The Effect of Upstream Orography on the Onset of Sundowner Winds in Coastal Santa Barbara, CA

Duine, Gert‐Jan; Carvalho, Leila M. V.; Jones, Charles; Zigner, Katelyn

doi:10.1029/2020jd033791

Cited by 5 publications

(20 citation statements)

References 37 publications

(82 reference statements)

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“…In contrast, RHWC1 records cooler temperatures and lower dew points during extreme winds, which may be from an oceanic influence. Similar to methods employed in Duine et al (2021) and Carvalho et al (2020), future study using back trajectory analysis could assist in determining the sources of air parcels, and may relate to or explain patterns observed in temperature and dew point during Sundowners.…”

Section: Discussionmentioning

confidence: 99%

“…Above the boundary layer, winds rapidly accelerate. Another observation is that the mean wind direction at and above 1,200 m AGL is commonly from the northwest for most of the day, intensifying and turning into a northerly direction at approximately above 500 m AGL (possibly indicating the top of the boundary layer, consistent with modelling studies-e.g., Duine et al, 2019Duine et al, , 2021. This occurs around sunset, indicating the formation of a low-level (super-geostrophic) nocturnal jet that lasts only a few hours (Stull and Ahrens, 2000).…”

Section: Seasonal Cycles Diurnal Cycles and Sundowner Winds Observed ...mentioning

confidence: 99%

“…This can be explained by the persistent northwesterly flow in this region (Dorman and Winant, 2000). Additionally, the strong winds (>8 m/s) recorded between 1500 and 1700 PST at RHWC1 (Figure 4) may reflect contributions from the early onset of Sundowners on the western SYM slopes (Carvalho et al, 2020; Duine et al, 2021; Jones et al, 2021).…”

Section: Observed Wind Patterns and Extremesmentioning

confidence: 99%

“…The variation in wind directions observed in the west and east regions of the south‐facing SYM have been shown in climatological simulations with WRF (Jones et al, 2021). Although more studies are necessary to evaluate all mechanisms explaining the behaviour of wind direction along the slopes of the SYM, sensitivity tests and simulations have shown that the upstream (north) San Rafael Mountains play a critical role in the timing of the onset of the northeasterly winds, and this effect is particularly important in the eastern SYM (Duine et al, 2021).…”

Section: Observed Wind Patterns and Extremesmentioning

confidence: 99%

“…Another unique feature of the region is the downslope windstorm frequently observed on the southern SYM slopes. These cross-mountain (northerly) winds are known as "Sundowners" due to their typical onset near sunset (Ryan, 1991;Ryan, 1996;Blier, 1998;Cannon et al, 2017;Smith et al, 2018aSmith et al, , 2018bDuine et al, 2019Duine et al, , 2021Carvalho et al, 2020;Jones et al, 2021). Sundowners are infamous for their role in rapidly spreading wildfires that often disrupt the community of ~130,000 inhabitants living in coastal SB (Zigner et al, 2020).…”

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confidence: 99%

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Extreme winds and fire weather in coastal Santa Barbara County, CA: An observational analysis

Zigner

Carvalho

Jones

et al. 2021

Intl Journal of Climatology

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Coastal Santa Barbara (SB) County in Southern California, characterized by a Mediterranean climate and complex topography, is a region prone to downslope windstorms that create critical fire weather conditions and rapidly spread wildfires. The Santa Ynez Mountains, oriented from east to west, rise abruptly from the coast, separating air masses from the ocean and the Santa Ynez Valley. The juxtaposition of these geographic features generates spatiotemporally variable wind regimes. This study analyzes diurnal-to-seasonal wind cycles and extremes in this region using hourly data from eight weather stations and four buoys for the period 1998-2019. Data from a vertical wind profiler at the Santa Barbara airport in Goleta, CA was extracted from August 2016 to September 2020. Air temperature, dew point temperature, and the Fosberg fire weather index are examined at land stations. We show that cycles in wind speed vary spatiotemporally; mountain (valley and coastal) stations exhibit a pronounced semiannual (annual) cycle, and wind maxima is observed during the evening (afternoon) at mountain (valley and coastal) stations. Differences in wind speed percentiles were evident among stations, particularly at and above the 75th percentile. Strong winds recorded at buoys were significantly correlated (between r = 0.3-0.5) to land stations. However, cross-correlational analysis did not reveal any temporal lags between mountain stations and buoys. Distributions of temperature and dew point during extreme winds differed between east and west mountain stations. Significant fire weather conditions were most frequent at mountain stations in Refugio and Montecito, with 5% occurrence in the spring and over 3% occurrence in fall. Weaker summertime winds lowered fire weather conditions at Montecito in the summer.extreme winds, fire weather, Mediterranean climate, mountain winds, Southern California, Sundowner winds, thermally driven circulations | INTRODUCTIONCoastal Southern California is characterized by a Mediterranean climate, with dry summers and wet winters. Nonetheless, regional differences in climate are attributed to the complex terrain spanning the U.S. West Coast. Santa Barbara (SB) County, situated in Southern California, provides an example of a region where

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Section: Discussionmentioning

confidence: 99%

Section: Seasonal Cycles Diurnal Cycles and Sundowner Winds Observed ...mentioning

confidence: 99%

Section: Observed Wind Patterns and Extremesmentioning

confidence: 99%

Section: Observed Wind Patterns and Extremesmentioning

confidence: 99%

mentioning

confidence: 99%

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Extreme winds and fire weather in coastal Santa Barbara County, CA: An observational analysis

Zigner

Carvalho

Jones

et al. 2021

Intl Journal of Climatology

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Mesoscale patterns associated with two distinct heatwave events in coastal Santa Barbara, California, and their impact on local fire risk conditions

Duine¹,

Carvalho²,

Jones³

2022

Weather and Climate Extremes

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Local and Remote Effects of the Sub‐Grid Turbulent Orographic Form Drag on the Summer Monsoon Precipitation Over Eastern China

Zhou,

Huang,

et al. 2024

JGR Atmospheres

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The sub‐grid turbulent orographic form drag (STOFD) significantly affects the regional circulation and precipitation. This study explores the local and remote effects of the STOFD on the summer monsoon precipitation across Eastern China using the Regional Climate Model Version 4 adopting a STOFD scheme. Results indicate that the local and remote effects of the STOFD primarily influence the improvement of summer precipitation simulation in the Southeastern and Northern China, respectively. The local effects of the STOFD can lead to 37.1% and 10.7% reduction of the absolute error and the root mean square error (RMSE) of simulated summer precipitation in the Southeastern China with complex sub‐grid terrains. The remote effects of the STOFD within the Indochina Peninsula and Yunnan‐Guizhou Plateau result in the absolute error and RMSE of simulated summer precipitation in the Northern China with mild sub‐grid terrain decreased by 90.1% and 32.9%, respectively. Moreover, the remote effects of the STOFD within the Tianshan Mountains and Tibetan Plateau can clearly improve the simulated precipitation in both the Southeastern and Northern China. The disturbances generated by the local effects of the STOFD are more locally concentrated than those produced by the STOFD remote effects, leading to a more significant improvement of precipitation simulation in the Southeastern China. While the disturbances resulted from the remote effects of the STOFD affect the summer precipitation in both the Southeastern and Northern China obviously. This study highlights the significance of the remote effects of the STOFD in improving the summer precipitation simulation in Eastern China.

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The Effect of Upstream Orography on the Onset of Sundowner Winds in Coastal Santa Barbara, CA

Cited by 5 publications

References 37 publications

Extreme winds and fire weather in coastal Santa Barbara County, CA: An observational analysis

Extreme winds and fire weather in coastal Santa Barbara County, CA: An observational analysis

Mesoscale patterns associated with two distinct heatwave events in coastal Santa Barbara, California, and their impact on local fire risk conditions

Local and Remote Effects of the Sub‐Grid Turbulent Orographic Form Drag on the Summer Monsoon Precipitation Over Eastern China

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