Pierce County is helping the federal government collect critical weather data used to predict river flooding in the Green River basin.

To assist the National Weather Service’s Seattle office with precipitation forecasting, the National Oceanic and Atmospheric Administration recently installed a temporary weather station at a Pierce County Public Works and Utilities (PWU) site near Spanaway. The station will provide information on the amount of moisture expected to fall in the Green River drainage basin above the Howard Hanson Dam in King County and elsewhere in the basin.

The new sensors measure how storms evolve as they move landward from the ocean into the mountains. That helps forecasters predict Green River flows, and it helps the Corps of Engineers estimate how much water is heading into the reservoir.

NOAA’s Earth System Research Laboratory in Boulder, Colo., installed the Atmospheric River Observatory meteorological equipment at the county’s PWU central maintenance facility in November.

Atmospheric rivers are narrow corridors of concentrated moisture in the atmosphere and are a key factor linking weather and climate. The Pacific Northwest regularly experiences this type of storm.

When atmospheric rivers strike land, they produce flooding rains. Satellites can detect their moisture content while over the ocean but cannot provide information on winds, a critical component for precipitation forecasting over land.

To provide the wind data, wind profiling radar was installed at the PWU site, along with a 30-foot meteorological tower that measures temperature, relative humidity, wind speed and direction, barometric pressure, and precipitation; a GPS receiver to measure water vapor in the atmosphere; and an 8×10-foot building to house the radar electronics. Data collected from the station is available in real time at http://www.esrl.noaa.gov/psd/data/obs/ (Spanaway listing).

The station will operate from until May 1, 2010, and again from Nov. 1, 2010 to May 1, 2011. NOAA personnel will perform monthly data backups and equipment maintenance.