Diagnostics for Near-Surface Wind Response to the Gulf Stream in a Regional Atmospheric Model*

Takatama, Kohei; Minobe, Shoshiro; Inatsu, Masaru; Small, R. Justin

doi:10.1175/jcli-d-13-00668.1

Cited by 22 publications

(18 citation statements)

References 54 publications

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“…This is consistent with previous observations (Minobe et al, ) and numerical works (Takatama et al, , ), where the PA mechanism was found to be dominant over large‐scale structures such as the western boundary currents. Thus, for a submesoscale structure SST field, where the variations of the forcing temperature felt by the air mass moving above it can be fast, the marine atmospheric boundary layer filters out the high frequencies through the PA mechanism.…”

Section: Discussionsupporting

confidence: 93%

“…All the above studies focus on structures with typical length scales of O (100km) and time scales of O (months). On the same climatological time scales, Takatama et al (, ) introduce some analytical diagnostics that help to discriminate the contribution of the two mechanisms outlined above, PA and DMM, in the control of the surface layer vertically integrated wind magnitude, wind convergence, and wind curl. At shorter time scales, idealized numerical studies focus on the understanding of the basic mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Role of SST Patterns on Surface Wind Modulation of a Heavy Midlatitude Precipitation Event

2018

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The mechanisms controlling the influence of the sea surface temperature (SST) structure on the surface winds are studied by means of numerical simulations run with a nonhydrostatic fully compressible state‐of‐the‐art numerical model in a realistic midlatitudes setup, leading to the 9 October 2014 Genoa heavy rainfall event. Starting from a simulation with high‐resolution submesoscale eddy‐permitting SST field, the surface temperature boundary conditions are changed to enhance, reduce, or smooth the SST gradient. It is found that the marine atmospheric boundary layer responds to the submesoscale SST forcing structures over time scales of the order of hours. In particular, through the downward momentum mixing mechanism, the presence of SST horizontal gradients impacts the spatial structure of the surface wind convergence, which can displace the convective heavy rain bands that develop over the sea.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Role of SST Patterns on Surface Wind Modulation of a Heavy Midlatitude Precipitation Event

2018

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“…At mid-latitudes the importance of the pressure term compared to vertical mixing still remains unclear, largely depending on the spatial scales (Small et al 2008) but also on the region of interest (Shimada and Minobe 2011) or on the season that is considered (Takatama et al 2015). Moreover the two mechanisms can be active together to force a surface divergence response.…”

Section: Introductionmentioning

confidence: 99%

Response of Surface Wind Divergence to Mesoscale SST Anomalies under Different Wind Conditions

Foussard

Lapeyre

Plougonven

2019

Journal of the Atmospheric Sciences

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The response of the atmospheric boundary layer to mesoscale sea surface temperature (SST) is often characterized by a link between wind stress divergence and downwind SST gradients. In this study, an idealized simulation representative of a storm track above a prescribed stationary SST field is examined in order to determine in which background wind conditions that relationship occurs. The SST field is composed of a midlatitude large-scale frontal zone and mesoscale SST anomalies. It is shown that the divergence of the surface wind can correlate either with the Laplacian of the atmospheric boundary layer temperature or with the downwind SST gradient. The first case corresponds to background situations of weak winds or of unstable boundary layers, and the response is in agreement with an Ekman balance adjustment in the boundary layer. The second case corresponds to background situations of stable boundary layers, and the response is in agreement with downward mixing of momentum. Concerning the divergence of the wind stress, it generally resembles downwind SST gradients for stable and unstable boundary layers, in agreement with past studies. For weak winds, a correlation with the temperature Laplacian is, however, found to some extent. In conclusion, our study reveals the importance of the large-scale wind conditions in modulating the surface atmospheric response with different responses in the divergences of surface wind and wind stress.

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“…For instance, studies in Turkey (1975Turkey ( to 2006, Brazil (1986 to 2011), China (1969China ( to 2005 and Canada (1940Canada ( to 2006 found that most stations were experiencing a decrease in seasonal and annual mean wind speed. [10][11][12][13] In contrast, wind speed trends have increased in several other regions such as over the global oceans and the Baltic region. 11,14 Most such changes were strongly linked to fluctuations in synoptic-scale circulation.…”

Section: Introductionmentioning

confidence: 99%

Wind speed characteristics and implications for wind power generation: Cape regions, South Africa

Wright¹,

Grab²

2017

S. Afr. J. Sci.

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Spatio-temporal dynamics of near-surface wind speeds were examined across the Northern, Western and Eastern Cape regions of South Africa. The regions assessed were geographically subdivided into three zones: coastal, coastal hinterland and inland. Wind speed data (10 m) were evaluated at monthly, seasonal, annual and zonal resolutions, with the aim to establish wind speed attributes and trends. Data from 19 weather stations with high-resolution wind records between 1995 and 2014 were evaluated. The majority of stations (79%) recorded a decrease in mean annual wind speed over the study period. The mean rate of decrease across all stations over the 20-year period equates to -1.25%, quantifying to an annual decrease of -0.002 m/s/year (-0.06% pa). The largest seasonal decline of -0.006 m/s/year (-0.15% pa) was recorded in summer. Statistically significant declines in mean annual wind speed are somewhat more pronounced for the coastal zone (-0.003 m/s/year, -0.08% pa) than over interior regions (-0.002 m/s/year, -0.06% pa) for the study period. The largest decrease (-0.08% pa) was recorded for the coastal zone, followed by the inland zone (-0.06% pa), equating to an annual reduction in available energy of 0.18% pa and 0.09% pa, respectively. When considering all stations over the study period, the mean inter-annual variability is 3.11%. Despite such decreases in wind speed, the variance identified in this study would not have posed any risk to power generation from wind across the assessed stations, based on the period 1995 to 2014.

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Diagnostics for Near-Surface Wind Response to the Gulf Stream in a Regional Atmospheric Model*

Cited by 22 publications

References 54 publications

Role of SST Patterns on Surface Wind Modulation of a Heavy Midlatitude Precipitation Event

Role of SST Patterns on Surface Wind Modulation of a Heavy Midlatitude Precipitation Event

Response of Surface Wind Divergence to Mesoscale SST Anomalies under Different Wind Conditions

Wind speed characteristics and implications for wind power generation: Cape regions, South Africa

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