CW3E Observations

Disdrometers

CW3E-deployed disdrometers measure precipitation type, drop size distribution, intensity, and velocity of all types of precipitation. The main interest of CW3E partners is in the precipitation type observations, or whether precipitation is occurring as rain or snow. Observations are collected every 10 seconds and the plots are updated hourly. The majority of our disdrometers are co-located with MRRs as well as surface meteorological stations. Images of the disdrometers are located below along with plots from current disdrometer data.

CW3E uses an OTT PARSIVEL-2 optical disdrometer, which measures the individual size and velocity of falling hydrometeors at the surface. This disdrometer uses a horizontal laser beam across from a receiving unit that converts the beam into an electrical signal. Each hydrometeor moving through the laser beam is placed into one of 32 different classes based on its size and velocity, calculated based upon the disruption to the laser beam. These data are used to calculate various characteristics of the precipitation including the type, amount, intensity, and kinetic energy, as well as the visibility and equivalent radar reflectivity. This system is able to measure precipitation intensity from 0.001 mm/h to 1,200 mm/h with accuracy of ± 5% for liquid and ± 20% for solid precipitation and can distinguish between 8 different types of precipitation (drizzle, drizzle/rain, mixed rain/snow, snow, snow grains, sleet, hail). This instrument provides critical information on whether precipitation is falling as solid or liquid. This disdrometer is heated during the winter.

Image on right shows a disdrometer (foreground) and MRR (background) set up as part of a radar meteorology station adjacent to the Granite Portal Valve House (GPO, in the Tuolumne/Merced watersheds).

CW3E would like to thank our sponsors, collaborators, and partners that enable the deployment of these instruments. For more information about CW3E’s sponsors and collaborators at the disdrometer sites, please see the bottom of the page.

CW3E precipitation type data calculated from the disdrometers is also available on CDEC.

Plot description: The plots below show data collected from a disdrometer deployed by CW3E at the location highlighted on the map. The top panel shows a scatter plot of rain intensity (mm/h) and the middle panel shows the radar reflectivity (dBZ). For the top two panels, the points are shaded according to the precipitation class determined by the disdrometer (see legend). The bottom panel shows the drop size distribution: the volume equivalent diameter (mm) is on the vertical axis, while each bin is shaded by the drop size frequency, which is expressed as a spectral number density (log scale). Measurements are recorded every 10 seconds. Each plot shows the current day’s data, updated once per hour, with time moving from left to right. Time is in UTC. For an archive of processed 5 minute data and images click here.

Watershed: Location: Green/DuwamishRussianSanta AnaTuolumne/MercedUpper Yuba/Feather Potter Valley

Our sponsors and collaborators

We would like to acknowledge our sponsors as well as our partners and collaborators that supported these instruments and allowed the deployment of these stations on their property.

CW3E’s stations in the Tuolumne-Merced watershed were initially sponsored by NOAA and are now supported by California Department of Water Resources (DWR). Station location support comes from our partners at San Francisco Public Utilities Commission, National Parks Service and private landowners. In the Russian River, the stations are sponsored by USACE, and the sites were made possible through collaboration with Potter Valley Fire Department and UC Davis Bodega Marine Lab. The stations in the Yuba-Feather watershed are sponsored by the Department of Water Resources and Yuba Water Agency and sites were made possible through Yuba Water Agency and private landowners. In the Santa Ana watershed, CW3E stations are sponsored by USACE, and sites were made possible in collaboration with San Bernardino County Flood Control District and University of Southern California Wrigley Marine Science Center.

The products are provided “as is” and are intended for research purposes only (disclaimer). All products on this page are considered experimental.