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Three-dimensional structure and evolution of the Sierra Barrier Jet

Three-dimensional structure and evolution of the Sierra Barrier Jet. Principal Investigator: Kingsmill Collaborators: Yuter, Neiman, Sukovich, Hughes Motivation:

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Three-dimensional structure and evolution of the Sierra Barrier Jet

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  1. Three-dimensional structure and evolution of the Sierra Barrier Jet • Principal Investigator: Kingsmill • Collaborators: Yuter, Neiman, Sukovich, Hughes • Motivation: • Atmospheric rivers (ARs) contribute significantly to water supply and flood generation in California, but the influence of mountains on precipitation distribution is still poorly understood. • Sierra barrier jets (SBJs) are a dominant feature in Sierra Nevada storms and have a large influence on precipitation distribution. • Documentation of the vertical profile and 2-D cross-barrier structure of SBJs has provided important insights, but a lack of 3-D documentation hinders understanding of many critical details, such as cross-barrier horizontal extent, along-barrier variability and interaction with ARs.

  2. Specific Testable Hypotheses • The strongest winds associated with atmospheric rivers are deflected upward and flow over the strongest terrain-parallel winds associated with the Sierra barrier jet. • Precipitation is enhanced by 50% within 10 km downstream from where atmospheric rivers are deflected upward by the Sierra barrier jet. • The width of blocked flow associated with the Sierra barrier jet is modulated by the Froude number (Fr) calculated from wind speeds upstream of the blocked flow and stability within the blocked flow. The smaller the Fr : • The further west the blocked flow extends. • The further east along the windward slope the blocked flow extends • The cross-barrier extent of the barrier jet exceeds 50% of the blocked-flow cross-barrier extent.

  3. Essential Observational Tools • ESRL Skywater C-band scanning Doppler radar at LHM (HYDRO-C) • NWS operational S-band scanning Doppler radars (KDAX and KBBX) • Wind profiling radars, particularly at SHS, CFC, SAC, CCO, CCR and BBY • GPS balloon soundings at LHM • GPS IWV receivers, particularly at SHS, CFC, CCO, CCR, BBY, FBG and STA (plus EFREP)

  4. Landfalling Atmospheric River on 30-31 December 2005

  5. Sloughhouse 915 MHz Profiler Time-Height Sections

  6. KDAX-KBBX Dual-Doppler31 December 2005 0830 UTCReflectivity and Vector Winds @ 1 km MSL CCO KBBX Amer. River Basin LHM SHS KDAX BBY

  7. KDAX-KBBX Dual-Doppler: 31 Dec 2005 1431 UTCU-component Winds @ 1, 2 and 3 km MSL

  8. KDAX-KBBX Dual-Doppler: 31 Dec 2005 1431 UTCV-component Winds @ 1, 2 and 3 km MSL

  9. Backup Slides

  10. Cross-SBJ G-1 flight profile (400 km; 1.3 h) Wind profiler observations can help select prior to flight 4 3 50 km leg Altitude (km, msl) 2 Sugar Pine (ATOFMS, S-Prof) 1 Colfax Sierra Nevada Concord Sacramento (profiler + ACARS) Sloughhouse Sierra Barrier Jet (SBJ) 150 km

  11. Next, Bodega Bay 915 MHz Profiler Time-Height Sections….

  12. …and Chico 915 MHz Profiler Time-Height Sections

  13. KDAX-KBBX Dual-DopplerReflectivity and Vector Winds @ 1 km MSL

  14. KDAX-KBBX Dual-DopplerReflectivity and Vector Winds @ 1 km MSL

  15. KDAX-KBBX Dual-DopplerU-component Winds @ 1 km MSL

  16. KDAX-KBBX Dual-DopplerU-component Winds @ 1 km MSL

  17. KDAX-KBBX Dual-DopplerV-component Winds @ 1 km MSL

  18. KDAX-KBBX Dual-DopplerV-component Winds @ 1 km MSL

  19. KDAX-KBBX Dual-Doppler: 31 Dec 2005 1431 UTCReflectivity and Winds @ 1, 2 and 3 km MSL

  20. First, some context: Base Maps

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