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Clifford F. Mass
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Clifford F. Mass
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Clifford F. Mass
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Clifford F. Mass

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The coastal regions of southern Oregon and northern California can be considerably warmer than locations to the north and south when air descends the substantial mountain barrier to the east. This paper describes the event of 27 February 1985, during which Brookings, Oregon experienced the highest February temperature ever observed in that state.

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Clifford F. Mass

This paper describes the current application of compact discs (CD-ROM) to the storage and distribution of datasets for atmospheric sciences and related disciplines. CD-ROM technology is reviewed, currently available discs are listed, and a look at future developments is provided.

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Clifford F. Mass

For over a half-century, the Bergen School conceptual model of cyclone structure and development has dominated the practice of synoptic meteorology, especially regarding the techniques by which surface synoptic charts are analyzed. Although the Norwegian paradigm captures some of the essential features of cyclone evolution, research and practical application over the last 60-odd years have revealed significant deficiencies, several of which are discussed in this paper. The Bergen model has also been applied in regions and under conditions quite unlike those for which the model was originally developed. Knowledge of these problems by many in the research and operational communities has had little impact on the manner in which synoptic charts are analyzed or the way the subject is described in many textbooks. Deficiencies in the underlying conceptual model of cyclone development have been compounded by a lack of consistent and well-defined procedures for defining fronts and for analyzing surface synoptic charts. Several examples of confusing and inconsistent surface analyses are presented in this paper.

To resolve these problems, the meteorological community should follow a two-pronged approach. First, the research and operational insights gained over the last half-century should be combined with recent numerical modeling and observational studies to establish improved conceptual models of cyclone evolution. Second, a clear and consistent methodology for analyzing synoptic charts should be devised. Several possible approaches for implementing these suggestions are presented in this paper.

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Clifford F. Mass

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Conor McNicholas and Clifford F. Mass

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Over half a billion smartphones worldwide are now capable of measuring atmospheric pressure, providing a pressure network of unprecedented density and coverage. This paper describes novel approaches for the collection, quality control, and bias correction of such smartphone pressures. An Android app was developed and distributed to several thousand users, serving as a test bed for onboard pressure collection and quality-control strategies. New methods of pressure collection were evaluated, with a focus on reducing and quantifying sources of observation error and uncertainty. Using a machine learning approach, complex relationships between pressure bias and ancillary sensor data were used to predict and correct future pressure biases over a 4-week period from 10 November to 5 December 2016. This approach, in combination with simple quality-control checks, produced an 82% reduction in the average smartphone pressure bias, substantially improving the quality of smartphone pressures and facilitating their use in numerical weather prediction.

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Conor McNicholas and Clifford F. Mass

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Over a half-billion smartphones are now capable of measuring atmospheric pressure, potentially providing a global surface observing network of unprecedented density and coverage. An earlier study by the authors described an Android app, uWx, that served as a test bed for advanced quality control and bias correction strategies. To evaluate the utility and quality of the resulting smartphone pressure observations, ensemble data assimilation experiments were performed for two case studies over the Pacific Northwest. In both case studies, smartphone pressures improved the analyses and forecasts of assimilated and nonassimilated variables. In case I, which considered the passage of a front across the region, cycled smartphone pressure assimilation consistently improved 1-h forecasts of the altimeter setting, 2-m temperature, and 2-m dewpoint. During a postfrontal period, cycled smartphone pressure assimilation improved mesoscale forecasts of hourly precipitation accumulation. In case II, which considered a major coastal windstorm, cycling experiments assimilating smartphone pressures improved 10-m wind forecasts as well as the predicted track and intensity. For both cases, free-forecast experiments initialized with smartphone data produced forecast improvements extending several hours, suggesting the utility of crowdsourced smartphone pressures for short-term numerical weather prediction.

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Justin Sharp and Clifford F. Mass

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This paper quantifies the impact of the Columbia Gorge on the weather and climate within and downstream of this mesoscale gap and examines the influence of synoptic-scale flow on gorge weather. Easterly winds occur more frequently and are stronger at stations such as Portland International Airport (KPDX) that are close to the western terminus of the gorge than at other lowland stations west of the Cascades. In the cool season, there is a strong correlation between east winds at KPDX and cooler temperatures in the Columbia Basin, within the gorge, and over the northern Willamette River valley. At least 56% of the annual snowfall, 70% of days with snowfall, and 90% of days with freezing rain at KPDX coincide with easterly gorge flow.

Synoptic composites were created to identify the large-scale patterns leading to strong winds, snowfall, and freezing rain in the gorge. These composites showed that all gorge gap flow events are associated with a high-amplitude 500-mb ridge upstream of the Pacific Northwest, colder than normal 850-mb temperatures over the study region, and a substantial offshore sea level pressure gradient force between the interior and the northwest coast. However, the synoptic evolution varies for different kinds of gorge weather events. For example, the composite of the 500-mb field for freezing rain events features a split developing in the upstream ridge with zonal flow at midlatitudes, while for easterly gap winds accompanied by snowfall, there is an amplification of the ridge.

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