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Convection-permitting numerical experiments using the Weather Research and Forecasting (WRF) Model are performed to examine the diurnal cycles of land and sea breeze and its related precipitation over the south China coastal region during the mei-yu season. The focus of the analyses is a 10-day simulation initialized with the average of the 0000 UTC gridded global analyses during the 2007-09 mei-yu seasons (11 May-24 June) with diurnally varying cyclic lateral boundary conditions. Despite differences in the rainfall intensity and locations, the simulation verified well against averages of 3-yr ground-based radar, surface, and CMORPH observations and successfully simulated the diurnal variation and propagation of rainfall associated with the land and sea breeze over the south China coastal region. The nocturnal offshore rainfall in this region is found to be induced by the convergence line between the prevailing low-level monsoonal wind and the land breeze. Inhomogeneity of rainfall intensity can be found along the coastline, with heavier rainfall occurring in the region with coastal orography. In the night, the mountain-plain solenoid produced by the coastal terrain can combine with the land breeze to enhance offshore convergence. In the daytime, rainfall propagates inland with the inland penetration of the sea breeze, which can be slowed by the coastal mountains. The cold pool dynamics also plays an essential role in the inland penetration of precipitation and the sea breeze. Dynamic lifting produced by the sea-breeze front is strong enough to produce precipitation, while the intensity of precipitation can be dramatically increased with the latent heating effect. [ABSTRACT FROM AUTHOR]

Summary Previous studies have shown that the majority of the lakes in the Tibetan Plateau (TP) started to expand rapidly since the late 1990s. However, the causes are still not well known. For Nam Co, being a closed lake with no outflow, evaporation ( E L ) over the lake surface is the only way water may leave the lake. Therefore, quantifying E L is key for investigating the mechanism of lake expansion in the TP. E L can be quantified by Penman- and/or bulk-transfer-type models, requiring only net radiation, temperature, humidity and wind speed for inputs. However, interpolation of wind speed data may be laden with great uncertainty due to extremely sparse ground meteorological observations, the highly heterogeneous landscape and lake-land breeze effects. Here, evaporation of Nam Co Lake was investigated within the 1979–2012 period at a monthly time-scale using the complementary relationship lake evaporation (CRLE) model which does not require wind speed data. Validations by in-situ observations of E601B pan evaporation rates at the shore of Nam Co Lake as well as measured E L over an adjacent small lake using eddy covariance technique suggest that CRLE is capable of simulating E L well since it implicitly considers wind effects on evaporation via its vapor transfer coefficient. The multi-year average of annual evaporation of Nam Co Lake is 635 mm. From 1979 to 2012, annual evaporation of Nam Co Lake expressed a very slight decreasing trend. However, a more significant decrease in E L occurred during 1998–2008 at a rate of −12 mm yr −1 . Based on water-level readings, this significant decrease in lake evaporation was found to be responsible for approximately 4% of the reported rapid water level increase and areal expansion of Nam Co Lake during the same period. [ABSTRACT FROM AUTHOR]

An experimental field campaign took place in September 2013 near the coastline in the southeastern Campos basin in the island of Mallorca to characterize experimentally the transition between the sea and the land breezes and to further study the successful cases with the corresponding high-resolution numerical simulations. Favorable weather conditions were only found for one episode that comprised a well-formed nocturnal land breeze, followed by the morning transition to sea breeze until noon the next day, when incoming clouds switched off the breeze regime. To analyse this transition between land and sea breezes, the official network of stations is used, supplemented by a portable station close to the shore and soundings of temperature (taken by a captive balloon and remotely controlled multicopter). These data are used to check the goodness of the corresponding simulation at a horizontal resolution of 1 km. Model and observations see similarly both regimes and the transition, showing some differences in the timing and the details in the surface layer. This transient event is analyzed in terms of phases, going consecutively through land breeze, phase previous to the sea breeze, when land heating starts, but it is still colder than the sea, the preparatory phase when the land becomes warmer than the sea, and the development phase when the breeze front progresses inland. [ABSTRACT FROM AUTHOR]

Mesoscale convective complexes (MCC) systems produce a wide variety of severe convective weather such as heavy rainfall. The MCC is a subclass of mesoscale convective systems (MCSs) defining as a convective cloud system that is large, long lived, and exhibits a quasi-circular cloud shield. This study evaluates spatial distributions of heavy rainfall over Java Sea region during wet season conditions; namely, December January February (DJF). Rainfall data set obtained from Tropical Rainfall Measuring Mission (TRMM) measurements for period 1998 - 2013. Heavy rainfall is represented by amount of maximum rainfall. Diurnal cycles of rainfall features present that the development and movement of convective rainfall is mainly related to the land and sea breezes. The evolution of hourly rainfall at 3 hourly intervals, illustrates a clear diurnal variation over Java Sea region. From 22 Local Time (LT) to 10 LT the large average rainfall mainly located in the Java Sea. Then from 13 LT to 19 LT the large average rainfall mainly located in the inland. While from 10 LT to 13 LT the large average rainfall located in both the Java Sea and the inland. And from 19 LT to 22 LT the large average rainfall located in Java coastwise. This situation has agreement with the formation of its maximum and standard deviation in diurnal cycles. The daily convective rainfall in the inland region is much more than that in the sea region, but heavy rainfall is often found over the sea. [ABSTRACT FROM AUTHOR]

Simultaneous measurements of wind profiles and of atmospheric substances such as aerosols and reactive gases were conducted at Fukuoka University in the western urban area of Japan to elucidate relations between local circulation and variations of aerosols and gases. Spatial variations of wind speed and direction over the Fukuoka Plain were measured using Doppler LIDAR. Some atmospheric substances such as black carbon, organic carbon, CO, and NO x were found to have maxima in morning (07–11 JST) and evening (18–20 JST), when diurnal cycles of wind direction and speed were observed near the surface. Doppler LIDAR data indicated clearly that the diurnal cycles of wind profiles were associated with sea breezes and land breezes over the Fukuoka Plain. The diurnal variations of aerosols and gases might be attributed to local anthropogenic emissions such as vehicle exhaust from Fukuoka city and vessels in the Hakata Bay and the sea and land breeze cycles. Strengths of morning peaks and evening peaks showed clear seasonal changes, with stronger peaks during the colder seasons and weaker peaks during the warmer and hot months. Slopes related to BC, OC, NO x , and CO were found to have seasonal changes. These seasonal changes were associated with the presence of a surface inversion layer in colder seasons, efficient photochemical reactions in the summer, and changes of fuel emission factors. • Diurnal gas and aerosol changes are related to sea–land breezes in coastal cities. • Local emissions and atmospheric chemistry cause diurnal gas and aerosol changes. • Diurnal changes of gases and aerosols show clear seasonal variations in Fukuoka. • These results indicate that numerous factors affect seasonal variations. • The factors include fuel combustion, local meteorology, and atmospheric chemistry. [ABSTRACT FROM AUTHOR]

This study examines the nocturnal wind systems of radiation nights on the Mediterranean island of Cyprus using the network of weather stations in and around the Troodos Mountains, which rise to more than 1900 m. These observations are supplemented by a series from the southern slopes of the mountains. Results indicate the typical development, depth and effects of these winds along the south coast of the island. The generation of these winds, their character and the forecasting challenges they present are also discussed, with an emphasis on the southward flow observed at the Royal Air Force (RAF) Akrotiri. The offshore winds are a combination of katabatic drainage, largely formed within incised valleys, with a land breeze. They bring cool dry air to the coast. The drainage winds commence above ~1200m and deepen to a depth of ~75m in the Kouris valley, becoming shallower as they move away from the valley mouth. The valley winds 'fan out' as they approach sea level to reach 20 km or more from the coast. [ABSTRACT FROM AUTHOR]

The combined analysis of 222 Rn activity concentrations and mesoscale meteorological conditions at Huelva city (Spain) was addressed in this study to understand the potential impact of phosphogypsum piles on the 222 Rn activity concentrations registered at this area. Hourly mean data from April 2012 to February 2013 registered at two sampling sites (Huelva city and in the background station of El Arenosillo, located 27 km to the south-east) have been used in the study. The results of the present study showed a large difference in mean radon concentrations between the two stations during the sampling period, 6.3 ± 0.4 Bq m −3 at Huelva and 3.0 ± 0.2 Bq m −3 at El Arenosillo. The analysis has demonstrated that hourly 222 Rn concentrations at Huelva city above 22 Bq m −3 , with nocturnal peaks up to 50 Bq/m 3 , mainly coincided with the occurrence of a pure sea-land breeze cycle. Mesoscale circulations in this region are mainly characterized by two patterns of sea-land breeze, pure and non-pure, with the phosphosypsum piles directly upstream (south) of the city during the afternoon on pure sea-breeze days. The difference between mean 222 Rn activity concentrations at Huelva city were 9.9 ± 1.5 Bq m −3 for the pure pattern and 3.3 ± 0.5 Bq m −3 for the non-pure pattern, while in the background station concentrations were 3.9 ± 0.4 Bq m −3 and 2.8 ± 0.4 Bq m −3 respectively. Considering these large differences, a detailed analysis of composites and case studies of representative sea-land breeze cycles of both types and their impact on 222 Rn activity concentration was performed. The results suggested that the presence of the phosphogypsum piles was necessary in order to justify the high 222 Rn activity concentrations observed at Huelva compared with the background station in the afternoons on pure sea breeze days (1.5–2.0 Bq m −3 ). On the other hand, large night time differences between the two sites on these days were likely to be associated with a combination of shallow density currents travelling down the Guadalquivir valley and, again, the presence of phosphogypsum piles. The results have demonstrated a significant impact of the phosphogypsum piles on 222 Rn activity concentrations in Huelva city during the occurrence of pure sea breeze days. [ABSTRACT FROM AUTHOR]

From in situ measurements taken over several sea-breeze cycles off a beach in southwest (SW) Australia, the evolution of the one-dimensional spectrum of wave energy is observed to have a distinctive spectral shape. During the land-breeze phase of the cycle, lower rates of dissipation of wave energy are seen at high frequencies compared to midrange frequencies above the remnant wind-sea peak. A simulation of waves was performed using the Simulating Waves Nearshore (SWAN) model and produced the same spectral evolution, by generating longshore modes, as seen in the observations. The performance of whitecapping schemes available in SWAN was assessed, and the Alves-Banner scheme was found to best simulate the observed growth and decay of the wave spectra. During the onshore phase of the sea-breeze cycle, local wave growth is duration limited, and during the offshore land-breeze phase, wave growth is fetch limited. From an examination of the modeled two-dimensional spectra it is found that quadruplet interactions play a key role in spreading high-frequency wave energy in frequency and direction space. [ABSTRACT FROM AUTHOR]

Over enclosed and semi-enclosed bodies of water, the land-breeze/sea-breeze circulation is expected to be modified by the presence of opposing coastlines. These effects are studied using satellite scatterometer surface wind observations from the QuikSCAT and ADEOS-2 tandem mission from April-October 2003. Winds are studied for six bodies of water: the Red Sea, the Gulf of California, the Mediterranean, the Adriatic Sea, the Black Sea and the Caspian Sea. These bodies of water are large enough for the geographic orientation of the diurnal winds relative to the coastline to match the expected orientation for a straight coastline. Land breezes from opposite coastlines converge in the middle of these bodies of water, and in some cases the convergence line is shifted substantially away from the midpoint between opposite coastlines. Displacements in the convergence line appear likely to be explained by differences in the strength of the diurnal winds emanating from opposite coastlines associated with differential heating or island/peninsula effects, and by geographic displacements associated with large-scale mean wind patterns. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air-Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions. The use of two gas tracers, N2O and C2HF5, resulted not only in gas transfer velocities, but also in the measurement of the Schmidt number exponent n with a precision of ±0.025. The original controlled flux or active thermographic technique proposed by Jähne et al. (1989) was applied by heating a large patch at the water surface to measure heat transfer velocities. Heating a large patch, the active thermography technique is laterally homogeneous and problems of lateral transport effects are avoided. Using the measured Schmidt number exponents, the ratio of the scaled heat transfer velocities to the measured gas transfer velocities is 1.046±0.040, a good agreement within the limits of experimental uncertainties. This indicates the possibility to scale heat transfer velocities measured by active thermography to gas transfer velocities, provided the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium. [ABSTRACT FROM AUTHOR]

Convective precipitation associated with tropical depression (TD) is one primary type of post-flooding season rainfall in South China (SC). Observations of the Tropical Rainfall Measuring Mission (TRMM) satellite have shown specific diurnal features of convective rainfall in South China, which is somewhat different from that in other seasons or regions of China. Convective precipitation is usually organized into a rainfall band along the southeastern coast of South China in the early morning hours. The rainfall band develops and intensifies quickly in the morning, then moves inland in the afternoon and, finally, diminishes at night. The daily convective rainfall along the coast is much more than that in the inland region, and heavy rainfall is often found along the coast. A long-duration heavy rainfall event associated with tropical depression "Fitow" during the period from 28 August to 6 September 2001, is selected in this study to explore the diurnal feature of convective rainfall and its formation mechanism. Modeling results of the 10-day heavy rainfall event are compared with both rain-gauge observation and satellite-retrieved rainfall. Total precipitation and its spatial distribution, as well as diurnal variations are reasonably simulated and agree well with observations. Further analysis reveals that the development and movement of convective precipitation is mainly related to the land and sea breezes. The anomalous height-latitudinal circulation in the morning-to-noon hours is completely reversed in the afternoon-to-late-evening hours, with the convective rainfall swinging back and forth, following its updraft branch. Sensitivity experiments show that the afternoon convective rainfall in the inland region of SC is caused by the diurnal variation of solar radiation forcing. The mountain range along the coast and the complex topography in the inland region of SC plays a critical role in the enhancement of diurnal convective rainfall everywhere. The formation of a heavy rainfall band along the southeastern coast of SC and the diurnal variation of the rainfall pattern are mainly the results of the land-sea thermal contrast. [ABSTRACT FROM AUTHOR]

Persistent northerly-to-easterly cold-air outbreaks affected the UK during the winters of 2009-10 and 2010-11, with the resulting convection frequently organizing into snowbands over the English Channel and Irish Sea. Sounding data and composite radar reflectivity images from the Met Office Nimrod precipitation radar network reveal that these bands formed along the major axis of each body of water (or sea) when the boundary-layer flow was roughly parallel to each of those axes (along-channel). For both seas, a band was present the majority of times that the 850 hPa flow was along-channel. Of these times of along-channel flow, the 850 hPa wind speed and surface-to-850 hPa temperature difference were significantly greater when bands were present than when they were not. For the English Channel only, the land-sea temperature difference was also significantly greater when bands were present than when they were not. In a real-data Weather Research and Forecasting model (WRF) control simulation of a typical band over the English Channel, a trough develops over the water and offshore air streams from either side converge along it. In the absence of surface fluxes, the trough, convergence and organized precipitation fail to develop altogether. Orography and roughness-length variations are less important in band development, affecting only the location and morphology. [ABSTRACT FROM AUTHOR]

Local air-sea interactions over the high sea surface temperature (SST) band along the Hawaiian Lee Countercurrent (HLCC) are examined with a focus on dynamical feedback of SST-induced wind stress to the ocean using the atmosphere-ocean coupled general circulation model (CGCM). A pair of ensemble CGCM simulations are compared to extract the air-sea interactions associated with HLCC: the control simulations and other simulations, the latter purposely eliminating influences of the high SST band on the sea surface flux computations in the CGCM. The comparison reveals that oceanic response to surface wind convergence and positive wind stress curl induced by the high SST band increases (decreases) the HLCC speed in the southern (northern) flank of the HLCC. The HLCC speed changes are driven by the Ekman suction associated with positive wind stress curl over the warm HLCC via the thermal wind balance. The HLCC speed increase is more significant than its decrease. This dynamical feedback is likely to be important to sustain the extension of the HLCC far to the west. The heat budget analysis confirms that advection of warm water from the west associated with this significant current speed increase plays a role in the southward shift of the HLCC axis. The dynamical feedback with the HLCC speed increase can potentially amplify the seasonal and interannual variations of HLCC. [ABSTRACT FROM AUTHOR]

This study analyses the atmospheric boundary layer over the Bilbao metropolitan area during summer (13-18 Jul 2009) and winter (20-29 Jan 2010) episodes using the Environment-High Resolution Limited Area Model (Enviro-HIRLAM) coupled with the building effect parameterisation (BEP). The main objectives of this study are: to evaluate the performance of the model to simulate the land-sea breezes over this complex terrain; to assess the simulations with the integration of an urban parameterisation in Enviro-HIRLAM and finally; and to analyse the urban-atmosphere interactions. Even if the hydrostraticity of the model is a limitation to simulate atmospheric flows over complex terrain, sensibility tests demonstrate that 2.4 km is the optimal horizontal resolution over Bilbao that allows at the same time: to obtain satisfactory reproducibility of the large-scale processes and to explore the urban effects at local scale. During the summer episode, a typical regime of diurnal sea breeze from the NW-N-NE direction and nocturnal valley breezes from the SE direction are observed over Bilbao. The urban heat island (UHI) phenomenon is developed in the city centre expanding to the suburbs from 22 to 10 local time (LT), covering an area of 130 km. The maximum UHI intensity, 1 °C, is reached at the end of the night (5 LT), and it is advected 12 km towards the sea by the land breezes. The urban boundary layer (UBL) height amplitude varies from 100 (night time) to 1,360 m (at 14 LT). During the winter episode, the land breeze dominates the atmospheric diffusion during the day and night time. The maximum UHI intensity, 1.7 °C, is observed at 01 LT. It is spread and remained over the city covering an area of 160 km, with a vertical extension of 33 m. The UBL reaches 780 m height at 16 LT the following day. [ABSTRACT FROM AUTHOR]

We investigate the effects of the cold tongue in the South China Sea (SCS) on the winter monsoon, rainfall and diurnal cycle in the maritime continent using a numerical model verified with satellite rainfall and reanalysis data. Composite analysis of the observation and reanalysis data based on cold tongue index indicates that the penetration of the monsoon to Java Sea is enhanced when the cold tongue is strong. A sensitivity experiment without the cold tongue shows that the winter monsoon is diminished over SCS and around coastal regions because of anomalous low-level cyclonic circulation associated with enhanced convection over SCS due to the warmer sea surface temperature (SST). The diurnal cycle, in particular the night-morning rainfall, over the sea in coastal regions is modified. The effect on daytime rainfall over the land is relatively weaker. Along the northern coast of Java far from the SCS, the night-morning rainfall is much reduced over the Java Sea when the cold tongue is suppressed because of the weakened land-breeze front as a result of the weakened northerly monsoon. In contrast, the afternoon-evening rainfall on Java Island is slightly enhanced, showing that the local impacts are not simply the result of large-scale subsidence from the convective anomaly in the SCS. Along the northwestern coast of Borneo adjacent to the SCS, the weakened winter monsoon tends to reduce the rainfall at the land-breeze front near the coastline. On the other hand, the warmer SST forces a stronger land breeze and the weakened monsoon encourages further and faster offshore propagation of the land-breeze front. Consequently, the rainfall peak shifts further offshore in the sensitivity experiment. We conclude that the cold tongue has two effects, the sustenance of a strong monsoon (indirect effect) and the cooling of local SST (direct effect), which have opposite influences on the diurnal cycle in the Maritime Continent. [ABSTRACT FROM AUTHOR]

The wind direction terms in the Sydney Language differ in the various sources (from the First Fleeters onwards), and at first sight look confused. After some sifting it emerges that the early sources fall into two sets partly relatable by a quarter-turn in the terms for the four cardinal directions. There are also terms for intermediate directions and probably sea and land breezes, and terms relatable to the sun and tides. A recent treatment of the wind direction data by Gibson, who draws as well on work by Troy, interprets the records as indicating that some word meanings shift so much according to context that he questions whether the Sydney Language had words at all. However, there is order discernible here, fitting with regional evidence for the salience of cardinal directions. The main four directions may have been aligned to axes offset from the cardinal directions, or else participate in a kind of location-dependent quarter-turn rotation. I conclude with brief remarks on the methods for detecting order in patchy historical data, and on the public communication of linguistic findings. [ABSTRACT FROM AUTHOR]

Abstract: An experiment is conducted over Cassava plant canopy at a coastal station at CTCRI, Thiruvananthapuram (8°29''N, 76°59E) to study the response of meteorological parameters and land–sea breeze circulations to the annular solar eclipse on January 15, 2010. Observations reveal decrease of solar radiation to a minimum of 96Wm−2 during the peak eclipse period. Air temperature drops by 4°C and relative humidity increases by 20%. Sensible heat flux reduces to zero. Transient land breeze occurs for a few minutes with a time lag of about 1h possibly due to outflow from the umbra region or temperature gradient over land with the eclipse progressing in the eastward direction. Sea breeze is delayed by about 3h on the next day of eclipse. Spectral energy density of wind (u, v, w) and temperature attains a minimum value during totality and increases later, attributable to reduction in turbulence due to eclipse-induced stability. [Copyright &y& Elsevier]

This is a numerical study of the effects of the Nile Delta (ND) man-made greening on local climate. We compared a control simulation, which employs the present-day ND vegetation, with a desertification experiment. It was found that the low surface albedo of the agricultural ND increases net radiation, which in turn raises potential evapotranspiration (PET). This suggests that agricultural use increases the water demand by enhancing PET. Non-local effects are also observed on a frontal system over the eastern Mediterranean Sea that shifted farther away from the coast. This shift is attributed to a stronger land breeze in the present-day land-cover. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the relationship between the occurrence of a sea breeze (SB) and cumulonimbus (Cb) clouds over the Istrian Peninsula. For this purpose, available standard surface measurements, i.e., the near-surface wind, the air and sea surface temperatures and cloudiness at two stations (Pula-Airport and Pazin), and satellite images were analyzed. The study was performed during the summer months (from June to September) for the years 1997-2006. The analysis showed that the Cb development was typically associated with certain meteorological conditions. These conditions were as follows: (i) SB speed at Pula-Airport in the range of 3-5 ms-1, (ii) maximum temperature difference between sea and land near Pula-Airport around 4 °C, and (iii) maximum air temperature in Pazin in the range of 25 to 31 °C. On average, during the days with simultaneous development of SB and Cb clouds, the land breeze was weaker and the air temperature was higher than on other analyzed days. Diurnal cloud evolution showed that Cb clouds usually develop (above Pazin) between 13 and 14 h of Central European Time (CET). Cumulus clouds, as indicators of the SB inland penetration, preceded the Cb development. Satellite images for 2000-2006 obtained by the geostationary satellites Meteosat 7 and 8 were investigated, and a spatial distribution and a temporal development of 30 chosen Cb events were detected. Two characteristic regions of the Cb origin were noted: the northern and southeastern parts of the Istrian Peninsula. The Cb clouds usually formed between 11 and 13 CET, lasting in general from 3 to 5 hours and disintegrating between 15 and 17 CET. [ABSTRACT FROM AUTHOR]

A case of offshore convective initiation by interacting land breezes near Darwin, Australia is investigated using convection-permitting model simulations, radar-derived precipitation observations, thermodynamic profiles from radiosonde soundings and surface measurements. These analyses elucidate the convergence of two land breezes in the Van Diemen Gulf, one originating from the Tiwi Islands and the other from mainland Australia; the convergence is sufficient to initiate a line of convection that forms parallel to the mainland coast in the early morning. While differing in small-scale features, the modeled system shows reasonably good agreement with the observed precipitation accumulations. However, using simulations with different initialization times and examining a second case, it is shown that the representation of the land-breeze system and subsequent convective initiation is very sensitive to the upstream wind and thermodynamic conditions, making correct simulation of these processes challenging. [ABSTRACT FROM AUTHOR]

A nested numerical simulation of a land breeze observed over the western Lake Michigan shoreline was completed using the University of Wisconsin Nonhydrostatic Modeling System. This simulation was compared against observations obtained using a variety of instrumentation, most notably a scanning lidar system. The simulated land breeze is shown to closely represent the observations. Most notably, the influence of synoptic scale evolution on the strength and extent of the land breeze is illustrated to be a critical factor in accurately simulating the lifetime of the land breeze. Additionally, model resolution is shown to impact the ability of the simulation to accurately portray the fine scale features of the land breeze circulation, including the depth of the land breeze front and interactions between the land breeze and prevailing synoptic scale flow. [ABSTRACT FROM AUTHOR]

Wintertime cold outbreaks were studied via a 2-D numerical model set across an 80 km wide non-frozen sea gulfalong 608N ('GulfofFinland'). In calm conditions, land breezes develop over both coasts with relatively large along-shore wind components. The mid-gulfconvergence of the colliding land breezes leads to a moderate rising motion at about 600 m height, forcing bands of low cloud and snowfall along the gulf, whereas the near-surface horizontal wind shear may induce 'mini-hurricanes'. A weak large-scale cold outbreak across the gulfdistorts the land breeze cells, damping the rising motion, whereas a moderate cross-coast outbreak modifies them into a typical heat island circulation pattern with only a modest rising motion over a flat windward shore. A cold outbreak along the non-frozen gulf leads to strong heat transfer from the sea. This maintains the embedded coastal land breeze circulations that contribute to a double low-level jet structure. The strongest rising motion was obtained for surface winds blowing along the gulf. It is suggested that the Swedish Ga vle snowstorm ofDecember 1998 was such a case. [ABSTRACT FROM AUTHOR]

This paper analyzes the effects of local sea-breeze circulation on power generation in a coastal wind farm in northern Cuba. This farm provided wind-generated power data during April-August 2008, which were combined with data from an exploratory meteorological tower located at a nearby coastal location. We analyze hourly data of land breeze and sea breeze separately, dividing these data sets also in first-class and second-class breezes. The breeze effects are quantified by the relation of the daily evolution of electricity generation and the breeze regimes. The results show a better coastal-wind resource usability under first-class breeze conditions, especially during meteorological synoptic conditions associated with an anticyclonic circulation and strong pressure gradient. A better maintenance planning for the wind farm by taking in consideration these breeze effects would contribute to a greater usable local-wind resource. [ABSTRACT FROM AUTHOR]

Abstract: This study reveals that land–sea breezes, atmospheric stability and influence of net ecosystem metabolism for the conversion of organic carbon to atmospheric CO2 are the major driving forces behind the variation of atmospheric CO2 at the land–ocean boundary, northeast coast of India. The seasonal variation of partial pressure of CO2 (pCO2) and its efflux from the coastal water were several fold higher in the pre-monsoon (1807.9 ± 757.03 μ atm; 579.03 ± 172.9 μM m−2 h−1) than in the monsoon (1070.5 ± 328.5 μ atm; 258.96 ± 185.65 μM m−2 h−1) and the post-monsoon (615.7 ± 121.6 μ atm; 53.27 ± 19.24 μM m−2 h−1). The mean photic zone productivity to column respiration ratio was 0.12 ± 0.08, revealing predominance of heterotrophic processes. Community respiration was at minimum during monsoon (38.82 ± 8.63 mM C m−2 d−1) but was at maximum (173.8 ± 111.8 mM C m−2 d−1) during pre-monsoon and intermittent (125.07 ± 11.97 mM C m−2 d−1) during post-monsoon. Diurnal variations of atmospheric CO2 concentration were determined by local air circulations and atmospheric stability. Seasonal variations of atmospheric CO2 bear a significant signature of biological processes occurring in the coastal water by means of air–sea exchange, markedly affected by the net ecosystem metabolism. Important predictors of coastal atmospheric CO2 in decreasing order of explained variability are wind direction, stability, CO2 efflux and wind velocity. [Copyright &y& Elsevier]

Decadal and centennial mean state changes in South American summer monsoon (SASM) precipitation during the last 2,300 years are detailed using an annually resolved authigenic calcite record of precipitation δ18O from a varved lake in the Central Peruvian Andes. This unique sediment record shows that δ18O peaked during the Medieval Climate Anomaly (MCA) from A.D. 900 to 1100, providing evidence that the SASM weakened considerably during this period. Minimum δ18O values occurred during the Little Ice Age (LIA) between A.D. 1400 and 1820, reflecting a prolonged intensification of the SASM that was regionally synchronous. After the LIA, δ18O increased rapidly, particularly during the current warm period (CWP; A.D. 1900 to present), indicating a return to reduced SASM precipitation that was more abrupt and sustained than the onset of the MCA. Diminished SASM precipitation during the MCA and CWP tracks reconstructed Northern Hemisphere and North Atlantic warming and a northward displacement of the Intertropical Convergence Zone (ITCZ) over the Atlantic, and likely the Pacific. Intensified SASM precipitation during the LIA follows reconstructed Northern Hemisphere and North Atlantic cooling, El Niño-like warming in the Pacific, and a southward displacement of the ITCZ over both oceans. These results suggest that SASM mean state changes are sensitive to ITCZ variability as mediated by Western Hemisphere tropical sea surface temperatures, particularly in the Atlantic. Continued Northern Hemisphere and North Atlantic warming may therefore help perpetuate the recent reductions in SASM precipitation that characterize the last 100 years, which would negatively impact Andean water resources. [ABSTRACT FROM AUTHOR]

Finding the point in time at which the wind pattern changes its direction is an important problem with a broad scope of application in atmospheric boundary layer modelling. In many cases such a change of pattern can be extracted using subjective methods, which involves a subjective post analysis of the measured time series. A considerably more difficult task is identifying such a change using an objective and automated method. This task is usually treated by smoothing the original time series, extracting threshold parameters using a statistical analysis of the past wind data, and setting threshold values via trial and error. We present here an objective and automatic method for solving this problem. The method identifies extrema and bending points in the cumulative sum terms of sine and cosine of the wind direction time series, which are based on the directional cumulative sum principle. Our method is non-parametric, and needs neither prior calibration of threshold values nor smoothing of the data. Furthermore, our method is unique in its ability to detect the pattern change even if the direction change occurs gradually. An example of the application of the method is presented using 6 months of data collected at a single meteorological station located on the central coastal plain of Israel. The method was applied to identify the timing of the occurrence of the nocturnal land wind period (beginning and end). Out of 176 days examined, the method identified correctly more than 90% of the periods. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Abstract: On 15th January 2010, Thumba (, ), witnessed one of the longest noontime Solar Eclipse centered at 13:14 LT. In the present case study, we report first observations on sensitivity of the sea breeze circulation cell to short-term obscuration in solar irradiance. Temporal evolution of surface layer windspeed segregated into right-angle components along the coastline on eclipse and normal days indicated a significant reduction in the intensity of sea breeze during the period of eclipse. Vertical thickness of the sea breeze cell was confined to 300m on the eclipse day, whereas it was extending to about 610m on the control day. [Copyright &y& Elsevier]

In this study, the land-sea breeze circulation model coupled with a random-walk model is developed by the analysis of the formation and the mechanism of the land-sea breeze. Based on the data of the land-sea circulation in Dalian, China, the model simulated the diurnal variation of pressure, flow, temperature, and turbulent kinetic energy field and also provides a basis for solving the air pollutant concentration in the land-sea breeze circulation so as to estimate the economic cost attributable to the atmospheric pollution. The air pollutant concentration in the background of land-sea circulation is also simulated by a Gaussian dispersion model, and the results revealed that the land-sea circulation model coupled with the random-walk model gives a reasonable description of air pollutant dispersion in coastal areas. [ABSTRACT FROM AUTHOR]

This study assesses the monthly climatology of the timing and placement of convective precipitation events induced by sea and land breezes in the Louisiana--Mississippi--Alabama region, and determines possible reasons for the monthly differences. These objectives were achieved through surface wind climatologies and radar composites from 2003 to 2005, supplemented by statistically significant tests. It is shown that June had an easterly--southeasterly wind regime, whereas July and August featured more southerly flow. These wind regimes may have influenced monthly diurnal wind patterns along the coast. While all months showed a typical pattern of sea-breeze evolution, the land breeze demonstrated monthly variations off the Mississippi and Louisiana coasts. July and August feature a westerly land breeze from Louisiana, while the Mississippi land breeze was stronger in August than in July. A daily wind speed minimum offshore from Mississippi indicates a local transition of influence from the land breeze to the sea breeze, and precedes the peak of the sea breeze at the coastline by about 2 h. During the nighttime hours, radar composites show that precipitation is most prevalent offshore of the Louisiana and Mississippi coastline. By 1100 central daylight time (CDT), precipitation is observed over coastal regions. Local afternoon precipitation is widespread throughout the inland areas, while precipitation is minimal offshore. Statistical significance tests show that areal precipitation coverage (APC) increases in mid- to late summer on the Mississippi coast are due to higher precipitable water and, to a lesser extent, additional CAPE. Greater offshore APC in July and August results from the influence of the local land-breeze setup. Convergence of a land breeze from eastern Louisiana and a stronger land breeze from Mississippi provides the additional lift needed to generate convection over a greater area. [ABSTRACT FROM AUTHOR]

Abstract: The nocturnal boundary layer in Houston, Texas was studied using a high temporal and vertical resolution tethersonde system on four nights during the Texas Air Quality Study II (TexAQS II) in August and September 2006. The launch site was on the University of Houston campus located approximately 4 km from downtown Houston. Of particular interest was the evolution of the nocturnal surface inversion and the wind flows within the boundary layer. The land–sea breeze oscillation in Houston has important implications for air quality as the cycle can impact ozone concentrations through pollutant advection and recirculation. The results showed that a weakly stable surface inversion averaging in depth between 145 and 200 m AGL formed on each of the experiment nights, typically within 2–3 h after sunset. Tethersonde vertical winds were compared with two other Houston data sets (High Resolution Doppler Lidar and radar wind profiler) from locations near the coastline and good agreement was found, albeit with a temporal lag at the tethersonde site. This comparison revealed development of a land breeze on three nights which began near the coastline and propagated inland both horizontally and vertically with time. The vertical temperature structure was significantly modified on one night at the tethersonde site after the land breeze wind shift, exhibiting near-adiabatic profiles below 100 m AGL. [Copyright &y& Elsevier]

Abstract: Weather Research and Forecast (WRF) model is applied to study the wind field over the east coast of central Greece under typical summer conditions. This study aims at identifying the major features of the sea breeze circulation that is very frequently developing in the area during the warm period of the year and at verifying the model''s ability to simulate the complex flow that is strongly influenced by the complicated coastline and very steep terrain. The simulation is carried out for a five-day period, characterized by sea breeze development. It is found that a complex meteorological phenomenon is evolving in the area, as two circulation systems are successively developing, the first over Pagasitikos Gulf, which is overridden by the system that develops later over the Aegean Sea. The major characteristics of the wind patterns and especially the sea breeze systems are identified and discussed. Additionally, the impact of topography and slope on sea breeze circulation is also commented. Model predictions agree fairly well with the observations taken at a near-surface meteorological station. [Copyright &y& Elsevier]

Abstract: Being a semi-enclosed area, the Eastern Mediterranean region experiences high Particulate Matter (PM) levels that could be attributed to sources originating from the region and from long-range transported pollutants. In this study, a long-term evaluation of PM10 and PM2.5 mass concentrations reveals that averages of PM10 and PM2.5 concentrations collected between 2003 and 2007 in several different sites in Beirut exceeded the World Health Organization (WHO) PM10 and PM2.5 annual averages (20 and 10µgm−3, respectively). When compared to other sites in the region, levels fell in general outside the usual range for most other urban sites that are not directly affected by industrial activity. The average PM2.5/PM10 ratios were about 0.42, a value that is typical of urban sites. The overall averages for different seasons were higher in fall and summer as a result of low precipitations, the increase of dust storm activities in fall and the enhancement of sea and land breezes in summer, along with the increase in traffic activities (summer is a high touristic season). Using the HYSPLIT model for about 500 sampled days in Beirut, Lebanon, it was found that 60% of the wind comes from the N, NW and NE, while the remaining 40% comes from the S, SW and SE. Comparing the sources assigned to the pre- (BH) and post- (HH) 2006-war sites, it was found that aged dust increased by 64% in total PM10 and secondary aerosols by 150% in fine PM in HH over BH. Furthermore, much higher average percentages of sulfates and nitrates were determined in fine PMs in HH, indicating increased levels of their precursors NOx, SOx and Ca generated from a higher density of gasoline, diesel vehicles and construction debris. [Copyright &y& Elsevier]

Abstract: We present a study of the characteristics and importance of breezes at a coastal site in the Central Mediterranean Basin. The site is located on the west coast of the Peninsular Calabria Region at the southern tip of Italy. This study adds new data on breeze circulations over a unique experimental coastal site characterized by the sea–land contrast in a flat area which is also influenced by the complex orography of the region. The first part of the study compares data from a surface meteorological station and meteorological analysis at 850hPa to show the importance of breeze circulation at the site. Results show that breezes dominate the local circulation and play a major role in the local climate. Moreover, the characteristics of the breeze exhibit significant differences between summer and fall. The second part of the paper examines the thermal and large-scale forcings that play an important role in the breeze circulation. A sharp difference in thermal forcing was observed between July–August and September. The diurnal breeze acts in phase with the large-scale flow and is particularly intense in summer. The modulation of the nocturnal breeze by the large-scale flow is also apparent. The third part of the paper focuses on two selected case studies one for summer and the other for fall and explains differences in the breeze circulation. Finally, the behaviours of summer and fall breezes are presented and discussed. [Copyright &y& Elsevier]

The levels and temporal variations of surface ozone at a coastal site in East China during summer and autumn were analyzed and the influences of meteorological parameters on ozone were investigated. An inland city was chosen as a comparison site. The main results and conclusions of this study are: (1) ozone pollution, with a maximum 1 h concentration of 150.98 ppbv, was severe during summer and autumn at the coastal site; (2) the ozone level was obviously higher at the coastal site than that at the inland site in September; (3) besides temperature and solar radiation, sea-land breeze circulation is an important factor influencing the ozone level at the coastal site, and sea breeze often induce high ozone levels (the average ozone concentration for sea breeze was about 13 ppbv higher than that for land breeze). [ABSTRACT FROM AUTHOR]

It is well established that surface ozone levels are greatly affected by orography, solar radiation intensity, meteorological conditions, and the levels of their precursors. In this work, the authors study the sea–land breeze circulation in its relation with the behavior of ozone in a coastal area, located in southwestern Europe, with high levels of solar radiation and an important industrial complex emitting air pollutants. Hourly mean data over a 7-yr period (1999–2005) have been used in the study. Two patterns of sea–land breeze have been identified after analyzing 2298 days of measurements: a “pure” breeze (179 cases) and another one, called a “nonpure” breeze (284 cases), which is the resulting flow of the former and northwesterlies synoptic forcing. Among other results, the highest levels of surface ozone were observed under pure sea–land breeze, with hourly values up to 100 μg m−3 in the mean daily evolution. In contrast, for a nonpure breeze, the 24-h average daily value was lower than the corresponding one under a pure breeze by a factor of 1.16 and could reach 1.60 in representative real cases. These findings give evidence that the formation and accumulation of ozone are favored by the conditions under a pure sea–land breeze: that is, perpendicular wind directions toward the coastline, effective recirculation of air masses, and formation of ozone residual layers above the sea. Because these atmospheric conditions occur in other coastal regions in the world, the conclusions of this study could be extended to them. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution Regional Model is used to study the structure and dynamics of Sea/Land Breeze Circulation along west coast of Indian Sub-continent during pre-monsoon season. Both the observations from ocean and land are in agreement with the model simulations. From the model simulations, a time delay of 3hours is observed in the onset of sea breeze over ocean and land (∼28km from the sea/land interface). The two main components of the sea breeze circulation cell, the sea breeze flow in the lower levels and the return current in the upper levels are clearly modeled. The vertical extent of sea breeze circulation cell is ∼1km and, the horizontal seaward and landward extensions are ∼100 and ∼75km respectively from the sea/land interface. Within the sea breeze circulation cell, during daytime, a shallow mixed layer (600–800m) over ocean and a convective mixed layer (1000–1200m) over the land are observed. Observations and simulations verified the pre-assumption of the near neutral lapse rate existing over ocean and transferring to the onshore regions. [Copyright &y& Elsevier]

The effect of air–sea coupling on tropical climate variability is investigated in a coupled linear inverse model (LIM) derived from the simultaneous and 6-day lag covariances of observed 7-day running mean departures from the annual cycle. The model predicts the covariances at all other lags. The predicted and observed lag covariances, as well as the associated power spectra, are generally found to agree within sampling uncertainty. This validates the LIM’s basic premise that beyond daily time scales, the evolution of tropical atmospheric and oceanic anomalies is effectively linear and stochastically driven. It also justifies a linear diagnosis of air–sea coupling in the system. The results show that air–sea coupling has a very small effect on subseasonal atmospheric variability. It has much larger effects on longer-term variability, in both the atmosphere and the ocean, including greatly increasing the amplitude of ENSO and lengthening its dominant period from 2 to 4 years. Consistent with these results, the eigenvectors of the system’s dynamical evolution operator also separate into two distinct, but nonorthogonal, subspaces: one governing the nearly uncoupled subseasonal dynamics and the other governing the strongly coupled longer-term dynamics. These subspaces arise naturally from the LIM analysis; no bandpass frequency filtering need be applied. One implication of this remarkably clean separation of the uncoupled and coupled dynamics is that GCM errors in anomalous tropical air–sea coupling may cause substantial errors on interannual and longer time scales but probably not on the subseasonal scales associated with the MJO. [ABSTRACT FROM AUTHOR]

The atmospheric haze over the Pearl River Delta (PRD) was investigated by using the Models-3 Community Multi-scale Air Quality modeling system with meteorological fields simulated by the Fifth-generation National Center for Atmospheric Research/Penn State University Mesoscale Model (MM5) from September 26th to September 30th, 2004. The model-simulated meteorological elements and particulate matter with aerodynamic diameter less than 10 μm (PM10) were compared with observations at four air quality-monitoring stations. The results showed that MM5 successfully reproduced the diurnal variations of temperature, wind speed, and wind directions at these stations. The temporal variations of the simulated values were consistent with those of the observed (such as temperature, wind speed, and wind direction). The correlation coefficient was 0.91 for temperature and 0.56 for wind speed. The modeling results show that the spatial distributions of simulated PM10 were closely related to the source emissions indicating three maxima of PM10 over the PRD. The sea–land breezes diurnal cycle played a significant role in the redistribution and transport of PM10. Nighttime land breeze could transport PM10 to the coast and the sea, while daytime sea breeze (SB) could carry the accumulated PM10 offshore back to the inland cities. PM10 could also be transported vertically to a height of up to about 1000 m because of strong turbulence in the SB front. Process analyses indicated that the emission sources and the vertical diffusion were the major processes to influence the concentrations of particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5). [ABSTRACT FROM AUTHOR]

Low-pressure system (LPS), a major rain-bearing synoptic circulation, forming over the Indian region, including Bay of Bengal and Arabian Sea plays a vital role in performance of southwest monsoon over the country. The term LPS includes lows, depressions and cyclonic storms. According to the intensities, LPS are categorized into two, one only low-pressure areas (LPA) and the other more intense systems like depressions/storms (DDS). Statistical analysis reveals some significant results. Decadal analysis shows that there is a significant increase(decrease) in the frequency and duration of LPA(DDS) during the monsoon season for the recent decades. SST of Bay of Bengal also increased significantly during recent period. It is also observed that frequency and duration of LPA(DDS) show significant positive(negative) trend and sea surface temperature (SST) of the Bay of Bengal shows significant positive trend for the period after 1960. The total frequency of LPS has neither increased nor decreased significantly but the duration of LPS has significantly increased. This means, while the average total formation of the systems remains the same, the duration has increased. It seems that there are some atmospheric and oceanic conditions which are responsible for not allowing the intensification of lows into depressions. The frequency and duration of LPA(DDS) during the monsoon season are positively(negatively) correlated with SSTs of the Bay of Bengal during winter, pre-monsoon and monsoon season indicating warmer SST of the Bay of Bengal may not be favourable for intensifying lows into depressions. [ABSTRACT FROM AUTHOR]