New drifting buoys in the northeast Pacific

Bruce Ingleby (ECMWF)
David Lavers (ECMWF)
Anna Wilson (Scripps Institution of Oceanography, US)
Marty Ralph (Scripps Institution of Oceanography, US)
Luca Centurioni (Scripps Institution of Oceanography, US)

 

In January 2019, 32 drifting buoys were added to the global observing network in the northeast Pacific Ocean. Critically, these buoys have pressure sensors which provide important sea-level pressure observations in this data-sparse region. Drifting buoy pressure measurements are very important for improving numerical weather predictions because (1) pressure at mean sea level is an important variable linked to the main mode of extratropical synoptic variability; (2) in this and many other ocean areas there are very few other in situ observations; and (3) satellite data still provide only a small amount of information about pressure at mean sea level. The buoys usually last about two years and are a very cost-effective component of the global observing system. Sadly, up to 50% of drifting buoys are deployed without a pressure sensor.

Drifting buoys in the northeast Pacific Ocean. The chart shows all drifting buoys in the northeast Pacific Ocean on 11/12 March 2019. The 32 new ones were dropped in two lines in mid-January and gradually separated as they moved with the ocean currents. Only 28 of them are shown as four have stopped reporting. They also provide valuable observations of sea-surface temperature. In this area, only 36% of the drifting buoys (fewer before the deployment) have pressure sensors. In the North Atlantic, the proportion of drifting buoys that have pressure sensors is slightly higher, at about 42%.

The deployment of these new buoys, made possible by funds from NOAA’s Global Drifter Program, the California Department of Water Resources and the U.S. Army Corps of Engineers, was prompted by a discussion during a visit by Scripps Institution of Oceanography researchers to ECMWF. The meeting, in early September 2018, was organised by Aneesh Subramanian and David Lavers. Preparations for the buoy deployment were co-ordinated by the Center for Western Weather and Water Extremes (CW3E) at Scripps in collaboration with ECMWF, the Lagrangian Drifter Laboratory also at Scripps, and the United States Air Force. These extra drifting buoy observations formed part of a broader ‘atmospheric river reconnaissance’ field campaign, a multi-agency observational effort led by CW3E, involving dropsondes and additional soundings on the coast that took place in February and March 2019. The field campaign aims to improve forecasts of storms and extreme precipitation affecting California and adjacent regions. The addition of these buoys should benefit the ECMWF Integrated Forecasting System in the Pacific region and could lead to forecast skill improvements over Europe in the medium range.

Further information on the impact of drifting buoy pressure data can be found in Ingleby & Isaksen (2018; doi.org/10.1002/asl.822), Centurioni et al. (2017; doi.org/10.1175/BAMS-D-15-00080.1), and Horányi et al. (2017; doi.org/10.1002/qj.2981).