NCAR ELECTRA, NOAA WP3D AIRCRAFT - MICROPHYSICS DATA R. Black (NOAA/AOML/HRD, USA)
F. Marks (NOAA/AOML/HRD, USA)
Announced availability: 1 June 1995
Data Access The NCAR Electra and NOAA WP3D 2-D microphysics data are located on the anonymous FTP site of ftp.aoml.noaa.gov in directory pub/hrd/rblack/tc*.
(March 1997 NOTE: NCAR Electra only, at this point. Since the WP3D data have significant sample volume problems, anyone who wants them should contact Robert Black directly (e-mail) at rblack@aoml.noaa.gov regarding their suitability for the user's needs.)
Background Microphysics data were collected during the TOGA COARE Intensive Observing Period from the NOAA WP3Ds, the NCAR Electra and the NASA DC-8 aircraft. The NOAA/AOML Hurricane Research Division (HRD) is acting as a TOGA COARE Data Processing, Archive and Distribution Center for both the P3 and Electra turboprop data. The DC-8 data are being processed by Rudy Pueschel at NASA/Ames.
Flight Summary
The NOAA WP3D aircraft participated in 24 of the 54 TOGA COARE aircraft sorties, flying 374.1 hours. The NCAR Electra participated in 32 missions, 17 of them flown in conjunction with one or both of the NOAA WP3D aircraft, for a total of 203.6 flight hours. Roughly 4-6 hours of microphysics data are available from both WP3D aircraft during each sortie, while 3-5 hours of microphysics data are available from each Electra mission. In the twelve sorties into Class 2-4 CEs (Cloudiness Elements), the microphysics data were collected by one WP3D below 1.5 km, the Electra at 3 km, and the second WP3D at 4.2 km. These data serve as the basis for the validation of the cloud microphysics data and the calibration of the airborne radars.
Instrument Information
A new generation of Knollenberg Particle Measurement System (PMS) probes were mounted on the NOAA and NCAR aircraft. The PMS probes were mounted in the airflow slightly behind and under the left wingtip of both NOAA WP3Ds, and above the cockpit of the NCAR Electra. The WP3Ds used the new Knollenberg Greyscale probes (64 diodes, 2 bits of intensity), while the Electra used the monoscale probes (32 diodes, 1 bit of intensity). Raw number distributions of particles are obtained from shadow images of the droplets/ice and are converted to mean distributions per unit volume. The major difference between the monoprobe and the Greyscale probe is in the effective array width, 6.4 and 1.6 mm for the 2D-P and 2D-C monoprobes versus 9.6 and 1.92 mm for the 2D-P and 2D-C Greyscale probes.
The processing involves computing the size and number concentration of the observed droplets, and computing parameters like radar reflectivity, rain rate, water content, and median volume diameter. With the 2-D monoprobe data, the averaging period necessary to obtain a stable drop size distribution could be as short as 5.0 sec. Because of data system sampling strategy employed for the TOGA COARE 2D-Greyscale probe data, this averaging time may need to be as much as 60 sec corresponding to a flight path of 8 km. With the monoprobes, the 10-sec sampling period is generally sufficient to allow between 500-800 drops to be included in the sample. The 10-sec sampling time is usually chosen as a compromise between sample volume and data homogeneity; i.e., 10 sec represents 1.0-1.6 km of flight distance.
HRD Involvement
HRD processes the PMS data from the turboprop aircraft as a means of evaluating the quality of the new PMS data system and probes. The validation includes an intercomparison of the rainfall statistics from the WP3D and Electra datasets. HRD will use the PMS data to calibrate the airborne radars on the NOAA WP3Ds using the approach outlined in a paper by Marks et al., 1993. HRD will calibrate the WP3Ds tail radars at the same time and envisions this data being used to calibrate the NCAR ELDORA and shipborne radars as well.
Data File Information NCAR ELECTRA Number of data files: 93
File name: tcyymmddD.2d, tcyymmddD.rain, tcyymmddD.spec where tcyymmdd is the flight date, 2d are the size distribution data, rain is the rainfall data and spec is the rainfall spectrum data.
Number of documentation files: 2
Data format: ASCII (.rain, .spec)
Data volume: 14,806,000 bytes
Inventory
tc921115D.2d.Z tc921119D.2d.Z tc921126D.2d.Z
tc921128D.2d.Z tc921202D.2d.Z tc921203D.2d.Z
tc921205D.2d.Z tc921206D.2d.Z tc921208D.2d.Z
tc921209D.2d.Z tc921210D.2d.Z tc921213D.2d.Z
tc921214D.2d.Z tc921215D.2d.Z tc921216D.2d.Z
tc930109D.2d.Z tc930112D.2d.Z tc930113D.2d.Z
tc930114D.2d.Z tc930116D.2d.Z tc930117D.2d.Z
tc930118D.2d.Z tc930126D.2d.Z tc930127D.2d.Z
tc930128D.2d.Z tc930204D.2d.Z tc930206D.2d.Z
tc930209D.2d.Z tc930210D.2d.Z tc930217D.2d.Z
tc930218D.2d.Z
tc921115D.rain.Z tc921119D.rain.Z tc921126D.rain.Z
tc921128D.rain.Z tc921202D.rain.Z tc921203D.rain.Z
tc921205D.rain.Z tc921206D.rain.Z tc921208D.rain.Z
tc921209D.rain.Z tc921210D.rain.Z tc921213D.rain.Z
tc921214D.rain.Z tc921215D.rain.Z tc921216D.rain.Z
tc930109D.rain.Z tc930112D.rain.Z tc930113D.rain.Z
tc930114D.rain.Z tc930116D.rain.Z tc930117D.rain.Z
tc930118D.rain.Z tc930126D.rain.Z tc930127D.rain.Z
tc930128D.rain.Z tc930204D.rain.Z tc930206D.rain.Z
tc930209D.rain.Z tc930210D.rain.Z tc930217D.rain.Z
tc930218D.rain.Z
tc921115D.spec.Z tc921119D.spec.Z tc921126D.spec.Z
tc921128D.spec.Z tc921202D.spec.Z tc921203D.spec.Z
tc921205D.spec.Z tc921206D.spec.Z tc921208D.spec.Z
tc921209D.spec.Z tc921210D.spec.Z tc921213D.spec.Z
tc921214D.spec.Z tc921215D.spec.Z tc921216D.spec.Z
tc930109D.spec.Z tc930112D.spec.Z tc930113D.spec.Z
tc930114D.spec.Z tc930116D.spec.Z tc930117D.spec.Z
tc930118D.spec.Z tc930126D.spec.Z tc930127D.spec.Z
tc930128D.spec.Z tc930204D.spec.Z tc930206D.spec.Z
tc930209D.spec.Z tc930210D.spec.Z tc930217D.spec.Z
tc930218D.spec.Z
Data Processing and Analysis NCAR Electra Microphysics Data
The NCAR 2-D monoprobes consist of a 0.2 mm resolution precipitation (2D-P) and a 0.025 mm resolution cloud (2D-C) probe. The size dependence of the 2D-C depth of field was NOT accounted for. These data were averaged for 6 sec. However, the inter-record times on the files are not always 6 sec apart because of the asynchronous data collection.
Images whose largest dimension was within the diode array were sized by the equivalent circle area. Partial images whose longest dimension was on an edge were sized by the longest dimension, but these particles were counted as fractional images defined as the image area divided by the area of an equivalent circle of diameter equal to the length of the longest dimension. Images that occulted both end diodes were rejected.
To account for the fact that the old PMS 2D monoprobes stripped the first slice off each image, zero-area images were added into the computations as particles with area of 0.5 diodes. All other images had areas increased according to the following:
Area (A) < 17, area=area +0.53707 +0.31552A -0.02030841A**2 +0.00050043A**3
Area (A) > 16, area=area +2.0385 +0.016346A
This correction procedure forces zero-area images into the smallest size category, and increases the size of some images in the first few size channels up to the next larger size. Computed parameters include rain rate (mm/hr), radar reflectivity factor (Z mm**6/m**3), liquid water content in both g/m**3 and n/l, liquid median volume diameter (mm), and the y-intercept and slope of the liquid particle size distribution when plotted as Log(n/l) vs. diameter in millimeters. Measured parameters included in the file are date, time, sample volume (liter) for both probes, and elapsed overload times in seconds for the averaging period.
File format
The physical records are organized as follows:
Each averaging period of 2-D monoprobe data from the NCAR Electra contains 7 to 128-byte direct-access records written as 32 4-byte IEEE real-format values associated with it. The first record of each group of seven contains computed data, plus the date (YYMMDD) and time (seconds). The contents of the header record are:
WORD CONTENTS
1 DATE (YYMMDD.)
2 TIME (SS.MSEC) (end time of averaging period)
3 5.5 cm radar attenuation from 2D-P (dBZ/km)
4 averaging time, seconds
5 True Airspeed (TAS), m/s
6 # records/time this file (7)
7 2DP liquid water content (LWC) (g/m**3)
8 2DP LWC (n/l)
9 2DP rain rate (mm/hr)
10 2DP ice water content (IWC) (g/m**3) (if any)
11 2DP IWC (n/l)
12 2DP radar reflectivity factor, Z (mm**6/m**3)
13 2DP liquid water (LW) Y-intercept, exponential fit)
14 2DP LW slope (exp. fit)
15 2DP ice water (IW) Y-intercept (exp. fit)
16 2DP IW slope (exp. fit)
17 2DP LW median volume diameter (mvd) (mm)
18 2DP Elapsed o/l time (s), this period
19 2DP sample volume (l)
20 2DC LWC (g/m**3)
21 2DC LWC (n/l)
22 2DC rain rate (mm/hr)
23 2DC IWC (g/m**3)
24 2DC IWC (n/l)
25 2DC Z (mm**6/m**3)
26 2DC LW A0 (exp. fit)
27 2DC LW slope (exp. fit)
28 2DC IW A0 (exp. fit)
29 2DC IW slope (exp. fit)
30 2DC LW mvd (mm)
31 2DC Elapsed o/l time (s)
32 2DC sample volume (l)
The second and third records are the 2D-P water size distribution as n/l per 0.2 mm-size channel, and the fractional image data in the same units, respectively. If one desires to exclude the partial images, simply subtract, element by element, the data in Record 3 from that in Record 2. The result will be the image data size spectra using the "center in" technique described by Black and Hallett (1986). Records 4 and 5 are the same as Records 2 and 3, except for the 2D-C. These are divided into number per liter per 0.025 mm-size channel. Records 6 and 7 are 2D-C graupel and 2D-C column data, unused for TOGA COARE.
Data Example
.rain
Rainfall rates file for :930118D tc
Flag #1:
Flag #2:
Flag #3:
Flag #4:
Flag #5:
0 entries from ******* to *******
0 entries from Cloud probe,NaN % of total.
Time Height Rainrate MVDprcp Tau MaxRf Atten Logical
Seconds m mm/hr mm mm2 dbZ dbZ/km flags
80277. 3000.0 .33 .60 -7.41 .703E+02 .00 FFFFF
82551. 3000.0 .12 .20 -6.90 .252E+01 .00 FFFFF
82864. 3000.0 .12 .50 -7.70 .287E+02 .00 FFFFF
82870. 3000.0 .91 .40 -6.73 .158E+03 .00 FFFFF
.spec
Rainfall spectrum for Storm tc and flight 930118D
Rainrate category 1 from .0 to .1 sample volume .22053E+06 and 129 entries
.62303E+05 .12450E+05 .23238E+04 .49415E+03 .10898E+03 .39910E+02 .10780E+02 .55968E+01
.13144E+01 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00
.00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00
.00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00 .00000E+00
NOAA WP3D The NOAA P3 data are handled in a manner similar to the NCAR data, except that images with their longest dimension on an edge are not utilized. Another difference is that the NOAA aircraft used the new 2D-Greyscale probes along with an SEA Inc. model 200 data system. These differences require a much longer averaging period (at least 60 sec) to obtain a stable size distribution. The 2D-Greyscale files are composed of seven records each 256 bytes long consisting of 64 IEEE real-format words.
File Format
As in the case of the 2-D files mentioned above, each N-sec average is represented by a group of seven 256-byte long records. Each record consists of 64 IEEE real-format 32-bit words. The first of these records contains the date, time, and parameters derived from the 2-D data. Similarly, the second and third records contain the 2DG-P water and ice distributions, and records 4 through 7 contain the 2DG-C water, ice, graupel, and column distributions, respectively. All concentrations are given in number/liter.
The derived parameters (as of 5 December 1994) are as follows:
WORD PARAMETER NAME UNITS
1 DATE (YYMMDD)
2 TIME (HHMMSS)
3 RAIN RATE mm/hr (MAX of 2D-P and 2D-C)
4 LWC g m-3 (MAX of 2D-P and 2D-C)
5 IWC g m-3 (MAX of 2D-P and 2D-C)
6 2D-P Radar reflectivity dBZ
7 5.5 cm 2-way attenuation dBZ/km
8 Averaging time seconds
9 True air speed m/s (related to the clock rate)
10 2D-P LWC g m-3
11 2D-P IWC g m-3
12 2D-C LWC g m-3
13 2D-C IWC g m-3
14 2D-C Sample vol. L
15 2D-P Sample vol. L
16 2D-C Rain rate mm/hr
17 2D-P Rain rate mm/hr
18 number of rejected records this interval
19 2D-C Radar reflectivity dBZ
20 2D-P "K" factor from Heymsfield et al., (1986)
21 unused
22 unused
23 2D-C "K"
24 unused
25 sum 2D-C pixel area mm**2
26 average 2D-C pixel area mm**2
27 sum 2D-P pixel area mm**2
28 average 2D-P pixel area
29 2D-P overload count (not valid for Grey probe data)
30 2D-C overload count
31 2D-P Liquid counts
32 2D-C Liquid counts
33 2D-P Ice counts
34 2D-C Ice counts
35 unused
36 unused
37 unused
38 unused
39 unused
40 unused
41 unused
42 unused
43 unused
44 unused
45 unused
46 unused
47 unused
48 unused
49 unused
50 unused
51 unused
52 unused
53 unused
54 unused
55 unused
56 unused
57 unused
58 unused
59 unused
60 2DG-C total count (?)
61 2DG-P total count (?)
62 2DG-C counts/record (?)
63 2DG-P counts/record (?)
64 Bulk ice density g m-3
FORTRAN programs for a quick look
FDUMP: FDUMP prints a specified number of direct-access records to a printer or the screen. This is useful for determining if the file was created properly. The user is responsible for output formatting.
USAGE: fdump2 1 999
CHECK: CHECK makes sure the times on the file were created properly, and it allows the user to change the date and times as necessary to account for times extending past midnight and other time problems.
USAGE: check3 2-d_ filename
EXTRACT2D: EXTRACT2D creates an ASCII file out of the computed parameters from the 2-D data file.
USAGE: extract2d
EXTR_HIST: EXTR_HIST creates an ASCII file out of the selected 2-D size distribution(s). The user selects the parameter, start, and stop times, plus provides the name of the output file.
CONCAT2D: CONCAT2D concatenates 2-D files if necessary. This routine is also useful for removing unwanted data from the direct access files.
USAGE: concat2d
PMS_EDIT: PMS_EDIT allows the user to modify and change any element in any one of the seven arrays (records) that make up a 2-D n-second average. Only one element may be changed at once, but this one parameter of the n-second average may be altered on all of the seven-record n-second averages in the entire file at once.
USAGE: pms_edit
PMS_MERGE: PMS_MERGE assembles the (separate) 2D-P and 2D-C n-second average files into one file, and resolves the conflicts in the record times such that if one time is more than one averaging time smaller, the data read from that file makes a separate entry in the merged file. If the time difference is less that half the averaging time, the 2D-P and 2D-C data are merged assuming the 2D-P time is applicable.
USAGE: pms_merge
For more information, please contact:
Robert A. Black
NOAA/AOML/HRD
4301 Rickenbacker Causeway
Miami, FL 33149-1097
USA
email: rblack@aoml.noaa.gov
Phone: (305) 361-4314
FAX: (305) 361-4402
or
Frank D. Marks
NOAA/AOML/HRD
4301 Rickenbacker Causeway
Miami, FL 33149-1097
USA
email: marks@aoml.noaa.gov
Phone: (305) 361-4321
FAX: (305) 361-4402
References Black, R. A. and J. Hallett, 1986: Observations of the distribution of ice in hurricanes. J. Atmos. Sci. 43, 802-822.
Marks et al., 1993: JAM, 32, 1134-1141.
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