12th Conference on Mountain Meteorology


Overview of the Sierra Hydrometeorology Atmospheric River Experiment (SHARE)

David Kingsmill, CIRES/Univ. of Colorado, Boulder, CO; and S. E. Yuter, B. A. Colle, R. A. Houze, B. Geerts, D. P. Lettenmaier, P. J. Neiman, G. S. Poulos, R. B. Smith, B. F. Smull, W. J. Steenburgh, and M. Steiner

The Sierra Hydrometeorology Atmospheric River Experiment (SHARE) is a multi-agency field program focused on the multi-scale physics of orographic precipitation development and air mass transformation associated with frontal systems crossing the northern California Sierra Nevada mountain range. The SHARE field phase is planned for December 2007 to January 2008, coinciding with the last winter season of the NOAA Hydrometeorology Testbed (HMT) program in the California Sierras. SHARE builds on previous orographic field studies and incorporates several unique elements. The large-scale characteristics and evolution of the air mass moisture flux associated with an atmospheric river as it approaches the California coast and crosses the Sierra Nevada mountains will be observed in conjunction with the medium-scale interactions of the atmospheric river, frontal system, barrier jet, and the smaller-scale orographic precipitation processes and their variability.

Requested NSF facilities include the University of Wyoming King Air, NCAR G-V HIAPER, NCAR S-POLKA, the Doppler on Wheels radar, and a variety of smaller surface-based remote sensing and in situ instruments. The NSF facilities will be deployed in conjunction with NOAA, Environment Canada, and university facilities to create a network that will permit coordinated observations of each storm as it moves toward the mountains, over the windward slope, and downstream of the mountain crest.

SHARE is the first orographic field program to integrate the larger-scale issue of airmass transformation with the smaller-scale issues of cloud structure, cloud physics, and precipitation distribution. Comparison of observations from recent field programs such as IMPROVE and IPEX to regional model output have revealed potentially large errors in model microphysics. These errors include overprediction of cloud water and underprediction of snow over the Wasatch mountains and overprediction of snow at the crest and in the lee of the Oregon Cascades. Recent work has also revealed the importance of sub-barrier scale 3-D topography and the associated 3-D velocity structure to orographic precipitation variability. While the diagnosis of problems in the model microphysics is clear, the treatment necessary for improved model performance is not. By placing equal emphasis on 3-D microphysics and kinematic measurements at a range of spatial scales, SHARE is poised to improve understanding of the joint interactions between 3-D microphysics and kinematics and to improve representations of these processes in numerical models.

The findings from SHARE will have potential extensions to other regions of the world and to longer time scales. Atmospheric rivers are an important mechanism for meridional transport of water vapor from the tropical oceans to midlatitudes. Improved understanding of the characteristics and evolution of atmospheric rivers offshore of California has potential application to the U.S. Gulf coast and eastern seaboard. Improved knowledge of the interaction of atmospheric rivers and topography may be applicable to other north-south mountain ranges such as the Andes in South America. The physical process studies in SHARE are focused on the time scale of individual storms but will have applicability to longer time scales associated with climate issues. Global Climate Models (GCMs) share similar microphysical parameterization issues with mesoscale weather prediction models. Improvements in the representation of precipitation in storm-scale hydrologic models will be applicable to hydrological models that focus on intra- and interseasonal scales. Understanding the fine-scale precipitation structures over a topographic barrier is important for hydrologic modeling and geologic studies of local mudslides and long-term erosion. SHARE will also have large societal impacts, spanning issues related to public safety, commerce, and human resources development. Knowledge gained from the project will contribute to improvement of forecast tools for flood warnings and other severe weather that may endanger lives, property, and impact the western regional economy in the sectors of freshwater management (quality and quantity), commercial transportation, fisheries, and recreation.

Poster Session 1, Precipitation and Boundary Layers in Complex Terrain
Monday, 28 August 2006, 2:30 PM-4:00 PM, Ballroom North

Next paper

Browse or search entire meeting

AMS Home Page