connectivity in socal bight
Download
Skip this Video
Download Presentation
Connectivity in SoCal Bight

Loading in 2 Seconds...

play fullscreen
1 / 33

Connectivity in SoCal Bight - PowerPoint PPT Presentation


  • 99 Views
  • Uploaded on

Connectivity in SoCal Bight. UCLA-UCSB Telecon 1/14/08. Lagrangian Particle Tracking. Used 6-hourly mean flow fields from 1996 thru 1999 (Thanks, Charles!) 1-hour time stepping for particle tracking Output particle data every 6 hours Used UCLA particle tracking code

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Connectivity in SoCal Bight' - gisela-randall


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
connectivity in socal bight
Connectivity in SoCal Bight
  • UCLA-UCSB Telecon 1/14/08
lagrangian particle tracking
Lagrangian Particle Tracking
  • Used 6-hourly mean flow fields from 1996 thru 1999
    • (Thanks, Charles!)
  • 1-hour time stepping for particle tracking
    • Output particle data every 6 hours
    • Used UCLA particle tracking code
  • Released within 10 km from coast
    • Every 1 km, every 6 hours (32,748 particles / day)
  • Depth is fixed at 5 m below top surface
single day single point release 30 day trajectories
Single-day, Single-point Release(30-day trajectories)

Release = Jan 1, 1996

Release = Jan 1, 1997

Red dots = location 30 days later

Release location

Release = Jan 1, 1998

Release = Jan 1, 1999

  • Particles released on the same date from the same location show different dispersal patterns every year
single day single point release 30 day trajectories1
Single-day, Single-point Release(30-day trajectories)

Release = Jan 1, 1996

Release = Jan 16, 1996

Red dots = location 30 days later

Release location

Release = Jan 31, 1996

Release = Feb 15, 1999

  • 2 weeks of difference in release timing can result in very different dispersal patterns
single day single point release 30 day trajectories2
Single-day, Single-Point Release(30-day trajectories)

Near San Diego

Palos Verdes

Release location

  • Dispersal patterns depend on release locations
points
Points
  • Dispersal patterns show strong intra- & inter-annual variability (turbulent dispersion)
    • Particles released at the same location on the same day shows different patterns every year
    • 15 days of difference in release timing can lead to different dispersal patterns
  • Dispersal patterns depend on release location
  • Trajectories show chaotic eddying motions, very different from a simple diffusion process
    • We need statistical description
comparison with drifter data
Comparison with Drifter Data

(Not done yet. Hopefully done by Monday)

lagrangian transition pdf
Lagrangian (Transition) PDF
  • Probability density of Lagrangian particle location after time interval tau from release
  • Estimate using all particles (1996-1999)
    • First, we neglect inter- & intra-annual variability
    • Pretend as if they were statistically stationary processes (i.e., independent of t0) and assume ergodicity...

Particle location after time interval tau

Particle release location & date

lagrangian transition pdf1
Lagrangian (Transition) PDF

x0 = San Nicholas Island

tau = 1 day

tau = 10 days

Release location

tau = 20 days

tau = 30 days

  • Spread out in 20-30 days; more isotropic

(Bin size: 5 km radius in space; 1 day in time)

lagrangian transition pdf2
Lagrangian (Transition) PDF

x0 = Near San Diego (Oceanside)

tau = 1 day

tau = 10 days

Release location

tau = 20 days

tau = 30 days

  • Strong directionality (pole-ward transport)

(Bin size: 5 km radius in space; 1 day in time)

from 9 different sites
From 9 Different Sites

tau = 30 days

pole-ward transport

eddy retention

Release location

more isotropic spread

  • Strong release-position dependence
connectivity matrix
Connectivity Matrix
  • Lagrangian PDF in a matrix form
  • Or, we can average Lagrangian PDF over some time interval (larval fish dispersal case)

(We can do weighted-mean, too)

site locations connectivity
Site Locations & Connectivity

S. Islands

N. Islands

Mainland

Mainland

N. Islands

S. Islands

  • Pole-ward transport & eddy retention show up in connectivity
as a function of evaluation time
As a Function of Evaluation Time

tau = 30 days

tau = 35 days

tau = 40 days

tau = 45 days

tau = 20 -- 40 days

tau = 24 -- 48 days

tau = 28 -- 56 days

tau = 32 -- 64 days

  • Spatial structures in connectivity fade away as tau increases (well mixed)
  • Time averaging does not change connectivity
source destination strength
Source & Destination Strength
  • Summation of connectivity matrix over i or j

(Would be useful for MPA design)

source destination strength1
Source & Destination Strength

tau = 30 days

tau = 30 days

tau = 40 days

tau = 40 days

  • Strongest Destination at Chinese Harbor
  • Match well with observation (not shown here)
summary
Summary
  • Lagrangian particle can reach entire Bight in 30 days
  • Dispersal patterns show release-position dependence
    • Strong directionality along mainland
    • More isotropic from Islands
    • Eddy retention in Channel & near San Clemente Island
  • After spreading out in entire Bight, spatial patterns in Lagrangian PDF gradually fade away
    • Particles either go out of domain or go any places in Bight (well mixed)
summary1
Summary
  • Connectivity shows spatial patterns, reflecting pole-ward transport along mainland & eddy retention
  • But, spatial patterns fade away in time (~ 60 days)
    • As particles from various sources become well mixed
  • Almost all sites can be connected in 30 days
  • Source & destination strength patterns:
    • Strong source: mainland (SD ~ SB)
    • Strong destination: Santa Cruz, E. Anacappa, E. San Nicolas, North mainland (Palos Verdes ~ SB)
    • Strongest destination: Chinese Harbor (self retention + transport from mainland)
inter annual variability
Inter-annual Variability
  • Compute Lagrangian PDF using particles released in a particular year instead of using all years
    • 1) 1996, 2) 1997, 3) 1998, or 4) 1998
  • Let’s see PDF shows inter-annual variability
lagrangian transition pdf3
Lagrangian (Transition) PDF

x0 = Near San Diego (Oceanside), tau = 30 days

Release location

  • Alongshore transport disappears in 1999 (La Nina); very strong in 1997 (El Nino)
  • Important for species invasion from Mexico
lagrangian transition pdf4
Lagrangian (Transition) PDF

x0 = north shore of Santa Cruz Island, tau = 30 days

Release location

  • Eddy retention does not occur every year
  • Important for species retention
source strength
Source Strength

tau = 30 days

summary2
Summary
  • Lagrangian PDF shows strong inter-annual variability
    • Northward transport is strongest in 1997 (El Nino), while it disappears in 1999 (La Nina).
    • Eddy retention does not appear every year
    • These will mean a lot to population ecology
  • Source & destination strength changes accordingly
seasonal variability
Seasonal Variability
  • Compute Lagrangian PDF using particles released in a particular season
    • 1) Winter of 1996-1999,
    • 2) Spring of 1996-1999,
    • 3) Summer of 1996-1999, and
    • 4) Autumn of 1996-1999
  • Seasonal variations are expected
lagrangian transition pdf5
Lagrangian (Transition) PDF

x0 = Near San Diego (Oceanside), tau = 30 days

Release location

  • Pole-ward transport disappears spring & summer when equator-ward wind is strong
lagrangian transition pdf6
Lagrangian (Transition) PDF

x0 = north shore of Santa Cruz Island, tau = 30 days

Release location

  • Eddy retention is weakened in spring & summer when equator-ward wind is strong
lagrangian transition pdf7
Lagrangian (Transition) PDF

x0 = Palos Verdes Peninsula, tau = 30 days

Release location

  • Palos Verdes shows self retention in summer possibly due to wind sheltering
inter annual seasonal variability in connectivity
Inter-annual & Seasonal Variability in Connectivity

tau = 30 days

Self retention at many sites

Self retention at limited sites

Pole-ward transport

  • Seasonal variability is stronger than inter-annual variability (as expected)
source strength1
Source Strength

tau = 30 days

summary3
Summary
  • Lagrangian PDF shows strong inter-seasonal variability (as expected)
    • Pole-ward transport along the mainland appears fall & winter; gone in spring & summer
    • Eddy retention in Channel appears fall & winter
    • Depending on strength of equator-ward wind
  • Seasonal patterns in connectivity are:
    • Winter: strong self retention at many sites
    • Spring & summer: strong self retention at limited places
    • Fall: strong pole-ward transport
applications to be done
Applications (to be done)
  • We need several applications here
    • Ex. 1. Dispersal of fish larvae
    • Ex. 2. Spread of pollutants
  • Given distributions of materials at x0 and t0, concentrations of materials after tau are given by

This can be larval production, oil spill distributions & etc

If molecular diffusion & chemical reactions are negligible, though

ad