Operations Updates
ARM Climate Research Facility Operations Update - May 15, 2004
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Mid-latitude Cirrus Cloud Experiment Underway
NASA's WB-57F research aircraft can carry an instrument payload up to 6,000 lbs.
In late April, scientific collaborators at the National Aeronautics and Space Administration (NASA) carried out two high-altitude flights over the ACRF Southern Great Plains (SGP) central facility. The purpose of these flights was to use a new suite of cloud property probes on the WB-57F aircraft to more accurately characterize the properties of mid-latitude cirrus clouds - which are composed solely of ice crystals - than has previously been possible. Eight flights over the SGP central facility were originally planned, but the expected cirrus clouds materialized on only two occasions during the flight schedule.
Researchers will use coincident soundings from SGP ground-based instrumentation to compare the following measurements from the WB-57F instrumentation: cirrus cloud particle distribution; ice crystal particle habit; ice-water content; volume extinction coefficient; and water vapor at upper-tropospheric temperatures. These data are necessary to validate and improve existing and emerging algorithms used to derive the microphysical properties of cirrus cloud systems from radiance and reflectivity measurements obtained using satellite-based remote sensing instruments launched (or scheduled to be launched) by NASA and ground-based remote sensors at the ACRF SGP locale.
The suite of satellite-borne sensors have the capacity to advance our understanding of the coupling between various components of the hydrologic cycle and atmospheric circulation, and hold the additional potential of leading to significant improvements in the characterization of cloud feedbacks in global climate models. Ground-based observations from ACRF locales in mid-latitudes, the arctic, and the tropics will play an important role in validating the satellite-based measurements.
Upgrade to Millimeter Wave Cloud Radar Increases Volume of Data Collection
In mid-April, hardware and software upgrades to the millimeter wave cloud radar (MMCR) at the ACRF North Slope of Alaska (NSA) were completed. Hardware upgrades included replacing the OS/2 and Solaris computers with two Windows 2000 computers. One of these computers is for the MMCR radar. It now has a new digital signal processing board that allows much more efficient processing of the radar return signals, resulting in higher temporal resolution. The receiver was also upgraded from a 12 bit to 14 bit analog-to-digital converter. Software on the MMCR radar computer was upgraded to run a modified version of Vaisala's LAP-XM software for controlling and acquiring the radar data. The other computer, for managing the MMCR data, monitors the system, controls calibration, and makes the processed radar "moments" data available to the site data system.
The MMCR probes the extent and composition of clouds at millimeter wavelengths. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). It also reports radar reflectivity of the atmosphere up to 20 km, and possesses a doppler capability that allows the measurement of cloud constituent vertical velocities. As a result of the MMCR upgrade, NSA operations staff are collecting 4 to 5 times the moments data compared to the old system, and are now recording radar spectra data continuously on a separate Firewire hard drive.
Sunphotometer Re-installed at North Slope of Alaska
The CIMEL sunphotometer takes sky radiance measurements during daylight hours, when the sun is above horizon.
In early May, a CIMEL sunphotometer owned by the National Aeronautics and Space Administration (NASA) was re-installed at Barrow, Alaska, one of two research sites that make up ACRF's North Slope of Alaska (NSA) locale. The CIMEL is a multi-channel, automatic sun-and-sky scanning radiometer that takes daytime measurements of direct solar radiance and sky radiance at the Earth's surface. Measurements are taken at discrete wavelengths in visible and near-infrared regions of the solar spectrum.
Four CIMEL instruments are routinely calibrated and rotated for use at ACRF's Southern Great Plains locale in Oklahoma (since 1998), and Tropical Western Pacific's Nauru site (since 1999), providing continual data on atmospheric transmission and scattering properties in mid-latitudes and the tropics, respectively. Because this instrument is weather-proof and requires little maintenance during periods of adverse weather conditions, it is an excellent addition to the instrument suite at Barrow. The CIMEL had been removed for service at NASA prior to the onset of polar night in Alaska, when darkness rules the sky from September through March.
Data from the CIMEL in Barrow are transmitted to a satellite, sent to the NASA Goddard Space Fight Center for processing, and then distributed to the ACRF External Data Center where they become part of the ARM Data Archive. Though installed at Barrow as part of NASA's AErosol RObotic NETwork, the newly installed CIMEL may be used to support ARM arctic experiments, and may further interest collaborators at NASA to conduct satellite validation activities at the NSA.
Helping Hands Make Strong Partnerships
The U.S. Department of Energy requires all contractors using LINUX-based computers to implement RedHat Enterprise Version 3.0 (RHE V3.0) software as their standard operating system. This applies to computer systems running at ACRF's Southern Great Plains (SGP) locale, and implementation there is planned for late 2004. All existing software packages will need to be tested to run under the new RHE V3.0 operating system, including SGP's SuomiNet software. This software integrates a network of global positioning systems to distribute spatially and temporally dense atmospheric data in real-time from broad and diverse regions.
Fortuitously, SGP's RedHat Certified Engineer had tested the SuomiNet software as the LINUX operating system there evolved. This expertise was called upon in April when a key collaborator at NASA found out that agency would not renew its computer security wavier for the Suominet system due to the lack of security updates available for the original RedHat operating system used to run SuomiNet. On a recommendation from research partners at the University Corporation for Atmospheric Research, or UCAR (the organization that receives SuomiNet data), the NASA representative contacted SGP's RedHat expert for help. After installing RHE V3.0 on a test machine and using a test global positioning system receiver provided by UCAR to verify performance, detailed instructions were prepared for installing the SuomiNet software on machines running RHE V3.0. These instructions were provided to NASA and UCAR users, and will be available to others that may require similar upgrades.
NASA is important to ARM as an instrument provider, participant and sponsor of extensive experiments, and research collaborator. The assistance provided by SGP data systems staff allows partners at NASA to continue the operation of their SuomiNet network utilizing the new RedHat Enterprise version for LINUX in conducting their research. It also provided the SGP RedHat expert with invaluable experience in the upgrade procedure that will pay dividends when the transition is implemented at SGP later this year. This move must be made to continue with support from RedHat, to take advantage of the latest security updates, and to comply with the DOE-standard LINUX operating system.
