UW Today

April 2, 2015

UW, NASA prepare for effort to measure rain, snow on Olympic Peninsula

News and Information

The University of Washington and NASA are preparing for a campaign next winter to measure rain in America’s rainiest place: the Olympic Peninsula, famed for its dripping rainforests, snowy mountain peaks and cloudy vampire novels.

trees and clouds

Clouds on the Olympic Peninsula’s Hurricane Ridge.Danny Novo / Flickr

This coming fall, the drops and flakes will be tracked as never before. Researchers are preparing for OLYMPEX, a ground-based effort to calibrate and validate precipitation measurements made by the Global Precipitation Measurement (GPM) constellation of satellites. An international collaboration including the Japanese Aerospace Exploration Agency and NASA recently launched the core GPM satellite, equipped with new instruments that can measure a range of precipitation intensities, from light snowfall to heavy tropical rain.

“It’s exciting to have all these things come together, measuring storm systems in all these different ways,” said Lynn McMurdie, a UW research scientist in atmospheric sciences.

Robert Houze, professor of atmospheric sciences, is the other UW lead on the project to validate the new satellites’ data.

The Olympic Peninsula is an ideal location to conduct a precipitation field campaign. It is situated within an active storm track and offers a unique venue to monitor storm systems and their evolution as they cross from the ocean to the coastal lowlands, and over complex terrain.

The high-tech storm watch will track weather from the air and on the ground. The most intense phase of the project is scheduled to start after the first week of November and continue for six weeks. Other sensors will stay on the ground throughout the winter until the spring thaw.

The ground campaign will include several dual-polarization weather radars to complement the one installed in 2011 on Washington’s coast, as well as other special ground instruments measuring the type and amount of precipitation. Research aircraft carrying instruments similar to those on the GPM core satellite will fly over the ocean and over the weather radars and other ground sensors.

Instruments will measure the exact amount of precipitation in different places, determine the height where snow turns to rain in a storm system, and even measure the size of the drops – whether the precipitation falls as many small drops, or fewer big drops.

“The size of the drops tells us something about the processes that are creating the rain, and is an important quantity used in the precipitation algorithms for the satellite,” McMurdie said.

clear plastic rain gauge

Rain gauges on volunteers’ property helps better track storms.CoCoRaHS

As part of the current gear-up phase, the team is asking the community for help. Residents from around the state, but especially from the Olympic Peninsula and Chehalis River basin to the south, are being sought to monitor precipitation. The citizen-science Community Collaborative Rain, Hail and Snow Network is helping with the recruitment. The network, which has operated in Washington since 2008, has more than 400 active volunteers, with 58 of those on the Olympic Peninsula.

The national volunteer rain-monitoring effort began in Colorado after a flash flood in 1997 was poorly forecasted by weather models and came as a surprise, killing five people and causing millions of dollars in damage.

Volunteers buy a $30 rain gauge, install it on their property, and then check it and report by computer each morning. Data from volunteers inside the study area will be entered into the NASA project database.

The data also will be used by UW doctoral student Diana Gergel, who is installing rain gauges throughout the Chehalis River basin to understand how satellite precipitation estimates match up with actual river flows. The project is starting now and next year Gergel expects to deploy 30 to 50 rain gauges. The NASA-funded study, led by Bart Nijssen, research associate professor in civil and environmental engineering, will help to predict flooding in that region by building better models that use satellite data to forecast extreme precipitation events.

Other UW researchers who are involved with the NASA rain-monitoring campaign include Cliff Mass in atmospheric sciences and Jessica Lundquist in civil and environmental engineering, and UW graduate students in those two departments.

More on the NASA GPM satellites, which launched in February 2014:


For more information, contact McMurdie at 206-685-9405 or mcmurdie@atmos.washington.edu. For information about the volunteer rain-gauge program contact Karin Bumbaco at 206-543-3145 or kbumbaco@uw.edu.