REVISION DATE: 11 August, 1995 This README document provides background for the bio-optical data collected on WOCE Hydrographic Program (WHP) leg P16C, September, 1991, aboard RV Thomas Washington. The background for this project can be found in Marra et al. (1992) and Marra (1992). 1. Cruise Description This was the first JGOFS bio-optics study in collaboration with the World Ocean Circulation Experiment Hydrographic Program (WHP). The cruise followed a transect along 150W from Papeete, Tahiti, to Honolulu, Hawaii. It was the third leg of an expedition that covered an area of the Pacific from San Diego, Calif., to Tahiti, south to approximately 35S and finally to Hawaii. Carol Knudson, from John Marra's laboratory at Lamont-Doherty Earth Observatory was responsible for collecting the optics data. Rather than having the optics casts from the stern of the ship as originally planned, we deployed our package from the port side of the ship, always in the direction of the sun. The small winch used for the casts was mounted on the upper deck. Using the hydro-boom with a traveling block, we deployed the package from the hydrobucket on the main deck. This handling system work well; with much appreciated help from members of the crew and scientific party, the profiling went smoothly. Optics casts were taken once daily, as near local noon as possible. Each profile went to a depth of about 200 m, and we sampled a total of 25 stations during the cruise. With its own winch and computer, the bio-optical profiler was independent from WOCE CTD operations. The optical profiler, a MER-2040 (Biospherical Instruments, San Diego Ca.) measures spectral downwelling irradiance and upwelling radiance (7 channels each) as well as broad-band PAR (photosynthetically available radiation), fluorescence, beam transmission, temperature and conductivity. We also placed a spectrally matching sensor on deck to measure total surface irradiance during the optical casts. In addition, we collected water samples from each cast and filtered them for particulate absorption, chlorophyll, and accessory pigment analyses. 2. The data a. Optics Profiler data The data in this directory were binned (averages) to 1 m depth increments. There are 41 fields per data record separated by white space. The naming convention for the files is 'pYYMMDDa.dec', where YY=year, MM=month, and DD=day. The fields (followed by their number in ) are as follows: depth<1> [8725]Ed410<2> [8725]Ed441<3> [8725]Ed488<4> [8725]Ed520<5> [8725]Ed565<6> [8725]Ed665<7> [8726]EdPAR<8> [8725]Lu410<9> [8725]Lu441<10> [8725]Lu488<11> [8725]Lu520<12> [8725]Lu565<13> [8725]Lu655<14> [8725]LuChl<15> [8725]Trans<16> [8725]Fluor<17> [8725]Depth<18> [8725]ExpGd<19> [8725]PCBTp<20> [8725]Volts<21> [8725]Angl1<22> [8725]Angl2<23> [8725]Temp<24> [8725]Cond<25> [8725]Salin<26> [8725]SgmaT<27> [8725]EdPAR<28> Time<29> [8726]410Ed<30> [8726]441Ed<31> [8726]488Ed<32> [8726]520Ed<33> [8726]565Ed<34> [8726]665Ed<35> [8726]Grnd<36> [8726]PAREd<37> [8726]STemp<38> [8726]Power<39> [8725]EdPAR<40> Time<41> [8725] and [8726] are the unit codes, the underwater and the deck units, respectively. The units are standard, micro-watts cm^-2 for the irradiance sensors, photons cm^-2 s^-1 for the PAR channels, and voltages for the transmissometer and fluorometer. The depth record at field #18 will be incorrect (a residue of the averaging routine). Field #8 is surface PAR, and #40 is underwater PAR. Here are a couple of sample records: 4.000000 7.847059e+01 8.582285e+01 9.220901e+01 8.532879e+01 8.441001e+01 6.173996e+01 7.163643e+16 1.440983e+00 9.788684e-01 7.796815e-01 3.107108e-01 1.343020e-01 7.330006e-03 2.125596e+01 1.072700e-01 6.740177e-02 4.156583e+00 -7.667043e-05 3.468073e+01 6.211406e+01 1.344687e+01 1.511931e+01 2.857717e+01 5.783368e+01 3.569439e+01 2.274742e+01 1.296205e-03 3.377794e+01 2.652751e+01 4.497425e+14 5.135000e+01 4.852398e+01 5.186762e+01 5.603456e+01 4.918020e+01 4.740604e+01 2.035711e+01 3.425119e+16 3.301276e+16 5.132500e+01 5.000000 7.887078e+01 8.636285e+01 9.288007e+01 8.602234e+01 8.515347e+01 6.251948e+01 7.208695e+16 1.440445e+00 9.732645e-01 7.837166e-01 3.097505e-01 1.312029e-01 5.135614e-03 1.498556e+01 1.089400e-01 6.827981e-02 5.166981e+00 -5.658546e-05 3.458456e+01 6.191959e+01 1.150072e+01 6.199285e+00 2.857987e+01 5.783372e+01 3.569209e+01 2.274479e+01 1.297433e-03 3.376083e+01 2.652146e+01 4.539413e+14 5.569773e+01 4.833075e+01 4.987498e+01 5.551921e+01 4.742028e+01 4.327817e+01 1.217093e+01 3.170658e+16 2.942143e+16 5.567500e+01 Although these numbers are recorded on the computer to 6-digit resolution, we regard only the first three to the right of the decimal point to be significant. If you wish the complete downcasts (*.csv files, about 1 MB each), contact me [or Carol] at marra[knudson]@lamont.ldgo.columbia.edu (phone requests will not be honored), and I will place the files on-line for a designated time. Upcasts will be added later. b. Pigment data Chlorophyll data are available at two depths (surface and fluorescence maximum) for each cast. They are in the file: chla . Samples have been sent out for HPLC analysis of all pigments. These are not processed as yet, however, they are being maintained under liquid nitrogen, and thus should be well-preserved. c. Particulate absorption data The absorption of particulate matter collected on GFF filters between 400 and 700 nm (5 nm intervals) are in the file: aptabs. The raw data (OD of the filter) are in the file: partabs.new. The procedure followed that in Mitchell and Kiefer (1988) and Cleveland and Weidemann (1993). Wavelength (wl) is column 1 and the samples are in the remainder. The format for this first line is 'mdd' followed by a depth (NNm) or an 's' indicating a surface value. These samples were collected at the same depths as the chlorophyll a analyses. We are still QC-ing these data, so there will be updates of various kinds in the near future. 3. Other Information I have plotted the data using the system of programs GMT2.1. This shareware program was developed at LDEO and UH. If you are interested in it, see Wessel and Smith (1991), EOS 72, 441, 445-446. The station log for the cruise is in the file: statlog 4. References Cleveland, J.S. and A.D. Weidemann. 1993. Quantifying absorption by aquatic particles: A multiple scattering correction for glass-fiber filters. Limnol. Oceanogr. 38, 1321-1327. Marra, J., T.D. Dickey and J.L. Mueller. 1992. Global Surveys of Bio-Optical Ocean Properties. EOS 72, 577 and 581. Marra, J. (Ed) 1992.'Report of the JGOFS Task Team on Optics' JGOFS. (Available from the U.S. JGOFS Project Office, WHOI.) Mitchell, B.G. and D.A. Kiefer. 1988. Chorophyll absorption and fluorescence excitation spectra for light-limited phytoplankton. Deep-Sea Res. 35, 855-879.