The Impacts of California's San Francisco Bay Area Gap on Precipitation Observed in the Sierra Nevada during HMT and CalWater

Details

• Journal Title:
  Journal of Hydrometeorology
• Personal Author:
  White, Allen B. ; Neiman, Paul J. ; Creamean, Jessie M. ; Coleman, Timothy ; Ralph, F. Martin ; Prather, Kimberly A.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory)
• Description:
  Atmospheric rivers (ARs) are narrow regions of enhanced water vapor transport, usually found on the warm-sector side of the polar cold front in many midlatitude storms formed primarily over the oceans. Nonbrightband (NBB) rain is a shallow orographic rainfall process driven by collision and coalescence that has been observed in some of these storms. NBB rain accounts for about one-third, on average, of the total winter season rainfall occurring at a coastal mountain site in Northern California. During the California Energy Commission's CalWater project, nearly the same fraction of NBB rain was observed at a northern Sierra Nevada foothills site as compared to the coastal mountains, whereas less than half of the fractional amount of NBB rain was observed at a southern Sierra Nevada foothills site. Both Sierra Nevada sites often experience terrain-induced blocked flow, that is, Sierra barrier jet (SBJ) during landfalling winter storms. However, the northern Sierra Nevada site often is oriented geographically downwind of a gap in the coastal terrain near San Francisco during AR landfall. This gap allows maritime air in the AR to arrive at the northern site and enhance the collision-coalescence process in orographic feeder clouds as compared with the southern site. As a result, a greater amount and intensity of NBB rain and overall precipitation was produced at the northern site. This study uses a variety of observations collected in the coastal and Sierra Nevada ranges from the Hydrometeorology Testbed and CalWater field campaigns to document this behavior. A detailed case study provides additional context on the interaction between AR flow, the SBJ, and precipitation processes.
• Source:
  Journal of Hydrometeorology, 16(3), 1048-1069.
• DOI:
  https://doi.org/10.1175/jhm-d-14-0160.1
• Document Type:
  Journal Article
• Rights Information:
  Other
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:229a90bfd6656d1c4ec7d83e261dc3ca45f53af657c1e1d304d2bebb04d2722a87a1f2e000b3e7650388fbea32d9df07779b506cb2f98873bc7a51a0615cc7ad
• Download URL:
  https://repository.library.noaa.gov/view/noaa/22379/noaa_22379_DS1.pdf
• File Type:
  [PDF - 10.62 MB ]