ARM Southern Great Plains, Cloud Measurements
Entry ID:
SGPcloud
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Summary
Abstract:
The Atmospheric Radiation Measurement (ARM) Program is the largest global change research program supported by the U.S. Department of Energy (DOE). ARM scientists focus on obtaining field measurements and developing models to better understand the processes that control solar and thermal infrared radiative transfer in the atmosphere (especially in clouds) and at the earth's surface. The URL for ... the ARM Data Archive is http://www.archive.arm.gov/. The URL for
general information about the ARM program is http://www.arm.gov/. The data
stored by the ARM Archive includes numerous parameters about radiative flux,
meteorology, water vapor and clouds.
The U.S. Southern Great Plains (SGP) site was the first field measurement site
established by DOE's Atmospheric Radiation Measurement (ARM) Program.
Scientists are using the information obtained from the SGP to improve cloud and
radiative models and parameterizations and, thereby, the performance of
atmospheric general circulation models used for climate research. Deployment of
the first instrumentation to the SGP site occurred in the spring of 1992.
Additional instrumentation and data processing capabilities have been
incrementally added in the succeeding years. The SGP was chosen as the first
ARM field measurement site for several reasons including its relatively
homogenous geography and easy accessibility, wide variety of climatic and cloud
conditions, surface flux properties, and large seasonal variation in
temperature and specific humidity. It also already had a large, existing
network of weather and climate research and instrumentation. The SGP site
consists of in situ and remote-sensing instrument clusters arrayed across
approximately 55,000 square miles (143,000 square kilometers) in north-central
Oklahoma. The ARM SGP site is the largest and most extensive climate research
field site in the world. The heart of the SGP site is the heavily instrumented
Central Facility located on 160 acres of cattle pasture and wheat fields
southeast of Lamont, Oklahoma. A staff of 30 scientists and technicians collect
and monitor data from the Central Facility instruments and from smaller,
unmanned facilities throughout the site. The instruments throughout the site
automatically collect data on surface and atmospheric properties, routinely
providing data to the Site Data System, which is linked by high-speed
communications to the ARM Archive and Data Center. The Data Center acquires
additional data from other sources, such as National Weather Service satellite
and surface data, and provides tailored data packages to ARM Science Team
members.
Atmospheric profiling data is available from numerous locations at the SGP
site. Site descriptions are available at
http://www.arm.gov/sites/sgp.stm. Detailed information on the
instruments used is at http://www.arm.gov/instruments.
The following list contains the instrumentation used for cloud measurements and
the data available for sites at SGP.
Vaisala Celiometer (VCEIL).
For complete VCEIL information, visit
http://www.arm.gov/instruments/instrument.php?id=vceil. The VCEIL is a
self-contained, ground-based, active, remote-sensing device designed to measure
cloud-base height at up to three levels and potential backscatter signals by
aerosols. Model CT25K has a maximum vertical range of 25,000 feet. The
ceilometer transmits near-infrared pulses of light, and the receiver telescope
detects the light scattered back by clouds and precipitation. The Vaisala
ceilometers measure the backscattered light intensity from a pulsed InGaAs
diode laser (905 nm) as a function of distance (15-m resolution for the CT25K).
These measurements are used to produce derived products that are recorded.
These products include (1) The backscatter profile with 15-m resolution; (2)
The cloud-bottom height determined with an algorithm to define cloud bottom as
the height corresponding to a visibility reduction to 100 m; (3) Secondary
cloud-bottom heights from a cloud above the lowest cloud; and (4) Tertiary
cloud-bottom heights from an even higher cloud.
VCEIL data at the Central Facility (C1; Lamont OK) are available for 2000-05-22
to present.
At Boundary Facilities 1 (Hillsboro, KS), 4 (Vici, OK), 5 (Morris, OK), and 6
(Purcell, OK), data are available from 1999-09-21 to present.
ARM data stream is coded sgpvceil25k: cloud base heights, 25,000 feet maximum
range.
Additional data streams or value added products may be added in the future.
Millimeter Wave Cloud Radar (MMCR).
For complete MMCR information, visit
http://www.arm.gov/instruments/instrument.php?id=mmcr. The MMCR systems probe
the extent and composition of clouds at millimeter wavelengths. The MMCR is a
zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose
of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops).
This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20
km. The radar possesses a doppler capability that will allow the measurement of
cloud constituent vertical velocities. The primary quantities measured with
this system are (1) radar doppler spectra, (2) radar doppler moments, (3) radar
reflectivity (dBZ), (4) vertical velocity, and (5) spectral width. Inversions
are in development to infer cloud microphysical properties.
At the Central Facility (CF1; Lamont OK), MMCR data are available from
1996-11-08 to present.
ARM data streams are coded as follows:
sgpmmcrmomentsC1: moments data
sgpmmcrmonC1: monitoring data
sgpmmcrpowC1: power data
sgpmmcrcalC1: calibration data
sgpmmcrmode01v0011clothC1: Derived: MMCR Mode 1 (stratus mode) moments
sgpmmcrmode01v0021clothC1: Derived: MMCR Mode 1 (stratus mode) moments)
sgpmmcrmode01v0031clothC1: Derived: MMCR Mode 1 (stratus mode) moments
sgpmmcrmode01v0041clothC1: Derived: MMCR Mode 1 (stratus mode) moments
sgpmmcrmode01v0051clothC1: Derived: MMCR Mode 1 (stratus mode) moments
sgpmmcrmode01v0061clothC1: Derived: MMCR Mode 1 (stratus mode) moments
sgpmmcrmode02v0011clothC1: Derived: MMCR Mode 2 (cirrus mode) moments
sgpmmcrmode02v0021clothC1: Derived: MMCR Mode 2 (cirrus mode) moments
sgpmmcrmode02v0031clothC1: Derived: MMCR Mode 2 (cirrus mode) moments
sgpmmcrmode03v0011clothC1: Derived: MMCR Mode 3 (general mode) moments
sgpmmcrmode03v0021clothC1: Derived: MMCR Mode 3 (general mode) moments
sgpmmcrmode03v0031clothC1: Derived: MMCR Mode 3 (general mode) moments
sgpmmcrmode04v0011clothC1: Derived: MMCR Mode 4 (robust mode) moments
sgpmmcrmode04v0021clothC1: Derived: MMCR Mode 4 (robust mode) moments
sgpmmcrmode04v0031clothC1: Derived: MMCR Mode 4 (robust mode) moments
sgpmmcrmode05v0011clothC1: Derived: MMCR Mode 5 (experimental mode) moments
Additional data streams or value added products may be added in the future.
Micropulse Lidar (MPL).
For complete MPL information, visit
http://www.arm.gov/instruments/instrument.php?id=mpl. The MPL is a
ground-based
optical remote sensing system designed primarily to determine the altitude of
clouds overhead and provides information on cloud base (thick clouds), cloud
base and top (optically thin clouds) and an aerosol profile. The physical
principle is the same as for radar. A pulse of energy is transmitted and the
energy reflected back is measured. From the time delay between the transmitted
pulse and the backscattered signal, the distance to the scatterer is inferred.
Besides real-time detection of clouds, post-processing can also characterize
the extent of the tropospheric mixing layer (the planetary boundary layer), or
other particle-laden regions. This eye-safe system is designed for continuous
operation. The MPL has one measurement channel that records backscatter signals
in 300 meter range bins, with the lowest valid range bin beginning at 120
meters above ground level, up to 20 kilometers. The primary quantity obtained
from this signal is the real-time reporting of the lowest detected cloud base
in meters, obtained from 60 sec averages. Additional quantities possible
through post-processing of the raw signal return include a relative backscatter
profile (counts/sec/meter) with instrument effects removed. Instrument effects
include a dead-time correction specific to the individual detector, near-range
corrections for the overlap of the transmitting and detection optics, and
removal of afterpulsing due to detector saturation from optical crosstalk as
the pulse is transmitted. From the relative backscatter profile, other data
products are possible. These include cloud boundaries, multiple cloud decks,
and layer boundaries.
At the Central Facility (C1; Lamont OK), MPL data are available from 1996-03-12
to present.
ARM data streams are coded as follows:
sgpmplC1: cloud base and top heights
sgpmplcmask1clothC1: MPL cloud mask using the first Clothiaux, et al. Algorithm
sgpmplsmask1clothC1: MPL significance mask using the first Clothiaux, et al.
Significance Algorithm
sgpmplcbh1scottC1: cloud base heights from the MPL using the Scott/Spinhirne
algorithm
sgpmplnor1campC1: backscatter profiles normalized and cloud detection routinely
applied
Additional data streams or value added products may be added in the future.
Microwave Radiometer (MWR).
For complete MWR information, see
http://www.arm.gov/instruments/instrument.php?id=mwr. The MWR provides
time-series measurements of column-integrated amounts of water vapor and liquid
water. The instrument itself is essentially a sensitive microwave receiver.
That is, it is tuned to measure the microwave emissions of the vapor and liquid
water molecules in the atmosphere at specific frequencies.
The MWR receives microwave radiation from the sky at 23.8 GHz and 31.4 GHz.
These two frequencies allow simultaneous determination of water vapor and
liquid water burdens along a selected path. Atmospheric water vapor
observations are made at the hinge point of the emission line where the vapor
emission does not change with altitude (pressure). Cloud liquid in the
atmosphere emits in a continuum that increases with frequency, dominating the
31.4 GHz observation, whereas water vapor dominates the 23.8-GHz channel. The
water vapor and liquid water signals can, therefore, be separated by observing
at these two frequencies.
At the Central Facility (C1; Lamont OK), MWR data is available for 1993-07-21
to present.
At Boundary Facilities 1 (Hillsboro KS), 4 (Vici OK), and 5 (Morris, OK), MWR
data is available for 1994-02-12 to present.
At Boundary Facility 6 (Purcell OK), MWR data is available for 1995-04-01 to
present.
ARM data streams are coded as follows:
sgpmwrlos: MWR: water liquid and vapor along line of sight path
sgpmwrtip: airmasses, brightness temperatures in TIP mode
sgp5mwravg: 5-minute average integrated vapor and liquid water
ARM data streams for quality measurement experiments (QME) are available and
are coded as follows:
sgpqmemwmwcol: Derived: QME comparing column water from MWR vs. instrument
model
sgpqmemwrlbl: Derived: QME comparing LBLRTM, MWR brightness temps. at 23.8 and
31.4 GHz
sgpqmemwrlblss: Derived: QME-LBLRTM, MWR bright. temps at 23.8 and 31.4 GHz,
scaled with lblsonde
sgpqmemwrprof: Derived: QME comparing MWR and sonde profiles of temperature and
water vapor
Additional data streams or value added products may be added in the future.
ARM data streams for quality measurement experiments (QME) are coded as
follows:
sgpqmemwmwcol: Derived: QME comparing column water from MWR vs. instrument
model
sgpqmemwrlbl: Derived: QME comparing LBLRTM, MWR brightness temps. at 23.8 and
31.4 GHz
sgpqmemwrlblss: Derived: QME-LBLRTM, MWR bright. temps at 23.8 and 31.4 GHz,
scaled with lblsonde
sgpqmemwrprof: Derived: QME comparing MWR and sonde profiles of temperature and
water vapor
Additional data streams or value added products may be added in the future.
Whole-Sky Imager (WSI).
For complete information on the WSI, see
http://www.arm.gov/instruments/instrument.php?id=wsi. The WSI is an automated
imager used for assessing and documenting cloud fields and cloud field
dynamics. The WSI is a ground-based electronic imaging system that monitors the
upper hemisphere. It is a passive, i.e., non-emissive, system that acquires
images of the sky dome through three spectral filters (neutral, red, and blue).
From these sky images, we can assess the presence, distribution, shape, and
radiance of clouds over the entire sky using automated cloud decision
algorithms and related processing. The current WSI model (EO System 6) is
capable of image acquisition under daylight, moonlight, and starlight
conditions. The WSI measures the sky radiance in approximately 1/3 degree
increments over the entire sky dome. The measurements are made in two narrow
spectral regions centered at 650 nm and 450 nm. The sky radiances are acquired
as two 16-bit images and are used to determine the presence of opaque clouds
and thin clouds in the line of sight on a pixel-by-pixel basis. These cloud
data are used to calculate the cloud cover and statistical quantities.
At the Central Facility (C1; Lamont OK), WSI data are available for 1995-09-19
to present.
ARM data streams are coded as follows:
sgpwsicloudC1: Derived: cloud numbers, area, perimeter, and more from the WSI
sgpwsicloudsummaryC1: cloud and aerosol information, classification summary
data
sgpwsifullradianceC1: calibrated radiances for each pixel, with multiple
filters
sgpwsipatchsummaryC1: radiances from red image for three patches (average and
standard deviation)
Additional data streams or value added products may be added in the future.
Belfort Laser Ceilometer (BLC).
For complete information on the BLC, see
http://www.arm.gov/instruments/instrument.php?id=blc. The BLC was replaced by
the Vaisala Ceilometer in 2000. The BLC unit is a self-contained, ground-based,
optical, active remote sensing instrument with the ability to detect and
process several cloud-related parameters. These parameters include cloud
height, extinction coefficient, cloud layers and time/date reference
information. The ceilometer system detects clouds by transmitting pulses of
infrared light vertically into the atmosphere. The receiver telescope detects
scattered light from clouds and precipitation. The BLC measures the following
quantities between the heights of 15 and 7350 m directly above ground level:
(1) base height of lowest cloud detected, (2) base height of second-lowest
cloud detected, (3) base height of third-lowest cloud detected. The base height
of the second- and third-lowest clouds are not always reported because they can
be optically obscured by the lower clouds. In addition, visibility is reported
and could be considered a secondary variable measured. The values for
visibility are a qualitative indication of vertical visibility. A precise
interpretation is difficult, because algorithm details have not been provided
by the manufacturer. Also, backscattering profiles are available as a measured
quantity. However, the files that contain these data in the ARM archive are
separate and contain the letters (prof) for profile in the file name.
At the Central Facility (C1; Lamont OK), BLC data are available for 1994-08-11
to 2000-05-23.
ARM data stream is coded sgpblc: 30-sec averages of cloud base heights at up to
3 levels
Additional data streams or value added products may be added in the future.
Active Remote Sensing Cloud Layer (ARSCL).
For the Central Facility (CF1; Lamont OK), there are two additional data
streams that use data from the Belfort laser ceilometer (BLC), MPL, and MMCR.
The BLC was replaced by the VCEIL in 2000. For information on the BCL, see
http://www.arm.gov/instruments/instrument.php?id=blc. These ARSCL data are
available from 1998-11-01 to present.
ARM data streams are coded as follows:
sgparsclbnd1clothC1: cloud boundaries from first Clothiaux algorithms on BLC,
MPL, MMCR
sgparsclcbh1clothC1: cloud base height from first Clothiaux algorithms on BLC,
MPL, MMCR
Additional data streams or value added products may be added in the future.
Raman Lidar (RL).
For a complete description of the RL, visit
http://www.arm.gov/instruments/instrument.php?id=rl. The RL is an active,
ground-based laser remote sensing instrument that measures vertical profiles of
water-vapor mixing ratio and several cloud- and aerosol-related quantities.
Lidar (light detection and ranging) is the optical analog of radar, using
pulses of laser radiation to probe the atmosphere. This system is fully
computer automated, and will run unattended for many days following a brief
(about 5-minute) startup period. The self-contained system (requiring only
external electrical power) is housed in a climate-controlled 8 ft. x 8 ft. x 20
ft. standard shipping container.
The Raman Lidar has independent measurement channels that record range-resolved
backscatter signals from molecular water vapor, molecular nitrogen, and
combined Rayleigh and aerosol contributions (the latter at polarizations
parallel and perpendicular to the polarization of the laser beam). Primary
quantities obtained from these backscatter signals are range-resolved vertical
profiles of water-vapor mixing ratio (g/kg), aerosol scattering ratio
(unitless), and backscatter depolarization ratio (percent). Additional cloud-
and aerosol-related measurements can also be derived from the backscatter
signals.
RL data are available for Central Facility (C1; Lamont OK), from 1996-06-03 to
present.
ARM data streams are coded as follows:
sgprl: Raw backscattered profiles at 355, 387, and 408 nm
sgprllog: surface log information
sgp30rlprofC1: Derived: 30-min RL profiles-water vapor mixing, aerosols,
scattering and depol.
sgp10rlprof: Derived: 10-min profiles of water vapor mixing, aerosols,
scattering and depol.
sgsp10rlprofasr1ferr: aerosol extinction profiles and aerosol optical
thickness)
sgp10rlprofbe1turn: Best-estimate state of the atmosphere product from the RL
and AERI (atmospheric emitted radiance interferometer) plus GOES (geostationary
operational environmental satellite) retrievals
sgp10rlprofdep1turn: depolarization profiles and single layer cloud optical
depths
sgp10rlprofmrlturn: water vapor mixing ratio and relative humidity profiles,
along with PWV
sgp10rlprofext1ferr: aerosol extinction profiles and aerosol optical thickness
from the Raman Lidar.
Additional data streams or value added products may be added in the future. 
Related URL
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Description:
NCVweb is an interactive web-based tool for viewing atmospheric radiation
measurement (ARM) data.
Description:
This catalog lists the data streams that are currently available from the ARM
Archive. The data streams are listed by file format type (i.e, CDF, HDF, RAW,
JPG, ASC, and Other) and then by the site where the data are collected. Each
list contains the name of the data streams in alphanumeric order, the number of
files within the data stream, the minimum data date, and the maximum data date.
The sites that have the word development in parenthesis are data processes
which are operated during the final phases of implementation of a data source,
resulting in data which are labeled as Development. Development data are
frequently available to users, but additional information about the operating
conditions and potential for errors must be considered. The files in CDF format
are also listed in preformatted lists for those browsers that have difficulty
handling large html tables. The information in this catalog is updated about
once a month.
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Geographic Coverage
(Click for Interactive Map)
Spatial coordinates
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N: 38.31
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S: 34.98
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E: -95.6
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W: -99.32
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Data Set Citation
Dataset Originator/Creator:
Wanda Ferrell, Ted Cress, Thomas Ackerman
Dataset Title:
ARM Southern Great Plains, Cloud Measurements
Data Presentation Form:
netCDF files
Online Resource:
http://www.arm.gov
Quality
One of the goals of the ARM Program is to provide data streams of reasonable
quality for scientific research. Traditionally, data quality issues have been
addressed within ARM at several levels, including by instrument mentors, site
scientists, value added product scientists, and Science Team members at large.
Maintaining data quality for a program of the size and ... complexity of ARM is a
significant challenge. Efforts toward this end have matured and evolved over
the life of the program. The ARM Program Data Quality (DQ) Office has the
responsibility for ensuring that quality assurance results are communicated to
(1) data users so that they may make informed decisions when using the data,
and (2) ARM's Site Operations and Engineers to facilitate improved instrument
performance and thereby minimize the amount of unacceptable data collected. For
additional information, visit http://www.arm.gov/data/data_quality.stm.
Access Constraints
Data of common interest from external sources are shared whenever possible, but
some sources restrict secondary distribution of data. In these cases, ARM will
seek specific allowances to distribute such data to members of the ARM Science
Team, but will observe restrictions on further distribution from the Archive if
required.
Use Constraints
Use-constraints, if any, are provided in Data Quality Reports sent with the
data files when data are requested. The automatic inclusion of a data
originator as a co-author is not insisted upon in the ARM program, but the
source of any data should be clearly recognized either as a co-author or
through an appropriate acknowledgment. The ARM Program should be acknowledged
... in publications as the programmatic origin of the field program. ARM-funded
investigators will use the following acknowledgment: "This research was
supported by the Office of Biological and Environmental Research of the U.S.
Department of Energy (under grant or contract number - if appropriate) as part
of the Atmospheric Radiation Measurement Program."The U.S. Department of
Energy's Atmospheric Radiation Measurement Program should be appropriately
acknowledged in publications resulting from collaborative efforts in which ARM
data or facilities were used. ARM-funded principal investigators will give
proper acknowledgment to cooperating or collaborating programs in those cases
where data originating therein are being used.
Distribution
Distribution Media:
FTP or request
Distribution Size:
Variable
Distribution Format:
netCDF
Fees:
None
Personnel
Role:
TECHNICAL CONTACT
Phone:
(630) 252-9540
Fax:
(630) 252-9792
Email:
liljegren at anl.gov
Contact Address:
Argonne National Laboratory
ER Division, Bldg. 203
9700 South Cass Ave.
City:
Argonne
Province or State:
IL
Postal Code:
60439
Country:
USA
Role:
INVESTIGATOR
Phone:
(405) 325-3041
Fax:
(405) 325-7614
Email:
plamb at ou.edu
Contact Address:
University of Oklahoma
CIMMS Department
100 E. Boyd, Rm. 1110
City:
Norman
Province or State:
OK
Postal Code:
73019
Country:
USA
Role:
DIF AUTHOR
Phone:
865-574-7827
Fax:
865-574-4665
Email:
mccordra at ornl.gov
Contact Address:
Building 1507, MS 6407
P.O. Box 2008
Oak Ridge National Laboratory
City:
Oak Ridge
Province or State:
TN
Postal Code:
37831-6407
Country:
USA
Publications/References
Ackerman, T. P. and G. M. Stokes. 2003. The Atmospheric Radiation Measurement
Program. Physics Today 56: 38-44. Science Plan for the Atmospheric Radiation
Measurement Program (ARM). 1996. U.S. Department of Energy, DOE/ER-0670T.
Atmospheric Radiation Measurement Program Plan. 1990. DOE/ER-0441. U.S.
Department of Energy, Office of Energy Research, Washington, D.C. NTIS
DE90008108.
Creation and Review Dates
DIF Creation Date:
2003-10-01
Last DIF Revision Date:
2005-11-16
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