Dynamically-Driven Winds

Jackson, Peter L.; Mayr, Georg J.

doi:10.1007/978-94-007-4098-3_3

Cited by 52 publications

(51 citation statements)

References 227 publications

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“…Horizontal resolution coarser than 2 km, however, exaggerated the spatial extent of the downslope flow, resulting in higher wind biases. Resolution also influences how well models can capture other aspects of terrain-induced flow (e.g., Jackson et al 2013;Reinecke and Durran 2009b) as well.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…This increases the horizontal gradient in sea level pressure (SLP) and helps to enhance flow speeds through prominent terrain gaps such as the Cajon Pass (leading to Santa Ana) and through the Soledad Pass (northwest of Los Angeles), creating prominent wind corridors in the northern part of the Los Angeles basin (Jackson et al 2013). Wind speeds can also be very large in San Diego County, where the terrain gaps appear less prominent but mountain heights are also generally lower.…”

Section: Introductionmentioning

confidence: 99%

“…Downslope windstorms are a type of large-amplitude mountain wave that can produce strong, often gusty winds on the lee side of a mountain barrier (Durran 1990(Durran , 2003Jackson et al 2013). They are observed in many areas of the world, and carry such names as the bora, chinook, foehn, zonda and taku winds (e.g., Schamp 1964;Durran 2003).…”

Section: Introductionmentioning

confidence: 99%

“…In complex terrain, the wind can vary greatly over small distances and gustiness is common in downslope windstorms, which may include rotors and subrotors embedded in the flow (Doyle and Durran 2004;Jackson et al 2013). Terrain-amplified winds and gusts can knock down trees and power lines, starting and spreading fires, making accurate forecasts in this region extremely important.…”

Section: Introductionmentioning

confidence: 99%

“…Despite steady improvement in operational numerical weather prediction models over the last several decades as well as advancements in the understanding of mountain meteorology dynamics, forecast skill for downslope windstorms is still limited by several factors, including dependence and/or sensitivity to model resolution (e.g., Reinecke and Durran 2009b;Jackson et al 2013), numerical schemes (e.g., Reinecke and Durran 2009b), vertical coordinates and diffusion (e.g., Smith et al 2007), physical formulations [especially the boundary layer; see Smith (2007)] and initial condition uncertainties (e.g., Reinecke and Durran 2009a). Our work was motivated by the need to forecast winds that could affect electrical transmission lines in San Diego County operated by the San Diego Gas and Electric (SDG&E) company.…”

Section: Introductionmentioning

confidence: 99%

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Downslope Windstorms of San Diego County. Part I: A Case Study

Yang

Fovell

2016

Monthly Weather Review

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The “Santa Ana” wind is an offshore flow that affects Southern California periodically during the winter half of the year, typically between September and May. The winds can be locally gusty, particularly in the complex terrain of San Diego County, where the winds have characteristics of downslope windstorms. These winds can cause and/or rapidly spread wildfires, the threat of which is particularly acute during the autumn season before the onset of winter rains. San Diego’s largest fires, including the Cedar fire of 2003 and Witch Creek fire of 2007, occurred during Santa Ana wind events. A case study of downslope flow during a moderately intense Santa Ana event during mid-February 2013 is presented. Motivated by the need to forecast winds impinging on electrical lines, the authors make use of an exceptionally dense network of near-surface observations in San Diego County to calibrate and verify simulations made utilizing the Advanced Research version of the Weather Research and Forecasting (WRF) Model, which in turn is employed to augment the observations. Results demonstrate that this particular Santa Ana episode consists of two pulses separated by a protracted lull. During the first pulse, the downslope flow is characterized by a prominent hydraulic jumplike feature, while during the second one the flow possesses a clear temporal progression of winds downslope. WRF has skill in capturing the evolution and magnitude of the event at most locations, although most model configurations overpredict the observed sustained wind and the forecast bias is itself biased.

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Section: Discussion and Summarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Downslope Windstorms of San Diego County. Part I: A Case Study

Yang

Fovell

2016

Monthly Weather Review

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The Importance of Soil‐Type Contrast in Modulating August Precipitation Distribution Near the Edwards Plateau and Balcones Escarpment in Texas

Xue

McPherson

2017

JGR Atmospheres

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The Balcones Escarpment in central Texas is a sloped region between the Edwards Plateau and the coastal plain. The metropolitan areas located along the Balcones Escarpment (e.g., San Antonio, Austin, and Dallas‐Fort Worth) are prone to heavy rain and devastating flood events. While the associated hydrological issues of the Balcones Escarpment have been extensively studied, the meteorological impacts of the Edwards Plateau and Balcones Escarpment are not well understood. The indeterminate impacts of the thermal and dynamic effects of the Edwards Plateau on August climatological precipitation are investigated in this study using the multisensor Stage IV precipitation data, high‐resolution dynamic downscaling, and short‐term sensitivity simulations. Analysis results indicate that the total August precipitation east of the Balcones Escarpment is suppressed and precipitation over the eastern part of the Edwards Plateau is enhanced. Locally initiated moist convection in the afternoon contributes most to the total precipitation during August in the region. The dynamic downscaling output captures the spatial pattern of afternoon precipitation, which is well aligned with the simulated upward motions. The clay‐based soil types that dominate the Edwards Plateau have great potential to retain soil moisture and limit latent heat fluxes, consequently leading to higher sensible heat flux than over the plain to the east. As a result, vertical motion is induced, triggering the afternoon moist convection over the Edwards Plateau under favorable conditions. In comparison, the sloping terrain plays a smaller role in triggering the convection. Short‐term sensitivity simulations for a clear day confirm and further prove such a diagnosis.

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A synoptic climatology of strong along‐channel winds on the Coast of British Columbia, Canada

Bakri

Jackson

Doherty³

2016

Intl Journal of Climatology

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A synoptic climatology using mean sea level pressure and 500‐hPa geopotential height composites is conducted for strong along‐channel winds that occur through five of the channels dissecting British Columbia's coast. Seasonal (winter, summer) and directional (inflow, air moving from the coast inland; outflow, air moving from inland towards the coast) partitioning of the winds, results in four distinct along‐channel winds that occur: summertime inflow, summertime outflow, wintertime inflow and wintertime outflow. Composite analyses using reanalysis data and in situ observations are used to examine each wind type at all locations. Wintertime composites produce patterns that are distinct from the overall winter climatology, in which outflows occur when an arctic surface high‐pressure area on the inland side of the coastal mountains is accompanied by the presence of an area of low surface pressure in the northeastern Pacific. Inflow composites in the winter indicate low‐pressure areas associated with mid‐latitude cyclones over the Gulf of Alaska. Summertime composites are similar to the overall summer climatology; therefore, other approaches are applied to explain these winds. We analyse 104 summertime inflow events at three locations using surface analysis charts for 13 summer seasons. The analysis reveals the importance of fronts at the time of inflows, with fronts associated with almost half of the events. Non‐hierarchical clustering analysis is applied for the summertime inflow events. The clustering analysis gives a better explanation of the summertime inflows than the composites. This is achieved by grouping events into different clusters, allowing for better illustration of the variance between the clusters.

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Dynamically-Driven Winds

Cited by 52 publications

References 227 publications

Downslope Windstorms of San Diego County. Part I: A Case Study

Downslope Windstorms of San Diego County. Part I: A Case Study

The Importance of Soil‐Type Contrast in Modulating August Precipitation Distribution Near the Edwards Plateau and Balcones Escarpment in Texas

A synoptic climatology of strong along‐channel winds on the Coast of British Columbia, Canada

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