OLYMPEX: Operations and Observations during the Intensive Field Phase

The Olympic Mountains Experiment (OLYMPEX) was a multi-faceted, international, multi-agency field campaign led by NASA that took place over the Olympic Mountains in the Pacific Northwest during fall 2015 –  winter 2016. The goals of OLYMPEX were to provide physical validation and verification of satellite-derived precipitation measurements by the Global Precipitation Measurement (GPM) satellites and to document the precipitation processes in land-falling wintertime cyclones as they approach the coast and are modified by complex terrain. The data assets of OLYMPEX included a vast array of rain gauges and disdrometers placed at a variety of elevations on the windward slopes and on the leeside of the Olympic Mountains, four dual-polarization radars and supplemental soundings on the windward side and lee side of the Olympic Range, and aircraft, 2 carrying satellite simulator instruments and the third microphysics instrumentation. During the intensive field phase, from 12 November 2015 through 19 December 2015, all observational assets documented 13 landfalling midlatitude cyclones passing over the Olympic Peninsula. The variety of storms that were sampled included:

• Warm, extensive storm systems characterized by a strong low-level moist flow, often referred to as an "Atmospheric River," with high melting level, long periods of stratiform rain, and various degrees of orographic enhancement. In one 30-h event, the precipitation totals on the coast were 80 mm whereas as much as 360 mm precipitation fell on the windward flanks of the Olympic Mountains.
• Colder, occluded frontal systems with a variety of melting level heights, where both stratiform and shallow-embedded convection was observed and the degree of orographic enhancement varied from case to case.
• Intense frontal bands, including 3 narrow cloud frontal rainbands, with strong wind shifts and changes in precipitation characteristics on each side of the front.
• Weakening frontal systems with shallow precipitating clouds exhibiting a variety of melting level heights and low-level flow patterns.
• Episodes of post-frontal convection with a variety of precipitation intensities, and degrees of orographic enhancement. In one case, there was no precipitation observed in the onshore flow coming from the ocean, but there was continuous precipitation forming over terrain features.

In this presentation, highlights of the special data collection documenting these storm systems will be shown.