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GPM Ground Validation Precipitation Video Imager (PVI) GCPEx

Table of Contents


Introduction
Citation
Campaign
Instrument Description
Investigators
File Naming Convention
Data Format
References
Contact Information

Introduction

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.

Citation

The 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.

Blivens, Larry F. 2014. GPM Ground Validation Precipitation Video Imager (PVI) GCPEx [indicate subset used]. Dataset available online, [http://ghrc.nssstc.nasa.gov] from the NASA EOSDIS Global Hydrology Resource Center Distributed Active Archive Center Huntsville, Alabama, U.S.A. doi: http://dx.doi.org/10.5067/GPMGV/GCPEX/PVI/DATA301

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:

CARE_cam1: Lat: 44.23, Lon: -79.78
CARE_cam2: Lat: 44.23, Lon: -79.78
Huronia_cam1: Lat: 44.69, Lon: -79.93
Steamshow_cam1: Lat : 44.18, Lon: -79.72

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 Description

The 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:

Care: 2 Sony Cameras with 1 PC, cam1 (id 101) has horizontal optical axis, cam2 (id 102) has optical axis approximately 30 from nadir
Huronia: 1 Classic Camera with 1 PC, camera (id 103) has horizontal optical axis
Steamshow: 1 Classic Camera with 1 PC, camera (id 104) has horizontal optical axis

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).

Investigators

Francis L. Blivens
NASA/GSFC, Wallop Flight Facility
Code 610.W.
Wallops Island, VA 23337

File Naming Convention

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:

GCPEx_pvi_YYYYMMDD_site_10#_catalog_XXX_dis2**.zip
GCPEx_pvi_ YYYYMMDD _site_10#_dsd_*_dis2**.bmp
GCPEx_pvi_ YYYYMMDD _site_10#_dsd_dis2**.xls

where,

GCPEx = GPM Cold-season Precipitation Experiment
pvi = Precipitation Video Imager
YYYYMMDD = the year, month, and day of the data
site = site name
# = collecting instrument number at site (1 & 2 = care; 3 = huronia; 4 = steamshow)
catalog = raw particle images catalog
dsd = drop size distribution
XXX = All or Big (All = contains all images; Big = contains particles bigger than 5 mm)
* = D, L, or W (DSDs are presented as: D = equivalent diameter with 2dvd linear-bin format; L = longest axis  with 2dvd linear-bin format; and W = max horizontal axis with Parsivel format log-bin format)
dis2 = indicates that these are the best current estimates
** = some files have  _air or _noair here (air means there was an Aircraft flown, while noair means there was not)
.zip = zip file (multiple files have been compressed into one file folder)
.bmp = bitmap file (image file)
.xls = excel file

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:

Priority Days 
Aircraft 
Sites 
2011 12 21  no  all 
2011 12 27  no  all 
2011 12 28  no  all 
2011 12 30  no  all 
2012 01 17  no  all 
2012 01 18  no  all 
2012 01 19  yes  CARE_Cam2; Huronia; Steamshow 
2012 01 23  no  all 
2012 01 30  yes  all 
2012 02 11  yes  all 
2012 02 12  yes  all 
2012 02 24  yes  all 
2012 02 27  yes  all 
2012 02 29  no  all 

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.

References

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 Information

To order these data or for further information, please contact:

Global Hydrology Resource Center
User Services
320 Sparkman Drive
Huntsville, AL 35805
Phone: 256-961-7932
E-mail: support-ghrc@earthdata.nasa.gov
Web: http://ghrc.nsstc.nasa.gov/

 

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