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GPM Ground Validation Two-Dimensional Video
Disdrometer (2DVD) Table of Contents
Important Notice Concerning LPVEX Data Between September 15-22, 2010, the 2DVD data sets collected at Emasalo (SN36) and Harmaja (SN37) are +2 hours offset from UTC, and the 2DVD data set collected at Jarvenpaa (SN35) is +3 hours offset from UTC. The time stamps in these data files will be corrected and re-posted to this archive by mid September 2012. A disdrometer is an instrument that measures the size of rain drops. The Two-Dimensional Video Disdrometer (2DVD), developed by Joanneum Research (Graz, Austria), is unique in that it records two side view optical images of each raindrop. Used for in situ measurements of precipitation drop size distribution, this instrument records orthogonal image projections of raindrops as they cross its sensing area and can provide a wealth of information, including velocity and shape of individual raindrops. An interesting article showing how the 2DVD can be used to analyze the microstructure of individual raindrops can be found here. This disdrometer data set gathers data during field experiments for the Global Precipitation Measurement (GPM) mission Ground Validation campaign. CampaignsThe Global Precipitation Measurement (GPM) mission Ground Validation (GV) campaign will use a variety of methods for validation of GPM satellite constellation measurements prior to launch of the GPM Core Satellite, which is currently scheduled for July 2013. The validation effort will entail numerous GPM-specific and joint-agency/international external field campaigns, using state of the art cloud and precipitation observational infrastructure (polarimetric radars, profilers, rain gauges, disdrometers). Surface rainfall will be measured by very dense rain gauge and disdrometer networks at various field campaign sites. These field campaigns will account for the majority of the effort and resources expended by Global Precipitation Measurement(GPM) mission Ground Validation (GV). The Light Precipitation Evaluation Experiment (LPVEx) took
place in September and October 2010 in the Gulf of Finland to characterize
the ability of CloudSat, the Global Precipitation Mission (GPM)
Dual-frequency Precipitation Radar (DPR), and existing/planned passive
microwave (PMW) sensors such as the GPM microwave imager (GMI) to detect
light rain and evaluate their estimates of rainfall intensity in high
latitude, shallow freezing level environments. The experiment leveraged in
situ microphysical property measurements, coordinated remote sensing
observations, and cloud resolving model simulations of high latitude
precipitation systems to conduct a comprehensive evaluation of
precipitation algorithms for current and future satellite platforms. The
campaign will use these measurements to better understand the process of
light rainfall formation at high latitudes and augment the currently
limited database of light rainfall microphysical properties that form the
critical assumptions at the root of satellite retrieval algorithm. The 2DVD
data files provide both binary preprocessed hydrometer files created by
the instrument manufacturer's software as well as ASCII files containing
rain The 2DVD instruments were located at 3 sites in Finland: Harmaja, Emasalo, and Jarvenpaa. The instrument name and coordinates of these sites are:
Information concerning coordinates and related instrumentation can be found in the LPVEX_Dataset_summary pdf document. The Midlatitude Continental Convective Clouds Experiment (MC3E) took place in central Oklahoma during the April-June 2011 period. The experiment was a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration's (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign leveraged the unprecedented observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation purchased with American Recovery and Reinvestment Act funding. The over arching goal was to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterization and space-based rainfall retrieval algorithms over land that had never before been available. Further details on GPM MC3E are available at http://gpm.nsstc.nasa.gov/mc3e/. Information on MC3E ARM is available at http://campaign.arm.gov/mc3e/. The 2DVD instruments were located at 5 sites in Oklahoma. The site name and coordinates are:
The 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.
Data was collected from 27 October 2011 to 27 February 2012. Further details on GCPEx are available at http://gpm.nsstc.nasa.gov/gcpex. Instrument DescriptionThe Two-Dimensional Video Disdrometer (2DVD) uses two high speed line scan cameras which provide continuous measurements of size distribution, shape and fall velocities of all precipitation particles and types. Two orthogonal light planes, provided by two internal lamps, transect the approximate 10x10 cm virtual measurement area and are projected onto two high speed line-scan cameras. Precipitation particles (hydrometeors) that fall through the light planes cast a shadow that is recorded by the two cameras nested within the instrument (this is analogous to flat-bed scanners, except here the scan head is stationary and the scanned object moves). Detailed shape and size information for each individual hydrometeor is available via the two "side image shadows" that are recorded by the cameras. The light planes are separated by a precisely calibrated distance (nominally 6 mm) from which the vertical fall velocity can be measured. The line scan cameras sample each plane at a rate of ~18 microseconds and a horizontal resolution of ~200 microns. Therefore, as a raindrop falls through the measurement area, several line scans of each image are recorded from two sides and two different heights, from which precise measurements can be made. Data ProducersWalter A. Petersen Larry Carey Patrick Gatlin The LPVEx data files are archived in a daily tar format with the following naming convention:
where,
The following files are contained within the tar archive:
The MC3E data files are archived in a daily tar format with the following naming convention:
where,
The following ASCII files are contained within the tar archive:
The 2DVD data files are archived in a daily tar format with the following naming convention:
where,
The tar files consist of binary and ASCII files containing information on each raindrop and snowflake sampled by both cameras. The following files are contained within the tar archive and follow a similar naming convention as above except for the file extension:
Note: Each daily tar archive may contain up to five files. However, only the daily tar archives associated with snowfall events will include all five files. Further information on the files contained within the tar archives is available in the Data Format document. The Two-Dimensional Video Disdrometer data sets consist of ASCII (.txt) files which contain information on the velocity, size, and size distribution of individual hydrometeors. The LPVEx 2DVD data additionally contains binary preprocessed hydrometer files created by the instrument manufacturer’s software (.hyd files). More detailed information on the Data Format and Data Levels on the LPVEx 2DVD and related data can be found in the DataFormat_2dvd_fieldCampaign.pdf document. More detailed information on the Data Format and Data Levels on the MC3E 2DVD and related data can be found in the DataFormat_2dvd_mc3e.pdf document. The GCPEx 2DVD data additionally contains compressed binary files (.sno and .shd) which can be viewed graphically using VIEW_HYD and MAKE_SNO software available from Joanneum Research. Also, these files can be read using the SNO2ASC program, available from the data provider upon request. More detailed information on the Data Format and Data Levels of the GCPEx 2DVD data can be found in the DataFormat_2dvd_gcpex.pdf 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 Contact InformationTo order these data or for further information, please contact:
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