TITLE: CSU_CloudChem.xlsx AUTHOR(S): Jeffery Collett, Jr., 970-491-8697, collett@lamar.colostate.edu Katherine B. Benedict, 970-491-8412, kbeem@atmos.colostate.edu Taehyoung Lee, 970-491-8102 , thlee@atmos.colostate.edu Colorado State University 1371-Campus Delivery Fort Collins, CO 80523 1.0 DATA SET OVERVIEW: Cloud water chemsitry data from samples collected during VOCALS-Rex on the NSF C-130. Sample collection took place from 10/14/2004 to 11/14/2004. 2.0 INSTRUMENT DESCRIPTION: Cloud water samples were collected during VOCALS-REx with the NCAR/CSU airborne cloud water collector. The collector is described thoroughly in Straub and Collett (2004) and Straub et al. (2007). The collector separates cloud drops from the air stream with an axial flow cyclone. A fixed vane creates rotational flow and the drops move to the duct wall via centrifugal force. Droplets then move along the wall to an extraction slot for removal to one of seven, operator-selectable sample bottles. The 50% size cut diameter for the collector is 8 µm which should collect most of the cloud liquid water content but exclude smaller, unactivated aerosol particles. The collector features a cover, which is opened only during cloud penetration, to prevent contamination of collection surfaces. The collector was mounted below the left wing on the NSF/NCAR C-130 in a modified Particle Measurement Systems (PMS) canister and was controlled from the cabin of the aircraft. An operator controlled the collector cover and selected which of the sample bottles would collect the cloudwater during each cloud penetration. 3.0 DATA COLLECTION AND PROCESSING: Samples were only collected during the in-cloud legs of the flights. Often several legs were combined into one sample bottle to obtain enough cloud water and to be able to collect sample during the entire flight (limited by 7 sampling bottles). The analysis for each sample collected depended on the volume of cloud water collected. Immediately after each flight, the sample pH values were measured and a variety of aliquots prepared for subsequent chemical analyses, adding preservatives as appropriate. A combination pH electrode was used, calibrated with pH 7 and pH 4 buffer, was used to measure cloud sample pH. Samples were aliquotted for analysis in the following priority order: major inorganic ions, peroxides, sulfur (IV), total Fe and Mn, carboxylic and dicarboxylic acids, formaldehyde, and total organic carbon (TOC). Sample preservation occurred in the field and chemical analysis was completed after returning the samples to CSU by the follwing methods: Major ions: ion chromatography Organic Acids: ion chromatography Hyrdogen Peroxide: Spectrophotometric technique S(IV): Spectrophotometric technique Formaldehyde: Spectrophotometric technique Fe and Mn: Atomic Absorption Spectrophotometery Total Carbon: Sievers Total Carbon Instrument The collector was cleaned before every flight. Using a wash bottle and spray bottle deionized water was sprayed into the collector to cover all interior surfaces. All seven sample valves were opened and the collector was rotated to get water to flow through all sample lines. After rinsing the collector several times, blanks were taken. In a similar manner as for cleaning, DI water was sprayed into collector and sampling valves were opened to allow blank to be collected into a set of sample bottles. The seven samples were combined for the blank. The blanks represent both the inlet of the collector and the sample lines. Blank averages and the detection limits are provided with the data. 4.0 DATA FORMAT: The chemistry data are in an excel file. For every sample there is atleast 1 line of data containing start and stop times of collection, total volume collected, pH, and concentration data. If the collector was opened and closed several times for a single sample those times are listed below the main line of the sample data. Samples are named according to the flight number(fn, 1-14) and sample bottle (SB, 1-7): VFfn-SB. Concentration data is present only if the sample was analyzed for the given species. All other cells were left blank. At the top of the spreadsheet the units, blank averages, and minimum detection limit (MDL) are given. 5.0 DATA REMARKS: 6.0 REFERENCES: Straub, D.J., Collett Jr., J.L. 2004. An axial-flow cyclone for aircraft-based cloud water sampling. Journal of Atmos. Oceanic Technol. 21, 1825-1839. Straub, D.J., Lee, T., Collett Jr., J.L., 2007. Chemical composition of marine stratocumulus clouds over the eastern Pacific Ocean. Journal of Geophysical Research, 112, D04307. List of documents cited in this data set description