- Mono probe data (2D-C + 2D-P; 2D-P only since 1993) NASA
DC-8 (CAMEX-III) also. Since 2001, a 2D-C mono probe is available on
some flights, but its quality is poor.
The NOAA 2-D mono probes consist of a 0.2 mm resolution
precipitation (2D-P) and a 0.050 mm resolution cloud (2D-C) probe.
The size dependence of the 2D-C depth of field noted in the PMS manual
is incorrect and is NOT used. Instead, the 2D-C corrections from
Korolev and Baumgardner (JAM, 1997) are utilized. These data are
normally averaged for 6-seconds, but any other interval may be used.
However, the inter-record times on the files are not always the same
because of the asynchronous data collection. NOTE: During the NASA
CAMEX-III project, the DC-8 used a 0.025 mm resolution 2D-C probe.
Ice particles and partial raindrop 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
rejected. Complete drop images were sized by the longest dimension
perpendicular to the diode array.
Computed parameters include rain rate (mm/hr), radar
reflectivity factor (Z, mm/hr), 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 (l) for both probes, and elapsed
over-load times in seconds for the averaging period.
Changes Since 1993: Added 4-digit year. Prior to 1993, these data were
usually processed together. Thus, both 2D-P and 2D-C data were usually
present in the files. Since then, the new DAS's recording method made
this practice unsatisfactory. These data are now processed separately
and written into separate files.
The physical records are organized as follows:
Each averaging period of 2-D MONO data from the WP-3D contains
7 128-byte direct-access records written as 32 4-byte IEE REAL format
values associated with it. The first record of each group of 7 contains
computed data, plus the date (YYYYMMDD) and time HHMMSS.msec. The
contents of the header record are:
| WORD | CONTENTS
|
| 1 | DATE (YYMMDD.) (Some have 4-digit year)
|
| 2 | TIME (HHMMSS.MSEC) (end time of averaging period)
|
| 3 | Rain rate (mm/hr), MAX of 2D-C and 2D-P (Old files only)
|
| 4 | LWC (g/m3), MAX of 2D-C and 2D-P. (Old)
|
| 5 | IWC (g/m3), MAX of 2D-C and 2D-P. (Old)
|
| 6 | 2DP radar reflectivity, dBZ
|
| 7 | 5.5 cm radar attenuation from 2D-P (dBZ/km)
|
| 8 | averaging time, seconds
|
| 9 | True Airspeed (TAS), m/s
|
| 10 | 2DP liquid water content (LWC) (g/m**3) (if any)
|
| 11 | 2DP ice water content (IWC) (g/m**3) (if any)
|
| 12 | 2DC liquid water content (LWC) (g/m**3) (if any)
|
| 13 | 2DC ice water content (IWC) (g/m**3) (if any)
|
| 14 | 2DC Sample Volume (Liters)
|
| 15 | 2DP Sample Volume (Liters)
|
| 16 | 2DC rain rate (mm/hr)
|
| 17 | 2DP rain rate (mm/hr)
|
| 18 | Number of bad records this averaging period
|
| 19 | 2DC reflectivity factor dBZ
|
| 20 | "K" from Heymsfield (1989) method of obtaining Z-M relation
|
| 21 | 2D-C Mass-weighted fall speed (cm/s)
|
| 22 | 2D-P Mass-weighted fall speed (cm/s) "K" from 2D-P
|
| 23 | (UNUSED) 2DC "K" from Heymsfield (1989) method of obtaining Z-M relations.
|
| 24 | (UNUSED) 2DC IWC ("measured" from Heymsfield (1989))
|
| 25 | Summation 2DC area (sq. mm)
|
| 26 | mean 2DC area (sq. mm)
|
| 27 | Summation 2DP area (sq. mm)
|
| 28 | mean 2DP area (sq. mm)
|
| 29 | 2DC overload percent
|
| 30 | 2DP overload percent
|
| 31 | 4-digit year (Since 6/28/01)
|
| 32 | Ice density used
|
The second and third records are the 2D-P water and 2D-P ice
size distribution as n/l per 0.2 mm size channel, respectively. For
TOGA, record 3 of 7 is the fractional image data in the same units.
If it is desired 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 BH. 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 0.05 mm size channel. Records 6 and 7 are 2D-C graupel and 2D-C
column data, unused for TOGA-COARE. For 2D-P data processed since 1996,
records 4 and 5 contain 2D-P graupel/round images and 2D-P columnar
images, respectively.
- NOAA WP-3D 2D-Grey probe data
PMS 2D-Greyscale data are significantly different from the
2D-Mono probe data, and they are consequently treated differently.
Grey images utilize 2 bits of information per pixel instead of one,
thus giving four levels of shadow depth. Further, the diode array is
64-pixels wide instead of 32 pixels. Thus, grey probes require four (4)
times the data of a mono probe to characterize one image. Since the
data path from the grey probes is no wider than that for the mono
probes, image throughput is significantly reduced, necesitating longer
averaging times. The NOAA WP-3D mounts two of these probes, usually, a
2DG-C with a 0.030 mm pixel size, and a 2DG-P with a 0.15 mm resolution
The NOAA-P3 Grey probe data are handled in a similar manner to
the Mono probe data, and partial images whose longest dimension is on
the edge are not utilized. A major difference is that the greyscale
information are used to eliminate out-of-focus images and most splashes
which results in "cleaner" size distributions. 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 12 s, 60 s or more for the TOGA data) to obtain a stable size
distribution. The 2D-Greyscale files are composed of 7 records, each
256 bytes long consisting of 64 IEEE real format words. Data from only
one probe at a time can be analyzed, so several of the records are
always blank. At this time, there is no merge program for 2D-Grey
records.
Water images are treated differently from ice particles. If
images are assumed to be water, the image is assumed to be an oblate
spheriod with an elliptical cross-section. A least-squares ellipse fit
to the image perimeter provides the particle area and equivalent
circle diameter.
Ice particles also have an ellipse fitted to their image
perimeter, but this is used for habit discrimination rather than
for sizing. Ice particles are sized by their equivalent circle
area unless they are deemed to be of type column or needle, in
which case the volume (and IWC) is computed as though the image
was of a rectangular prism, whereas the diameter is still the
equivalent circle diameter as before.
The physical records are organized as follows:
Each averaging period of 2-D Grey data from the WP-3D contains
7 256-byte direct access records written as 64 4-byte IEE REAL format
values associated with it. The first record of each group of 7 contains
computed data, plus the date (YYYYMMDD) and time HHMMSS.msec. If the
images are assumed to be rain, the program offers the option to filter
the spectra to remove extraneous large images from ice particles and
un-rejected splashes.
IMPORTANT CHANGES
Recent papers by Baumgardner, Korlorev, and others have pointed out
the need for complex airspeed and Depth of Field corrections for the
2DG-C. SUCH CORRECTIONS HAVE NOT BEEN MADE TO THESE DATA. FURTHER,
THE 2DG-P ALSO REQUIRES SUCH CORRECTIONS. Use these data with
appropriate caution, as the number concentrations, water contents,
etc. are somewhat smaller than they should be.
6/2001: The year was stripped from the date because of word overflow
during the 1998 season. Now, the 4-digit year is stored in word 59 of
the first buffer. Some 1998 files have NO YEAR. ALso, GRAUPEL and
NEEDLE categories are now also kept for the 2DG-P data. No more merged
data files will be created. These are stored in the same positions as
the 2D-C categories.
The contents of the header record are:
| WORD | CONTENTS
|
| 1 | DATE (YYYYMMDD.) 1998+ MMDD only. Year is in Word 59.
|
| 2 | TIME (HHMMSS.MSEC) (end time of averaging period)
|
| 3 | Rain rate (mm/hr), MAX of 2D-C and 2D-P. (Pre-1998 only)
|
| 4 | LWC (g/m3), MAX of 2D-C and 2D-P. (Old)
|
| 5 | IWC (g/m3), MAX of 2D-C and 2D-P. (Old)
|
| 6 | 2DP radar reflectivity, dBZ
|
| 7 | 5.5 cm radar attenuation from 2D-P (dBZ/km)
|
| 8 | averaging time, seconds
|
| 9 | True Airspeed (TAS), m/s
|
| 10 | 2DP liquid water content (LWC) (g/m**3) (if any)
|
| 11 | 2DP ice water content (IWC) (g/m**3) (if any)
|
| 12 | 2DC liquid water content (LWC) (g/m**3) (if any)
|
| 13 | 2DC ice water content (IWC) (g/m**3) (if any)
|
| 14 | 2DC Sample Volume (Liters)
|
| 15 | 2DP Sample Volume (Liters)
|
| 16 | 2DC rain rate (mm/hr)
|
| 17 | 2DP rain rate (mm/hr)
|
| 18 | Number of bad records this averaging period
|
| 19 | 2DC reflectivity factor dBZ
|
| 20 | "K" from Heymsfield (1989) method of obtaining Z-M relation
|
| 21 | 2D-C Mass-weighted fall speed (cm/s)
|
| 22 | 2D-P Mass-weighted fall speed (cm/s) "K" from 2D-C
|
| 23 | (UNUSED) 2DC "K" from Heymsfield (1989) method of obtaining Z-M relations.
|
| 24 | (UNUSED) 2DC IWC ("measured" from Heymsfield (1989))
|
| 25 | Summation 2DC area (sq. mm)
|
| 26 | mean 2DC area (sq. mm)
|
| 27 | Summation 2DP area (sq. mm)
|
| 28 | mean 2DP area (sq. mm)
|
| 29 | 2DC overload fraction
|
| 30 | 2DP overload fraction
|
| 31 | 2DG-P accepted water particle count
|
| 32 | 2DG-P accepted ice particle count
|
| 33 | 2DG-C accepted water particle count
|
| 34 | 2DG-C accepted ice particle count
|
| 59 | YEAR (4-digit, 1998+)
|
| 60 | raw total count (images saved and unsaved) from 2DG-C
|
| 60 | raw total count (images saved and unsaved) from 2DG-P
|
| 64 | Ice density used
|
NOTE :
Some 1998 analysis files DO NOT contain the year.
- NASA DC-8 2D-Grey probe data (CAMEX-III and TOGA_COARE)
Same as for the WP-3D, except that during TOGA-COARE, the DC-8 used a
0.025 mm pixel 2DG-C and a 0.040 mm pixel 2DG-C as a precipitation
probe. During CAMEX-III, they used a 0.025 mm 2D-C mono probe and the
NOAA 0.2 mm pixel 2D-P Mono probe, the 0.040 mm 2DG-C was used instead
of the 2D-P for some flights.
Please contact Mr. Robert A. Black
or Phone (305) 361-4314 for information about the status and availability of
these data.
- NCAR rain data (TOGA-COARE ONLY)
The NCAR 2-D mono probes 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 accounted for.
These data were averaged for 6 seconds. However, the inter-record
times on the files are not always 6-s 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.
To account for the fact that the old PMS 2D-Mono probes
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 > 16, area=area +2.0385 +0.016346A.
This correction procedure forces zero-area images into the smallest
size category, and increased the size of some images in the first few
size channels up to the next larger size.
The distributions of the partial images included above are saved in
the (unused) ice array so that the effects of this usage can be removed
if necessary.
Computed parameters include rain rate (mm/hr), radar
reflectivity factor (Z, mm/hr), 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
(l) for both probes, and elapsed over-load times in seconds for
the averaging period.
The physical records are organized as follows:
Each averaging period of 2-D MONO data from the NCAR ELECTRA
contains 7 - 128-byte direct-access records written as 32 4-byte IEE
REAL format values associated with it. The first record of each group
of 7 contains computed data, plus the date (YYMMDD) and time
HHMMSS.msec. 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)
|
| 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)
|
| 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 it is desired 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 BH. 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..
- FSSP-100 files.
Since 1992, the newer FSSP-100 probes now properly account for
"Activity", which allows coincidence errors to be accounted for. These
data are also written to a 32-word buffer written as a direct-access
record. The parameters in each position are:
| WORD | CONTENTS
|
| 1 | YEAR (YY or YYYY)
|
| 2 | Month
|
| 3 | day
|
| 4 | hour
|
| 5 | minute
|
| 6 | seconds
|
| 7 | milliseconds
|
| 8 | FSSP Range
|
| 9 | 23 FSSP size distribution, (n/cc)
|
| 24 | Sample volume (cc)
|
| 25 | liquid water content (g/cc)
|
| 26 | Total droplet concentration (n/cc)
|
| 27 | True Air Speed (TAS), m/s
|
| 28 | total accepted particle count
|
| 29 | total strobe count (includes rejected strobes)
|
| 30 | FSSP Activity counter
|
| 31 | FSSP reference volts
|
| 32 | unused
|
FSSP Range values are as follows:
| WORD | CONTENTS
|
| Value | Nominal Size Range (microns)
|
| 0 | 3 - 45
|
| 1 | 2 - 30
|
| 3 | 1 - 15
|
| 4 | 0.5 - 7.5
|
- Archive Image appearance
Mono Probes
- 2D-C images are sorted by image class and within each class,
presented in order of occurrence from left to right. The images
themselves are red. Each class is separated by a vertical dashed
line. The classes are:
| WORD | CONTENTS
|
| 0 | liquid water
|
| 1 | undifferentiated ice.
|
| 2 | round ice or graupel
|
| 3 | columns and needles
|
Classes higher than 3 are rejects,
not included in the size distributions.
Class 4 images are NOT included in the image archive.
|
| 4 | streaks
|
| 5 | Too small a time interval
|
| 6 | Zero area
|
| 7 | Image has a y-gap
|
| 8 | Multiple image (x-gap)
|
| 9 | Partial image caused by probe overload
|
| 10 | First (incomplete) image in the record
|
| 11 | Time interval too large to be real
|
- 2D-P images are green. These are classed as above, except that
round and columns (Classes 2 and 3) are not used. This changed for
all revisions of the analysis software in use since 1996, as I have
permanently abandoned the option of merging 2D-C and 2D-P data files.
2D-P and 2DG-P files processed since then include round/graupel and
column categories
Grey Probes
- 2DG-C images are colored according to their depth of shadow. The
darkest shadow (75%) is green, the middle level depth (50%) is blue,
and the minimum shadow depth (25%) is red. Image type is identified by
colored vertical bars. A wide yellow bar separates 2D-Grey records.
Within a record, a colored bar following the image identifies its
class. No rejected images appear in the archive.
The accepted image classes are:
| WORD | CONTENTS
|
| 0 | Liquid water, multi-colored dashed line
|
| 1 | undifferentiated ice, solid red line
|
| 2 | round ice or graupel, solid green line
|
| 3 | column or needle, red/yellow dashed line
|
Images classed 4 and higher do not apppear.