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