Improving Short-Term (0–48 h) Cool-Season Quantitative Precipitation Forecasting: Recommendations from a USWRP Workshop

Ralph, F. Martin; Rauber, Robert M.; Jewett, Brian F.; Kingsmill, David E.; Pisano, Paul; Pugner, Paul E.; Rasmussen, Roy; Reynolds, David W.; Schlatter, Thomas; Stewart, Ronald E.; Tracton, S.; Waldstreicher, Jeff S.

doi:10.1175/bams-86-11-1619

Cited by 107 publications

(61 citation statements)

References 15 publications

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“…Major investments in flood control infrastructure have reduced risks from storms, but the risk of catastrophic flooding remains very real, as evidenced by major floods in 1986 and 1997, and by the continuing history of flood-caused levee breaches in the Central Valley (Florsheim and Dettinger 2007). The 1986 and 1997 storms came close to overwhelming flood-control systems, threatening inundation of downtown Sacramento, and led to National Research Council studies (NRC 1995(NRC , 1999, planned major enhancements to flood control, and long-term research (e.g., Ralph et al 2005a). …”

Section: Introductionmentioning

confidence: 99%

Design and quantification of an extreme winter storm scenario for emergency preparedness and planning exercises in California

et al. 2011

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The USGS Multihazards Project is working with numerous agencies to evaluate and plan for hazards and damages that could be caused by extreme winter storms impacting California. Atmospheric and hydrological aspects of a hypothetical storm scenario have been quantified as a basis for estimation of human, infrastructure, economic, and environmental impacts for emergency-preparedness and flood-planning exercises. In order to ensure scientific defensibility and necessary levels of detail in the scenario description, selected historical storm episodes were concatentated to describe a rapid arrival of several major storms over the state, yielding precipitation totals and runoff rates beyond those occurring during the individual historical storms. This concatenation allowed the scenario designers to avoid arbitrary scalings and is based on historical occasions from the 19th and 20th Centuries when storms have stalled over the state and when extreme storms have arrived in rapid succession. Dynamically consistent, hourly precipitation, temperatures, barometric pressures (for consideration of storm surges and coastal erosion), and winds over California were developed for the so-called ARkStorm scenario by downscaling the concatenated global records of the historical storm sequences onto 6-and 2-km grids using a regional weather model of January 1969 and February 1986 storm conditions. The weather model outputs were then used to force a hydrologic model to simulate ARkStorm runoff, to better understand resulting flooding risks. Methods used to build this scenario can be applied to other emergency, nonemergency and non-California applications.

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Section: Introductionmentioning

confidence: 99%

Design and quantification of an extreme winter storm scenario for emergency preparedness and planning exercises in California

et al. 2011

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“…Reducing uncertainty associated with winter storm precipitation type, accumulation, and timing is a major forecasting, safety, and socioeconomic challenge (Ralph et al 2005;Kringlebotn Nygaard et al 2011;Smith et al 2012). These rapidly evolving mesoscale systems will be better understood with the national dual-polarization radar upgrade through use of hydrometeor classification algorithms (HCAs; Liu and Chandrasekar 2000;Zrni c et al 2001;Park et al 2009;Chandrasekar et al 2013).…”

Section: Introductionmentioning

confidence: 99%

A Dual-Polarization Radar Hydrometeor Classification Algorithm for Winter Precipitation

Thompson

Rutledge

Dolan

et al. 2014

Journal of Atmospheric and Oceanic Technology

101

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The purpose of this study is to demonstrate the use of polarimetric observations in a radar-based winter hydrometeor classification algorithm. This is accomplished by deriving bulk electromagnetic scattering properties of stratiform, cold-season rain, freezing rain, sleet, dry aggregated snowflakes, dendritic snow crystals, and platelike snow crystals at X-, C-, and S-band wavelengths based on microphysical theory and previous observational studies. These results are then used to define the expected value ranges, or membership beta functions, of a simple fuzzy-logic hydrometeor classification algorithm. To test the algorithm's validity and robustness, polarimetric radar data and algorithm output from four unique winter storms are investigated alongside surface observations and thermodynamic soundings. This analysis supports that the algorithm is able to realistically discern regions dominated by wet snow, aggregates, plates, dendrites, and other small ice crystals based solely on polarimetric data, with guidance from a melting-level detection algorithm but without external temperature information. Temperature is still used to distinguish rain from freezing rain or sleet below the radar-detected melting level. After appropriate data quality control, little modification of the algorithm was required to produce physically reasonable results on four different radar platforms at X, C, and S bands. However, classification seemed more robust at shorter wavelengths because the specific differential phase is heavily weighted in ice crystal classification decisions. It is suggested that parts, or all, of this algorithm could be applicable in both operational and research settings.

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“…This article therefore examines a subset of the overall needs identified in Ralph et al (2005) in the report on a workshop addressing improvements in short-term cool season quantitative precipitation forecasting (QPF). All four workshop working groups reporting in Ralph et al (2005) identified issues and challenges associated with precipitation type among their key findings, with the data assimilation and modeling working group stating that "the most serious problem associated with wintertime QPF is the accurate determination of precipitation type when the surface temperature is near freezing.…”

mentioning

confidence: 99%

“…All four workshop working groups reporting in Ralph et al (2005) identified issues and challenges associated with precipitation type among their key findings, with the data assimilation and modeling working group stating that "the most serious problem associated with wintertime QPF is the accurate determination of precipitation type when the surface temperature is near freezing. "…”

mentioning

confidence: 99%

On the Characteristics of and Processes Producing Winter Precipitation Types near 0°C

Stewart

Thériault

Henson³

2015

Bulletin of the American Meteorological Society

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This article examines the types of winter precipitation that occur near 0°C, specifically rain, freezing rain, freezing drizzle, ice pellets, snow pellets, and wet snow. It follows from a call by M. Ralph et al. for more attention to be paid to this precipitation since it represents one of the most serious wintertime quantitative precipitation forecasting (QPF) issues. The formation of the many precipitation types involves ice-phase and/or liquid-phase processes, and thresholds in the degree of melting and/or freezing often dictate the types occurring at the surface. Some types can occur simultaneously so that, for example, ensuing collisions between supercooled raindrops and ice pellets that form ice pellet aggregates can lead to substantial reductions in the occurrence of freezing rain at the surface, and ice crystal multiplication processes can lead to locally produced ice crystals in the subfreezing layer below inversions. Highly variable fall velocities within the background temperature and wind fields of precipitation-type transition regions lead to varying particle trajectories and significant alterations in the distribution of precipitation amount and type at the surface. Physically based predictions that account for at least some of the phase changes and particle interactions are now in operation. Outstanding issues to be addressed include the impacts of accretion on precipitation-type formation, quantification of melting and freezing rates of the highly variable precipitation, the consequences of collisions between the various types, and the onset of ice nucleation and its effects. The precipitation physics perspective of this article furthermore needs to be integrated into a comprehensive understanding involving the surrounding and interacting environment.

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Improving Short-Term (0–48 h) Cool-Season Quantitative Precipitation Forecasting: Recommendations from a USWRP Workshop

Cited by 107 publications

References 15 publications

Design and quantification of an extreme winter storm scenario for emergency preparedness and planning exercises in California

Design and quantification of an extreme winter storm scenario for emergency preparedness and planning exercises in California

A Dual-Polarization Radar Hydrometeor Classification Algorithm for Winter Precipitation

On the Characteristics of and Processes Producing Winter Precipitation Types near 0°C

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