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Sensitivity Analysis of SST along NJ coast with ADROMS Weifeng (Gordon) Zhang John Wilkin Julia...
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Sensitivity Analysis of SST along NJ coast with ADROMS
Weifeng (Gordon) ZhangJohn WilkinJulia Levin
Hernan Arango
Institute of Marine and Coastal Sciences, Rutgers University
Oct. 2005
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Background
Plenty of measurement in New Jersey shore area;
Ocean forecast and hind-cast with forward ROMS has been running;
To use data assimilation in these area to improve the forecast and measurement;
Adjoint sensitivity analysis with ADROMS is applied first to test the model based on our understanding of the physics in this area.
Adjoint sensitivity analysis: What causes the event?
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Forward Model – Background for Adjoint model
Three idealized cases (steady low river discharge, no tide, no surface exchange):
No wind Southwestward wind Northeastward wind
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Adjoint sensitivity set-up
For upwelling event:
Background state: 5 days bi-hourly forward model output.
Event time:
Adjoint forcing:
Adjoint variable:
FORWARD_MIXING: Adjoint model reads mixing coefficients from forward output
5.0 4.75t DendS DstrS days
21
2J SST dAdt
A t
SST dA dtscope
A t
, , , ,J J J J
temp salt zeta sustr
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No wind case
J
SST
J
SSS
J
u
SST
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Nowind case (cont’d)
Adjoint variable Magnitude of adjoint variable
Standard deviation of variable
ad_SST (0, 0.02) 5 0.1ad_SSS (-0.002, 0.002) 5 0.01ad_u/ad_v (-0.05, 0.05) 0.5 0.025ad_Akv (-100, 100) 10-4 10-2
ad_Akt (0, 60) 10-5 10-4
ad_Aks (-3, 3) 10-5 10-5
xx
J J J J JJ T S u Akt
T S u Akt
JX
X
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Southward wind case
J
SST
J
sustr
J
SSS
J
SST
SST
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Southward wind case (cont’d)
Adjoint variable Magnitude of adjoint variable
Standard deviation of variable
ad_SST (0, 0.02) 5 0.1ad_SSS (-0.005, 0.005) 5 0.025ad_sustr/ad_svstr (-100, 100) 0.002 0.2ad_u/ad_v (-0.05, 0.05) 0.5 0.025ad_Akv (-150, 150) 10-4 0.015ad_Akt (0, 15) 10-5 10-4
ad_Aks (-10, 5) 10-5 10-4
JX
X
xx
J J J J JJ T S u Akt
T S u Akt
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Northward wind caseJ T T
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Northward wind case (cont’d)
J
SSS
J
svstr
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Summary
ADROMS gives physically reasonable results for sensitivity analysis on idealized application in NJ shore area
Users need to think about the definition of the measure of certain event, J
The validity of linearization to the nonlinear model has to be considered carefully and proved first
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Great appreciation goes to
John Wilkin, Hernan Arango, Julia Levin, Andrew Moore and B-J Choi!