West_Campus_Station_Data_1990-2020.dat.zip West Campus Station data are from Jan 1 1990 to Sept 25 2019, as a comma-separated ascii file in format “day-month-year hour:minute:second” in local time, total hydrocarbon in units of ppm, wind speed in units of meters per second and wind direction in degrees. File is zip compressed. Seep_Survey_27,28May2016.dat Seep survey data are for data collected 27 May 2016 and 28 May 2016 as a comma-separated ascii file in format “day-month-year hour:minute:second” in universal time, methane in units of parts per million, wind speed in units of meters per second, and wind direction in degrees. Seep_Survey_28May2016_Sample_Composition.xls Excel file of samples collected in the seep field, time and location, and trace gas composition. CH4 and carbon dioxide CO2 in parts per million by volume, CO in parts per billion by volume, other trace gases in parts per trillion by volume. -888 means not detected. SonarReturn_Apr2005.csv Seep sonar survey data for data collected April 2005, analysis and details described in (1), in a comma separated ascii file of format Longitude in degrees, latitude in degrees, and sonar return in units of decibels. 1. I. Leifer, M. Kamerling, B. P. Luyendyk, D. Wilson, Geologic control of natural marine hydrocarbon seep emissions, Coal Oil Point seep field, California. Geo-Marine Letters 30, 331-338 (2010).
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Offshore in situ survey data were collected by the Double Bogey, a 12-m, 9-ton, fishing vessel with a near waterline deck (~0.2 m) and low overall profile (cabin at ~2.2 m). A sonic anemometer (VMT700, Vaisala) was mounted on a 6.5 m, 5-cm (2”) diameter aluminum mast to measure 3D winds. Continuous, 5 Hz CH4 and CO2 data were collected by a Cavity Enhanced Absorption Spectroscopy analyzer (FGGA, LGR Inc., San Jose, CA). Vessel location and time were from GPS at 1 Hz (19VX HVS, Garmin, KS). CH4 and CO2 calibration with a greenhouse gas air calibration standard (CH4: 1.981 ppmv; CO2: 404 ppmv, Scott Marin, CA, purchased 2015, Sigma Aldritch, St Louis, MO). Data are real time integrated and visualized in Google Earth using custom software written for AutoMObile trace Gas (AMOG) Surveyor, described elsewhere (Leifer et al., 2018a; Leifer et al., 2014; Leifer et al., 2018b; Leifer et al., 2016). Real-time visualization facilitates adaptive surveys (Thompson et al., 2015) by allowing plume tracking and ensuring transects are near-orthogonal to winds. Whole air samples were collected in evacuated 2-liter stainless steel canisters which were opened ~1 m above the sea surface and filled over ~1 minute. Filled canisters were analyzed in the Rowland/Blake laboratory at the Univ. Calif., Irvine for CO, CH4, and C2-C7 organic compounds. Samples were analyzed by a gas chromatography multi-column/detector analytical system by flame ionization detection. West Campus station data are described in Bradley et al. (2010). Bradley ES, Leifer I, Roberts DA. 2010. Long-term monitoring of a marine geologic hydrocarbon source by a coastal air pollution station in Southern California. Atmos Environ 44(38): 4973-4981. doi:10.1016/j.atmosenv.2010.08.010. Leifer I, Melton C, Fischer ML, Fladeland M, Frash J, et al. 2018a. Atmospheric characterization through fused mobile airborne and surface in situ surveys: methane emissions quantification from a producing oil field. Atmos Meas Tech 11(3): 1689-1705. doi:10.5194/amt-11-1689-2018. Leifer I, Melton C, Manish G, Leen B. 2014. Mobile monitoring of methane leakage. Gases and Instrumentation July/August 2014: 20-24. Leifer I, Melton C, Tratt DM, Buckland KN, Chang C, et al. 2018b. Validation of mobile in situ measurements of dairy husbandry emissions by fusion of airborne/surface remote sensing with seasonal context from the Chino Dairy Complex. Environ Poll 242(Pt B): 2111-2134. doi:10.1016/j.envpol.2018.03.078. Leifer I, Melton C, Tratt DM, Buckland KN, Clarisse L, et al. 2016. Remote sensing and in situ measurements of methane and ammonia emissions from a megacity dairy complex: Chino, CA. Environ Poll 221: 37-51. doi:10.1016/j.envpol.2016.09.083. Thompson D, Leifer I, Bovensman H, Eastwood M, Fladeland M, et al. 2015. Real-time remote detection and measurement for airborne imaging spectroscopy: A case study with methane. Atmospheric Measurement Techniques 8: 1-46. doi:10.5194/amtd-8-1-2015.