The project’s goal is to calibrate measurements made by the Global Precipitation Measurement satellite, which promises a next-generation view of rain and snow around the planet. The Olympic Peninsula is one of the few rainforests in the world located outside the tropics.

Scientists and 91̽»¨graduate students have spent the fall placing storm-tracking equipment on the ground. The same topography and unique climate that made it a natural laboratory for the experiment have earned much of the area status as a national park. The team has carried equipment in by truck, by foot and even by mule.

Now the scientific storm-watchers hope Mother Nature will deliver some good material in the weeks to come.

“We’re not just checking the satellite’s observations, the way you might double-check a simple distance measurement,” said project manager , a 91̽»¨research scientist in atmospheric sciences. “We’re checking the connection between what the satellite sees from space, what’s happening in the middle of the storm system, and what reaches the ground, which is what most people ultimately want to know. So we’re not just improving the satellite’s performance — we’re learning how storm systems work.”

The Olympic Peninsula gets an average of 16 inches of precipitation in November alone. The region is a natural laboratory to study precipitation, and one that will benefit from better precipitation forecasts, flood warnings and model estimates for how precipitation may change in the future.

The core , launched in early 2014, carries technology for the next generation of precipitation observations, including the new capability to detect snow and light rain. The next few weeks will test its space-based electronic eyes.

“We’ve designed an experiment where we have aircraft that are pretending to be the satellite,” said OLYMPEX principal investigator , a 91̽»¨professor of atmospheric sciences.

Starting Thursday, Nov. 12, NASA’s will operate out of Joint Base Lewis McChord and fly at an altitude of 39,000 feet above storm clouds moving toward the Quinault and Chelhalis river basins. In mid-November it will be joined by NASA’s , which will fly farther above the clouds at 65,000 feet. Both planes will carry instruments similar to those used in space, to simulate satellite observations. A third aircraft, the University of North Dakota’s , will actually fly through the clouds to take direct measurements of the droplets and ice crystals.

Incoming storms from the Pacific Ocean hit the coast and quickly reach the Olympic Mountains. The bumps act like rocks in a river, forcing the clouds in the storm system up and around the rocks, which changes the character of the precipitation. Following the storms from the ocean to the mountains provides highly variable terrain that leads to fast-changing conditions for rainfall and snowfall — which are a challenge to measure from space because they change quickly and over short distances.

On the ground, a large weather radar by the mouth of the Quinault River and a Doppler-on-Wheels on the shore of Lake Quinault will be gazing up at the clouds, studying their internal structure and how this changes as the storms move from the ocean inland. Arrays of rain gauges and other instruments on the ground — including  — will collect data on how much rainfall or snowfall reaches Earth’s surface. More ground instruments will image and count individual raindrops and snowflakes to get accurate small-scale pictures of heavy or light rain and snowfall.

“This stack of measurements lets us connect the dots between what we see from space, what happens in the clouds and what we measure on the ground,” said NASA scientist , who is leading the field campaign. Detailed ground measurements will help the team understand the fundamental processes within clouds that cause rain to fall as snow, sleet, rain or hail, driving downpour or light mist.

“All of these measurements are aimed at determining if the assumptions that we’re making about interpreting the satellite measurements are correct,” Houze said.

Houze, McMurdie, Petersen and 91̽»¨graduate students will hold weather briefings each morning at the mission’s control room in the 91̽»¨Atmospheric Sciences building. The large weather radars will be dismantled and flight missions will end by Dec. 21. Other equipment will continue to record data in the field until the team retrieves it in the spring.

The Global Precipitation Measurement is an international mission led by NASA and the Japan Aerospace Exploration Agency. Partners on the OLYMPEX mission are researchers at the University of Illinois, University of Utah, Texas A&M University, McGill University, Stony Brook University, Colorado State University, State University of New York, Environment Canada, as well as the U.S. Forest Service, the National Science Foundation, Quinault Indian Nation and the National Park Service.

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For more information, contact McMurdie at 206-685-9405 or mcmurdie@atmos.washington.edu. NASA will hold a and tour of the DC-8 aircraft Wednesday, Nov. 11 and can host media on flights throughout the week. Field sites will be operating most days; to arrange a visit, contact 91̽»¨research scientist Angela Rowe at akrowe@uw.edu.

More photos are at and .

This article was adapted from a NASA .

This coming fall, the drops and flakes will be tracked as never before. Researchers are preparing for , a ground-based effort to calibrate and validate precipitation measurements made by the Global Precipitation Measurement () 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 , a 91̽»¨research scientist in atmospheric sciences.

, professor of atmospheric sciences, is the other 91̽»¨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 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.

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 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 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 91̽»¨doctoral student , 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 , 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 91̽»¨researchers who are involved with the NASA rain-monitoring campaign include in atmospheric sciences and in civil and environmental engineering, and 91̽»¨graduate students in those two departments.

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

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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.