GPM Ground Validation Joss-Waldvogel Disdrometer (JW) at the NSSTC

Table of Contents

Introduction

The Joss-Waldvogel Disdrometer (JWD) is one of several instruments being used for Global Precipitation Measurement (GPM) mission Ground Validation (GV). These instruments are used for measurement of rain rate, drop size distribution (DSD) and radar reflectivity factor. It has been widely used in many field campaigns to complement validation efforts of radar rainfall estimation. This dataset collects data at the National Space Science and Technology Center, Huntsville, AL.

Note:This is a preliminary dataset which will be updated periodically as it is received. The Data Format document will be distributed upon request by contacting the GHRC User Services Office.

Campaign

The 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 Joss-Waldvogel Disdrometer (JWD) is an impact-type electromechanical counter considered to be a
reference instrument for drop size distribution (DSD) measurements. It has been commercially available for over 30 years (Joss and Waldvogel 1967) and has been widely used in many field campaigns to complement validation efforts of radar rainfall estimation. The JWD has been used for measurements of: dead-time corrected raindrop count, number concentration (N(D)), reflectivity, rain rate, liquid water content, mass-weighted mean diameter, and normalized scale parameter (Nw). The full 127 diameter (size) channels are distributed exponentially from 0.3 mm to 5.3 mm (class sizes range from 0.1 mm to 0.5 mm ) within a 50 cm2 area.

How it works:

The Joss-Waldvogel sensor transforms the mechanical momentum of an impacting drop into an electrical pulse. The amplitude of the pulse is roughly proportional to the mechanical momentum. The sensor consists of a cylindrical metal housing containing an electromechanical transducer and an amplifier module. The processer contains circuitry to eliminate unwanted signals (acoustic noise), and produces a seven bit code at the output for every drop hitting the sensitive surface of the sensor.

Data are in daily tar files of the form:

jw_lllll_yyyymmdd.tar

where,

jw = Joss-Waldvogel disdrometer
lllll  = Represents the location of the instrument (NSSTC, others)
yyyymmdd  = Is the year, month and day of the data
tar = "tar archive" a method of bundling  multiple files into one file

Inside each tar file are hourly files of the form:

DDmmddyy.hh

where,

mmddyy = two digit month,day,year
hh = two digit hour of the day (01-23)

Within each hourly file, data are sampled every 10 seconds.

Data are in ascii format. (more to come here) May be hex. How many bins ?

The data producers are:

Walter A.Petersen
NASA Marshall Space Flight Center
Huntsville, Alabama, 35805

Larry Carey
Earth Systems Science Center
UAHuntsville
Huntsville, AL 35805

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/