Operations Updates
ARM Climate Research Facility Operations Update - June 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).
Satellite Service Conserves Cash
In April, operations personnel completed a series of cost-saving data communication changes at the ACRF Southern Great Plains (SGP) locale. The T-1 telephone lines at the four SGP boundary facilities were replaced with satellite dish technology. This change still allows large data sets to be transferred at acceptable bandwidth but at substantial savings.
Inexpensive satellite services now meet data transmission needs at the SGP boundary facilities.
Huge amounts of data are collected daily by SGP site instruments. These data must be transmitted rapidly and reliably from remote measurement locations to the central facility computers. For years, transfers were made via high-speed T1 telephone lines (usually fiber optic) at a rate up to 1.5 megabits per second. Though fast and reliable, T1 lines can be quite costly. The recently removal of an instrument from each SGP boundary facility greatly reduced the demand for dedicated, high-capacity T-1 data transmission lines. Communications specialists found a cost-effective way to replace the T1 data lines with satellite internet service. Although data transfer via satellite is slower than with T1 lines, the rates are still adequate for SGP transmission needs.
Testing for acceptable performance of the newly installed satellite internet was completed in May. The T1 lines will be disconnected at the end of June, and data transfers will then be made by satellite communications. The SGP site will realize savings of about $100k per year by switching to the satellite-based internet link.
New Data Stream Available from Millimeter Wave Cloud Radar
Inside the instrument shelter, the MMCR data system collects radar spectral data and processes these into reflectivity, vertical velocities, and spectral width.
As a result of upgrades to the Millimeter Wave Cloud Radar (MMCR) processors (see http://www.arm.gov/acrf/updates051504.stm#nsammcr) at the ACRF Southern Great Plains (SGP) and North Slope of Alaska (NSA) locales, two MMCR data streams—mmcrcalC1.a1 (calibration data) and mmcrmomentsC1.a1 (spectral "moments" data)—have been combined to produce a new data stream—mmcrmomC1.b1. The data Archive contains the new data stream for SGP as of September 9, 2003, and for NSA as of April 14, 2004. Processor upgrades for the MMCR at the ACRF Tropical Western Pacific (TWP) locale are expected to occur this coming fall and winter. Until then, the TWP MMCRs will continue to generate the mmcrcalC1.a1 and mmcrmomentsC1.a1 data streams.
A data stream represents the output of a single data source (i.e., instrument, instrument group, or algorithm). Overhauling the MMCR processors has brought faster data collection, continuous collection of spectral data, and (currently at NSA only) new modes of data collection intended to improve boundary layer cloud detection. The new mode sequence, with the addition of a polarization mode, is planned to begin running at SGP in July. MMCR data are now being collected approximately every 2 seconds! The new MMCR processors also continuously record spectral data, which is available in a separate data stream—mmcrspecmom. Spectral data from the SGP and NSA are available via the "Power User" option at the Archive.
Although every effort was made to preserve the previous data formats where feasible, a number of changes needed to be made to the field names in the interest of improving the MMCR data product. A field-by-field comparison of the data streams and a sample netCDF header for the new sgpmmcrmomC1.b1 files are available at http://www.gim.bnl.gov/armclouds/mmcr/mmcrMomNewVsOldDataStreams.html. However, the data stream naming convention remains the same; depending on the parameters, the file name identifies the site, time intervals, instrument, type of data collected, facilities, and level of data processing, in that order. Previous mmcrcal and mmcrmoments data are expected to be reprocessed using the new mmcrmom data format.
