Operations Updates
ARM Climate Research Facility Operations Update - September 30, 2005
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Mission Under Control: Scientists Simulate Upcoming Field Campaign
The Egrett will fly in stacked formations with the Proteus during the upcoming Tropical Warm Pool International Cloud Experiment. This flight pattern will allow simultaneous sampling of the upper and lower parts of the cirrus anvils as well as remote measurements.
Between September 7-9, ARM researchers and international collaborators involved in flight operations for the Tropical Warm Pool International Cloud Experiment, or TWP-ICE, met at Sandia National Laboratories to simulate daily mission planning during the month-long field campaign, which begins in January 2006. With the possibility of up to five aircraft in the sky at one time at various altitudes, coordination and communication between the pilots and ground control will be critical to the success of the experiment. About 25 scientists and pilots discussed how they would handle the decision process for whether to fly or not on a given day; communications protocols while planes are in the air; and a nominal schedule for pre- and post-mission briefings.
Each day of the meeting, the team ran several days worth of actual mission planning, starting with a weather forecast to determine conditions suitable for science flights. If all agreed to fly the following day, the next step would be a meeting of the mission planning and flight management team to determine a primary mission and alternate mission for the aircraft identified to participate the following day. A follow-up meeting would be held the following morning, a few hours prior to a prospective mission to verify that conditions were favorable for flying. The activities would then move to the air base, where the pilots would be briefed on their missions and prepare their aircraft for the day's missions. Mission control during the experiment will be at the Australian Bureau of Meteorology (BOM) Northern Territory regional office where continual monitoring of the aircraft and weather radars will take place. At the end of each day's flights, a post-mission briefing will be held between the flight and science teams.
The international TWP-ICE campaign will take measurements of cloud and radiative properties from instrumentation located at a network of ground stations, on a ship off the coast of Darwin, and on a fleet of research aircraft. The aircrafts' scientific mission is to obtain measurements of cloud microphysics in situ microphysics and the atmospheric state in different regions of cirrus anvils and at different altitudes. These data will be used to validate data obtained from the surface, particularly the ACRF site in Darwin. To achieve their scientific objectives, the science team must also take advantage of the right weather conditions. Continual weather forecasting, provided by the BOM, will help the science team determine flight days and the appropriate mission objectives for each plane.
Bigger, Better Cessna Ready to Record Aerosol and Carbon Cycle Data
Replacing the smaller Cessna 172, the new turbo-charged Cessna 206 prepares for departure to Ponca City, Oklahoma, where it will be managed by Greenwood Aviation.
To meet new requirements in the airborne aerosol and carbon-cycle measurements taken over the ACRF's Southern Great Plains (SGP) site, a new Cessna Turbo 206 is replacing the smaller Cessna 172XP. The new aircraft has been contracted by ACRF to conduct combined in situ aerosol profiling and airborne carbon measurements for the next two years. Airborne measurements of carbon cycle trace gases at the SGP will provide data to quantify profiles of carbon dioxide (CO2) concentration from the surface to midtroposphere, carbon dioxide budgets in air-mass (in follow-on experiments), and contributions of fossil fuel combustion to atmospheric carbon dioxide. These data are considered essential for quantifying regional carbon exchange and tracing the balance between anthropogenic (human-produced) emissions and biogeochemical cycling, which are identified as priorities by the U.S. Climate Change Research Program and the North American Carbon Program.
The aircraft's new, improved sampling probe design will provide much better measurements of larger particles
Outfitted in collaboration with the National Oceanic and Atmospheric Association (NOAA), the Cessna Turbo 206 aircraft offers several improvements over the Cessna 172, which has been monitoring vertical profiles of aerosol properties over SGP since March 2000. One noteworthy advancement is its increased payload capability, in terms of weight, space, and electrical power. Another important improvement is the ability to provide measurements at an increased altitude of up to 18,000 feet.
While the Cessna 172 optics rack only had two nephelometers, the Cessna 206 will be equipped with four. These extra nephelometers will provide scattering data at two additional relative humidities, which give much better measurements of aerosol hygroscopic growth. The Cessna 206 system also provides data on the scattering of particles that are larger than 1 micrometer, which were not sampled by the Cessna 172.
The original carbon flask collection system from the Cessna 172 will be upgraded soon to provide samples at 12 heights or positions, rather than one. New instruments will be added to enable continuous carbon dioxide concentration profiles; CO and CH4 are also planned. In addition, event sampling for radiocarbon (14CO2) and radon will be used to quantify anthropogenic combustion emissions and vertical mixing, respectively. These data will facilitate calibration of the NASA Orbiting Carbon Observatory and, in combination with the tracers of fossil fuel and biomass combustion, will provide data for inverse methods that infer ecosystem exchange and anthropogenic emission of carbon dioxide on regional scales.
As its first assignment, the new turbo-charged Cessna 206 arrived at the SGP site in time to participate in the Aerosol Lidar Validation Experiment (ALIVE). (See below.)
Aircraft Comes ALIVE During Field Campaign at the Southern Great Plains
Outside the hangar in Ponca City, Oklahoma, the optical head of the AATS-14 (inset) can be seen as the white dome on the roof of the Jetstream-31 aircraft
Researchers from ARM Program and National Aeronautical and Space Administration (NASA) took to the skies in September for an 11-day Aerosol Lidar Validation Experiment (ALIVE) at the ACRF Southern Great Plains (SGP) site. The ALIVE field campaign was conducted to collect airborne remote sensing data on atmospheric aerosols for validation studies of the Raman lidar and micropulse lidars at the SGP site. Measurements from the SGP Raman lidar and micropulse lidars will be validated through comparison with data from the NASA Ames Airborne Tracking 14-Channel Sunphotometer (AATS-14) flown aboard a Jetstream-31 research aircraft from Sky Research. These validations are important to the ARM Program because by calibrating all measurements to consistent standards, the data can help reduce scientific uncertainties in computer models used to simulate climate change.
In 2003, the Aerosol Intensive Operational Period (IOP) at the SGP provided one of the best measurement sets obtained to date for evaluating the scientific capability for measuring the vertical profile of ambient aerosol extinction in the lower troposphere. However, validation results showed that an undetected loss of sensitivity of the SGP Raman lidar had occurred leading up to the Aerosol IOP, resulting in a significant high bias in derived aerosol extinction. To fix this problem, major upgrades were made to the Raman lidar in 2004 to restore and improve its data-gathering capabilities and sensitivity. To prove the integrity of the entire Raman lidar aerosol extinction record, researchers will test the upgraded Raman lidar against data obtained by the AATS-14 and compare its measurements with validated data from the Aerosol IOP.
During the course of 20 flight hours aboard the Jetstream-31, the AATS-14 obtained extinction vertical profiles at altitudes between 500-23,000 ft from spiral ascents and descents over the SGP site. A Scanning Polarimeter instrument from NASA's Goddard Institute for Space Studies Research also operated aboard the Jetstream-31 as a piggyback instrument, contributing an additional 3-flight hours to the ALIVE field campaign and will provide multi-spectral measurements of the upwelling polarization and radiance. ALIVE also coordinated flights with the new ARM in situ aerosol profile aircraft, a Cessna Turbo 206, to help evaluate the new installation of the instruments that collect in situ aerosol profile measurements.
