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What is the entrainment process in the ocean mixed layer?
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What is the entrainment process in the ocean mixed layer?
Dear Ziguang The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)). The entrainment is composed of three terms: 1. the entrainment due to the vertical velocity (w*|T-T(-h)[) 2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)]) 3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h)) Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress. To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site). hope this can help you! Don't hesitate to ask me explanation bey email! G.C.
Dear Ziguang The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)). The entrainment is composed of three terms: 1. the entrainment due to the vertical velocity (w*|T-T(-h)[) 2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)]) 3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h)) Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress. To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site). hope this can help you! Don't hesitate to ask me explanation bey email! G.C.
Hi Ziguang, In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface. By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process. In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping). Benjamin
Hi Ziguang, In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface. By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process. In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping). Benjamin
Ziguang Li, well, it depends on what you wish to achieve. The idea/notion of a mixed-layer depth is a strong simplification of the upper ocean which is actually continuously stratified. On a global scale today we have high-resolution numerical models wherein the current knowledge of small scales is more or less embedded. Great deficits we still have in the understanding of the deep-reaching internal waves which mix scalars like heat down into the abyssal. This is a great theoretical challenge because the heat household of the Planet Earth is mainly governed by the oceans, and because it is difficult to design a reasonable theory with real results -- in terms of effectively applicable diffusivities and Prandtl numbers etc.
Ziguang Li, well, it depends on what you wish to achieve. The idea/notion of a mixed-layer depth is a strong simplification of the upper ocean which is actually continuously stratified. On a global scale today we have high-resolution numerical models wherein the current knowledge of small scales is more or less embedded. Great deficits we still have in the understanding of the deep-reaching internal waves which mix scalars like heat down into the abyssal. This is a great theoretical challenge because the heat household of the Planet Earth is mainly governed by the oceans, and because it is difficult to design a reasonable theory with real results -- in terms of effectively applicable diffusivities and Prandtl numbers etc.
Dear Ziguang The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)). The entrainment is composed of three terms: 1. the entrainment due to the vertical velocity (w*|T-T(-h)[) 2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)]) 3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h)) Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress. To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site). hope this can help you! Don't hesitate to ask me explanation bey email! G.C.
Dear Ziguang The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)). The entrainment is composed of three terms: 1. the entrainment due to the vertical velocity (w*|T-T(-h)[) 2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)]) 3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h)) Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress. To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site). hope this can help you! Don't hesitate to ask me explanation bey email! G.C.
Hi Ziguang, In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface. By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process. In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping). Benjamin
Hi Ziguang, In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface. By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process. In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping). Benjamin
Dear Ziguang
The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)).
The entrainment is composed of three terms:
1. the entrainment due to the vertical velocity (w*|T-T(-h)[)
2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)])
3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h))
Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress.
To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site).
hope this can help you! Don't hesitate to ask me explanation bey email!
G.C.
Dear Ziguang
The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)).
The entrainment is composed of three terms:
1. the entrainment due to the vertical velocity (w*|T-T(-h)[)
2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)])
3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h))
Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress.
To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site).
hope this can help you! Don't hesitate to ask me explanation bey email!
G.C.
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Hi Ziguang,
In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface.
By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process.
In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping).
Benjamin
Hi Ziguang,
In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface.
By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process.
In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping).
Benjamin
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Ziguang Li, well, it depends on what you wish to achieve. The idea/notion of a mixed-layer depth is a strong simplification of the upper ocean which is actually continuously stratified. On a global scale today we have high-resolution numerical models wherein the current knowledge of small scales is more or less embedded. Great deficits we still have in the understanding of the deep-reaching internal waves which mix scalars like heat down into the abyssal. This is a great theoretical challenge because the heat household of the Planet Earth is mainly governed by the oceans, and because it is difficult to design a reasonable theory with real results -- in terms of effectively applicable diffusivities and Prandtl numbers etc.
Ziguang Li, well, it depends on what you wish to achieve. The idea/notion of a mixed-layer depth is a strong simplification of the upper ocean which is actually continuously stratified. On a global scale today we have high-resolution numerical models wherein the current knowledge of small scales is more or less embedded. Great deficits we still have in the understanding of the deep-reaching internal waves which mix scalars like heat down into the abyssal. This is a great theoretical challenge because the heat household of the Planet Earth is mainly governed by the oceans, and because it is difficult to design a reasonable theory with real results -- in terms of effectively applicable diffusivities and Prandtl numbers etc.
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A good started in the literature would be the paper by Williams, Spall and Marshall (1995): Does Stommel's Mixed Layer Demon Work? Journal of Physical Oceanography, 25. You can find it online at
http://www.whoi.edu/science/po/people/mspall/pdfs/spall_stommel_jpo1995.pdf
A good started in the literature would be the paper by Williams, Spall and Marshall (1995): Does Stommel's Mixed Layer Demon Work? Journal of Physical Oceanography, 25. You can find it online at
http://www.whoi.edu/science/po/people/mspall/pdfs/spall_stommel_jpo1995.pdf
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Thanks for your explanations - they were really helpful!
All the best
Jan
Thanks for your explanations - they were really helpful!
All the best
Jan
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Dear Ziguang
The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)).
The entrainment is composed of three terms:
1. the entrainment due to the vertical velocity (w*|T-T(-h)[)
2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)])
3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h))
Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress.
To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site).
hope this can help you! Don't hesitate to ask me explanation bey email!
G.C.
Dear Ziguang
The entrainment process in the ocean mixed layer is the product of the entremaint velocity (We) and the difference of temperature between the mean temperature in the mixed layer (T) with the temperature just below the mixed layer base (T(-h)).
The entrainment is composed of three terms:
1. the entrainment due to the vertical velocity (w*|T-T(-h)[)
2. the entrainment due to the tendency of the mixed layer depth (dh/dt*[T-T(-h)])
3. the entrainent due to "advection of the mixed layer depth" ((U(-h).Grad(h))
Strictly speaking the Ekman pumping is the vertical velocity induced by the wind-stress curl., and is not exactly a process. The process associated would be vertical advection induced by the Ekman pumping. This advection is one component of the entrainment (1) because w includes implicitely the vertical velocity due to the wind stress.
To see how the entrainment appears in the primitive equation system, you have to derive the evolution of the heat content in the mixed layer (or more generally between two levels in the ocean). You can find this derivation in some of my papers (see my Research Gate site).
hope this can help you! Don't hesitate to ask me explanation bey email!
G.C.
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Hi Ziguang,
In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface.
By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process.
In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping).
Benjamin
Hi Ziguang,
In this answer, I am assuming you are referring to vertical entrainment across the ocean mixed layer (OML) base. Vertical entrainment is a turbulent irreversible process where turbulent vertical velocities mix OML warmer waters with cooler thermocline waters. This diabatic process causes OML deepening where the resulting OML temperatures are cooler (because of the turbulent vertical mixing). That is, vertical entrainment produces a new OML with different thickness, salinity and temperature. Vertical entrainment is typically caused by instantaneous wind stirring, by vertical shear instability of wind-driven horizontal currents, and by buoyancy forcing at the sea surface.
By contrast, Ekman pumping (or upwelling process) generates a vertical advection velocity that does not cause vertical mixing (or entrainment) between isopycnal surfaces. Vertical advection of temperature caused by Ekman upwelling is an adiabatic, reversible process.
In summary, during wind-forcing events, the OML temperature and thickness are impacted by the total vertical velocity, which consist of a turbulent component (irreversible turbulent entrainment) and an advective component (reversible Ekman pumping).
Benjamin
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