GPM Ground Validation Autonomous Parsivel Unit (APU) IFloodS

Table of Contents

Introduction

The GPM Ground Validation Autonomous Parsivel Unit (APU) IFloodS dataset includes measurements of precipitation rate, reflectivity, mass-weighted mean diameter and drop size distribution. The APU collected data at 14 sites in eastern Iowa from April 2013 through June 2013 for the Iowa Flood Studies (IFloodS) campaign. The APU is an optical disdrometer capable of measuring precipitation particle size and fall velocity. The APU used for the IFloodS campaign 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.

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.

Petersen, W. and P. Gatlin. 2013. GPM Ground Validation Autonomous Parsivel Unit (APU) IFloodS [indicate subset used]. Dataset available online [http://ghrc.nsstc.nasa.gov/ ] from the NASA EOSDIS Global Hydrology Resource Center Distributed Active Archive Center, Huntsville, Alabama, U.S.A. doi: 10.5067/GPMGV/IFLOODS/APU/DATA301

Campaign

The Iowa Flood Studies (IFloodS) was a ground measurement campaign that took place in eastern Iowa from May 1 to June 15, 2013. The goals of the campaign were to collect detailed measurements of precipitation at the Earth's surface using ground instruments and advanced weather radars and, simultaneously, collect data from satellites passing overhead. The ground instruments characterized precipitation -- the size and shape of raindrops, the physics of ice and liquid particles throughout the cloud and below as it falls, temperature, air moisture, and distribution of different size droplets -- to improve rainfall estimates from the satellites, and in particular the algorithms that interpret raw data for the upcoming Global Precipitation Measurement (GPM) mission's Core Observatory satellite, which launches in 2014.

The APU instruments were located at 14 sites in Iowa. The serial number and geographic location of each APU are:

apu01: Lat: 42°14'19.54, Lon: 92°27'49.33
apu02: Lat: 42°10'56.33, Lon: 92°21'55.55
apu03: Lat: 43°07'33.52, Lon: 92°16'54.17
apu04: Lat: 42°07'20.75, Lon: 92°16'50.32
apu05: Lat: 41°59'33.62, Lon: 92°03'36.74
apu06: Lat: 41°58'41.36, Lon: 92°04'32.68
apu07: Lat: 41°59'33.63, Lon: 92°05'28.97
apu08: Lat: 41°59'33.63, Lon: 92°04'15.06
apu09: Lat: 41°51'41.03, Lon: 91°53'07.24
apu10: Lat: 41°51'37.75, Lon: 91°52'25.37
apu11: Lat: 41°50'49.41, Lon: 91°51'37.04
apu12: Lat: 41°50'50.52, Lon: 91°50'44.87
apu13: Lat: 41°38'26.23, Lon: 91°32'30.40
apu14: Lat: 41°38'26.29, Lon: 91°32'29.86

Further details on the IFloodS campaign are available at http://gpm.nsstc.nasa.gov/ifloods. Additional information about the Iowa Flood Center can be found at http://iowafloodcenter.org. Information on the Global Precipitation Measurement (GPM) mission is available at http://pmm.nasa.gov/GPM.

Instrument Description

The APU used for the IFloodS campaign 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 OTT Parsivel² disdrometer is a modern, laser-based optical system for measuring all types of precipitation. The transmitter unit of the sensor generates a flat, horizontal beam of light, which the receiver converts into an electrical signal. The signal changes whenever a hydrometeor falls through the beam anywhere within the measurement area. The degree of dimming is a measure of the size of the hydrometeor, and together with the duration of the signal, the fall velocity can be derived.

Additional campaign collections containing APU data can be found at http://ghrc.nsstc.nasa.gov.

Walter A. Petersen
NASA Wallops Flight Facility
Wallops, VA 23337

Patrick Gatlin
Earth Science Office
NASA-MSFC
Huntsville, AL 35805

The GPM Ground Validation Autonomous Parsivel Unit (APU) IFloodS data set is contained within daily tar archives. The daily archives are named with the following convention:

ifloods_apu[sn]_[YYYYMMDD]_[latitude_longitude].tar

where,

ifloods = Iowa Flood Studies
apu = Autonomous Parsivel Unit
sn = serial number of APU platform (e.g., apu01)
YYYYMMDD = the year, month and day of the data (e.g., 20110422)
latitude_longitude = geographic location of instrument (e.g., N363442.07_W0972640.90 is North 36 degrees 34'42.07" and West 97 degrees 26'40.90")
tar = "tar archive" is a method of bundling multiple files into one file

and consists of ASCII encoded files containing information on the drop size distribution and integral precipitation parameters such as precipitation rate, reflectivity and mass-weighted mean diameter.

The following files are found within the daily tar archive:

*_dropCounts.txt: quality-controlled number of hydrometeors in each diameter bin each minute hydrometeors were detected
*_rainDSD.txt: quality-controlled raindrop size distribution (based on measured fall velocities) for each diameter bin each minute rain was detected
*_rainDSD_vT.txt: quality-controlled raindrop size distribution (based on terminal fall velocities) for each diameter bin each minute rain was detected
*_rainParams.txt: quality-controlled integral parameters (based on measured fall velocities) for each minute hydrometeors were detected
*_rainParams_vT.txt: quality-controlled integrated parameters for rain (based on terminal fall velocities) for each minute hydrometeors were detected

More information on bin definitions can be found in the Data Format document.

Additional processed Parsivel datasets, which are not contained within a daily tar archive but use a similar file naming convention, provide a summary of the precipitation events measured by the Parsivel during the entire campaign. The additional datasets are named with the following convention:

ifloods_apu[sn]_[YYYYMMDD]_[latitude_longitude]_rainEvents.txt : quality-controlled total rainfall measured for a continuous period of precipitation

Data Format

The APU dataset consists of ASCII text files with a file extension of .txt. More detailed information on the Data Format and Data Levels of the APU data can be found in the Data Format document.

References

Beard, K.V., 1976: Terminal velocity and shape of cloud and precipitation drops aloft. J. Atmos. Sci., 33, 851 - 864.

Gunn, R. and G.D. Kinzer, 1949: The terminal velocity of fall for water drops in stagnant air. J. Meteor., 6, 243 - 248.

Jaffrain, Joel, Alexis Berne, 2011: Experimental quantification of the sampling uncertainty associated with measurements from PARSIVEL Disdrometers. J. Hydrometeor, 12, 352 - 370.

Tokay, A., Kruger, and W. Krajewski, 2001: Comparsion of drop size distribution measurements by impact and optical disdrometers. J. Appl. Meteor., 40, 2083 - 2097.

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: ghrcdaac@itsc.uah.edu
Web: http://ghrc.nsstc.nasa.gov/