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The ceilometer data set was acquired on the Research Vessel Ron H. Brown under the direction of principal investigator Allen B. White during the KWAJEX field campaign.
The Instrument
The maximum range of the ceilometer is 7620 m, and the resolution in the profiles is 15 m (50 ft). Other details on operation of the Vaisala
CT25K are given by White, 1997. A comparison of ceilometer data collected in four different climate regimes (FIRE/SCOPE, ASTEX, TIWE, COARE) is
given by White et al. 1995. A comparison of ceilometer data recorded on Manus Island and onboard the R/V Discoverer
during the 1996 Combined Sensor Program is included in Post et al. 1997.
The distribution of these data sets is funded by NASA's
Earth Science Enterprise. The data are not copyrighted;
however, we request that when you
publish data or results using these data, please
acknowledge as follows:
The authors wish to thank Dr. Allen White, NOAA Environmental Technology
Laboratory's Air Sea Interaction Group, Boulder, CO for the production of
these data and the Data and Information Services Center(Code 610.2) at the Goddard
Space Flight Center, Greenbelt, MD, 20771, which archives and distributes them
under sponsorship of NASA's Earth Science Enterprise.
Here is some information regarding the ceilometer data recorded on the R/V
Ron Brown during KWAJEX. The user has the option of getting the raw 15-s time
resolution data and/or statistics of the 15-s data. The 15-s data and
statistics are contained in ASCII-based files. Daily and experiment summary
plots of the statistics are available in postscript.
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Characteristics and Naming Conventions
All files are compressed with Winzip and stored in the following archive files:
|
| | rawbase_data.zip | 15-s raw sky designation and cloud base data |
| stat_data.zip | Daily files of hourly summary statistics |
| basedist_data.zip | Daily files of cloud base frequency distributions |
| stat_plots.zip | Postsript images of daily summary statistics |
| experiment_summary.zip | Statistical summary files |
| realtime_displays.zip | Data acquisition program display images |
Rawbase_data.zip
- The file names in the rawbase_data.zip archive are of the form
MM_DD_YY.cld,
- where
- MM = month (i.e., 01 = Jan.)
- DD = day of the month
- YY = year (i.e., 99 = 1999).
In these files there are 7 columns of data:
| Column | Parameter |
|---|
| 1 | sky designation
- 0 = clear
- 1 = single cloud layer detected
- 2 = two cloud layers detected
- 3 = three cloud layers detected
- 4 = totally obscured conditions
- 5 = partially obscured conditions
|
| | 2 | height of lowest detected cloud base in meters |
| 3 | height of second detected cloud base in meters |
| 4 | height of third detected cloud base in meters |
| 5 | GMT hour |
| 6 | GMT minute |
| 7 | GTM second | |
"Totally obscured" conditions usually occur in fog or precipitation.
"Partially obscured" conditions occur when the ceilometer algorithm detects a
signal that does not fit the pattern of a "hard" cloud boundary. When the sky
designation is totally obscured, the value reported in the second column is a
calculation of vertical visibility. In these cases, the third column reports
the maximum height that a signal was detected. The totally obscured data were
included in the computation of cloud fraction statistics, but not of cloud base
statistics. The partially obscured data were thrown out before any statistics
were computed. |
stat_data.zip
- The 15-s ceilometer
data were used to generate hourly cloud base and cloud fraction statistics.
These data are contained in files sMMDDYY.dat in the stat_data.zip archive.
These daily files contain 16 columns:
| Column | Parameter |
|---|
| 1 | month |
| 2 | day |
| 3 | Julian day |
| 4 | GMT (middle of hour) |
| 5 | # of "total" 15-s data points |
| 6 | # of "clear" data points |
| 7 | # of "single cloud base" data points |
| 8 | # of "multiple cloud base" data points |
| 9 | # of "totally obscured" data points |
| 10 | # of "partially obscured" data points |
| 11 | clear fraction |
| 12 | cloud fraction without including totally obscured points |
| 13 | * cloud fraction including totally obscured points |
| 14 | 20th percentile cloud base (m) |
| 15 | 50th percentile (median) cloud base (m) |
| 16 | 80th percentile cloud base (m) |
|
basedist_data.zip
|
stat_plots.zip
- The cMMDDYY.ps files in the stat_plots.zip archive are postscipt images
containing summary graphs for the daily ceilometer data.
|
experiment_summary.zip
- The expdiurn.dat file in the experiment_summary.zip archive contains diurnal averages of cloud fraction and cloud base. This
file contains three columns:
| Column | Parameter |
|---|
| 1 | Time (center of GMT hour) |
| 2 | cloud fraction |
| 3 | cloud base (km) |
- The expfdst.dat file in the experiment_summary.zip archive contains a number and frequency distribution of hourly cloud
fractions. This file contains three columns:
| Column | Parameter |
|---|
| 1 | cloud fraction (center of 1/10 range) |
| 2 | number of hourly occurrences |
| 3 | frequency/100 of occurrence |
- The file expstat.ps in the experiment_summary.zip archive is a postscript image containing experimental summary graphs.
| realtime_displays.zip
- The MM_DD_YY.am or .pm files in the
realtime_displays.zip archive contain the data acquisition program screen
display stored at the end of each 12-hour period. These files may be imported
into a word processor (e.g., WordPerfct v9) for viewing.
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FTP Site
The ceilometer data from KWAJEX may be accessed from this page,
Ceilometer Data Online
or directly via ftp:
ftp disc2.nascom.nasa.gov
logon: anonymous
passwd:
cd data/KWAJ/surface_data/rv_rhbrown/ceilometer
The Principal Investigator for the ceilometer data is
Dr. Allen White
NOAA Environmental Technology Laboratory
325 Broadway
Boulder, CO 80303,
awhite@etl.noaa.gov
(303) 497-5155
For KWAJEX user services at the DISC contact:
NOAA Tech Memo. ERL ETL-281, NOAA Environmental
Technology Laboratory, 325 Broadway, Boulder, CO 80303, 1997
White et al., 1995. J. Atmospheric Science, 52:2827-2838
Post et al., 1997. Bull. American Meteorology Society, 78:2797-2815
For additional information, please contact the GES DISC User Services:
Last update:Thu Dec 4 14:50:59 EST 2003
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