Light Attenuation along the California Coast By: LT Lars Lone Completed for OC3570

Overview Reason for research Attenuation revisited Data used Results Conclusions Follow on studies

Reason for Research Thesis research Use of hyperspectral imagery in visible to near IR range Understand more why visibility so limited Not really discussed in my other OC classes and wanted to look at it more

Attenuation Beer’s Law: Iz = Io*exp(-k*z) So: k = -ln(Iz/ Io)/z Where Iz = PAR, Io = SPAR, k = attenuation, z = depth So: k = -ln(Iz/ Io)/z

Data Used Sites Used 2,12,23 Sites Used 40,45,46,69

Data Used Data sets taken from local apparent noon Mitigates need for use of Snell’s Law and refraction issues Looked at: SPAR PAR (photosynthetic active radiation) Transmissivity Fluorometer

Results: Station 2 Attenuation and Par have similar curve shape No extreme changes in any of the data sets looked at

Results: Station 12 Largest variation of attenuation Water depth greater here Similar Transmissivity and Fluorometer as before Interesting values for PAR sensor

Results: Station 23 Abnormal attenuation curve And lowest variation in attenuation Transmissivity and Fluorometer look fairly normal Par sensor off by factor of 10 compared to previous 2 stations.

Results: Station 40 Attenuation Similar to station 12 Fluorometer readings remain constant longer Interesting spikes in SPAR at same depth Note surface PAR as well

Results: Station 45 Interesting attenuation shift Very short attenuation range Large PAR values near surface similar to Station 23

Results: Station 46 Less variation in attenuation Interesting PAR results as well No significant changes in Fluorometer or Transmissivity

Results: Station 69 Again, abnormal attenuation results PAR sensor has a factor of 10 greater than normal once again No significant value difference for Fluorometer or Transmissivity

Conclusions: Deep water had greater overall attenuation values Typical ocean values range from .02-2 My results agree with this Unsure of cause for spike in PAR values at half of the sites More research needs to be done

Future Studies: Attenuation at times other than local apparent noon Nearshore vs. offshore Attenuation loss due to reflectance vs. absorption