Ground Validation

Snowflake Size Distribution Measurements in South Central Ontario, Canada

Parsivel Distrometer Results presented at the American Geophysical Union, Spring 2007.

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Parsivel (Laser Optical) Disdrometer

Overview of the Parsivel instrument:

  • Measures size and fall velocity of hydrometeors
  • Present weather sensor
  • Sampling area: ~50 cm2, varies with drop diameter
  • Number of size and velocity bins: 32 x 32 matrix
  • Drop size range: 0.06-24.5 mm
  • Velocity range: 0.05-20.8 m/sec
  • Operation period at Wallops Island: Spring 2002 - present
  • Manufacturer: OTT in Germany www.ott-hydrometry.de
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Snowflake Video Imager at C3VP

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The NASA Snowflake Video Imager obtained nearly continuous data from 1 Dec 06 thru 7 Mar 07.

This presentation contains a summary for the entire data set, which is sorted into (a) priority days selected by GSFC investigators, and (b) non-priority days.

The results are displayed in images of DSD(t), which reveal (a) the large variability of snowflakes sizes during events and (b) the intermittency of snowfall – even during intense storms.

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The Statistical Analysis and Display Program for GPM Validation Network Geometry-Matched PR and GV Data Sets

The IDL procedure geo_match_z_pdf_profile_ppi_bb_prox_sca_ps.pro provides the capability to compute statistics and generate displays of PR and GV reflectivity from geometry-matched data produced by the GPM Validation Network prototype. These data are contained in a set of netCDF data files, one per “rainy” site overpass: a TRMM PR overpass of a ground radar (GV) site, with precipitation echoes present, referred to below as an “event”.

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The Vertical Cross Section Display Program for GPM Validation Network Geometry-Matched PR and GV Data Sets

The IDL procedure pr_and_geo_match_x_sections.pro provides the capability to interactively select locations for, and display, vertical cross sections of PR and GV reflectivity from geometry-matched data produced by the GPM Validation Network prototype. These data are contained in a set of netCDF data files, one per “rainy” site overpass (a TRMM PR overpass of a GV radar site, with precipitation echoes present). By default, the procedure also displays a vertical cross section of the difference (PR-GV) between the PR and GV reflectivity from the geo-matched data.

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A Global Precipitation Mission (GPM) Validation Network Prototype

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A Validation Network (VN) prototype is currently underway that compares data from the Tropical Rainfall Measuring Mission (TRMM) satellite Precipitation Radar (PR) to similar measurements from the U.S. national network of operational weather radars. This prototype is being conducted as part of the ground validation activities of the Global Precipitation Measurement (GPM) mission. The purpose of the VN is to provide a means for the precipitation community to identify and resolve significant discrepancies between the U.S.

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GPM Ground Validation System Level 3 Operations Concept

This specification defines the Level 3 functional and performance requirements for NASA’s Global Precipitation Measurement (GPM) mission Ground Validation System (GVS). Overall, the GPM mission has defined a series of scientific objectives which include improvement in predicting terrestrial weather, climate, and hydrometeorology through a better observational understanding of the global water cycle. The purpose of the GPM GVS is rooted in the need for independent and objective evaluation of the precipitation products generated by the GPM mission.

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