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GPM Ground Validation Precipitation Video Imager (PVI) GCPEx Table of Contents
The GPM Ground Validation Precipitation Video Imager (PVI) GCPEx dataset includes drop size distribution (DSD) data from November 4, 2011 through March 10, 2012 as part of the GPM Cold-season Precipitation Experiment (GCPEx) in Ontario, Canada. Data files are in excel spreadsheet format and contain the average, minimum, and logarithmic DSD bin sizes and number of particles per unit time. Browse images are available which show the particle number concentrations and can be used to quickly see if any snow was recorded on a certain day; the actual raw images of observed particles are also available. The dataset was collected to aid in achieving the overarching goal of GCPEx, to characterize the ability of multi-frequency active and passive microwave sensors to detect and estimate falling snow. CitationThe following example shows how to cite the use of this dataset in a publication. For more information, please see our Citing GHRC DAAC and Data page. Campaign The GPM Cold-season Precipitation Experiment (GCPEx) occurred in Ontario, Canada during the winter season of 2011-2012. GCPEx addressed limitations in the GPM snowfall retrieval algorithm through the collection of microphysical properties, associated remote sensing observations, and coordinated model simulations of precipitating snow. The dataset was collected to aid in achieving the overarching goal of GCPEx, to characterize the ability of multi-frequency active and passive microwave sensors to detect and estimate falling snow. During GCPEx, the PVI instrument was located at three sites (one with two locations) in Ontario, Canada. The coordinates of the sites are:
It should be noted that there is some variation in the dates that data is available for each site; an excel spreadsheet is available which makes it easy to see when data is available and for what sites. Further information on the GCPEx campaign is available at http://gpm.nsstc.nasa.gov/gcpex and more detailed information at GCPEx Campaign Description. Information on the Global Precipitation Measurement (GPM) mission is available at http://pmm.nasa.gov/GPM. Instrument DescriptionThe PVI instrument (sometimes called Snowflake Video Imager (SVI)) was designed by Dr. Larry Bliven at NASA Wallops Flight Facility. It is an automated sampling system which records greyscale images at a high frame rate, enabling the particle size in rain and snow to be determined. The instrument measures snowflake size distribution and snowflake orientation distribution; the nominal pixel size of an image is 0.05 mm by 0.1 mm. Instruments at each facility:
In all cases, the field of view is 32x24 mm at the focal plane, and the depth of field is approximately 117 times the particle equivalent diameter. Sony cameras have 640x480 pixels, pixel resolution is 0.05x0.05 mm. Classic cameras have 640x240 pixels, pixel resolution is 0.05x0.10 mm. PVIs operate at a nominal 60 fps, 24/7; some data gaps do occur during power outages, periods of clear weather when acquisition was halted for processing of quick look data products, data backups, and system alignments. A more detailed description of PVI/SVI is documented in the journal article Presenting the Snowflake Video Imager (SVI). InvestigatorsFrancis L. Blivens The GPM Ground Validation Precipitation Video Imager (PVI) GCPEx dataset consists of excel spreadsheet files and bmp image files. There are two directories, one for the image files and one for the excel files. The files are named with the following convention:
where,
The files contain detailed measurements of the precipitation (.xls files) as well as graphs of the data (.bmp files) and the raw images the PVI instrument recorded (.zip files). It should be noted that fourteen days during data collection were considered priority days, the table below lists these priority days for each site and indicates if an aircraft was also flown on that day: Data Format The GPM Ground Validation Precipitation Video Imager (PVI) GCPEx data is available in excel spreadsheet file format; raw image files and graphs of the data are available in bitmap image files. Newman A., Kucera P., and L. Bliven, 2009: Presenting the Snowflake Video Imager (SVI). Journal of Atmospheric and Oceanic Technology, 26, 167 - 179. doi: 10.1175/2008JTECHA1148.1 Contact InformationTo order these data or for further information, please contact:
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