Land-sea Breeze Research Articles

Diurnal Cycle of Heating and Water Vapor in the Metropolitan Area of Porto in Portugal

In this work, it is investigated the Urban Heat Island (UHI) using conservative thermodynamic variables observed by surface weather stations on the Metropolitan Area of Porto (Oporto) in Portugal, under adiabatic conditions at the surface. These conditions are usually present and associated with the development of a mixture layer into the diurnal Convective Boundary Layer (CBL), which residual layer in the late afternoon defines the initial state for the development of the nocturnal UHI. Both the spatial structure and temporal variation of potential temperature and specific humidity were considered, along the hours and days of the year, from a statistical point of view, resulting in hourly climatology. Details of the hourly evolution of the meteorological variables on the Oporto surface are presented and discussed. Results show a seasonal variation of the potential temperature up to 17°C throughout the year, which is associated with horizontal thermal gradients that can control and trigger mesoscale circulations such as sea-land, urban and valley-mountain breezes.

Atmospheric PM2.5 near an Urban-Industrial Complex during Air-pollution Episodes with Various Meteorological Conditions

This study investigates the atmospheric fine particulate matter (PM2.5) issue caused by the multi-effect of complicated sources, terrain, and meteorology at Southern Taiwan. Three sampling stations represent an urban, a rural, and a coastal sites near an urban-industrial complex. The atmospheric PM2.5 were measured during a pollution episode from November to February, when the reference samples were collected in April. The sample was collected with a constant-flow sampler with the Federal Reference Method performance. After determining the PM2.5 mass, their chemical compositions of ions, metals, and carbons were analyzed for the different properties caused by the multi-factors. The chemical mass balance (CMB) model was employed to evaluate the emission contributions. Additionally, an inverse trajectory model is used to analyze the pollutant transport and support the CMB results. The air-pollution episodes occurred within the winter to spring. The PM2.5 were composed of 51-69% ions, 18-31% carbonaceous species, and 1.5-3.0% metals. The SO42-, NH4+ and NO3- contributed 92-96% of the ions. Most of the organic/elemental carbon ratios were low, suggesting more primary carbon emissions. The metal contents were minor and dominated by Fe and Zn. The CMB model indicated the PM2.5 were dominated by 24% secondary SO42-, 14.7% traffics, 8.3% petrochemical emissions, 6.8% soil dust, and 4.5% sintering plant emission. For non-episode days, the PM2.5 were contributed by 34.9% traffics, 30% the secondary SO42-, 10.3% secondary NO3- , and 6.8% soil dust. Nevertheless, the frequent sea-land breeze might lead to more powerful wind eddies and bring the primary PM2.5 and the aerosol precursors from the emission areas. Consequently, the uncontrollable meteorological changings would lead to the pollution issues at the lowly convective area. Therefore, the averaging emissions of the PM2.5 and precursors should be lowered; meanwhile, the rapid controls of the primary emissions are suggested when the high-level PM2.5 are forecasted.

Investigation on Applicability of Planetary Boundary Layer Schemes in Wrf Model for Simulating Sea-Land Breeze in Shanghai, China

Investigation on Applicability of Planetary Boundary Layer Schemes in Wrf Model for Simulating Sea-Land Breeze in Shanghai, China

Diurnal Variations in Primary and Secondary Organic Aerosols in an Eastern China Coastal City: The Impact of Land-Sea Breezes

Diurnal Variations in Primary and Secondary Organic Aerosols in an Eastern China Coastal City: The Impact of Land-Sea Breezes

Effects of Land-Sea Breeze Features to Long Term Pm2 . 5 Prediction in Central and Southern Taiwan Using Composite Neural Network

Effects of Land-Sea Breeze Features to Long Term Pm2 . 5 Prediction in Central and Southern Taiwan Using Composite Neural Network

Impact of Different Wind Representations on Resonant Ocean Near-inertial Motions in the Gulf of Mexico

This study investigates the resonated diurnal impact of the surface wind forcing from several atmospheric wind products, including CCMP (Cross-Calibrated Multi-Platform), ERA Interim, NCEP-2 (NCEP-DOE AMIP-II Reanalysis), MERRA (Modern-Era Retrospective analysis for Research and Application), NARR (Northern American Regional Reanalysis) and NAM (North American Mesoscale Forecast System), on the wind-driven near-inertial ocean motions in the northern Gulf of Mexico by numerical simulation, and in comparison, with NDBC buoy surface observed winds. Our analyses show that the near-inertial wind power input, which can affect vertical mixing in the water column, is closely associated with the variability of land-sea breeze by various wind products. In comparison with buoy observations in the northern Gulf of Mexico, the MERRA has the worst land-sea breeze representation, while the NCEP2 and CCMP, which are chosen to represent the coarsest and medium–high horizontal resolution, have the best performance. We further show that by comparison of the buoy data, that the near-inertial wind power input derived from all the wind products is underestimated by 30–50% approximately.

Air quality deterioration episode associated with a typhoon over the complex topographic environment in central Taiwan

Abstract. Air pollution is typically at its lowest in Taiwan during summer. The mean concentrations of PM10, PM2.5, and daytime ozone (08:00–17:00 LST) during summer (June–August) over central Taiwan were 35–40 µg m−3, 18–22 µg m−3, and 30–42 ppb, respectively, between 2004 and 2019. Sampling analysis revealed that the contribution of organic carbon (OC) to PM2.5 could have exceeded 30 % in urban and inland mountain sites during July in 2017 and 2018. Frequent episodes of air quality deterioration occur over the western plains of Taiwan when an easterly typhoon circulation interacts with the complex topographic structure of the island. We explored an episode of air quality deterioration that was associated with a typhoon between 15 and 17 July 2018 using the Weather Research Forecasting with Chemistry (WRF-Chem) model. The results indicated that the continual formation of low-pressure systems or typhoons in the area between Taiwan and Luzon island in the Philippines provided a strong easterly ambient flow, which lasted for an extended period between 15 and 17 July. The interaction between the easterly flow and Taiwan's Central Mountain Range (CMR) resulted in stable weather conditions and weak wind speed in western Taiwan during the study period. Numerical modeling also indicated that a lee side vortex easily formed, and the wind direction could have changed from southwesterly to northwesterly over central Taiwan because of the interaction between the typhoon circulation and the CMR. The northwesterly wind coupled with a sea breeze was conducive to the transport of air pollutants from the coastal upstream industrial and urban areas to the inland area. The dynamic process for the wind direction changed given a reasonable explanation for why the observed SO42- became the major contributor to PM2.5 during the episode. SO42- contribution proportions (%) to PM2.5 at the coastal, urban, and mountain sites were 9.4 µg m−3 (30.5 %), 12.1 µg m−3 (29.9 %), and 11.6 µg m−3 (29.7 %), respectively. Moreover, the variation of the boundary layer height had a strong effect on the concentration level of both PM2.5 and ozone. The lee vortex and land–sea breeze, as well as the boundary layer development, were the key mechanisms in air pollutant accumulation and transport. As typhoons frequently occur around Taiwan during summer and fall, their effect on the island's air quality merits further research attention.

Effects of the sea-land breeze on coastal ozone pollution in the Yangtze River Delta, China

Aim at the effects of the coastal characteristic on ozone pollution in the Yangtze River Delta (YRD), a campaign was launched at the Ningbo, China in the summer of 2020, which mainly covered the monitoring of the vertical profiles of ozone (O3) concentration, three-dimensional wind field, temperature and humidity profiles and parameters of boundary layer dynamic-thermodynamic structure. At the coastal research station, a sea-land breeze (SLB) circulation accompanied by a concurrent coastal low-level jets (CLLJ) structure was observed and identified during 11–12 May 2020. The sea breeze first formed at 10:00 LT on 11 May, turned to land breeze at night, and returned to sea breeze again at 10:00 LT the next morning, prevailing at altitudes of 0–0.5 km and 0–0.3 km respectively. Land breeze at night carries O3 from the inland to the sea forming high ozone levels over the sea, and the shift of the sea breeze during daytime further blew pollution back to the land. Additionally, the conversion of SLB contributed to the occurrence of CLLJ at the altitudes of ~0.3–0.7 km by 02:00 and 06:00 LT, of which the center of wind speed reached ~13 m s−1. The CLLJ-induced turbulent activity decoupled the residual layer (RL) and stable boundary layer, leading to a reduction of RL-O3 levels and an increase of ~50 μg m−3 in surface-O3 concentration. The YRD's unique coastal characteristics make O3 pollution causes in coastal areas more complicated.

Mesoscale variations of the chemical composition of submicron aerosols and its influence on the cloud condensation nuclei activation

Mesoscale variation of the chemical composition of submicron aerosol concentrations and their influence on cloud condensation nuclei (CCN) activation have been examined over a tropical coastal location in peninsular India during the winter season. The land-sea breeze circulation, boundary layer evolution, and photochemical processes significantly influence the diurnal variation of the aerosol chemical composition over the region. Broadly, the organic aerosols (mean ∼37.50 ± 27.00 μg m−3) dominated the submicron mass loading with a mass fraction (MF) of 0.66, followed by sulfate (∼10.92 ± 6.13 μg m−3; MF ∼0.19), ammonium (3.46 ± 1.71 μg m−3; MF∼0.06) and a small contribution from nitrate (1.7 ± 1.5 μg m−3; MF ∼0.03). The average mass concentration of organic carbon (OC) is 8.84 ± 6.42 μg m−3 with a mean organics/OC ratio of ∼3, indicating the presence of aged, highly oxidized organics. The diurnal variation of all the aerosol species, except sulfate, depicted daytime-low and nighttime-high. The photochemical formation of sulfate aerosols overwhelms the reduction in concentration due to boundary layer mixing and sea-land breeze circulation during the daytime. The decrease in the organics/sulfate ratio during the daytime has significant implications on the CCN concentration and its activation properties. The average CCN number concentration and activation ratio (ratio of CCN to total aerosol number concentration) at 0.38% supersaturation during the study period are ∼3756 ± 1609 cm−3 and 0.52 ± 0.17, respectively. The diurnal variation of CCN concentrations and activation ratio is distinctly different. The change in the mode diameter of the number size distribution between sea-land breeze was found to be less (∼8 nm) compared to the large variation in chemical composition. This suggested the importance of mesoscale variations of aerosols, especially the contrasting diurnal variation of organics and sulfate aerosols in CCN activation.

Investigation on Global Distribution of the Atmospheric Trapping Layer by Using Radio Occultation Dataset

The trapping layer refers to the atmospheric layer with vertical gradient of atmospheric refractivity less than −157 N-Units/km or vertical gradient of atmospheric modified refractivity 0 M-unit/km, which has a significant impact on radar and radio communication systems. Based on COSMIC and other radio occultation data, we show the statistical characteristics of the global trapping layer during 2005–2020.The statistical results show that the occurrence rate of the trapping layers is mainly concentrated between 50°S and 50°N, and higher occurrences of the trapping layers with more than 50% mainly occur in the boundary area between ocean and land, such as the northwest coastal area of Mexico, the west coastal area of Africa, the Mediterranean Sea, the Red Sea and the Arabian Sea, and the northwest area of Australia, etc. The altitude of the trapping layer is lower near the land and increases with the distance away from the coastline. The intensity is mainly between 6 M-unit and 24 M-unit (an M-unit is the unit of atmospheric modified refractivity), and the average value in some regions is above 24 M-unit, such as in the Arabian Sea area. In addition, the thickness of the trapping layer is between 50 and 240 m, and is generally larger over the ocean than over the land. These results reveal that the generation of the trapping layer is the result of the interaction of various background environmental factors such as radiation band migration, trade winds, monsoons, solar radiation heating, sea–land breezes and so on.

Svalbard’s Mesoscale Environmental Factor Impact on the Wind Field

The mesoscale circulation along the west shore of Spitsbergen is largely controlled by the difference in temperature between the glaciers and surface sea temperatures. We describe how the mesoscale effect influences the atmospheric circulation patterns. The conducted research was based on reanalysis data, model data, and atmospheric measurements; wind data from different sources and scales were compared and analysed. We discuss the situations wherein the mesoscale effect can be identified by analysing the wind direction or its velocity. This study shows the role of the mesoscale effect on the wind in the Svalbard region. Different situations according to the atmospheric patterns taken from a catalogue of 21 circulation types for each day created for Svalbard are analysed and compared with cases of land-sea breeze type circulation for the 20-year period between 1994 and 2013. It is proved that even if it is not possible to distinguish this mesoscale effect based on the difference between local and large-scale wind directions, this factor can be observed by studying the wind speeds. It is claimed that as long as there are glaciers on Spitsbergen, there will be a mesoscale land-sea breeze type circulation controlled by the difference in air temperature over land and water.

Influences of offshore background wind on the formation of sea-land breeze and the characteristics of pollutant diffusion.

The formation of sea-land breeze (SLB) is primarily affected by background wind and temperature difference between the sea and nearby land. Because the intensity of sea breeze is significantly stronger than that of land breeze, land breeze may result in more accumulated pollutants under the condition of offshore background wind (OBW) than under the condition of no OBW in coastal areas. The formation process of sea-land breeze and the dispersion trajectory and accumulation effect of pollutants are studied under different velocities of OBW with the same sea-land temperature difference by employing computational fluid dynamics (CFD). The results reveal that the depth and the duration of sea breeze decrease with the increase of the velocity of OBW. The most unfavorable velocity of OBW (0.2 m s-1) exists when the concentration affected by OBW is higher than that by no OBW in coastal areas. The pollutants close to the ground will be blown to the inland by sea breeze when the velocity of OBW is less than 1.0 m s-1. When the velocity of OBW is larger than 2.0 m s-1, the pollutants will not occur on the inland due to the influence of OBW.

Physical processes controlling the diurnal cycle of convective storms in the Western Ghats

Diurnal variation of convective storms (CSs) during monsoon season and associated physical mechanisms are significantly important for accurate forecast of short-time and extreme precipitation. The diurnal cycle of CSs is investigated using ground-based X-band radar, Tropical Rainfall Measuring Mission Precipitation Radar, and reanalysis data during the summer monsoon (June–September of 2014) over complex mountain terrain of Western Ghats, India. Diurnally, CSs show a bimodal distribution in the coastal areas, but this bimodality became weak along the upslope regions and on the mountain top. The first occurrence mode of CSs is in the afternoon–evening hours, while the second peak is in the early-morning hours. The diurnal cycle’s intensity varies with location, such that it reaches maximum in the afternoon–evening hours and early morning on the mountain top and coastal areas, respectively. Two possible mechanisms are proposed for the observed diurnal variation in CSs (a) the radiative cooling effect and (b) the surface wind convergence induced by the interaction between land-sea breeze, local topography and large-scale monsoon winds. It is also observed that the CSs developed on the mountain top during afternoon–evening hours are deeper than those along the coast. The higher moisture in the lower- and mid-troposphere, higher instability and strong upward motion facilitate deeper CSs during afternoon–evening hours.

Switching to electric vehicles can lead to significant reductions of PM2.5 and NO2 across China

Switching to electric vehicles can lead to significant reductions of PM2.5 and NO2 across China

The interaction of an urban heat island with a sea breeze front during moist convection over Tianjin, China

The interaction of an urban heat island with a sea breeze front during moist convection over <scp>Tianjin, China</scp>

Climatology of Sea–Land Breezes Along the Southern Coast of the Levantine Basin

The present work can be considered the first to examine the sea–land breeze phenomenon along the southern border of the Levantine Basin. Hourly records of wind regime (speed and direction) from five coastal meteorological stations distributed over this coastline were analyzed to characterize sea and land breezes in this region. The meteorological data also comprised simultaneous hourly air temperature and relative humidity records. The data covered 13 years from January 2007 to December 2019, with 0% missed data. The diurnal inversion of wind direction was utilized to recognize sea and land breeze days. This was verified by the reversal daily behavior of temperature and relative humidity. Statistics describing the onset, cessation, and seasonality of sea breeze occurrence are presented. Seasonally, sea breezes are most frequent in summer and early autumn months (July–October). Land breeze appears at most stations during night, with direction varying from one location to another among the five examined coastal stations.

Hourly Variation of Wind Speeds in the Philippines and Its Potential Impact on the Stability of the Power System

Wind energy development has been limited by concerns associated to the varying features in wind speed which tends to destabilize the power system. This study aims to clarify the variability of winds within a day in the Philippines, specifically the hourly changes of onshore horizontal winds at 100-m hub-heights. A whole one-year experiment using the Weather Research and Forecasting model shows that onshore wind speeds decrease during the transitional hours between land breeze and sea breeze. The decreases in wind speed are most significant over coastal regions with high sloping topography. The extreme decreases in wind speed during morning hours, due to the natural processes, are found to often occur at the same time as the extreme electricity undersupply caused by the morning increase in energy demand. This result warns that the power system stability in the Philippines may become more sensitive to the variability of wind as the share of wind energy generation increases in the future. The findings of this study can contribute to promote sustainability in the operation of existing wind-reliant power systems and planning of future wind energy developments.

The Crucial Role of Synoptic Pattern in Determining the Spatial Distribution and Diurnal Cycle of Heavy Rainfall over the South China Coast

AbstractThe South China coast suffers frequent heavy rainfall every warm season. Based on the objective classification method of principal components analysis, the key role of the synoptic pattern in determining the heavy rainfall processes that occurred over the South China coast in the warm season during 2008–18 is examined in this study. We found that heavy rainfall occurs most frequently under three typical synoptic patterns (P1–P3 hereafter) characterized by strong low-level onshore winds. P1 and P3 feature a prevailing southwesterly monsoonal flow in the lower troposphere, with heavy rainfall frequently occurring over the inland windward region in the afternoon associated with the orographic lifting and solar heating. The onshore wind of P3 is stronger than P1 as the western Pacific subtropical high extends more westward to 122°E, which induces stronger low-level convergence along the coastline than P1 when the ageostrophic wind veers from the offshore to onshore direction in the early morning. Hence, a secondary early morning rainfall peak can be found along the coastline. P2 is characterized by a low-level vortex located over the southwest portion of south China. Heavy rainfall under P2 usually initiates over the western part of the coastal region in the morning and then propagates inland in the afternoon. Overall, the synoptic patterns strongly determine the spatial distribution and diurnal cycle of heavy rainfall over the South China coast. This heavy rainfall is closely related to the diurnally varying low-level onshore winds rather than the low-level jets, as well as the different interactions between the low-level onshore winds and the local orography, coastline, and land–sea breeze circulations under different synoptic patterns.

Insight Into the Seasonal Variations of the Sea‐Land Breeze in Los Angeles With Respect to the Effects of Solar Radiation and Climate Type

AbstractThis study uses 20 years of observation data to analyze the long‐term trend of the sea‐land breeze (SLB) in the city of Los Angeles. The focus of the study is on the seasonal variation of the SLB and the main influencing factors both regionally and at a large scale. A new method which is suitable for automatic processing is introduced to analyze the SLB and determine the specific characteristics of the local SLB. The results show the sea wind speed has an obvious seasonal variation with peak value in summer and minimum value in winter. Note the sea wind speed is generally positively related to the in situ solar radiation. In contrast, the seasonal variation of the land wind speed is much weaker. Two main factors are responsible for this phenomenon. First, the response of the temperature difference between land and sea (TDLS) to the season is much more insensitive during nighttime than during daytime, and the TDLS is the direct driver of SLB. Second, the magnitude of the upper layer westerlies has an obvious seasonal variation under the local climate background, which is called the Mediterranean climate. During winter, the stronger upper westerlies enhance the land wind circulation, which further offsets the seasonal gap, and this even causes the fact that there is no corresponding relationship between the season and wind speed. In contrast, the seasonal variation of the westerlies has little effect on the sea wind speed, and the in situ solar radiation remains the determinant factor.

Study of the Characteristics of Wind over Nuclear Power Plants in Korea

To establish a strategy for public protective action from radioactive leakage in the event of Nuclear Power Plant (NPP) accidents, long-term records of wind data collected at the Korean NPPs were analyzed. Wind characteristics related to the advection and diffusion of radioactive pollutants were examined by analyzing the wind direction, speed, and land-sea breezes for NPPs (Hanbit, Hanul, Wolsong, Kori, and Shin-Kori) in Korea. The study also analyzed the characteristics of calm winds causing the accumulation of radioactive materials. The wind characteristics of each NPP differ depending on the seasonal and daily variabilities; thus, a detailed time-scaled airflow database is required. In addition, the findings, through continuous updates of the airflow database, will contribute to improving preparedness.