Pananjady Swathi | CSIR Centre for Mathematical Modelling and Computer Simulation (original) (raw)
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Papers by Pananjady Swathi
Journal of Climate, 2005
A number of recent papers have argued that the mechanical energy budget of the ocean places const... more A number of recent papers have argued that the mechanical energy budget of the ocean places constraints on how the thermohaline circulation is driven. These papers have been used to argue that climate models, which do not specifically account for the energy of mixing, potentially miss a very important feedback on climate change. This paper reexamines the question of what energetic arguments can teach us about the climate system and concludes that the relationship between energetics and climate is not straightforward. By analyzing the buoyancy transport equation, it is demonstrated that the large-scale transport of heat within the ocean requires an energy source of around 0.2 TW to accomplish vertical transport and around 0.4 TW (resulting from cabbeling) to accomplish horizontal transport. Within two general circulation models, this energy is almost entirely supplied by surface winds. It is also shown that there is no necessary relationship between heat transport and mechanical energy supply.
Global Biogeochemical Cycles, 2004
Differing models of the ocean circulation support different rates of ventilation, which in turn p... more Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
Journal of Climate, 2005
A number of recent papers have argued that the mechanical energy budget of the ocean places const... more A number of recent papers have argued that the mechanical energy budget of the ocean places constraints on how the thermohaline circulation is driven. These papers have been used to argue that climate models, which do not specifically account for the energy of mixing, potentially miss a very important feedback on climate change. This paper reexamines the question of what energetic arguments can teach us about the climate system and concludes that the relationship between energetics and climate is not straightforward. By analyzing the buoyancy transport equation, it is demonstrated that the large-scale transport of heat within the ocean requires an energy source of around 0.2 TW to accomplish vertical transport and around 0.4 TW (resulting from cabbeling) to accomplish horizontal transport. Within two general circulation models, this energy is almost entirely supplied by surface winds. It is also shown that there is no necessary relationship between heat transport and mechanical energy supply.
Global Biogeochemical Cycles, 2004
1] Differing models of the ocean circulation support different rates of ventilation, which in tur... more 1] Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
Global Biogeochemical Cycles, 2004
1] Differing models of the ocean circulation support different rates of ventilation, which in tur... more 1] Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
Journal of Thermophysics and Heat Transfer, 1987
Title: Radiative heat transfer in emitting-absorbing-scattering spherical media. Authors: Tong, T... more Title: Radiative heat transfer in emitting-absorbing-scattering spherical media. Authors: Tong, Timothy W.; Swathi, Pananjady S. Affiliation: AA(Kentucky, University, Lexington), AB(Kentucky, University, Lexington). Publication ...
Journal of Thermophysics and Heat Transfer, 1987
Radiative heat transfer in spherical media that emit, absorb, and scatter radiation is analyzed. ... more Radiative heat transfer in spherical media that emit, absorb, and scatter radiation is analyzed. Linear anisotropic scattering is considered. The spherical harmonics method is used to solve the equation of transfer. The P-1, P-2, P-3, P-7, and P-11 solutions are presented and their accuracy is discussed. Numerical results presented include the radiant heat fluxes at the inner and outer walls of the spherical enclosure and the distribution of the blackbody emissive power in the medium. The effect of scattering on the transfer of radiant energy is illustrated.
Global Biogeochemical Cycles, 2003
1] The carbon budget for the eastern and central Arabian Sea was constructed using results from t... more 1] The carbon budget for the eastern and central Arabian Sea was constructed using results from the Modular Ocean Model and biogeochemical data collected largely under the Indian Joint Global Ocean Flux Study programme. The study region (east of 64°E and between 11°and 21°N) was divided into two vertical boxes; a surface box of the top 100 m that largely undergoes exchanges with atmosphere and exhibits relatively strong seasonal variability and a subsurface box between 100 and 1000 m. Water transport rates in surface layers were maximal (up to 83 Â 10 12 m 3 ) in the southwest monsoon season. Sinking from surface driven by convection (25 Â 10 12 m 3 ) largely supports lateral outflows of water in subsurface layers in the northeast monsoon. Surface waters are renewed 10 times faster (t = 0.8 years) than intermediate waters (t = 8 year). A net supply of 25 Tg C yr À1 is estimated to the upper 1000-m water column of the study area by the physical pump. Photosynthetic activity (234 Tg C yr À1 ) does not seem to support total carbon demands (1203 Tg C yr À1 ) by bacteria and microzooplankton and mesozooplankton in the surface layers. Carbon demand rate requires organic carbon nearly double that of the total living biomass production rate (644 Tg yr À1 ) suggesting that most of the demand might be met from internal cycling involving zooplankton grazing/excretion activities. Sinking flux (69 Tg C yr À1 ) from surface accounts for about 30% of the total photosynthetic production rate indicating intense remineralization of organic matter in the surface layers of the Arabian Sea. Grazing and excretion of carbon by the microzooplankton and mesozooplankton appear to easily sustain perennial supersaturation of carbon dioxide in surface waters of the Arabian Sea and emission of 32 Tg C yr À1 to the atmosphere.
Global Biogeochemical Cycles, 2003
1] The carbon budget for the eastern and central Arabian Sea was constructed using results from t... more 1] The carbon budget for the eastern and central Arabian Sea was constructed using results from the Modular Ocean Model and biogeochemical data collected largely under the Indian Joint Global Ocean Flux Study programme. The study region (east of 64°E and between 11°and 21°N) was divided into two vertical boxes; a surface box of the top 100 m that largely undergoes exchanges with atmosphere and exhibits relatively strong seasonal variability and a subsurface box between 100 and 1000 m. Water transport rates in surface layers were maximal (up to 83 Â 10 12 m 3 ) in the southwest monsoon season. Sinking from surface driven by convection (25 Â 10 12 m 3 ) largely supports lateral outflows of water in subsurface layers in the northeast monsoon. Surface waters are renewed 10 times faster (t = 0.8 years) than intermediate waters (t = 8 year). A net supply of 25 Tg C yr À1 is estimated to the upper 1000-m water column of the study area by the physical pump. Photosynthetic activity (234 Tg C yr À1 ) does not seem to support total carbon demands (1203 Tg C yr À1 ) by bacteria and microzooplankton and mesozooplankton in the surface layers. Carbon demand rate requires organic carbon nearly double that of the total living biomass production rate (644 Tg yr À1 ) suggesting that most of the demand might be met from internal cycling involving zooplankton grazing/excretion activities. Sinking flux (69 Tg C yr À1 ) from surface accounts for about 30% of the total photosynthetic production rate indicating intense remineralization of organic matter in the surface layers of the Arabian Sea. Grazing and excretion of carbon by the microzooplankton and mesozooplankton appear to easily sustain perennial supersaturation of carbon dioxide in surface waters of the Arabian Sea and emission of 32 Tg C yr À1 to the atmosphere.
Journal of Climate, 2005
A number of recent papers have argued that the mechanical energy budget of the ocean places const... more A number of recent papers have argued that the mechanical energy budget of the ocean places constraints on how the thermohaline circulation is driven. These papers have been used to argue that climate models, which do not specifically account for the energy of mixing, potentially miss a very important feedback on climate change. This paper reexamines the question of what energetic arguments can teach us about the climate system and concludes that the relationship between energetics and climate is not straightforward. By analyzing the buoyancy transport equation, it is demonstrated that the large-scale transport of heat within the ocean requires an energy source of around 0.2 TW to accomplish vertical transport and around 0.4 TW (resulting from cabbeling) to accomplish horizontal transport. Within two general circulation models, this energy is almost entirely supplied by surface winds. It is also shown that there is no necessary relationship between heat transport and mechanical energy supply.
Global Biogeochemical Cycles, 2004
Differing models of the ocean circulation support different rates of ventilation, which in turn p... more Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
Journal of Climate, 2005
A number of recent papers have argued that the mechanical energy budget of the ocean places const... more A number of recent papers have argued that the mechanical energy budget of the ocean places constraints on how the thermohaline circulation is driven. These papers have been used to argue that climate models, which do not specifically account for the energy of mixing, potentially miss a very important feedback on climate change. This paper reexamines the question of what energetic arguments can teach us about the climate system and concludes that the relationship between energetics and climate is not straightforward. By analyzing the buoyancy transport equation, it is demonstrated that the large-scale transport of heat within the ocean requires an energy source of around 0.2 TW to accomplish vertical transport and around 0.4 TW (resulting from cabbeling) to accomplish horizontal transport. Within two general circulation models, this energy is almost entirely supplied by surface winds. It is also shown that there is no necessary relationship between heat transport and mechanical energy supply.
Global Biogeochemical Cycles, 2004
1] Differing models of the ocean circulation support different rates of ventilation, which in tur... more 1] Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
Global Biogeochemical Cycles, 2004
1] Differing models of the ocean circulation support different rates of ventilation, which in tur... more 1] Differing models of the ocean circulation support different rates of ventilation, which in turn produce different distributions of radiocarbon, oxygen, and export production. We examine these fields within a suite of general circulation models run to examine the sensitivity of the circulation to the parameterization of subgridscale mixing and surface forcing. We find that different models can explain relatively high fractions of the spatial variance in some fields such as radiocarbon, and that newer estimates of the rate of biological cycling are in better agreement with the models than previously published estimates. We consider how different models achieve such agreement and show that they can accomplish this in different ways. For example, models with high vertical diffusion move young surface waters into the Southern Ocean, while models with high winds move more young North Atlantic water into this region. The dependence on parameter values is not simple. Changes in the vertical diffusion coefficient, for example, can produce major changes in advective fluxes. In the coarse-resolution models studied here, lateral diffusion plays a major role in the tracer budget of the deep ocean, a somewhat worrisome fact as it is poorly constrained both observationally and theoretically.
Journal of Thermophysics and Heat Transfer, 1987
Title: Radiative heat transfer in emitting-absorbing-scattering spherical media. Authors: Tong, T... more Title: Radiative heat transfer in emitting-absorbing-scattering spherical media. Authors: Tong, Timothy W.; Swathi, Pananjady S. Affiliation: AA(Kentucky, University, Lexington), AB(Kentucky, University, Lexington). Publication ...
Journal of Thermophysics and Heat Transfer, 1987
Radiative heat transfer in spherical media that emit, absorb, and scatter radiation is analyzed. ... more Radiative heat transfer in spherical media that emit, absorb, and scatter radiation is analyzed. Linear anisotropic scattering is considered. The spherical harmonics method is used to solve the equation of transfer. The P-1, P-2, P-3, P-7, and P-11 solutions are presented and their accuracy is discussed. Numerical results presented include the radiant heat fluxes at the inner and outer walls of the spherical enclosure and the distribution of the blackbody emissive power in the medium. The effect of scattering on the transfer of radiant energy is illustrated.
Global Biogeochemical Cycles, 2003
1] The carbon budget for the eastern and central Arabian Sea was constructed using results from t... more 1] The carbon budget for the eastern and central Arabian Sea was constructed using results from the Modular Ocean Model and biogeochemical data collected largely under the Indian Joint Global Ocean Flux Study programme. The study region (east of 64°E and between 11°and 21°N) was divided into two vertical boxes; a surface box of the top 100 m that largely undergoes exchanges with atmosphere and exhibits relatively strong seasonal variability and a subsurface box between 100 and 1000 m. Water transport rates in surface layers were maximal (up to 83 Â 10 12 m 3 ) in the southwest monsoon season. Sinking from surface driven by convection (25 Â 10 12 m 3 ) largely supports lateral outflows of water in subsurface layers in the northeast monsoon. Surface waters are renewed 10 times faster (t = 0.8 years) than intermediate waters (t = 8 year). A net supply of 25 Tg C yr À1 is estimated to the upper 1000-m water column of the study area by the physical pump. Photosynthetic activity (234 Tg C yr À1 ) does not seem to support total carbon demands (1203 Tg C yr À1 ) by bacteria and microzooplankton and mesozooplankton in the surface layers. Carbon demand rate requires organic carbon nearly double that of the total living biomass production rate (644 Tg yr À1 ) suggesting that most of the demand might be met from internal cycling involving zooplankton grazing/excretion activities. Sinking flux (69 Tg C yr À1 ) from surface accounts for about 30% of the total photosynthetic production rate indicating intense remineralization of organic matter in the surface layers of the Arabian Sea. Grazing and excretion of carbon by the microzooplankton and mesozooplankton appear to easily sustain perennial supersaturation of carbon dioxide in surface waters of the Arabian Sea and emission of 32 Tg C yr À1 to the atmosphere.
Global Biogeochemical Cycles, 2003
1] The carbon budget for the eastern and central Arabian Sea was constructed using results from t... more 1] The carbon budget for the eastern and central Arabian Sea was constructed using results from the Modular Ocean Model and biogeochemical data collected largely under the Indian Joint Global Ocean Flux Study programme. The study region (east of 64°E and between 11°and 21°N) was divided into two vertical boxes; a surface box of the top 100 m that largely undergoes exchanges with atmosphere and exhibits relatively strong seasonal variability and a subsurface box between 100 and 1000 m. Water transport rates in surface layers were maximal (up to 83 Â 10 12 m 3 ) in the southwest monsoon season. Sinking from surface driven by convection (25 Â 10 12 m 3 ) largely supports lateral outflows of water in subsurface layers in the northeast monsoon. Surface waters are renewed 10 times faster (t = 0.8 years) than intermediate waters (t = 8 year). A net supply of 25 Tg C yr À1 is estimated to the upper 1000-m water column of the study area by the physical pump. Photosynthetic activity (234 Tg C yr À1 ) does not seem to support total carbon demands (1203 Tg C yr À1 ) by bacteria and microzooplankton and mesozooplankton in the surface layers. Carbon demand rate requires organic carbon nearly double that of the total living biomass production rate (644 Tg yr À1 ) suggesting that most of the demand might be met from internal cycling involving zooplankton grazing/excretion activities. Sinking flux (69 Tg C yr À1 ) from surface accounts for about 30% of the total photosynthetic production rate indicating intense remineralization of organic matter in the surface layers of the Arabian Sea. Grazing and excretion of carbon by the microzooplankton and mesozooplankton appear to easily sustain perennial supersaturation of carbon dioxide in surface waters of the Arabian Sea and emission of 32 Tg C yr À1 to the atmosphere.