Ramping - Revision history

Taylorgasher: /* Ramping Method */

2018-10-15T15:36:36Z

Ramping Method

← Older revision		Revision as of 11:36, 15 October 2018
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	*[[DRAMPMete]] - meteorological forcing		*[[DRAMPMete]] - meteorological forcing
	*[[DRAMPWRad]] - wave radiation stress forcing		*[[DRAMPWRad]] - wave radiation stress forcing
	Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]], affect the timing of the ramping terms.		Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]] (also in days), affect the timing of the ramping terms.
	*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.		*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.
	If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime		If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime

Taylorgasher: Added typical values, cleaned up usage case, added Zach's note about IBTYPE=52

2018-10-15T15:35:07Z

Added typical values, cleaned up usage case, added Zach's note about IBTYPE=52

← Older revision		Revision as of 11:35, 15 October 2018
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	*[[DRAMPIntFlux]] - internal flux BC		*[[DRAMPIntFlux]] - internal flux BC
	*[[DRAMPElev]] - elevation specified BC		*[[DRAMPElev]] - elevation specified BC
	*[[DRAMPTip]] - tidal potential BC		*[[DRAMPTip]] - tidal potential forcing
	*[[DRAMPMete]] - meteorological forcing		*[[DRAMPMete]] - meteorological forcing
	*[[DRAMPWRad]] - wave radiation stress forcing		*[[DRAMPWRad]] - wave radiation stress forcing
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	If NRAMP=8, then all DRAMP terms are as above, except DRAMPMete is relative to coldstart plus FluxSettlingTime plus DUnRampMete		If NRAMP=8, then all DRAMP terms are as above, except DRAMPMete is relative to coldstart plus FluxSettlingTime plus DUnRampMete

	~~FluxSettlingTIme~~ is used because for large river systems such as the Mississippi River, it can take several days to initialize them and equilibrate~~; this may be partially relieved by~~ using ~~more advanced initialization schemes are used like~~ the [[~~initial river elevation~~]] ~~nodal attribute~~. DUnRampMete is ~~used~~ because often a simulation ~~will be initiated~~ without meteorological forcing, such as a tide-only simulation, and meteorological ramping is needed when this forcing is added at a ~~later time~~.		FluxSettlingTime is used because, for large river systems such as the Mississippi River, it can take several days to initialize them and equilibrate. It is a requirement when using the radiation flux boundary condition ([[IBTYPE]]=52) because instabilities can quickly form otherwise. DUnRampMete is useful because often a simulation is coldstarted without meteorological forcing (such as a tide-only simulation), and meteorological ramping is needed later when this forcing is added to a hotstarted simulation.

	There are also namelist controls for some ramping terms, such as water level offset forcing.		There are also namelist controls for some ramping terms, such as water level offset forcing.

			== Typical Values ==
			The following is a list of typical number of days for DRAMP* variables for different forcing terms.
			* Flux: 0.5-5 days
			* Tide: 5-30 days
			* Meteorology: 0.5-2 days

	== Example Usage Case ==		== Example Usage Case ==
	Consider the following illustrative example of how one might use all of these. Let's say someone by the name of Arturo wants to run a hindcast simulation of Hurricane Katrina impacting Louisiana and Mississippi with SWAN+ADCIRC, and needs to get an accurate sense of the surge traveling up the Mississippi ~~and Atchafalaya Rivers~~. Doing so requires specifying realistic flux boundary conditions at the upstream end of the ~~rivers~~. Feeling ambitious, Arturo sets NRAMP=1 and (because he has just 5 days of met. forcing) sets DRAMP=1. His model goes unstable in the rivers. Now feeling cautious, he first does a 30-day simulation to ramp in the river and tide forcing, with NRAMP=3, DRAMP=15 days, DRAMPExtFlux=3 days, and FluxSettlingTime=10 days. This means the coldstart simulation runs ~~(per the definition of FluxSettlingTime)~~ with only river (external flux) forcing for the first 10 days, after which the tides are ramped in over 15 days, and then the model is left at full-strength forcing for 5 days (10+15+5=30)). A hotstart file is generated at the end of the run. Arturo uses this to hotstart his 5-day ([[RNDAY]]=35) storm simulation, where DUnRAMPMete=30 ensures the meteorological forcing ramping starts at the 30-day mark, and DRAMPMete=0.5 ensures a quick ramping of the meteorological forcing. Everything works great. He's probably been overly cautious here, and might want to play around with shortening some of the ramping times, but hey, at least it works. Note that in the hotstart simulation, Arturo does not need to set any of the other values on the DRAMP line non-zero because 30-days has already passed, and so anything less than this is ignored by ADCIRC. Furthermore, note that DRAMPWRad has been left at zero since ramping in the meteorological forcing implies that the waves, and so the wave radiation stresses, should grow slowly.		Consider the following illustrative example of how one might use all of these. Let's say someone by the name of Arturo wants to run a hindcast simulation of Hurricane Katrina impacting Louisiana and Mississippi with SWAN+ADCIRC, and needs to get an accurate sense of the surge traveling up the Mississippi River. Doing so requires specifying realistic flux boundary conditions at the upstream end of the river. Feeling ambitious, Arturo sets NRAMP=1 and (because he has just 5 days of met. forcing) sets DRAMP=1. His model goes unstable in the rivers. Now feeling cautious, he first does a 30-day simulation to ramp in the river and tide forcing, with NRAMP=3, DRAMP=15 days, DRAMPExtFlux=3 days, and FluxSettlingTime=10 days. This means the coldstart simulation runs with only river (external flux) forcing for the first 10 days, after which the tides are ramped in over 15 days, and then the model is left at full-strength forcing for another 5 days to equilibrate (10+15+5=30 days). A hotstart file is generated at the end of the run. Arturo uses this to hotstart his 5-day ([[RNDAY]]=35) storm simulation, where DUnRAMPMete=30 ensures the meteorological forcing ramping starts at the 30-day mark, and DRAMPMete=0.5 ensures a quick ramping of the meteorological forcing. Everything works great. He's probably been overly cautious here, and might want to play around with shortening some of the ramping times, but hey, at least it works.

			Note that in the hotstart simulation, Arturo does not need to set any of the other values on the DRAMP line non-zero because 30-days has already passed, and so anything less than this is ignored by ADCIRC. Furthermore, note that DRAMPWRad has been left at zero since ramping in the meteorological forcing implies that the waves, and so the wave radiation stresses, should grow slowly.

Taylorgasher: Revised example

2018-10-10T03:55:31Z

Revised example

← Older revision		Revision as of 23:55, 9 October 2018
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	== Example Usage Case ==		== Example Usage Case ==
	Consider the following illustrative example of how one might use all of these. Let's say someone by the name of Arturo wants to run a hindcast simulation of Hurricane Katrina impacting Louisiana and Mississippi with SWAN+ADCIRC, and needs to get an accurate sense of the surge traveling up the Mississippi and Atchafalaya Rivers. Doing so requires specifying realistic flux boundary conditions at the upstream end of the rivers. Feeling ambitious, Arturo sets NRAMP=1 and (because he has just 5 days of met. forcing) sets DRAMP=1. His model goes unstable in the rivers. Now feeling cautious, he ~~sets~~ NRAMP=8, ~~uses FluxSettlingTime~~=10 days, DRAMPExtFlux=3 days, ~~DRAMPTip~~=~~15 days, DRAMPUnMete=30 days, DRAMPMete=0.5~~ days~~, and all the other DRAMP* values are set to zero~~. ~~That~~ means ~~in this scenario, Arturo runs a 30-day~~ coldstart simulation ~~where~~ (per the definition of FluxSettlingTime) only river (external flux) forcing ~~is applied~~ for the first 10 days, after which the tides are ramped in over 15 days, and then the model is left at full-strength forcing for 5 days (10+15+5=30). A hotstart file is generated at the end of the run. Arturo uses this to hotstart his 5-day storm simulation, where DUnRAMPMete=30 ensures the meteorological forcing ramping starts at the 30-day mark. Everything works great. He's probably been overly cautious here, and might want to play around with shortening some of the ramping times, but hey, at least it works.		Consider the following illustrative example of how one might use all of these. Let's say someone by the name of Arturo wants to run a hindcast simulation of Hurricane Katrina impacting Louisiana and Mississippi with SWAN+ADCIRC, and needs to get an accurate sense of the surge traveling up the Mississippi and Atchafalaya Rivers. Doing so requires specifying realistic flux boundary conditions at the upstream end of the rivers. Feeling ambitious, Arturo sets NRAMP=1 and (because he has just 5 days of met. forcing) sets DRAMP=1. His model goes unstable in the rivers. Now feeling cautious, he first does a 30-day simulation to ramp in the river and tide forcing, with NRAMP=3, DRAMP=15 days, DRAMPExtFlux=3 days, and FluxSettlingTime=10 days. This means the coldstart simulation runs (per the definition of FluxSettlingTime) with only river (external flux) forcing for the first 10 days, after which the tides are ramped in over 15 days, and then the model is left at full-strength forcing for 5 days (10+15+5=30)). A hotstart file is generated at the end of the run. Arturo uses this to hotstart his 5-day ([[RNDAY]]=35) storm simulation, where DUnRAMPMete=30 ensures the meteorological forcing ramping starts at the 30-day mark, and DRAMPMete=0.5 ensures a quick ramping of the meteorological forcing. Everything works great. He's probably been overly cautious here, and might want to play around with shortening some of the ramping times, but hey, at least it works. Note that in the hotstart simulation, Arturo does not need to set any of the other values on the DRAMP line non-zero because 30-days has already passed, and so anything less than this is ignored by ADCIRC. Furthermore, note that DRAMPWRad has been left at zero since ramping in the meteorological forcing implies that the waves, and so the wave radiation stresses, should grow slowly.

Taylorgasher: Added example use case and some other stuff

2018-10-10T03:47:57Z

Added example use case and some other stuff

← Older revision		Revision as of 23:47, 9 October 2018
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	Ramping is a way by which terms can be steady increased over some period of time in a simulation. This is most often done for model forcing terms, ~~principally~~ in order to avoid applying a shock to the model.		Ramping is a way by which terms can be steady increased over some period of time in a simulation. This is most often done for model forcing terms like tides or winds, in order to avoid applying a shock to the model.

	== Conceptual Justification ==		== Conceptual Justification ==
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	== Ramping Method ==		== Ramping Method ==
	[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. All ramps in ADCIRC are applied as (truncated) [https://en.wikipedia.org/wiki/Hyperbolic_function hyperbolic tangent] functions over a specified number of days. The various DRAMP* ~~terms~~ control the number of days over which the ramping is applied. Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]], affect the timing of the ramping terms.		[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. All ramps in ADCIRC are applied as (truncated) [https://en.wikipedia.org/wiki/Hyperbolic_function hyperbolic tangent] functions over a specified number of days. The various DRAMP* variables control the number of '''days''' over which the ramping is applied for individual forcing terms, they are:
			[[DRAMP]] - any forcing terms not covered by the other DRAMP terms
			*[[DRAMPExtFlux]] - external flux boundary condition (BC)
			*[[DRAMPIntFlux]] - internal flux BC
			*[[DRAMPElev]] - elevation specified BC
			*[[DRAMPTip]] - tidal potential BC
			*[[DRAMPMete]] - meteorological forcing
			*[[DRAMPWRad]] - wave radiation stress forcing
			Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]], affect the timing of the ramping terms.
	*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.		*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.
	If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime		If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime
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	There are also namelist controls for some ramping terms, such as water level offset forcing.		There are also namelist controls for some ramping terms, such as water level offset forcing.

			== Example Usage Case ==
			Consider the following illustrative example of how one might use all of these. Let's say someone by the name of Arturo wants to run a hindcast simulation of Hurricane Katrina impacting Louisiana and Mississippi with SWAN+ADCIRC, and needs to get an accurate sense of the surge traveling up the Mississippi and Atchafalaya Rivers. Doing so requires specifying realistic flux boundary conditions at the upstream end of the rivers. Feeling ambitious, Arturo sets NRAMP=1 and (because he has just 5 days of met. forcing) sets DRAMP=1. His model goes unstable in the rivers. Now feeling cautious, he sets NRAMP=8, uses FluxSettlingTime=10 days, DRAMPExtFlux=3 days, DRAMPTip=15 days, DRAMPUnMete=30 days, DRAMPMete=0.5 days, and all the other DRAMP* values are set to zero. That means in this scenario, Arturo runs a 30-day coldstart simulation where (per the definition of FluxSettlingTime) only river (external flux) forcing is applied for the first 10 days, after which the tides are ramped in over 15 days, and then the model is left at full-strength forcing for 5 days (10+15+5=30). A hotstart file is generated at the end of the run. Arturo uses this to hotstart his 5-day storm simulation, where DUnRAMPMete=30 ensures the meteorological forcing ramping starts at the 30-day mark. Everything works great. He's probably been overly cautious here, and might want to play around with shortening some of the ramping times, but hey, at least it works.

Taylorgasher: Finishing up Ramping Method section

2018-10-10T03:01:25Z

Finishing up Ramping Method section

← Older revision		Revision as of 23:01, 9 October 2018
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	== Ramping Method ==		== Ramping Method ==
	[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. All ramps in ADCIRC are applied as (truncated) hyperbolic tangent functions over a specified number of days. The various DRAMP* terms control the number of days over which the ramping is applied. Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]], affect the timing of the ramping terms.		[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. All ramps in ADCIRC are applied as (truncated) [https://en.wikipedia.org/wiki/Hyperbolic_function hyperbolic tangent] functions over a specified number of days. The various DRAMP* terms control the number of days over which the ramping is applied. Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]], affect the timing of the ramping terms.
	*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.		*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.
	If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime		If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime
	*If NRAMP=8,		If NRAMP=8, then all DRAMP terms are as above, except DRAMPMete is relative to coldstart plus FluxSettlingTime plus DUnRampMete

			FluxSettlingTIme is used because for large river systems such as the Mississippi River, it can take several days to initialize them and equilibrate; this may be partially relieved by using more advanced initialization schemes are used like the [[initial river elevation]] nodal attribute. DUnRampMete is used because often a simulation will be initiated without meteorological forcing, such as a tide-only simulation, and meteorological ramping is needed when this forcing is added at a later time.

	There are also namelist controls for some ramping terms, such as water level offset forcing.		There are also namelist controls for some ramping terms, such as water level offset forcing.

Taylorgasher: Adding more, still have work to do

2018-10-09T23:29:44Z

Adding more, still have work to do

← Older revision		Revision as of 19:29, 9 October 2018
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	To understand why ramping of forcing terms is needed, consider tides. Starting a model with the water surface and velocity as zero everywhere, but with full tidal forcing, is analogous to having a planet at rest, then instantly putting a moon and sun in place, in motion with each other. This large, instantaneous change in conditions (forcing) is what creates the shock, which tends to result in spurious waves being formed. Ideally, one would initialize a tidal simulation with the water surface and velocity at all points matching what it should be at the point in time the model is initiated, given the phase of the tides, however this is not generally achievable. Gradually scaling up forcing terms helps avoid this problem.		To understand why ramping of forcing terms is needed, consider tides. Starting a model with the water surface and velocity as zero everywhere, but with full tidal forcing, is analogous to having a planet at rest, then instantly putting a moon and sun in place, in motion with each other. This large, instantaneous change in conditions (forcing) is what creates the shock, which tends to result in spurious waves being formed. Ideally, one would initialize a tidal simulation with the water surface and velocity at all points matching what it should be at the point in time the model is initiated, given the phase of the tides, however this is not generally achievable. Gradually scaling up forcing terms helps avoid this problem.

	== Ramping ~~Parameters~~ ==		== Ramping Method ==
	[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. The various DRAMP* terms...		[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. All ramps in ADCIRC are applied as (truncated) hyperbolic tangent functions over a specified number of days. The various DRAMP* terms control the number of days over which the ramping is applied. Two other variables, [[FluxSettlingTime]] and [[DUnRampMete]], affect the timing of the ramping terms.
			*If NRAMP=1, then DRAMP is relative to [[coldstart]] time.
			If 1<NRAMP<8, then all DRAMP terms are relative to coldstart time plus FluxSettlingTime
			*If NRAMP=8,

			There are also namelist controls for some ramping terms, such as water level offset forcing.

Taylorgasher: Initial work on page

2018-10-09T22:41:03Z

Initial work on page

New page

Ramping is a way by which terms can be steady increased over some period of time in a simulation. This is most often done for model forcing terms, principally in order to avoid applying a shock to the model.

== Conceptual Justification ==
To understand why ramping of forcing terms is needed, consider tides. Starting a model with the water surface and velocity as zero everywhere, but with full tidal forcing, is analogous to having a planet at rest, then instantly putting a moon and sun in place, in motion with each other. This large, instantaneous change in conditions (forcing) is what creates the shock, which tends to result in spurious waves being formed. Ideally, one would initialize a tidal simulation with the water surface and velocity at all points matching what it should be at the point in time the model is initiated, given the phase of the tides, however this is not generally achievable. Gradually scaling up forcing terms helps avoid this problem.

== Ramping Parameters ==
[[NRAMP]] controls whether ramping is enabled, as well as how many ramping terms there are. This is to permit users to apply different ramping times for different forcing terms. The various DRAMP* terms...