scholarly journals Dynamical analysis of sea-breeze hodograph rotation in Sardinia

2014 ◽  
Vol 14 (16) ◽  
pp. 22881-22904
Author(s):  
N. Moisseeva ◽  
D. G. Steyn
Keyword(s):  
Sea Breeze ◽  
Dynamical Analysis ◽  
Complex Topography ◽  
Coastal Zones ◽  
Wind Fields ◽  
Clockwise Rotation ◽  
Near Surface ◽  
Sea Breezes ◽  
Horizontal Momentum ◽  
Diurnal Rotation

Abstract. This study investigates the diurnal evolution of sea-breeze rotation over an island in the mid-latitudes. Earlier research on sea-breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anti-clockwise rotation. A non-hydrostatic fully compressible numerical model (WRF) is used to simulate wind fields on and around the island on previously-studied sea-breeze days and is shown to accurately capture the circulation on all coasts. Diurnal rotation of wind is examined and patterns of clockwise and anti-clockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography, yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with complex topography and/or coastline.

scholarly journals Dynamical analysis of sea-breeze hodograph rotation in Sardinia

2014 ◽  
Vol 14 (24) ◽  
pp. 13471-13481 ◽  
Author(s):  
N. Moisseeva ◽  
D. G. Steyn
Keyword(s):  
Sea Breeze ◽  
Dynamical Analysis ◽  
Coastal Zones ◽  
Wind Fields ◽  
Near Surface ◽  
Sea Breezes ◽  
Middle Latitudes ◽  
Anticlockwise Rotation ◽  
Horizontal Momentum ◽  
Diurnal Rotation

Abstract. This study investigates the diurnal evolution of sea-breeze (SB) rotation over an island at the middle latitudes. Earlier research on sea breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anticlockwise rotation. A non-hydrostatic fully compressible numerical model (WRF) is used to simulate wind fields on and around the island on previously studied sea-breeze days, and is shown to capture the circulation on all coasts accurately. Diurnal rotation of wind is examined, and patterns of clockwise and anticlockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with a complex topography and/or coastline.

scholarly journals Toward Improved Forecasts of Sea-Breeze Horizontal Convective Rolls at Super High Resolutions. Part II: The Impacts of Land Use and Buildings

2015 ◽  
Vol 143 (5) ◽  
pp. 1873-1894 ◽  
Author(s):  
Guixing Chen ◽  
Xinyue Zhu ◽  
Weiming Sha ◽  
Toshiki Iwasaki ◽  
Hiromu Seko ◽  
...  
Keyword(s):  
Land Use ◽  
Sea Breeze ◽  
Secondary Flows ◽  
Wake Flow ◽  
Near Surface ◽  
Sea Breezes ◽  
Regional Features ◽  
Secondary Circulations ◽  
Forecast Models ◽  
Convective Rolls

Abstract Horizontal convective rolls form in coastal areas around Sendai Airport during sea-breeze events. Using a building-resolving computational fluid dynamics model nested in an advanced forecast system with a data assimilation scheme, the authors perform a series of sensitivity experiments to investigate the impacts of land use and buildings on these rolls. The results show that the roll positions, intensities, and structures are significantly affected by variations in land use and the presence of buildings. Land-use heterogeneity is responsible for generating rolls with evident regional features. Major rolls tend to develop downwind of warm surfaces, and they dominate over neighboring rolls; thus, a heterogeneity-scale mode is imposed on the inherent roll wavelength. The roll’s rapid growth is attributable to warm surfaces that initiate a strong coupling among turbulent thermals, convective updrafts, pressure perturbations, and secondary flows in sea breezes. The heterogeneity-induced features differ considerably from the nearly homogeneous features that form over uniform surfaces. Additionally, the wake flow behind buildings helps organize near-surface warm air into streamwise bands that drive streaky ejections. The building-induced turbulence acts to modify secondary flows and displace roll updrafts toward building wakes. Such effects are most effective over villages with scattered houses that are aligned with the ambient wind. Building signatures are elongated in downwind open areas due to sustained secondary circulations. An analysis of turbulent kinetic energy shows that both land use and buildings regulate energy generation and transport, resulting in a clear response in roll growth. Thus, including complex surfaces in forecast models helps determine detailed characteristics and structures of roll convection over coastal regions.

scholarly journals A numerical investigation of the influence of land-sea breeze on the atmospheric effluents released at a coastal site

MAUSAM ◽  
2022 ◽  
Vol 46 (4) ◽  
pp. 393-400
Author(s):  
R. VENKATESAN
Keyword(s):  
Boundary Layer ◽  
Sea Breeze ◽  
Boussinesq Approximation ◽  
Internal Boundary Layer ◽  
Momentum Equation ◽  
Internal Boundary ◽  
Sea Breezes ◽  
Hydrostatic Approximation ◽  
Continuous Point ◽  
Horizontal Momentum

ABSTRACT. Mesoscale features of a coastal atmospheric boundary layer such as the land-sea circulation and the thermal internal boundary layer (TIBL) structure have been simulated using a two-dimensional numerical boundary layer model. Using Boussinesq approximation for horizontal momentum equations and hydrostatic approximation for vertical momentum equation the model solves the 'shallow water' equations year over a grid domain 80 km length on either side of the coastline and 2 km height. The influence of the land-sea breezes on the dispersion of pollutants released from a continuous point source located at the roast has been studied. The fumigation of pollutants from an offshore source into TIBL over the land has also been illustrated. The limitations associated with the model are also discussed.    

scholarly journals Frequency and Characteristics of Inland Advecting Sea Breezes in the Southeast United States

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 950
Author(s):  
Brian Viner ◽  
Stephen Noble ◽  
Jian-Hua Qian ◽  
David Werth ◽  
Paul Gayes ◽  
...  
Keyword(s):  
Sea Breeze ◽  
Dew Point ◽  
Savannah River ◽  
Atmospheric Measurements ◽  
Southeast United States ◽  
Near Surface ◽  
Sea Breezes ◽  
Synoptic Classification ◽  
Synoptic Conditions ◽  
Cloud Development

Sea breezes have been observed to move inland over 100 km. These airmasses can be markedly different from regional airmasses, creating a shallow layer with differences in humidity, wind, temperature and aerosol characteristics. To understand their influence on boundary layer and cloud development on subsequent days, we identify their frequency and characteristics. We visually identified sea breeze fronts on radar passing over the Savannah River Site (SRS) between March and October during 2015–2019. The SRS is ~150 km from the nearest coastal location; therefore, our detection suggests further inland penetration. We also identified periods when sea breeze fronts may have passed but were not visually observed on radar due to the shallow sea breeze airmass remaining below the radar beam elevation that ranges between approximately 1–8 km depending on the beam angle and radar source (Columbia, SC or Charleston, SC). Near-surface atmospheric measurements indicate that the dew point temperature increases, the air temperature decreases, the variation in wind direction decreases and the aerosol size increases after sea breeze frontal passage. A synoptic classification procedure also identified that inland moving sea breezes are more commonly observed when the synoptic conditions include weak to moderate offshore winds with an average of 35 inland sea breezes occurring each year, focused primarily in the months of April, May and June.

scholarly journals A Long-Term Study of Sea-Breeze Characteristics: A Case Study of the Coastal City of Adelaide

2019 ◽  
Vol 58 (2) ◽  
pp. 385-400 ◽  
Author(s):  
Zahra Pazandeh Masouleh ◽  
David John Walker ◽  
John McCauley Crowther
Keyword(s):  
Wind Speed ◽  
Air Temperature ◽  
Sea Breeze ◽  
Detection Algorithm ◽  
Near Surface ◽  
Sea Breezes ◽  
Long Term Study ◽  
Average Maximum ◽  
Hourly Data ◽  
Maximum Air Temperature

AbstractThe sea-breeze characteristics of the Adelaide, Australia, coastline have been studied by applying a sea-breeze detection algorithm to 3- and 6-hourly meteorological records of near-surface and upper-air data at Adelaide Airport from 1955 to 2007. The sea breeze is typically a westerly gulf breeze combined with a later-occurring southerly ocean breeze. Regression analysis showed a significant increasing trend in the intensity of sea breezes but not in their frequency. Over the 52-yr period, there was an average increase of 1 m s−1 in zonal and 0.7 m s−1 in meridional sea-breeze wind speed components. The annually and seasonally averaged maximum wind speeds on sea-breeze days increased significantly over the 52-yr period of the study by 0.65 m s−1 for the whole year, 0.48 m s−1 in spring, 1.02 m s−1 in summer, and 1.10 m s−1 in autumn. A comparison of hourly data for 1985–95 with those for 1996–2007 showed frequencies of sea-breeze onset times less than 4 h from sunrise increasing from 29% to 36%, durations greater than 8 h increasing from 51% to 59%, and times of maximum sea breeze between 2 and 6 h after sunrise increasing from 44% to 50%. The monthly frequency of sea breezes was found to increase by 2.8 percentage points for each degree Celsius rise in monthly average maximum air temperature at Adelaide Airport. The meridional ocean-breeze wind speed, unlike the gulf-breeze wind speed, is also correlated with maximum air temperature at Adelaide Airport.

scholarly journals Verifying Operational Forecasts of Land–Sea-Breeze and Boundary Layer Mixing Processes

2020 ◽  
Vol 35 (4) ◽  
pp. 1427-1445
Author(s):  
Ewan Short
Keyword(s):  
Boundary Layer ◽  
Diurnal Cycle ◽  
Spatial Scales ◽  
Sea Breeze ◽  
Absolute Error ◽  
Wind Fields ◽  
Mixing Processes ◽  
Relative Contribution ◽  
The Mean ◽  
Diurnal Wind

AbstractForecasters working for Australia’s Bureau of Meteorology (BoM) produce a 7-day forecast in two key steps: first they choose a model guidance dataset to base the forecast on, and then they use graphical software to manually edit these data. Two types of edits are commonly made to the wind fields that aim to improve how the influences of boundary layer mixing and land–sea-breeze processes are represented in the forecast. In this study the diurnally varying component of the BoM’s official wind forecast is compared with that of station observations and unedited model guidance datasets. Coastal locations across Australia over June, July, and August 2018 are considered, with data aggregated over three spatial scales. The edited forecast produces a lower mean absolute error than model guidance at the coarsest spatial scale (over 50 000 km2), and achieves lower seasonal biases over all spatial scales. However, the edited forecast only reduces errors or biases at particular times and locations, and rarely produces lower errors or biases than all model guidance products simultaneously. To better understand physical reasons for biases in the mean diurnal wind cycles, modified ellipses are fitted to the seasonally averaged diurnal wind temporal hodographs. Biases in the official forecast diurnal cycle vary with location for multiple reasons, including biases in the directions that sea breezes approach coastlines, amplitude biases, and disagreement in the relative contribution of sea-breeze and boundary layer mixing processes to the mean diurnal cycle.

scholarly journals Influence of Complex Terrain on Near-Surface Turbulence Structures over Loess Plateau

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 930
Author(s):  
Jiening Liang ◽  
Qi Guo ◽  
Zhida Zhang ◽  
Min Zhang ◽  
Pengfei Tian ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Complex Terrain ◽  
Longitudinal Velocity ◽  
Complex Topography ◽  
Horizontal Scale ◽  
Flux Footprint ◽  
Near Surface ◽  
Turbulence Structures ◽  
Vertical Scale ◽  
Surface Turbulence

To study the influence of complex terrain with different scales on the structure of near-surface turbulence, the turbulence observational data from Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) were analyzed. SACOL is located in typical Loess Plateau topography. The terrain around the site varies greatly with the direction. Representative data from the Northeast, Southeast, Southwest, and Northwest were selected to study the structure characteristics of the near surface turbulence. The complex topography within the flux footprint enhances the vertical scale of turbulence σw and thereby increases the vertical–longitudinal ratio of turbulence Ar. While the turbulent horizontal scale σu is also significantly affected by the distant terrain beyond the flux footprint. The upwind terrain undulation increases σu and reduces Ar. Affected by the complex terrain, the ratio of the spectrum of the vertical velocity to that of the longitudinal velocity, Sw(n)/Su(n), is far less than 4/3 in the southwest direction, and the turbulence is significantly anisotropic.

Diurnal and Seasonal Lightning Variability over the Gulf Stream and the Gulf of Mexico

2015 ◽  
Vol 72 (7) ◽  
pp. 2657-2665 ◽  
Author(s):  
Katrina S. Virts ◽  
John M. Wallace ◽  
Michael L. Hutchins ◽  
Robert H. Holzworth
Keyword(s):  
Gulf Of Mexico ◽  
Diurnal Cycle ◽  
Gulf Stream ◽  
Land Surface ◽  
Southeastern United States ◽  
Surface Wind ◽  
Tropical Rainfall Measuring Mission ◽  
Sea Breeze ◽  
Near Surface ◽  
Early Evening

Recent observations from the World Wide Lightning Location Network (WWLLN) reveal a pronounced lightning maximum over the warm waters of the Gulf Stream that exhibits distinct diurnal and seasonal variability. Lightning is most frequent during summer (June–August). During afternoon and early evening, lightning is enhanced just onshore of the coast of the southeastern United States because of daytime heating of the land surface and the resulting sea-breeze circulations and convection. Near-surface wind observations from the Quick Scatterometer (QuikSCAT) satellite indicate divergence over the Gulf of Mexico and portions of the Gulf Stream at 1800 LT, at which time lightning activity is suppressed there. Lightning frequency exhibits a broad maximum over the Gulf Stream from evening through noon of the following day, and QuikSCAT wind observations at 0600 LT indicate low-level winds blowing away from the continent and converging over the Gulf Stream. Over the northern Gulf of Mexico, lightning is most frequent from around sunrise through late morning. During winter, lightning exhibits a weak diurnal cycle over the Gulf Stream, with most frequent lightning during the evening. Precipitation rates from a 3-hourly gridded dataset that incorporates observations from Tropical Rainfall Measuring Mission (TRMM), as well as other satellites, exhibit a diurnal cycle over the Gulf Stream that lags the lightning diurnal cycle by several hours.

scholarly journals Impact of topography on black carbon transport to the southern Tibetan Plateau during the pre-monsoon season and its climatic implication

2020 ◽  
Vol 20 (10) ◽  
pp. 5923-5943 ◽  
Author(s):  
Meixin Zhang ◽  
Chun Zhao ◽  
Zhiyuan Cong ◽  
Qiuyan Du ◽  
Mingyue Xu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Monsoon Season ◽  
Radiative Heating ◽  
The Tibetan Plateau ◽  
Complex Topography ◽  
Meridional Transport ◽  
Near Surface ◽  
Mass Volume

Abstract. Most previous modeling studies about black carbon (BC) transport and its impact over the Tibetan Plateau (TP) conducted simulations with horizontal resolutions coarser than 20 km that may not be able to resolve the complex topography of the Himalayas well. In this study, the two experiments covering all of the Himalayas with the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) at the horizontal resolution of 4 km but with two different topography datasets (4 km complex topography and 20 km smooth topography) are conducted for pre-monsoon season (April 2016) to investigate the impacts of topography on modeling the transport and distribution of BC over the TP. Both experiments show the evident accumulation of aerosols near the southern Himalayas during the pre-monsoon season, consistent with the satellite retrievals. The observed episode of high surface BC concentration at the station near Mt. Everest due to heavy biomass burning near the southern Himalayas is well captured by the simulations. The simulations indicate that the prevailing upflow across the Himalayas driven by the large-scale westerly and small-scale southerly circulations during the daytime is the dominant transport mechanism of southern Asian BC into the TP, and it is much stronger than that during the nighttime. The simulation with the 4 km topography resolves more valleys and mountain ridges and shows that the BC transport across the Himalayas can overcome the majority of mountain ridges, but the valley transport is more efficient. The complex topography results in stronger overall cross-Himalayan transport during the simulation period primarily due to the strengthened efficiency of near-surface meridional transport towards the TP, enhanced wind speed at some valleys and deeper valley channels associated with larger transported BC mass volume. This results in 50 % higher transport flux of BC across the Himalayas and 30 %–50 % stronger BC radiative heating in the atmosphere up to 10 km over the TP from the simulation with the 4 km complex topography than that with the 20 km smoother topography. The different topography also leads to different distributions of snow cover and BC forcing in snow. This study implies that the relatively smooth topography used by the models with resolutions coarser than 20 km may introduce significant negative biases in estimating light-absorbing aerosol radiative forcing over the TP during the pre-monsoon season. Highlights. The black carbon (BC) transport across the Himalayas can overcome the majority of mountain ridges, but the valley transport is much more efficient during the pre-monsoon season. The complex topography results in stronger overall cross-Himalayan transport during the study period primarily due to the strengthened efficiency of near-surface meridional transport towards the TP, enhanced wind speed at some valleys and deeper valley channels associated with larger transported BC mass volume. The complex topography generates 50 % higher transport flux of BC across the Himalayas and 30 %–50 % stronger BC radiative heating in the atmosphere up to 10 km over the Tibetan Plateau (TP) than the smoother topography, which implies that the smooth topography used by the models with relatively coarse resolution may introduce significant negative biases in estimating BC radiative forcing over the TP during the pre-monsoon season. The different topography also leads to different distributions of snow cover and BC forcing in snow over the TP.

scholarly journals Investigation of local meteorological events and their relationship with ozone and aerosols during an ESCOMPTE photochemical episode

2006 ◽  
Vol 24 (11) ◽  
pp. 2809-2822 ◽  
Author(s):  
P. Augustin ◽  
H. Delbarre ◽  
F. Lohou ◽  
B. Campistron ◽  
V. Puygrenier ◽  
...  
Keyword(s):  
Transit Time ◽  
Prediction Models ◽  
Sea Breeze ◽  
City Centre ◽  
Breeze Circulation ◽  
Sea Breezes ◽  
Pollutant Concentrations ◽  
Time Space ◽  
Marine Air ◽  
The City

Abstract. The international ESCOMPTE campaign, which took place in summer 2001 in the most highly polluted French region, was devoted to validate air pollution prediction models. Surface and remote sensing instruments (Lidar, Radar and Sodar) were deployed over the Marseille area, along the Mediterranean coast, in order to investigate the fine structure of the sea-breeze circulation and its relationship with the pollutant concentrations. The geographical situation of the Marseille region combines a complex coastline and relief which both lead to a peculiar behaviour of the sea-breeze circulation. Several local sea breezes, perpendicular to the nearest coastline, settled in during the morning. In the afternoons, when the thermal gradient between the continental and marine surface grows up, a southerly or a westerly sea breeze may dominate. Their respective importance is then a function of time, space and altitude. Furthermore, an oscillation of the westerly sea breeze with a period of about 3 h is also highlighted. We show that these dynamical characteristics have profound influences on the atmospheric boundary-layer (ABL) development and on pollutant concentrations. In fact, the direction and intensity of the sea-breeze determine the route and the transit time of the stable marine air flow over the continental surface. Thus, the ABL depth may exhibit several collapses correlated with the westerly sea-breeze pulsation. The ozone and aerosol concentrations are also related to the dynamical features. In the suburbs and parts of the city under pulsed sea breezes, a higher ABL depth and higher ozone concentrations are observed. In the city centre, this relationship between pulsed sea-breeze intensity and ozone concentration is different, emphasising the importance of the transit time and also the build-up of pollutants in the marine air mass along the route. Finally, the variations of aerosol concentration are also described according to the breeze direction.

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