Modelling sea breeze climatologies and interactions on coasts in the southern North Sea: Implications for offshore wind energy

Current understanding of the behaviour of sea breezes in the offshore environment is limited but rapidly requires improvement due, not least, to the expansion of the offshore wind energy industry. Here we report on contrasting characteristics of three sea-breeze types on five coastlines around the southern North Sea from an 11 year model-simulated climatology. We present and test an identification method which distinguishes sea-breeze types which can, in principle, be adapted for other coastlines around the world. The coherence of the composite results for each type demonstrates that the method is very effective in resolving and distinguishing characteristics and features. Some features, such as jets and calm zones, are shown to influence offshore wind farm development areas, including the sites of the proposed wind farms up to 200 km offshore. A large variability in sea-breeze frequency between neighbouring coastlines of up to a factor of 3 is revealed. Additionally, there is a strong association between sea-breeze type on one coastline and that which may form coincidentally on another nearby. This association can be as high as 86% between, for example, the North Norfolk and East Norfolk coasts. We show, through associations between sea-breeze events on coastlines with contrasting orientations, that each coastline can be important for influencing the wind climate of another. Furthermore, we highlight that each sea-breeze type needs separate consideration in wind power resource assessment and that future larger turbines will be more sensitive to sea-breeze impacts

The potential of the sea breeze for wind energy generation in peri-urban coastal areas using small wind turbines

This work investigates the potential of the sea breeze for wind energy generation with small wind turbines. For this purpose, we used wind data recorded in the Llobregat Delta (NE of the Iberian Peninsula) from 1993 to 2010 and turbine power curves obtained from QBlade, FAST and AeroDyn freeware tools, and from the manufacturer. The HP-600W turbine, with hub-height 8 m, would deliver 126 kWh in a year (53 kWh during the sea breeze period, i.e., March 1 to September 30, 10 to 19h LT), with average power of 14 W (27 W). The results for the entire year agree with data measured in situ in 2015, but it is not the case for the sea breeze period. Therefore, more research is necessary to validate completely the proposed approach, and to confirm the real potential of the sea breeze for micro-generation in a peri-urban coastal area like the one under study, where large wind farms are not feasible.Peer ReviewedPostprint (author's final draft

An assessment of the sea breeze energy potential using small wind turbines in peri-urban coastal areas

From wind speed data recorded hourly at 2 m high during 18 years (1993-2010) in the Llobregat Delta (15 km south of Barcelona city; northeast of the Iberian Peninsula), wind speed distributions at 10 m high were computed for the whole year and for the sea breeze period (from March 1 to September 30, from 10 to 19 local time). Weibull probability density functions fitted to the distributions were used to assess the wind energy generated by two off-grid small wind turbines: the IT-PE-100 and the HP-600W. Results from FAST and AeroDyn simulation tools were compared with those obtained by applying measured wind speeds to manufacturer power curves. Using manufacturer data, the IT-PE-100 would deliver 132 kWh during the whole year (70 kWh during the sea breeze period). From the simulations, the IT-PE-100 would deliver 155 kWh during the whole year (80 kWh during the sea breeze period). It is concluded that the sea-breeze is an interesting wind energy resource for micro-generation, not only in the Mediterranean basin but in other areas of the world with similar wind regimes, and particularly in peri-urban coastal areas where large-scale wind farms cannot be implemented.Peer ReviewedPostprint (published version

Characterizing the Frequency and Seasonal Dependence of the Sea Breeze in Houston, Texas and Its Impact on Surface Ozone

Sea breezes arise from temperature differences between land and an adjacent body of water, forming a thermally direct circulation within the boundary layer. During summer, the resulting circulation carries air offshore during the nighttime and early morning and onshore during the afternoon. Banta et al. [2005] noted the impact of recirculation of pollution on high ozone events in Houston. This study characterizes the frequency of flow reversals that accompany the arrival of sea breeze fronts in Houston and the seasonal dependence of that frequency. Furthermore, we quantitatively analyze the effect of the sea breeze on ozone concentrations in the Houston area

The central New England sea breeze study

The synoptic and mesoscale environments conducive to the formation of sea breezes were examined, as well as the spatial and temporal evolution of sea-breeze circulations, gravity currents, and fronts along the central New England coast. Sea breeze events were defined as occurring when the observed surface wind direction began the day outside the southeast quadrant, shifted to southeast by afternoon, then shifted back out of the southeast quadrant in the evening, driven by mesoscale, insolation-induced cross-shore temperature gradients. The meso-alpha (200--2000 km) sea-breeze forcing in the study area was defined as a combination of the cross-shore potential temperature gradient (deltatheta/deltax) that may drive sea breezes inland, and the cross-shore geostrophic wind component (uG) that may resist the landward movement of sea breezes. It was found that the peak values and temporal evolution of the meso-alpha forcing were dependent on the locations and relative dominance of synoptic-scale surface pressure systems in the eastern United States. These conclusions can often be used to accurately predict sea-breeze events, and their time of onset, using surface observations recorded in the early morning. The forecasting technique is adaptable to any coastal location in the world. Meso-beta (20--200 km) horizontal variations in the sea-breeze circulation, gravity current, and front were compared to deltatheta/deltax and the cross-shore wind component at 925 hPa (u925) in the study area. The latter was substituted for uG because it also accounts for the synoptic-scale temperature gradient between the surface and 925 hPa via the thermal wind relation. Near-surface potential temperature (isentropic) fields were used to examine the sea-breeze gravity current, and the wind (kinematic) fields were used to examine the sea-breeze circulation. Isentropic gradient fields were used to examine the thermodynamic sea-breeze front, and convergence fields were used to examine the kinematic sea-breeze front. It was found that the most developed pattern the sea-breeze gravity current achieved, the time of the sea-breeze circulation\u27s first contact with the coast and its most advanced inland distance, and the peak meso-beta strength of the sea-breeze frontal components were all functions of the meso-alpha forcing

Impact of Afternoon Thunderstorms on the Land–Sea Breeze in the Taipei Basin during Summer: An Experiment

Environmental conditions for the roughly three million people living in the Taipei basin of Taiwan are greatly affected by the land–sea breeze and afternoon thunderstorm activities. A new perspective on the land–sea breeze life cycle and how it is affected by afternoon thunderstorm activity in the Taipei basin during the dry season is provided. During the summer monsoon break–revival phase, about 75% of rainfall in the Taipei basin is produced by afternoon thunderstorms triggered by sea-breeze interactions with the mountains to the south of this basin. Because the basic characteristics of the land–sea breeze and the changes it undergoes through the influence of afternoon thunderstorms have not been comprehensively analyzed/documented, a mini–field experiment was conducted during the summers of 2004 and 2005 to explore these aspects of the land–sea breeze in this basin. Thunderstorm rainfall is found to change not only the basin’s land–sea-breeze life cycle, but also its ventilation mechanism. On the nonthunderstorm day, the sea breeze supplies the open-sea fresh air for about 8 h during the daytime, but the land breeze persists on the thunderstorm day from afternoon to the next morning, acting to sweep polluted urban air out of the basin

Sea breeze: Induced mesoscale systems and severe weather

Sea-breeze-deep convective interactions over the Florida peninsula were investigated using a cloud/mesoscale numerical model. The objective was to gain a better understanding of sea-breeze and deep convective interactions over the Florida peninsula using a high resolution convectively explicit model and to use these results to evaluate convective parameterization schemes. A 3-D numerical investigation of Florida convection was completed. The Kuo and Fritsch-Chappell parameterization schemes are summarized and evaluated

A case study of boundary layer ventilation by convection and coastal processes

It is often assumed that ventilation of the atmospheric boundary layer is weak in the absence of fronts, but is this always true? In this paper we investigate the processes responsible for ventilation of the atmospheric boundary layer during a nonfrontal day that occurred on 9 May 2005 using the UK Met Office Unified Model. Pollution sources are represented by the constant emission of a passive tracer everywhere over land. The ventilation processes observed include shallow convection, turbulent mixing followed by large-scale ascent, a sea breeze circulation and coastal outflow. Vertical distributions of tracer are validated qualitatively with AMPEP (Aircraft Measurement of chemical Processing Export fluxes of Pollutants over the UK) CO aircraft measurements and are shown to agree impressively well. Budget calculations of tracers are performed in order to determine the relative importance of these ventilation processes. Coastal outflow and the sea breeze circulation were found to ventilate 26% of the boundary layer tracer by sunset of which 2% was above 2 km. A combination of coastal outflow, the sea breeze circulation, turbulent mixing and large-scale ascent ventilated 46% of the boundary layer tracer, of which 10% was above 2 km. Finally, coastal outflow, the sea breeze circulation, turbulent mixing, large-scale ascent and shallow convection together ventilated 52% of the tracer into the free troposphere, of which 26% was above 2 km. Hence this study shows that significant ventilation of the boundary layer can occur in the absence of fronts (and thus during high-pressure events). Turbulent mixing and convection processes can double the amount of pollution ventilated from the boundary layer

Simulating Sea Breeze Type Climatologies: Implications for Wind Energy, Weather Forecasting and Sailing in the Southern North Sea

The energy industry is currently undergoing a revolution. In the southern North Sea, renewable energy production targets, set by European governments to counter growing concerns over climate change, have sparked an initiative to rapidly construct a large number of offshore wind farms. To meet the targets, the industry must overcome many challenges, one of which is to capitalize on the coastal and offshore wind resource. One particular relative component of the sea breeze system, including the contrasting individual sea breeze types, in the offshore environment and requires further study. Here it is shown through idealized model simulations, that each sea breeze type has distinctive characteristics and that the scales involved have the potential to influence opposing coastlines at length scales equivalent to the southern North Sea. It is revealed, through model sensitivity experiments, that variations due to the choice of model boundary layer scheme significantly alter the characteristics of the sea breeze and verification against onshore and offshore measurement data is conducted in order to quantify model performance. A unique simulated climatology of sea breezes is constructed for 5 different coastlines in the southern North Sea spanning from 2002-2012 using an identification method created to distinguish between the sea breeze types. Crucially, it is found that the frequency of sea breezes is highly dependant on coastal orientation with respect to the gradient wind and that total sea breeze frequency varies by more than a factor of two between coastlines. Furthermore, sea breezes forming on one coastline are shown to directly influence those on another. In order to quantify the impact of each sea breeze on wind energy, the climatology is used to assess wind power production on both spatial and temporal scales. It is found that sea breezes do have the potential to significantly impact offshore wind energy production, including the proposed round 3 farms which are further offshore. Furthermore, the precise impact is dependant on sea breeze type. Pure sea breezes reduce power output through the generation of offshore calm zones, whilst corkscrew sea breezes can add to the wind resource through the formation of coastal jets. The lesser known corkscrew sea breeze is attributed to 70% of the total power contribution of all sea breeze events. As turbines increase both in size and power capabilities, it is also demonstrated that the impact of sea breezes on wind turbine output will be greater in the future

Occurrence of Kelvin-Helmholtz Billows in Sea-breeze Circulations

Centred at the interface between the sea-breeze and the return flow aloft, Kelvin-Helmholtz billows (KHB) are an important feature of the turbulent structure of some sea-breeze circulations (SBCs). In other SBCs, there are no prominent KHBs observed. Factors governing the appearance of billows are determined from a database of 139 sea breezes, constructed from two years of summertime surface observations at a site on the south coast of England. Post-frontal oscillations occur in the surface data for some SBCs and are interpreted as indicating possible KHBs aloft. The SBCs are formed under a wide range of synoptic conditions, enabling various measures of possible billow occurrence to be related to properties of the large-scale, ambient flow. Consistent with laboratory experiments of density currents, KHBs are suppressed for propagation into a head wind and enhanced with a tail wind. They are also found to be enhanced for stronger ambient wind speeds, while large-scale coast-parallel flow is effective in suppressing the billows