scaling and modeling of larval settlement satoshi mitarai oct. 19, 2005
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Scaling and Modeling of Larval Settlement
Satoshi Mitarai
Oct. 19, 2005
GOAL OF “FLOW”
• Assess larval dispersal scales using idealized simulations of California Current
• Develop simple modeling to establish source-destination relationships– Without fluid dynamics simulations, which are
time consuming
WHAT’S NEW?
• Weak upwelling case is added
• Larval dispersal scales are quantified
• A simple model to establish source-destination relationships is proposed– Accounts for spatial scales properly
TEMPERATURE FIELD(TOP VIEW)
Strong upwelling Weak upwelling
Summer Winter
MEAN TEMPERATURE FIELD(SUMMER)
Simulation CalCOFI
Shows reasonable agreement with CalCOFI data
(Averaged over 6 realizations)
MEAN TEMPERATURE FIELD(WINTER)
Simulation CalCOFI
Shows a good agreement with CalCOFI data
(Averaged over 6 realizations)
LARVAL TRAJECTORIESSummer Winter
Eddies sweep larvae into “packet” which stays together thru much of pelagic stage
LAGRANGIAN STATISTICS
3.4 / 4.340 / 484.2 / 4.6Poulain et al
(1998)
4.3 / 4.532 / 382.9 / 3.5Swenson et al
(2001)
1.6 / 1.829 / 296.9 / 5.7Winter
Simulations
3.1 / 4.131 / 353.7 / 3.7Summer
Simulations
Diffusivity
Zonal / Merid
Length Scale
Zonal / Merid
Time scale
Zonal / MeridData Set
Winter shows more correlation in time
& less diffusivity
LARVAL TRANSPORT& SETTLEMENT
Summer Winter
More settlers are observed in winter
ONLY SETTLERSSummer Winter
ALONGSHORE DISPERSAL KERNEL
Summer Winter
Gaussian fitting
More alongshore travel distance in summer
(Obtained from 6 realizations)
AVG = -122 km, STD = 103 km AVG = -80 km, STD = 92 km
CROSS-SHORE DISPERSAL KERNEL
Lognormal fitting
Summer Winter
More offshore travel distance in summerSettlers move out nearshore habitat before settle
(Obtained from 6 realizations)
ARRIVAL DIAGRAMSummer
15 days
21 days
43 km
64 km
Using variogram …
Winter
CONNECTIVITY MATRIXSummer Winter
48 km 53 km
SUMMARY
• Travel distance & survivability shows difference between summer & winter– More travel distance in summer
– Lower survivability in summer
• Settlement scales do not show much difference between summer & winter– Arrival length ~ 50 km
– Arrival time ~ a few weeks
– Connectivity length ~ 50 km
CONNECTIVITY MATRIX MODELDiffusion model Spiky kernel model
Neither one accounts for spatial structures
A NEW MODEL FOR CONNECTIVITY MATRIX
• Idea: model settlement events as a summation of “settlement packets”– Number
– Size
– Source locations
– Travel distance
Rossby radius (~50 km)
Randomly (uniform distribution)
Randomly (dispersal kernel)
• Determine # of settlement packets N = (T/t) (L/l) f (D/l)
NUMBER OF SETTLEMENT PACKETS
T: Larval release duration t: Lagrangian correlation time L: domain size l: Rossby radius f: survivabilityD: standard deviation of dispersal kernel
Total # of released packets
# of settlement events per packet
MODEL PREDICTIONSSummer Winter
Accounts for spatial structures
DIFFUSION LIMIT
Packet model
1 season 6 seasons 12 seasons 120 seasons
1 season 6 seasons 12 seasons Diffusion
Flow simulation Diffusion model
NEXT STEPS
• Use proposed model in F3 model
• Investigate effect of larval behavior– Preliminary study has been already done
• Investigate effect of coastal topography
LAGRANGIAN STATISTICS
3.4 / 4.340 / 484.2 / 4.6Poulain et al
(1998)
4.3 / 4.532 / 382.9 / 3.5Swenson et al
(2001)
1.6 / 1.829 / 296.9 / 5.7Winter
Simulations
3.1 / 4.131 / 353.7 / 3.7Summer
Simulations
Diffusivity
Zonal / Merid
Length Scale
Zonal / Merid
Time scale
Zonal / MeridData Set
Simulations: 6 realizations, 6000 particles
Swenson et al (2001): late spring to early fall, 1985-1990, 124 drifters, 18N-40N
Poulain et al (1998): early spring to late fall, 1985-1986, 29 drifters, 18N-36N
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