Showing papers on "Sea breeze published in 2018"

The monsoon system: Land–sea breeze or the ITCZ?

Abstract: For well over 300 years, the monsoon has been considered to be a gigantic land–sea breeze driven by the land–ocean contrast in surface temperature. In this paper, this hypothesis and its implications for the variability of the monsoon are discussed and it is shown that the observations of monsoon variability do not support this popular theory of the monsoon. An alternative hypothesis (whose origins can be traced to Blanford’s (1886) remarkably perceptive analysis) in which the basic system responsible for the Indian summer monsoon is considered to be the Intertropical Convergence Zone (ITCZ) or the equatorial trough, is then examined and shown to be consistent with the observations. The implications of considering the monsoon as a manifestation of the seasonal migration of the ITCZ for the variability of the Indian summer monsoon and for identification of the monsoonal regions of the world are briefly discussed.

Maritime continent coastlines controlling Earth’s climate

Abstract: During the Monsoon Asian Hydro−Atmosphere Scientific Research and Prediction Initiative (MAHASRI; 2006–16), we carried out two projects over the Indonesian maritime continent (IMC), constructing the Hydrometeorological Array for Intraseasonal Variation−Monsoon Automonitoring (HARIMAU; 2005–10) radar network and setting up a prototype institute for climate studies, the Maritime Continent Center of Excellence (MCCOE; 2009–14). Here, we review the climatological features of the world’s largest “regional” rainfall over the IMC studied in these projects. The fundamental mode of atmospheric variability over the IMC is the diurnal cycle generated along coastlines by land−sea temperature contrast: afternoon land becomes hotter than sea by clear-sky insolation before noon, with the opposite contrast before sunrise caused by evening rainfall-induced “sprinkler”-like land cooling (different from the extratropical infrared cooling on clear nights). Thus, unlike the extratropics, the diurnal cycle over the IMC is more important in the rainy season. The intraseasonal, seasonal to annual, and interannual climate variabilities appear as amplitude modulations of the diurnal cycle. For example, in Jawa and Bali the rainy season is the southern hemispheric summer, because land heating in the clear morning and water vapor transport by afternoon sea breeze is strongest in the season of maximum insolation. During El Nino, cooler sea water surrounding the IMC makes morning maritime convection and rainfall weaker than normal. Because the diurnal cycle is almost the only mechanism generating convective clouds systematically near the equator with little cyclone activity, the local annual rainfall amount in the tropics is a steeply decreasing function of coastal distance (e-folding scale 100–300 km), and regional annual rainfall is an increasing function of “coastline density” (coastal length/land area) measured at a horizontal resolution of 100 km. The coastline density effect explains why rainfall and latent heating over the IMC are twice the global mean for an area that makes up only 4% of the Earth’s surface. The diurnal cycles appearing almost synchronously over the whole IMC generate teleconnections between the IMC convection and the global climate. Thus, high-resolution (<< 100 km; << 1 day) observations and models over the IMC are essential to improve both local disaster prevention and global climate prediction.

Observation-based solar and wind power capacity factors and power densities

Abstract: Power density is the rate of energy generation per unit of land surface area occupied by an energy system. The power density of low-carbon energy sources will play an important role in mediating the environmental consequences of energy system decarbonization as the world transitions away from high power-density fossil fuels. All else equal, lower power densities mean larger land and environmental footprints. The power density of solar and wind power remain surprisingly uncertain: estimates of realizable generation rates per unit area for wind and solar power span 0.3–47 We m−2 and 10–120 We m−2 respectively. We refine this range using US data from 1990–2016. We estimate wind power density from primary data, and solar power density from primary plant-level data and prior datasets on capacity density. The mean power density of 411 onshore wind power plants in 2016 was 0.50 We m−2. Wind plants with the largest areas have the lowest power densities. Wind power capacity factors are increasing, but that increase is associated with a decrease in capacity densities, so power densities are stable or declining. If wind power expands away from the best locations and the areas of wind power plants keep increasing, it seems likely that wind's power density will decrease as total wind generation increases. The mean 2016 power density of 1150 solar power plants was 5.4 We m−2. Solar capacity factors and (likely) power densities are increasing with time driven, in part, by improved panel efficiencies. Wind power has a 10-fold lower power density than solar, but wind power installations directly occupy much less of the land within their boundaries. The environmental and social consequences of these divergent land occupancy patterns need further study.

Diurnal Cycle of Rainfall and Winds near the South Coast of China

Abstract: The characteristics and mechanisms of diurnal rainfall and winds near the south coast of China are explored using satellite data (CMORPH), long-term hourly WRF Model data (Du model data), a simple 2D linear model, and 2D idealized simulations. Both the CMORPH and Du model data indicate that the diurnal cycle of rainfall has two propagation modes near the coast: onshore and offshore. The diurnally periodic winds (vertical motions) also show a similar propagation feature. Analysis of the rainfall budget indicates that vertically integrated vertical vapor advection plays a key role in the diurnal cycle of rainfall and thus provides a physical connection between winds and rainfall in the diurnal cycle. It was found that a simple 2D linear land–sea breeze model with a background wind can well capture the two propagation modes, which are associated with inertia–gravity waves, in terms of speed and phase. The background wind changes the pattern of the inertia–gravity waves and further affects the diurnal...

Estimating the value of offshore wind along the United States’ Eastern Coast

Abstract: Author(s): Mills, AD; Millstein, D; Jeong, S; Lavin, L; Wiser, R; Bolinger, M | Abstract: Offshore wind power deployment has been concentrated in Europe, and remains limited in other areas of the world. Among the many challenges to deployment is the need to understand the value that offshore wind provides within electricity markets. This article develops a rigorous method to assess the economic value of offshore wind along the eastern coastline of the United States, seeking improved understanding of how the value of offshore wind varies both geographically and over time, and what has driven that variation. The article uses historical (2007-2016) weather data at thousands of potential offshore wind sites, combined with historical wholesale electricity market outcomes and renewable energy certificate (REC) prices at hundreds of possible transmission interconnection points. We find that the average historical market value of offshore wind from 2007 to 2016 - considering energy, capacity, and RECs - varies significantly by project location, from $40/MWh to more than $110/MWh, and is highest for sites off of New York, Connecticut, Rhode Island, and Massachusetts. As energy and REC prices have fallen in recent years, so too has the market value of offshore wind. The historical value of offshore wind is found to exceed that of onshore wind, due to offshore wind sites being located more favorably in terms of constrained pricing points, and also due to a more-favorable temporal profile of electricity production. Cost reductions that approximate those witnessed recently in Europe may be needed for offshore wind to offer a credible economic value proposition on a widespread basis in the United States.

Features of sea–land-breeze circulation over the Seoul Metropolitan Area

Abstract: Local circulation plays an important role in producing high-resolution meteorological and air quality information. In this study, detailed surface meteorological and vertical profile features about sea and land breezes in the Seoul Metropolitan Area (SMA) were investigated using the data from urban meteorological observation system in SMA (UMS-Seoul). These data were obtained from high-resolution surface meteorological stations and three wind lidar stations for 6 consecutive days (17–22 May 2016) with very weak synoptic winds and low cloud covers. The 6-day average diurnal variations of surface meteorological variables revealed temperature differences between land and sea, driving the pressure differences between the two. This induced sea–land-breeze circulation. The resulting sea breeze began at the shoreline at 1200 local standard time (LST), moved landward at a rate of about 10 km h−1, and reached 60 km from the shoreline at 1800 LST. The land breeze occurred within 50 km of the shoreline until noon. The sea-breeze front was identified by a steep horizontal temperature gradient, and its passage was accompanied by an abrupt temperature drop as well as vapor pressure and wind increases. The time–height cross section of wind indicated that the top of sea (land) breeze reached a maximum height of 1.5 km (0.8 km) with maximum winds 0.4 km (0.3–0.4 km) high in the late afternoon (early morning). The returning (easterly) flow at 1.5–1.6 km was clearly observed over the sea-breeze cells.

Tides in the Black Sea: Observations and Numerical Modelling

Abstract: Longterm hourly data from 28 tide gauges were used to examine the main features of tides in the Black Sea. The tides in this basin are directly caused by tide-generating forces and the semidiurnal tides prevail over diurnal tides. Based on the Princeton Ocean Model (POM), a numerical model of tides in the Black Sea and adjacent Sea of Azov was developed and found to be in good agreement with tide gauge observations. Detailed tidal charts for amplitudes and phase lags of the major tidal harmonics in these two seas were constructed. The results of the numerical modelling and observations reveal for the semidiurnal tides the presence of an amphidromy with clockwise rotation and another one with counterclockwise rotation for the diurnal tides, both located in the central part of the sea near the Crimean Peninsula. Therefore, for this part of the sea the amplitudes of harmonics M2 and K1 are less than 0.1 cm. Relatively larger M2 amplitudes are observed on the east and west coasts of the sea (2–3 cm). The maximum amplitude of the harmonic M2 was found at Karkinit Bay—up to 4.5 cm—while the maximum tidal range varies from 1 cm near the Crimean Peninsula to 18–19 cm in the Dnieper–Bug Estuary and Karkinit Bay. Radiational tides, initiated mainly by sea breezes, make an important contribution to the formation of tidal oscillations in the Dnieper–Bug Estuary.

Meteorological and Land Surface Properties Impacting Sea Breeze Extent and Aerosol Distribution in a Dry Environment

Abstract: The properties of sea breeze circulations are influenced by a variety of meteorological and geophysical factors that interact with one another. These circulations can redistribute aerosol particles and pollution and therefore can play an important role in local air quality, as well as impact remote sensing. In this study, we select 11 factors that have the potential to impact either the sea breeze circulation properties and/or the spatial distribution of aerosols. Simulations are run to identify which of the 11 factors have the largest influence on the sea breeze properties and aerosol concentrations and to subsequently understand the mean response of these variables to the selected factors. All simulations are designed to be representative of conditions in coastal sub tropical environments and are thus relatively dry, as such they do not support deep convection associated with the sea breeze front. For this dry sea breeze regime, we find that the background wind speed was the most influential factor for the sea breeze propagation, with the soil saturation fraction also being important. For the spatial aerosol distribution, the most important factors were the soil moisture, sea‐air temperature difference, and the initial boundary layer height. The importance of these factors seems to be strongly tied to the development of the surface‐based mixed layer both ahead of and behind the sea breeze front. This study highlights potential avenues for further research regarding sea breeze dynamics and the impact of sea breeze circulations on pollution dispersion and remote sensing algorithms.

North-western Mediterranean sea-breeze circulation in a regional climate system model

Abstract: In the Mediterranean basin, moisture transport can occur over large distance from remote regions by the synoptic circulation or more locally by sea breezes, driven by land-sea thermal contrast. Sea breezes play an important role in inland transport of moisture especially between late spring and early fall. In order to explicitly represent the two-way interactions at the atmosphere-ocean interface in the Mediterranean region and quantify the role of air-sea feedbacks on regional meteorology and climate, simulations at 20 km resolution performed with WRF regional climate model (RCM) and MORCE atmosphere-ocean regional climate model (AORCM) coupling WRF and NEMO-MED12 in the frame of HyMeX/MED-CORDEX are compared. One result of this study is that these simulations reproduce remarkably well the intensity, direction and inland penetration of the sea breeze and even the existence of the shallow sea breeze despite the overestimate of temperature over land in both simulations. The coupled simulation provides a more realistic representation of the evolution of the SST field at fine scale than the atmosphere-only one. Temperature and moisture anomalies are created in direct response to the SST anomaly and are advected by the sea breeze over land. However, the SST anomalies are not of sufficient magnitude to affect the large-scale sea-breeze circulation. The temperature anomalies are quickly damped by strong surface heating over land, whereas the water vapor mixing ratio anomalies are transported further inland. The inland limit of significance is imposed by the vertical dilution in a deeper continental boundary-layer.

A Characterization of the Delaware Sea Breeze Using Observations and Modeling

Abstract: Sea-breeze circulations are a prominent source of diurnal wind variability along coastlines throughout the world. For Delaware, the sea breeze is the largest source of variability in the co...

Impacts of afternoon and evening sea-breeze fronts on local turbulence, and on CO2 and radon-222 transport

Abstract: We investigated sharp disruptions of local turbulence and scalar transport due to the arrival of sea-breeze fronts (SBFs). To this end, we employed a comprehensive 10-year observational database from the Cabauw Experimental Site for Atmospheric Research (CESAR, the Netherlands). Sea-breeze (SB) days were selected using a five-filter algorithm, which accounts for large-scale conditions and a clear mesoscale-frontal signal associated with the land-sea contrast. Among those days (102 in all, 8.3%), based on the value of the sensible-heat flux at the onset of SB, we identified three atmospheric boundary-layer (ABL) regimes: convective, transition and stable. In the convective regime, the thermally driven convective boundary layer is only slightly altered by a small enhancement of the shear when the SBF arrives. Regarding the transition regime, we found that the ABL afternoon transition is accelerated. This was quantified by estimating the contributions of shear and buoyancy to the turbulent kinetic energy. Other relevant disruptions are the sharp reduction in ABL depth (similar to 250 m/hr) and the sudden increase in average wind speed (> 2 m/s). In the stable regime, the arrival of the SB leads to disturbances in the wind profile at the surface layer. We observed a deviation of more than 1 m/s in the observed surface-layer wind profile compared with the profile calculated using Monin-Obukhov Similarity Theory (MOST). Our findings furthermore reveal the determinant role of the SB direction in the transport of water vapour, CO2 and Rn-222. The return of continental air masses driven by the SB circulation generates sharp CO2 increases (up to 14 ppm in half an hour) in a few SB events. We suggest that the variability in Rn-222 evolution may also be influenced by other non-local processes such as the large-scale footprint from more remote sources.

Major role of water bodies on diurnal precipitation regimes in Eastern Africa.

Abstract: Mean diurnal rainfall regimes over Eastern Africa (also referred to as the Greater Horn of Africa) are studied based on 3-hourly data from the TRMM 3B42 data set, averaged over a 17-year period (1998–2014). The consistency with long-term mean raingauge data, available for partly independent periods, varies from good (Sudan, Ethiopia, Eritrea and Somalia) to very good (Kenya, Tanzania and Uganda). Over sea (Indian Ocean and Red Sea), the diurnal rainfall distribution is quite uniform; however, a morning peak dominates and there is evidence of offshore phase propagation south of the equator. Over land, both rainfall frequency and rainfall amounts show a dominant afternoon maximum (1500–1800 East African Time, i.e. GMT + 3). However, many inland regions show a delayed rainfall maximum (evening, night-time or morning). The evening to night-time maximum found over some land areas is associated with a phase propagation from areas showing an afternoon peak. This occurs west of high ground areas (Sudan and parts of the Great Lakes region) and in belts parallel to the seashores (Eritrea, northeastern Ethiopia, Somalia and eastern Kenya). The latter provide indirect evidence that sea breeze effects can be detected at unexpectedly great distances from the coast (up to 300–400 km) in parts of Eastern Africa. A remarkable ring of early afternoon (1500) maxima is found around most lakes, although some east–west asymmetries occur. Over the lakes, a morning or late night maximum is mostly found. It is generally inversely related to the distance to the shorelines for the larger lakes, but over the mid-size lakes it is replaced by or competes with a late afternoon to evening maximum.

Investigating the mechanisms of diurnal rainfall variability over Peninsular Malaysia using the non-hydrostatic regional climate model

Abstract: This study aims to provide a basis for understanding the mechanisms of diurnal rainfall variability over Peninsular Malaysia by utilising the Non-Hydrostatic Regional Climate Model (NHRCM). The present day climate simulations at 5 km resolution over a period of 20 years, from 1st December 1989 to 31st January 2010 were conducted using the six-hourly Japanese re-analysis 55 years (JRA-55) data and monthly Centennial in situ Observation Based Estimates (COBE) of sea surface temperature as lateral and lower boundary conditions. Despite some biases, the NHRCM performed reasonably well in simulating diurnal rainfall cycles over Peninsular Malaysia. During inter-monsoon periods, the availability of atmospheric moisture played a major role in modulating afternoon rainfall maxima over the foothills of the Titiwangsa mountain range (FT sub-region). During the southwest monsoon, a lack of atmospheric moisture inhibits the occurrence of convective rainfall over the FT sub-region. The NHRCM was also able to simulate the suppression of the diurnal rainfall cycle over the east coast of Peninsular Malaysia (EC sub-region) and afternoon rainfall maximum over the Peninsular Malaysia inland-valley (IN sub-region) area during the northeast monsoon. Over the EC sub-region, daytime radiational warming of the top of clouds enhanced atmospheric stability, thus reducing afternoon rainfall. On the other hand, night-time radiational cooling from cloud tops decreases atmospheric stability and increases nocturnal rainfall. In the early morning, the rainfall maximum was confined to the EC sub-region due to the retardation of the north-easterly monsoonal wind by the land breeze and orographic blocking. However, in the afternoon, superimposition of the sea breeze on the north-easterly monsoonal wind strengthened the north-easterly wind, thus causing the zone of convection to expand further inland.

Two years observations on the diurnal evolution of coastal atmospheric boundary layer features over Thiruvananthapuram (8.5∘ N, 76.9∘ E), India

Abstract: The atmospheric boundary layer (ABL) over a given coastal station is influenced by the presence of mesoscale sea breeze circulation, together with the local and synoptic weather, which directly or indirectly modulate the vertical thickness of ABL (z ABL). Despite its importance in the characterization of lower tropospheric processes and atmospheric modeling studies, a reliable climatology on the temporal evolution of z ABL is not available over the tropics. Here, we investigate the challenges involved in determination of the ABL heights, and discuss an objective method to define the vertical structure of coastal ABL. The study presents a two year morphology on the diurnal evolution of the vertical thickness of sea breeze flow (z SBF) and z ABL in association with the altitudes of lifting condensation level (z LCL) over Thiruvananthapuram (8.5∘ N, 76.9∘ E), a representative coastal station on the western coastline of the Indian sub-continent. We make use of about 516 balloon-borne GPS sonde measurements in the present study, which were carried out as part of the tropical tropopause dynamics field experiment under the climate and weather of the sun-earth system (CAWSES)–India program. Results obtained from the present study reveal major differences in the temporal evolution of the ABL features in relation to the strength of sea breeze circulation and monsoonal wind flow during the winter and summer monsoon respectively. The diurnal evolution in z ABL is very prominent in the winter monsoon as against the summer monsoon, which is attributed to the impact of large-scale monsoonal flow over the surface layer meteorology. For a majority of the database, the z LCL altitudes are found to be higher than that of the z ABL, indicating a possible decoupling of the ABL with the low-level clouds.

Atmospheric Dynamics and Ozone Cycle during Sea Breeze in a Mediterranean Complex Urbanized Coastal Site

Abstract: Persistent high pressure conditions over the Mediterranean Basin favor the occurrence of sea breezes that can lead to ozone transport through complex recirculation patterns. These features ...