LT Erica A Museler OC3570 16 September 2002 Operational Oceanography Project: comparison of in-situ and measured optical properties LT Erica A Museler OC3570 16 September 2002
Presentation Outline Guide to Ocean Optics Transmissometer SeaWiFS/ Ocean Color In-situ work Leaps Reference to Navy Operations
Quick Guide to Ocean Optics Ocean optics: study of the propagation of light and it’s interactions with the materials in the ocean. IOP’s and AOP’s ctotal and Kd http://www.bigelow.org/~ahb/gomoosopticalweb/Ocean_optics/oceanoptics.htm
Transmissometer *Instrument that measures a collimated beam of light transmission with-in 25cm (z), using the 670nm wavelength. *Range in water is 0-100% (0-5 VDC) % Transmission = 20 x Volts c = -ln (%Transmission)/[z] (1) __________________________________________________ *For Diver Visibility take (1) and solve for z (call it R for range of visibility and assume % transmission is constant): R ~ 4.0/[c] *Where did 4.0 come from?
CTD Transmissometer % Dive 1 Results c R 3.05 77.5 1.02 3.92 6.1 77.4 Depth % c R 3.05 77.5 1.02 3.92 6.1 77.4 9.14
CTD Transmissometer % Dive 2 Results c R 3.05 72.5 1.29 3.1 6.1 72.0 Depth % c R 3.05 72.5 1.29 3.1 6.1 72.0 1.31 9.14 75.8 1.11 3.6
CTD Transmissometer % Dive 4 Results (*) c R Depth % c R 3.05 75.1 1.15 3.49 6.1 9.14 75.4 1.13 3.54 (*) Dive 3 was a hull dive
CTD Transmissometer % Dive 5 Results c R 3.05 90.0 .42 9.5 6.1 91.0 Depth % c R 3.05 90.0 .42 9.5 6.1 91.0 .38 10.5 9.14 90.5 .40 10.0
Transmissometer
In-situ work (the fun stuff.) 4 Dives for measurements (1,2,4,5) Note: dive #3 was a hull dive and not counted for experimental measurements. All dives with the exception of the last one showed greater visibility below ~4.6 m The last dive had decreased visibility at the 9.14 m mark.
Dive Location Depths(m) Visibilities(m) 1 2 4 5 3.05 6.1 2.08 4.32 ~ Monterey Bay 36 46.7 121 50.4 3.05 6.1 2.08 4.32 2 ~ Port San Luis 35 07.9 120 41.156 9.14 4.57 4.7 6.15 4 35 05.9 120 45.7 7.36 7.62 5 ~ Santa Barbara 34 24.6 119 57.1 6.25
SeaWiFS K532 (Diffuse Attenuation Coefficient at 532nm) August 2002 monthly composite DIVE 5: K532~ 0.1 m-1 Light intensity will be reduced one Natural log (1db) within 10 meters. (ie: Visibility is 10 m deep) The darker blue regions reveal an area with greater visibility.
Observations Visibility and Transmissivity values do not match exactly but do show the same trend for each station This difference is associated with the different wavelengths viewed and how light is scattered -- Transmissometer, well collimated beam of red light -- The human eye, un-collimated view of light in the green to blue spectrum
Leaps Assumption that the eye attenuates like a narrow beam of light, ie: transmissometer How accurate is the ‘transmissometer’? No consideration for scattering and types of scatterers. Assumed same contrasts Lighting conditions and look directions are not addressed.
Reference to Navy Operations: Planning, Time, Operations, Money… Salvage Ops: ‘Is it too turbid to send divers to recover this aircraft this week?’ EOD: ‘Should we send a diver (clear vis) or a dolphin (muddy waters) to ID/locate the threat?’ MIW: ‘Will our ROV camera’s see the target before physical contact is made?’ SPECOPS: ‘Will the beach insertion during the day be compromised by airborne visual contacts?’
End of Presentation References National Research Counsel: Oceanography and Naval SPECWAR National Research Counsel: Oceanography and Mine Warfare www7240.nrlssc.navy.mil/ocolor/HOTEL Sea Tech Transmissometer Manual Light and Water Radiative Transfer in Natural Waters, Mobley, Curtis D. 1994 NRL: Kernal Blitz Report, April 5, 2001 DiVA Final Report, Maffione, Robert A. August 2002 Mr. Tarry Rago