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GPM Ground Validation Autonomous Parsivel Unit (APU) GCPExTable of Contents
The Autonomous Parsivel Unit (APU) provides a means for measuring the particle size and fall velocity of liquid and solid precipitation. The APU consists of the Parsivel2, which was developed by OTT in Germany, and its support systems, which were designed and built by the University of Alabama in Huntsville. The APU data set for the GPM Cold-season Precipitation Experiment (GCPEx) provides precipitation data including drop size, snowflake size, precipitation rate,and precipitation distribution. The GCPEx APU data was collected from several sites in Canada during the Winter 2011-2012 season. CampaignThe GPM Cold-season Precipitation Experiment (GCPEx) occurred in Ontario, Canada during the winter season of 2011-2012. GCPEx addressed shortcomings in the GPM snowfall retrieval algorithm by collecting microphysical properties, associated remote sensing observations, and coordinated model simulations of precipitating snow. These data sets were collected to aid in the achievement of the over arching goal of GCPEx which is to characterize the ability of multi-frequency active and passive microwave sensors to detect and estimate falling snow. During GCPEx, two Parsivel2 sensors were installed at five sites in Ontario, Canada. The site name and location of the instruments are:
The two Parsivel sensors were located side by side and oriented perpendicular to one another. Data was collected from 26 October 2011 to 10 March 2012. Further details on GCPEx are available at http://gpm.nsstc.nasa.gov/gcpex. Information on the Global Precipitation Measurement (GPM) mission is available at http://pmm.nasa.gov/GPM. Additional campaign collections containing Parsivel data can be found at http://ghrc.nsstc.nasa.gov. Instrument DescriptionThe Parsivel2 is a laser-based disdrometer produced by OTT Hydromet. The laser sensor in the Parsivel2 produces a horizontal strip of light. When no particles pass through the horizontal beam, the maximum voltage is detected at the receiver. When a precipitation particle passes through the laser beam, a portion of the beam corresponding to the particle's diameter is blocked. The blocked portion of the laser results in a reduced voltage output. This reduction in voltage can be used to determine the particle size. Particle speed can also be found by measuring the duration of signal. The signal begins as soon as a particle enters the laser beam and ends when the particle completely leaves the laser beam. The Parsivel2 can also classify precipitation particles into 32 separate size classes and 32 velocity classes. Further information on the Parsivel2 can be found at http://www.hachhydromet.com/web. InvestigatorsWalter A. Petersen Patrick Gatlin The Parsivel 2 data set is contained within daily tar archives. The daily archive is named with the following convention:
where,
and consists of ASCII encoded files. The following ASCII files are contained within the tar archive:
*Please note: Each daily tar archive may not contain all the files listed above. Additional Parsivel data files, not contained within a daily tar archive but with a similar file naming convention, provide a summary of the precipitation events for the entire campaign. The files provide a summary of total rainfall or snowfall measured for a continuous period of precipitation. The additional data files are named with the following convention: Data Format The Parsivel2 data set consists of ASCII text files with a file extension of .txt. More detailed information on the Data Format and Data Levels of the Parsivel2 data can be found in the Data Format document. CitationOur data sets are provided through the NASA Earth Science Data and Information System (ESDIS) Project and the Global Hydrology Resource Center (GHRC) Distributed Active Archive Center (DAAC). GHRC DAAC is one of NASA's Earth Observing System Data and Information System (EOSDIS) data centers that are part of the ESDIS project. ESDIS data are not copyrighted; however, in the event that you publish our data or results derived by using our data, we request that you include an acknowledgment within the text of the article and a citation on your reference list. Examples for general acknowledgments, data set citation in a reference listing, and crediting online web images and information can be found at: http://ghrc.nsstc.nasa.gov/uso/citation.html To order these data or for further information, please contact:
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