 km for SPS1 and MUMBA, and surface PM10 predictions at all grid resolutions for all field campaigns. A more important role of chemical BCONs in the Southern Hemisphere, compared to that in the Northern Hemisphere reported in this work, indicates a crucial need in developing more realistic chemical BCONs for O3 in the relatively clean SH.

The Role of Low-Level Flow Direction on Tropical Cyclone Intensity Changes in a Moderate-Sheared Environment

2021 ◽  
Author(s):  
Tsung-Yung Lee ◽  
Chun-Chieh Wu ◽  
Rosimar Rios-Berrios
Keyword(s):  
Inner Core ◽  
Deep Layer ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Background Flow ◽  
Surface Heat Fluxes ◽  
Low Level ◽  
Flow Profiles ◽  
Group Experiences ◽  
The Impact

AbstractThe impact of low-level flow (LLF) direction on the intensification of intense tropical cyclones under moderate deep-layer shear is investigated based on idealized numerical experiments. The background flow profiles are constructed by varying the LLF direction with the same moderate deep-layer shear. When the maximum surface wind speed of the simulation without background flow reaches 70 knots, the background flow profiles are imposed. After a weakening period in the first 12 h, the members with upshear-left-pointing LLF (fast-intensifying group) intensify faster between 12–24 h than those members (slow-intensifying group) with downshear-right-pointing LLF. The fast-intensifying group experiences earlier development of inner-core structures after 12 h, such as potential vorticity below the mid-troposphere, upper-level warm core, eyewall axisymmmetrization, and moist entropy gradient, while the inner-core features of the slow-intensifying group remain relatively weak and asymmetric. The FI group experiences smaller tilt increase and stronger mid-level PV ring development. The upshear-left convection during 6–12 h is responsible for the earlier development of the inner core by reducing ventilation, providing axisymmetric heating and benefiting the eyewall development. The LLF of the fast-intensifying group enhances surface heat fluxes in the downshear side, resulting in higher energy supply to the upshear-left convection from the boundary layer. In all, this study provides new insights on the impact of LLF direction on intense storms under moderate shear by modulating the surface heat fluxes and eyewall convection.

GFDL's CM2 Global Coupled Climate Models. Part III: Tropical Pacific Climate and ENSO

2006 ◽  
Vol 19 (5) ◽  
pp. 698-722 ◽  
Author(s):  
Andrew T. Wittenberg ◽  
Anthony Rosati ◽  
Ngar-Cheung Lau ◽  
Jeffrey J. Ploshay
Keyword(s):  
Thermal Structure ◽  
Tropical Pacific ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Trade Winds ◽  
Equatorial Undercurrent ◽  
Surface Heat Fluxes ◽  
Zonal Winds ◽  
Sst Anomalies

Abstract Multicentury integrations from two global coupled ocean–atmosphere–land–ice models [Climate Model versions 2.0 (CM2.0) and 2.1 (CM2.1), developed at the Geophysical Fluid Dynamics Laboratory] are described in terms of their tropical Pacific climate and El Niño–Southern Oscillation (ENSO). The integrations are run without flux adjustments and provide generally realistic simulations of tropical Pacific climate. The observed annual-mean trade winds and precipitation, sea surface temperature, surface heat fluxes, surface currents, Equatorial Undercurrent, and subsurface thermal structure are well captured by the models. Some biases are evident, including a cold SST bias along the equator, a warm bias along the coast of South America, and a westward extension of the trade winds relative to observations. Along the equator, the models exhibit a robust, westward-propagating annual cycle of SST and zonal winds. During boreal spring, excessive rainfall south of the equator is linked to an unrealistic reversal of the simulated meridional winds in the east, and a stronger-than-observed semiannual signal is evident in the zonal winds and Equatorial Undercurrent. Both CM2.0 and CM2.1 have a robust ENSO with multidecadal fluctuations in amplitude, an irregular period between 2 and 5 yr, and a distribution of SST anomalies that is skewed toward warm events as observed. The evolution of subsurface temperature and current anomalies is also quite realistic. However, the simulated SST anomalies are too strong, too weakly damped by surface heat fluxes, and not as clearly phase locked to the end of the calendar year as in observations. The simulated patterns of tropical Pacific SST, wind stress, and precipitation variability are displaced 20°–30° west of the observed patterns, as are the simulated ENSO teleconnections to wintertime 200-hPa heights over Canada and the northeastern Pacific Ocean. Despite this, the impacts of ENSO on summertime and wintertime precipitation outside the tropical Pacific appear to be well simulated. Impacts of the annual-mean biases on the simulated variability are discussed.

scholarly journals Precipitation Sensitivity to Surface Heat Fluxes over North America in Reanalysis and Model Data

2013 ◽  
Vol 14 (3) ◽  
pp. 722-743 ◽  
Author(s):  
Alexis Berg ◽  
Kirsten Findell ◽  
Benjamin R. Lintner ◽  
Pierre Gentine ◽  
Christopher Kerr
Keyword(s):  
North America ◽  
Rainfall Variability ◽  
Surface Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Eastern United States ◽  
Convective Rainfall ◽  
Surface Heat Fluxes ◽  
Functional Relationships ◽  
The Impact

Abstract A new methodology for assessing the impact of surface heat fluxes on precipitation is applied to data from the North American Regional Reanalysis (NARR) and to output from the Geophysical Fluid Dynamics Laboratory’s Atmospheric Model 2.1 (AM2.1). The method assesses the sensitivity of afternoon convective rainfall frequency and intensity to the late-morning partitioning of latent and sensible heating, quantified in terms of evaporative fraction (EF). Over North America, both NARR and AM2.1 indicate sensitivity of convective rainfall triggering to EF but no appreciable influence of EF on convective rainfall amounts. Functional relationships between the triggering feedback strength (TFS) metric and mean EF demonstrate the occurrence of stronger coupling for mean EF in the range of 0.6 to 0.8. To leading order, AM2.1 exhibits spatial distributions and seasonality of the EF impact on triggering resembling those seen in NARR: rainfall probability increases with higher EF over the eastern United States and Mexico and peaks in Northern Hemisphere summer. Over those regions, the impact of EF variability on afternoon rainfall triggering in summer can explain up to 50% of seasonal rainfall variability. However, the AM2.1 metrics also exhibit some features not present in NARR, for example, strong coupling extending northwestward from the central Great Plains into Canada. Sources of disagreement may include model hydroclimatic biases that affect the mean patterns and variability of surface flux partitioning, with EF variability typically much lower in NARR. Finally, the authors also discuss the consistency of their results with other assessments of land–precipitation coupling obtained from different methodologies.

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.

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