DYCOMS-II Aircraft: C-130 Cloud Droplet Spectrum Fast-FSSP 1. Authors Jean-Louis Brenguier (PI), Phone: 33 5 61 07 93 21 (jlb@meteo.fr) Frederic Burnet, Phone: 33 5 61 07 93 27 (burnet@cnrm.meteo.fr) METEO-FRANCE, CNRM/GMEI/MNP 42 Av Coriolis, 31057 TOULOUSE cedex, FRANCE Fax: 33 5 61 07 96 27 2. Data overview Fast-FSSP (FFSSP) data were acquired during the DYCOMS-II field campaign in Summer 20001. There were 10 research flights studying stratus clouds. FFSSP data is available for almost the complete duration of the last 8 flights (from RF03 to RF10) except for flights RF04 and RF08 for which some cloudy legs are missing. Available time sections for each flight are listed in Table 1. 3. Instrument description The FFSSP is a modified version of the FSSP-100 with new electronics that record for each detection individually, the pulse amplitude (255 size classes), pulse duration and inter-arrival time from the previous detection with a resolution of 1/16 īs and a flag for the position of the particle with respect to the depth of field (DOF) (Brenguier et al. 1998). Comparisons with measurements from FSSP-100 and LWC devices such as PVM or CSIRO hot wire probe, can be found in Burnet et Brenguier (2001). Diameter range for this project: from 5.5 to 44 microns. 4. Data collection and processing Data recorded asynchronously for each detection, allow us to rebuild the complete time series of counts. Standard processing at 1 or 10 Hz provides mean sample values of microphysical parameters such as cloud droplet number concentration, liquid water content, mean volume diameter, etc... Since complete droplet size distribution over the 255 size classes will lead to huge data files, the spectrum is represented by its 5% percentiles. 5.0 Data format a. File Naming Convention These are gzipped tar files (one per flight) containing ASCII data files. The tar file names are structured as follows: Fltno_FFSSP.tar.gz, where Fltno is the flight number (RFxx, xx from 03 to 10) The name of the ASCII data files (one per time section listed in Table 1) in the gzipped tar files gives the time at the beginning of the section and the sampling rate. For example 150902.3R0001 means that the section starts at 15:09:02 (UTC) and that the sampling rate is 1 Hz. b. File format Format of R files: synchronous sampling. The header provides information about processing and calibration coefficients: # File created on: 22 11 1 at: 16 56 16 # startime= 6249000 duration= 4100000 delay= 2000 (ms) # filtering level= 4 modetype=1 # DOF sampling section= .0730 (mm2) # Calibration Coeff(5)= # .36605E+01 .46491E+00 -.37340E-02 .17857E-04 -.31135E-07 The following lines are the data in the following order from var (1) to var (45), all integers. var(1) : elapsed time (ms) since the beginning of the section (for example, with a 1 Hz processing, var(1) is incremented by 1000 for each sample). var(2) : Fast FSSP record and bloc at the end of the sample var(3) : control on the bloc duration var(4) : control of synchronization SOME DATA FROM THE BASIC ACQUISITION SYSTEM var(5) : True air speed*1000 (m/s) from TASX+ var(6) : Altitude*1000 (m) from GALT+ var(7) : Pressure*1000 (mbar) from PSXC+ var(8) : Temperature*1000 (C) from ATX+ var(9) : Water vapor mixing ratio*1000 (g/m3) from RHOLA+ var(10): Vertical velocity*1000 (m/s) from WIC+ var(11): PVM LWC*1000 (used for synchronization) from XGLWC+ var(12): Air density*1000 (Kg/m3) + parameter name of the netcdf RAF file. FAST FSSP DATA var(13): Total droplet rate (s^-1) var(14): Mean pulse duration over all detections (digit) var(15): Droplet rate in DOF (s^-1) var(16): Mean pulse duration for DOF detections (digit) var(17): Coincidence correction*1000 var(18): Droplet concentration (cm^-3) var(19): Integral diameter*1000 (micron x cm^-3) var(20): LWC*1000 (g m^-3) var(21): Reflectivity*1000 (dBz) var(22): Mean diameter*1000 (micron) var(23): Mean volume diameter*1000 (micron) var(24): Effective Diameter*1000 (micron) var(25): Main mode in the diameter distribution*1000 (micron) var(26): Second mode in the diameter distribution*1000 (micron) var(27): 5% percentile*1000 (micron) ................. var(45): 95% percentile*1000 (micron) 6. Data quality The overall data quality is quite good as indicated in the Table 1. However, preliminary analysis shows that some malfunctioning occurs during parts of some flights. The corresponding sections are labeled "bad" (or "medium" if only part of the section is concerned). Further work must be done to correct them. 7. References J.-L. Brenguier, T. Bourrianne, A. Coelho, J. Isbert, R. Peytavi, D. Trevarin and P. Weschler, 1998: Improvements of droplet size distribution measurements with the Fast-FSSP (Forward Scattering Spectrometer Probe)., J. Atmos. Oceanic Technol., 15, 1077-1090. F. Burnet and J.-L. Brenguier, 2001: Comparative study of microphysical measurements during SCMS, J. Atmos. Oceanic Technol., Accepted. Table I: Overview of Fast-FSSP data for DYCOMS-II Fltno Time section Duration Quality start end (s) -------------------------------------------------- RF03 08:19:36.3 09:27:56.3 4100 good 09:59:46.3 11:09:46.3 4200 good 11:45:53.0 12:55:53.0 4200 good 14:00:13.3 14:02:13.3 60 good RF04 08:20:30.6 08:30:30.6 600 good 09:15:30.1 09:44:41.1 1751 good 10:50:55.1 10:54:55.1 240 good 11:25:14.9 12:01:34.9 2180 bad 12:04:36.6 13:01:53.6 3437 medium RF05 08:09:13.0 09:19:13.0 4200 good 10:26:27.9 10:28:27.9 120 good 10:57:57.7 12:04:57.7 4020 good 12:04:27.4 12:29:57.4 1530 good 12:29:27.2 13:03:27.2 2040 good RF06 07:25:49.3 07:42:49.3 1020 good 08:06:59.1 08:13:59.1 420 good 08:17:17.8 09:16:17.8 3540 medium 09:18:58.5 09:38:58.5 1200 good 09:58:38.2 10:06:38.2 480 good 10:23:48.2 11:10:48.2 2820 medium 11:14:47.9 11:42:47.9 1680 bad 12:01:56.5 12:05:26.5 210 good 12:14:07.5 12:23:07.5 540 good 12:29:57.4 12:49:57.4 1200 good 13:06:27.1 13:37:27.1 1860 medium RF07 08:38:05.0 09:59:05.0 4860 good 11:02:34.3 11:05:34.3 180 medium 11:36:04.0 13:06:04.0 5400 bad RF08 23:54:02.5 00:31:02.5 2220 good 01:03:05.2 01:39:05.2 2160 good 02:20:30.8 02:42:30.8 1320 good 02:42:34.7 03:40:04.7 3450 medium RF09 20:14:53.3 20:30:43.3 950 good 21:31:32.9 22:44:32.9 4380 good 23:17:22.4 23:29:22.4 720 good 00:20:32.0 01:35:32.0 4500 good 02:12:44.4 02:20:44.4 480 good RF10 20:27:37.9 20:28:47.9 70 good 21:37:36.6 22:08:36.6 1860 good 22:35:07.4 23:05:57.4 1850 good 1 parameter name of the netcdf RAF file.