file: Guide-Summary version: 17July2000 CONTENTS: DATA SUMMARY INSTRUMENT DESCRIPTIONS (CFD Chamber and CN Counter) DATA DESCRIPTION SEE ALSO APPENDIX ---------------------------------------------------------------- DATA SUMMARY This document describes the instrumentation and aerosol data obtained by Colorado State University during May 1998 on NCAR C-130 research flights as part of the FIRE3 Arctic Cloud Experiment. The primary measurements were of ice nuclei and condensation nuclei. These measurements are identified in Appendix G of the FIRE.ACE Operations Plan (page G-10). The following table summarizes the research flights of the NCAR C-130 when CSU data were obtained. Test flights and ferry flights are not included. Times are UTC. Mb Date Take-Off Landing Hours Data #CFD #PIXE #IN Filters ------------------------------------------------------------- 980504 18:51 03:50 9.0 3.4 1 1 1 980507 18:49 03:15 8.4 5.9 4 2 2 980511 18:09 03:12 9.1 3.3 3 2 1 980515 18:24 02:56 8.5 5.0 4 3 2 980518 18:30 03:36 9.1 3.5 5 3 2 980520 18:26 03:00 8.6 6.1 5 3 2 980524 18:02 03:26 9.4 6.2 3 3 2 980527 18:20 03:45 9.4 7.4 2 2 2 ------------------------------------------------------------- 11 84.5 44.6 27 19 14 TOTALS # PIXE = number of samples collected with PIXE impactor. All aerosol particles are collected on transmission electron microscope (TEM) grids for later examination. # CFD = number of samples collected with impactor at outlet of CFD chamber. These are IN particles only and are collected on TEM grids # IN Filter = number of filter samples collected. These are polycarbonate membrane filters that collect all aerosol particles; they are processed later in the laboratory. ---------------------------------------------------------------- INSTRUMENT DESCRIPTIONS instrument name (1): Continuous Flow Diffusion (CFD) Chamber operating principles: Air flows in the space between two cylinders that coated with ice and held at different temperatures. Ice forming nuclei (IFN) activate in this supersaturated region and grow to crystals a few microns in size. The crystals are counted at the chamber outlet with an optical particle counter. Operation and data logging use a PC-based data system. There are three fundamental limitations for this technique: (1) measures at one temperature and humidity (no capability for instantaneous spectra); (2) statistical sampling limit when IFN concentrations are low; and (3) no sensitivity to contact-freezing or homogeneous freezing nucleation. measurement characteristics: Range of Sample Temperatures: -10 to -35C Range of Sample Humidities: ice saturation to 20% water supersaturation Temperature Change Rate: 0-1.5C per minute Humidity Change Rate: 0-10% per minute Sample Flow Rate: 1-2 liters per minute Accuracy: temperature 1C, humidity +/-1%, air flow +/-5%, pressure +/-2% Response Time: ~5 seconds (0%-95%) + piping delay Temporal Resolution: ~1s Data Sample Rate: ~5Hz for particle count; 1Hz for temperature, flow and pressure data products: Number concentration of ice forming nuclei (IFN) at sampling conditions. Derived products to be provided: time, sampling conditions (temperature, water and ice supersaturation, pressure, flow rate), IFN count Other possible derived products: freezing nucleation spectra; contributions from different ice nucleation modes (condensation- freezing and deposition); fraction of total aerosol represented by IFN; size and chemical composition of IFN options: Ice crystals >3um that form in the CFD can be collected by impaction onto an electron microscope grid. These crystals contain the nucleating particles, and when the crystals evaporate, the IFN are left behind. The nuclei can be analyzed using electron microscopy and X-ray microprobe techniques to determine the morphology and elemental composition. Collections are typically accumulated for ~30 minutes to get a few hundred particles. ---------------------------------------------------------------- instrument name (2): Condensation Nuclei (CN) Particle Counter operating principles: This is a butanol type CN counter, commercially manufactured by TSI, Inc., Model 3010. It measures the concentration of all particles larger than about 0.012um diameter. Sample air flows over a heated reservoir of butyl alcohol and becomes saturated with the vapor. It then flows into a pipe that is about 15C cooler, which creates a high supersaturation (~300%). Butanol droplets nucleate, grow to a few microns and are counted with an optical particle counter. Coincidence errors become significant for concentrations greater than 10^4/cc. measurement characteristics: Range of Particle Concentration: 0 to 10^4/cc Particle Size Detection Limit: 50% at 0.012um diameter, increasing to ~100% at 0.025um Sample Flow Rate: 1 liter per minute Accuracy: air flow +/- 2% Response Time: < 5 seconds (0%-95%) + piping delay Data Sample Rate: approx. 5Hz for particles, 1Hz for flow data products: Number concentration of CN (total particles larger than ~0.012um diameter). Derived products to be provided: time, CN concentration at STP Other possible derived products: fraction of total aerosol active as CCN and IFN; indicator of air mass origin (clean or polluted, boundary layer, etc.); in-cloud particle scavenging ---------------------------------------------------------------- DATA DESCRIPTION Two kinds of aerosol data were obtained: (1) continuous measurements of ice nuclei and CN (2) post-flight analyses of aerosol particles collected on electron microscope grids. Data of type (2) are available as brief narrative descriptions of the sampling conditions and tabular summaries of the number of particles, sizes, and elemental compositions. There are also electron microscope images and energy dispersive x-ray spectra of selected particles. To obtain these data, contact Dave Rogers. Data of type (1) are available in the archive as compressed ASCII text files, one file for each flight. File names indicate the kind and date of measurements. For example, IN980504.dat indicates "Ice Nuclei" measurements on 1998-May-04. Each data file begins with about 20 lines that describe the contents, as illustrated by the example appended to this note. Records are spaced approximately one second apart. There are occasional gaps. In order to conserve disk space, the ASCII data files were compressed with gzip, version 1.2.4 from the Free Software Foundation, Inc. (675 Mass Ave, Cambridge, MA 02139, USA). Online information can be found at several Internet locations, including: http://www.cis.ohio-state.edu/hypertext/faq/usenet/compression-faq/part1/faq-doc-2.html Data analysis and quality assurance are continuing. Data files posted here will be updated and revised as necessary. The file creation date is in the header information. ---------------------------------------------------------------- SEE ALSO INyymmdd.txt - flight observation notes Blower.txt - air sampling/operation notes of C-130 community air sample inlet Calibration.txt - describes calibration and quality assurance procedures Strategy.txt - describes sampling strategy and procedures http://lamar.colostate.edu/~dcrogers/CFD/cfd.html - describes CFD chamber contact: Dave Rogers (970) 491-8667, dcrogers@lamar.colostate.edu ---------------------------------------------------------------- APPENDIX Following data example is from CSU data file IN980504.dat ---------------------------------------------------------------------- 20 lines in header Rogers, Dave; DeMott, Paul; Kreidenweis, Sonia Colorado State University (CSU); Dept. of Atmospheric Science; (970) 491-8667 CSU CFD Ice Nucleus Counter data from (YrMoDa) 980504. File created YrMoDa 1998-11-20 Values listed are: UTsec = time, seconds after midnight (UTC) hh:mm:ss = time, hour:minute:second (UTC) Ts = CFD sample temperature (deg C) SSw = CFD sample liquid water vapor supersaturation (%) SSi = CFD sample ice supersaturation (%) Pmb = CFD chamber pressure (mb) Qs = CFD sample volume flow rate (standard liters/min) at STP (1013.25mb, 0 Celcius) IN# = Ice nuclei count since previous record CNconc = number concentration of Condensation Nuclei (aerosol with d>0.012um) at STP INconc = number concentration of Ice Nuclei at STP, averaged over 10.0 sec IN and CN values are the sum of 5 measurements per time interval. IN and CN concentrations are corrected for particle loss and time response. degC % % mb LPM #/cc #/L UTsec hh:mm:ss Ts SSw SSi Ps Qs IN# CNconc INconc 79388 22:03:08 -24.6 -13.9 9.7 1000.4 1.60 0 5.60 0.00 79390 22:03:10 -24.6 -13.8 9.8 1000.4 1.55 0 191.59 0.00 79391 22:03:11 -24.6 -13.8 9.8 1000.5 1.54 0 192.97 0.00 etc. ----------------------------------------------------------------------