Program Description
The Department of Energy’s (DOE) Atmospheric Radiation
Measurement - Unmanned Aerial Vehicle (ARM-UAV) Program was originally
established to develop measurement techniques and instruments suitable
for use with a new class of high altitude, long endurance UAVs,
and to demonstrate these instruments and measurement techniques in a series
of field campaigns designed to support the climate change community with
valuable data sets.
The
ARM
-UAV Program is part of the
ARM
Climate Research Facility and has the role of providing the high altitude
measurements for the program. These
measurements are designed to address the
ARM
objective of improving the understanding of the role of clouds in global
climate change and complement the
ARM
long-term ground-based measurements. Although the long-term objective of
the
ARM
-UAV program was to conduct regular high altitude airborne measurements
using UAVs, the program now uses both piloted and unpiloted aircraft.
Program Objectives
The scope of the
ARM
UAV Program is being restructured to include both routine, continuous observations
of cloud properties and participation in IOPs. Both activities will respond to scientific requirements
for contributing to the understanding of the role of clouds, aerosols,
and radiation in the climate system. These measurements will be made with
in-situ and remote sensing instruments on both piloted and unpiloted platforms
depending on operational constraints including platform availability and
suitability.
Because a long-term goal of the
ARM
-UAV program requires the acquisition of routine, long-term observations
at altitudes above the tropopause at heights
up to 70,000 feet, the
ARM
-UAV program will continue to support the development of miniaturized instruments
for remote sensing and in-situ observations of cloud, aerosol and radiative
properties. Hence, the
ARM
UAV Program will support three types of activities as summarized below:
1)
Routine observations of cloud, aerosol and radiative properties
2)
Participation in IOPs designed to contribute
to our fundamental understanding of clouds, aerosols and their impacts
on radiation.
3)
Foster an instrument development program whereby miniaturized in-situ and
remote sensing instruments will be purchased or developed to provide measurement
capabilities that minimize space and energy requirements.
Accomplishments
From
its inception in 1993 to date, the ARM-UAV Program has successfully completed
12 major field measurement campaigns. Of those campaigns, 7 were conducted
at the DOE CART site in
Oklahoma and another two series at the DOE sites at the North Slope
of Alaska (NSA) and at the Tropical Western Pacific (TWP) in
Darwin. These flights were generally planned to coincide with IOPs being conducted at the ARM sites to investigate topics
such as the impacts of clouds or aerosols on the atmospheric column radiation
budget or better determining cloud properties. Experiments were also conducted at
other locations such as Edwards Air Force Base (clear sky flux profiling),
Monterey
Bay
(maritime stratus cloud properties) and
Kauai
(sub-tropical cirrus cloud properties).
The
combination of ground-based measurements from the ARM surface sites,
airborne measurements from ARM-UAV aircraft and other aircraft, and satellite
over flights have provided valuable data sets that have made important
contributions to understanding cloud properties and effects. Although
the ARM-UAV Program has made observations of atmospheric, cloud
and radiative properties, emphasizing instruments and data collection
techniques amenable to UAVs, both UAVs and
piloted aircraft have been used depending on the availability and suitability
of the platforms. To date, ARM-UAV flights have been conducted with General
Atomics - Aeronautical Systems (GNAT), “Altus 1” and “Altus
2” UAVs, and instrumented Grob “Egrett”,
the DOE “Twin Otter” and the Scaled Composites Proteus piloted
aircraft.
In
the course of the ARM-UAV Program, a number of notable accomplishments
have advanced the state of the art in airborne measurements and demonstrated
the utility of UAVs. Specific accomplishments
include the first science flights using a UAV in 1994, the development
of a GPS-based system that allows precise vertically stacked flight of
a UAV and a piloted aircraft for cloud absorption measurements in 1995,
the first use of an unescorted UAV in general use airspace in 1996, a
data-taking flight of over 26 hours in duration over the SGP site in
1996, and the development of several compact instruments suitable for
UAV applications in the 1990s and 2000s. The ARM UAV Program has also
collected unique data that have contributed to radiation and cloud research.
During the Mixed-Phase Arctic Cloud Experiment (M-PACE) in 2004, the
Proteus aircraft with the ARM-UAV Program’s suite of instruments
flew 5 missions over the North Slope of Alaska. The project collected
critical information on cloud macrophysical and
radiative properties that are currently being used to address the important
and poorly understood interactions between clouds, the ocean and atmosphere
in the
Arctic. During the Tropical Warm Pool International Cloud Experiment
(TWP ICE), detailed in-situ cloud observations were made by the Proteus
with the goal of examining the radiative impacts over the complete life
cycle of ice clouds generated by tropical convection, including investigating
the importance of ice crystals smaller than 50
µm that have previously
been poorly measured.
Available Instrumentation
The current instrumentation
available in the ARM-UAV suite of instruments include state-of-the-art
instruments for measuring the sizes and shapes of ice crystals and atmospheric
state parameters in-situ along with passive and active remote sensing
instruments. These instruments and the associated software controlling
them have been developed so that they can be operated remotely from the
ground in the manner that instruments on a UAV platform would operate.
Specific instruments available include the following: four Kipp and Zonen
CM-22s pyranometers (0.4 to 4.0
µm), zenith looking on a stabilized
platform and on the aircraft fuselage, and nadir viewing mounted to the payload
pod deck with and without an affixed dark cover; three CG-4s pyrgeometers
(4 to 40
µm), zenith looking on the stabilized platform and
2 nadir viewing mounted to the payload pod deck with and without an affixed
dark cover; a pair of nadir viewing infrared thermometers (IRTs)
operating in the wavelength ranges 8 to 10
µm and 9.6
to 11.5
µm; three narrow field of view spectrometers (SSFR)
measuring upwelling spectral radiance in the ranges 0.385 to 1.05
µm,
0.72 to 0.8
µm, and 1.3 to 1.5
µm;
a pair of diffuse field cameras (DFCs), digital
cameras providing a hemispheric field of view of the sky centered at
wavelengths of 0.645 and 1.61
µm; and a cloud detection
lidar (CDL) operating at 1.053
µm that is used for detecting
cloud boundaries.
The in-situ sensors for measuring
cloud and atmospheric state parameters include the following: a Nevzorov probe providing bulk measures of liquid and total
water content; a Counterflow file Impactor (CVI) providing a bulk measure of total water
content; a cloud, aerosol and precipitation spectrometer (CAPS) consisting
of a cloud aerosol spectrometer (CAS) measuring hydrometeor size distributions
between 0.35 and 50
µm, a cloud imaging probe (CIP) giving two-dimensional images
and size distributions nominally between 25 and 1550
µm,
a bulk liquid water content detector (LWCD), and an air speed sensor
and temperature probe; a cloud particle imager (CPI) providing high resolution
(2.3
µm) images of ice crystals; a cloud droplet probe (CDP) providing
size distributions between 1 and 50
µm; a dual path laser hygrometer
(TDL) providing fast response measurements of water vapor; and a cryogenic
hydrometer (CR-2) providing high accuracy measurements of water vapor.
There are also instruments measuring differential and static pressure,
true and indicated air speed, total and static air temperature, payload
temperatures, instrument currents, the GPS/INS location and the IRIG-B
time code. Other sensors used for specific ARM-UAV campaigns include
a high-altitude fast-response in-situ CO2 analyzer, a Micromaps CO
remote sensor and a scanning high-resolution interferometer (S-HIS) have
also flown on specific ARM-UAV campaigns.
Program Manager
Mr. Rickey Petty
Climate and Environmental Sciences Division, SC-23.1
Department of Energy GTN Bldg
1000 Independence Ave, SW
Washington, DC 20585-1290
(301) 903-5548
Fax: (301) 903-8519
Internet:rick.petty@science.doe.gov