ASTEX C-13lA FLIGHTS CLOUD MICROPHYSICS PROBE (PVM-lOOA) DATA: ~10 HZ, 1 HZ; ASCII; DOS COMPATIBLE 1) LWC (LIQUID WATER CONTENT; G/M^3) 2) PSA (PARTICLE SURFACE AREA; CM^2/M^3) 3) R(EFF) (EFFECTIVE DROPLET RADIUS, UM) (H. GERBER; 1643 BENTANA WAY, RESTON, VA 22090) (PHONE 703-742-9844; FAX 703-742-3374) FLIGHT INTERVAL U. OF WASH. 10 HZ 1 HZ NO. NO. TIME INTERVAL DATA DATA (hhmmss - hhmmss) FILE FILE 1557 1 092900 - 100300 ASTEX01.10 ASTEX01.lHZ 2 June 2 101000 - 105656.1 ASTEX02.10 ASTEX02.lHZ 3 112600 - 122000 ASTEX03.10 ASTEX03.lHZ 1558 4 110500 - 115700 ASTEX04.10 ASTEX04.lHZ 4 June 5 123100 - 133300 ASTEX05.10 ASTEX05.1HZ 6 140800 - 145200 ASTEX06.10 ASTEX06.lHZ 1559 7 104333 - 104800 ASTEX07.10 ASTEX07.lHZ 8 June 8 115000 - 125600 ASTEX08.10 ASTEX08.1HZ 1560 NO CLOUDS 10 June 1561 9 093600 - 101100 ASTEX09.10 ASTEX09.lHZ 12 June 10 102200 - 111200 ASTEX10.10 ASTEX10.lHZ 11 113500 - 121800 ASTEX11.10 ASTEXll.lHZ 12 131300 - 134500 ASTEX12.10 ASTEX12.lHZ 13 142100 - 144000 ASTEX13.10 ASTEX13.lHZ 1562 15 100900 - 101600 ASTEX15.10 ASTEX15.lHZ 13 June 16 110000 - 111000 ASTEX16.10 ASTEX16.lHZ 17 114300 - 114900 ASTEX17.10 ASTEX17.lHZ 18 125700 - 135800 ASTEX18.10 ASTEX18.lHZ 19 140100 - 144900 ASTEX19.10 ASTEXl9.lHZ 1563 20 151200 - 160500 ASTEX20.10 ASTEX20.lHZ 15 June 21 161100 - 165000 ASTEX21.10 ASTEX21.1HZ 1564 22 115500 - 122500 ASTEX22.10 ASTEX22.lHZ 16 June 23 150500 - 154000 ASTEX23.10 ASTEX23.lHZ 1565 24 091000 - 091500 ASTEX24.10 ASTEX24.lHZ 17 June 25 093700 - 103700 ASTEX25.10 ASTEX25.1HZ 26 103700 - 113200 ASTEX26.10 ASTEX26.lHZ 27 (1) 114500 - 123600 ASTEX27.10 ASTEX27.lHZ ASTEX27.1 28 125800 - 130100 ASTEX28.10 ASTEX28.lHZ 1566 NO CLOUDS 19 June 1567 29 161500 - 161800 ASTEX29.10 ASTEX29.lHZ 20 June 31 200200 - 201200 ASTEX31.10 ASTEX31.1HZ 1568 32 090100 - 090600 ASTEX32.10 ASTEX32.lHZ 21 June 33 093800 - 103800 ASTEX33.10 ASTEX33.1HZ 34 103800 - 110000 ASTEX34.10 ASTEX34.lHZ 35 111600 - 112900 ASTEX35.10 ASTEX35.lHZ 1569 36 050800 - 051100 ASTEX36.10 ASTEX36.lHZ 22 June 37 053100 - 053300 ASTEX37.10 ASTEX37.lHZ 38 055300 - 061100 ASTEX38.10 ASTEX38.lHZ 39 070800 - 071100 ASTEX39.10 ASTEX39.lHZ 40 072600 - 073000 ASTEX40.10 ASTEX40.lHZ 41 081000 - 090600 ASTEX41.10 ASTEX41.lHZ 1570 42 131500 - 135000 ASTEX42.10 ASTEX42.lHZ 23 June 1571 43 094200 - 104000 ASTEX43.10 ASTEX43.lHZ 26 June 44 104000 - 114000 ASTEX44.10 ASTEX44.lHZ 45 114000 - 124000 ASTEX45.10 ASTEX45.lHZ 46 124100 - 134200 ASTEX46.10 ASTEX46.lHZ 47 140000 - 150200 ASTEX47.10 ASTEX47.lHZ 1572 NO CLOUDS 27 June NOTES: (1) PSA channel inoperative during this interval. R(EFF) estimated by correcting FSSP data; see ASTEX27.1. (2) Due to digital round-off errors in the raw data, the data rate in the 10 HZ DATA FILES is 9.84572 Hz, except for files 32,36,37,38,39,40,41 where the data rate is 10.03773 Hz, and except for file 33 where the rate is 10.00000 Hz. All the ~10 Hz data has been synchronized with the U. of Washington 1.00000 Hz data files. DATA REDUCTION 1. INTRODUCTION - The raw data of LWC and PSA collected with the PVM-lOOA on the C-131A flights resides in the U. of Washington ASTEX data base. The following summarizes the reduction of this raw data. 2. SCALING CONSTANTS - The following equations relate LWC and PSA to output voltages and scaling constants of the PVM-lOOA: LWC (G/M^3) = LWC (VOLTAGE) x 2.515 PSA (CM^2/M^3) = PSA (VOLTAGE) x 7,700 The raw data set consists of LWC and PSA voltages. The reduced data set consist of values to which the scaling constants have been applied. The scaling constants were determined in a calibration as described in "New Microphysics Sensor for Aircraft Use" by H. Gerber; Preprint Volume, 11th Intern. Conf. On Clouds and Precipitation, Montreal, Aug. 17-21, 1992. 3. VOLTAGE OFFSETS - The raw voltage data for the LWC and PSA channels contained voltage offsets which were typically -.050 V for each channel. The reduced data has most of the offset removed. 4. CALCULATION OF R(EFF) - The equation for R(EFF) is given by R(EFF) = 30,000 x (LWC/PSA) Since R(EFF) is proportional to the ratio of LWC/PSA, large errors in R(EFF) will result when LWC and PSA approach zero value. Conditional statements are applied to the LWC and PSA data, which return the relationship R(EFF) = 0 when the values of LWC and PSA are smaller than a specified value: IF LWC < .020 G/M^3 THEN R(EFF) = 0 IF PSA < 60 CMA2/M^3 THEN R(EFF) = 0 The reduced R(EFF) data contains the effect of these conditional statements. The reduced R(EFF) data shows single data-point spikes that can occur when there are large changes in the density of the cloud, such as at cloud edge. These spikes are a result of a 26ms displacement of the A to D conversion between LWC and PSA channels; this displacement corresponds to about a 2-m distance along the C-131A flight path given the ~80 m/s speed of the aircraft. Spikes in R(EFF) occur when the PSA measurement occurs out of cloud and the LWC measurement occurs incloud; and spurious 0 values of R(EFF) occur when the measurement sequence of LWC and PSA is reversed with repect to the cloud edge. Spikes and spurious 0 values have not been removed from the reduced data set. 5. ACCURACY - The accuracy of the LWC channel is ~5%, and the precision of the LWC and PSA channels is ~2%, for the dropletsize bandpass of the instrument's design. The accuracy of the PSA channel is estimated to be similar to the accuracy of the LWC channel, because of calibration, and of the physical consistency of the data produced by both channels in this ASTEX data base. However, some doubt must remain as to the accuracy of PSA, since the calibration of this channel depended in part on the performance of a FSSP used during the instrument's calibration in the cloud chamber at ECN, Petten. The instrument's response gradually rolls off for cloud droplets < 5 um and > 50 um; 50% points are ~2 um and ~70 um for LWC. 6. 1 HZ DATA - Each ~10 Hz ASTEX*.10 data file was averaged over ~1-s increments. A 1 Hz data file titled ASTEX*.lHZ was generated from each averaged file. The 1 Hz files contain LWC, PSA, and R(EFF) measured by the PVM. The 1 Hz files also contain LWC, PSA, R(EFF) found by summing the measurements of the PVM and the U. of Washington's OAP-200X drizzle probe that has 15 droplet size channels ranging from 20 um to 320 um. (The ~10 Hz data leads the 1 Hz data by 0.5 s, because the OAP-200X produces an output at the end of its 1-s sampling time.) Given that the PVM has a gradual roll off in response for larger droplets, requires that only a portion of the output of each channel of the OAP-200X is used when summing with the PVM to determine the 1 Hz data. The estimated response of the PVM as a function of OAP-200X channel droplet diameter is as follows: OAP-200X % Measured by PVM-10OA Channel Droplet LWC Channel PSA Channel No. Size (um) 1 20 - 40 100 100 2 40 - 60 81 100 3 60 - 80 46 88 4 80 - 100 22 55 5 100 - 120 12.3 33 6 120 - 140 8.3 29 7 140 - 160 6.0 26 8 160 - 180 4.2 24 9 180 - 200 3.2 22 10 200 - 220 2 20 11 220 - 240 2 18 12 240 - 260 1 16 13 260 - 280 1 12 14 280 - 300 0 8 15 300 - 320 0 6 SAMPLE DATA: "ASTEX21 l0" FLT 1563 June 15 Interval No. 21 U.W. Time frl61100 tol65000 time LWC PSA r(eff) (S) (g/m^3) (cm^2/m^3) (um) 0.000 -0.008 -38.500 0.000 0.102 -0.008 -38.497 0.000 0.203 -0.008 -38.494 0.000 0.305 -0.008 -15.391 0.000 0.406 -0.008 -15.388 0.000 0.508 -0.008 -15.385 0.000 0.609 -0.008 -38.482 0.000 0.711 -0.008 -38.479 0.000 0.813 -0.008 -38.476 0.000 0.914 -0.008 -15.373 0.000 1.016 -0.008 -38.470 0.000 1.117 -0.008 -15.367 0.000 1.219 -0.008 -15.364 0.000 1.320 -0.008 -15.361 0.000 1.422 -0.013 -15.358 0.000 1.524 -0.008 -15.355 0.000 1.625 -0.008 -15.352 0.000 1.727 -0.008 -15.349 0.000 1.828 -0.008 -38.446 0.000 1.930 -0.008 -15.343 0.000 2.031 -0.008 -38.440 0.000 SAMPLE DATA: "ASTEX21.lHZ" FLT 1563 June 15 Interval No.21 U.W. Time frl61100 tol65000 -- WITH WITH WITH DRIZZLE DRIZZLE DRIZZLE time LWC PSA r(eff) LWC PSA r(eff) (s) (g/m^3) (cm^2/m^3) (um) (g/m^3) (cm^2/m^3) (um) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.016 -0.008 -29.243 0.000 -0.008 -29.243 0.000 2.031 -0.009 -19.973 0.000 -0.009 -19.973 0.000 3.047 -0.008 -24.564 0.000 -0.008 -24.564 0.000 4.063 0.009 26.286 0.000 0.009 26.286 0.000 5.078 0.003 10.147 0.000 0.003 10.147 0.000 6.094 0.000 -1.373 0.000 0.000 -1.373 0.000 7.008 0.000 -2.886 0.000 0.000 -2.886 0.000 8.024 -0.001 0.224 0.000 -0.001 0.224 0.000 9.039 -0.002 0.255 0.000 -0.002 0.255 0.000 10.055 0.000 -1.256 0.000 0.000 -1.256 0.000