Disdrometer Product Available for Tropical Western Pacific Sites

Published: 20 November 2025

Time series of (a) rain rate, (b) radar reflectivity factor at S band, and (c) total droplet number concentration from the VDISQUANTS value-added product are shown for February 2, 2014, at the Tropical Western Pacific (TWP) sites on Manus Island, Papua New Guinea (C1), and at Darwin, Australia (C3). Red indicates data from C1, and blue indicates C3 data. — Time series of (a) rain rate, (b) radar reflectivity factor at S band, and (c) total droplet number concentration from the VDISQUANTS value-added product are shown for February 2, 2014, at the Tropical Western Pacific (TWP) sites on Manus Island, Papua New Guinea (C1), and at Darwin, Australia (C3). Data plots were generated by Aifang Zhou, Brookhaven National Laboratory.

The Atmospheric Radiation Measurement (ARM) User Facility released the Video Disdrometer Quantities value-added product (VDISQUANTS VAP) for two sites that operated as part of the previously active Tropical Western Pacific (TWP) atmospheric observatory.

VDISQUANTS provides quality-controlled measurements of drop size distributions (DSDs), rain rates, and polarimetric radar quantities based on data from video disdrometers.

DSD measurements from disdrometers can be used to estimate key precipitation properties, including the rainfall rate, number concentration of drops, and mean raindrop size information. For these quantities to be useful for activities such as model evaluation or radar monitoring, disdrometer data sets require careful quality control and processing. VDISQUANTS uses standard methods adapted from the literature to filter spurious drops and extract important microphysical quantities of parameterized DSDs (e.g., gamma/exponential DSD assumptions and fitting).

In support of radar-based research interests and radar monitoring activities, this VAP also estimates radar-equivalent dual-polarization quantities (e.g., Reflectivity Factor Z, Differential Reflectivity ZDR) using the T-matrix scattering technique and several wavelength, temperature, and drop shape assumptions.

More information about the VAP, including the technical report, is available on the VDISQUANTS web page.

VDISQUANTS data are now available for the TWP C1 site on Manus Island, Papua New Guinea, from December 10, 2011, to July 3, 2014, as well as the TWP C3 site at Darwin, Australia, from February 28, 2011, to January 3, 2015. This completes the VDISQUANTS processing for both sites.

The Manus Island and Darwin data are available as daily netCDF files.

Access the TWP VDISQUANTS data in the ARM Data Center. (To download the data, first create an ARM account.)

To ask questions, provide feedback, or report data issues, please contact VDISQUANTS’ interim translator, Scott Giangrande, or VAP developer Aifang Zhou.

VDISQUANTS data can be referenced as doi:10.5439/1592683.

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ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.