Atmospheric gaseous HCl influenced by sea-land breeze circulation in a southeast Chinese coastal city

Onshore winds amplify shipping PM2.5 exposure in a coastal megaport city: Insights from source apportionment and machine learning.

Understanding the mechanisms of coastal PM2.5 formation driven by land-sea breeze recirculation and ship emissions.

Abstract The Organization of Tropical East Pacific Convection (OTREC) experiment took place from 5 August to 9 October 2019 in Costa Rica, with additional measurements collected in July and August of 2022. To observe the interaction of tropical easterly waves (TEWs) with the diurnal cycle over Central America and to assess the wave vertical structure over land, we installed a network of 15 global positioning system receivers with meteorological packages (GPS-Met), as well as two radiosonde sites, from the Caribbean to the Pacific coast. An outgoing longwave radiation (OLR)-based wave index indicates that 13 TEWs passed over the surface network during OTREC, with an additional 15 waves during 2022. The relative phasing of peak GPS column precipitable water vapor (PWV) with peak rainfall, together with vertical velocity and moisture profiles of wave active phases from reanalyses, suggests that isolated convective systems with lower-tropospheric heating and moisture evolve into more organized convective systems with elevated heating and moistening as the wave’s active phase progresses inland over Costa Rica. The signatures of propagation in rainfall, PWV, and cloud-top temperature are most pronounced for the active phase, with rain events observed to propagate westward across the network with about a 12-h lag from coast to coast. In contrast, local diurnal land–sea-breeze interactions with strong surface heating play an important role in the timing of convection during the suppressed phase. Significance Statement The results of this study shed light on how tropical easterly waves, westward-propagating disturbances observed over tropical latitudes, interact with the diurnal cycle in rainfall, land–sea-breeze circulations, and low- and midlevel easterly winds over Central America, enhancing the frequency and amount of rainfall and modulating its timing over the region. These results not only highlight the importance of scale interactions in rainfall processes for tropical land areas with strong oceanic influences but also provide situational awareness to operational forecasters tasked with predicting local-scale impacts of synoptic weather events.

This study examined air quality data collected from 2015 to 2023 across Shenyang, Dalian, Changchun, and Harbin to assess interannual and monthly variations in PM2.5, PM10, SO2, NO2, and O3, along with their correlations, seasonal meteorological influences, and potential source regions. Annual mean concentrations of PM2.5, PM10, SO2, and NO2 declined substantially (by 39.9–79.3%), whereas O3 showed a fluctuating pattern, remaining persistently high in the coastal city of Dalian. Seasonally, PM2.5, PM10, SO2, and NO2 concentrations peaked in winter and decreased in summer, while O3 displayed the opposite trend. Particulate levels in Liaoning rebounded earlier in spring than in Jilin and Heilongjiang. Correlation analysis revealed strong positive relationships among particulate and gaseous pollutants, but O3 generally exhibited negative correlations with other species. Haze events occurred mainly in winter, whereas complex pollution episodes were more frequent in summer. Meteorological analysis indicated that relative humidity was negatively correlated with PM2.5, PM10, SO2, and NO2 in summer but positively correlated in winter. Elevated temperatures outside the winter months promoted NO2 dispersion and enhanced O3 formation. Strong winds in spring and winter markedly reduced PM2.5 and SO2 levels, though this effect was less evident in Shenyang. WPSCF results identified significant cross-regional transport from the southwest contributing to PM2.5, PM10, and NO2 during spring and winter, while O3 was primarily affected by long-range transport in spring and only marginally in winter. In Dalian, sea–land breeze circulation further intensified transport processes in summer and autumn. Overall, this work provides an integrated, multi-year, and multi-city assessment of pollution dynamics, meteorological drivers, and transboundary transport in Northeast China, offering new insights into regional air quality improvement and its spatial heterogeneity relative to other regions of China.

Abstract The characteristics of the land and sea breeze near the west coast of Sumatra are studied using hourly 10-m wind observations from the Bengkulu Airport for the year 2018, with an emphasis on the properties of the land breeze. Spectral analysis shows that the land–sea breeze cycle is a dominant part of the overall circulation in the region, with disturbances at the diurnal frequency accounting for roughly half the overall disturbance kinetic energy. A method is presented for isolating the near-diurnal parts of the flow through a combination of high- and low-pass filtering, with land and sea breezes defined in terms of the shore-perpendicular component of the filtered winds. By this definition, a land breeze occurs each day, with a median onset time of 1900 LT, a median duration of 15 h, and a median maximum speed of 1.8 m s−1 occurring near 0200 LT. The characteristics of the land breeze are found to depend strongly on the phase of the Madden–Julian oscillation. A dependence was also found during the Asian and Australian monsoons, particularly for the onset time and maximum speed. Sea breezes occur almost every day but are much shorter (about 8.5 h) and stronger (>3 m s−1) than land breezes. Comparisons between airport observations and ERA5 surface winds show that while ERA5 accurately captures the onset time, duration, and timing of the maximum speed for sea breezes, it only captures the onset time and duration for land breezes. For both, the maximum speed is significantly underestimated. Significance Statement Detailed characteristics of tropical land and sea breezes are lacking in the literature. Utilizing 1 year of hourly wind observations from the west coast of Sumatra and a newly developed detection algorithm, we found that land and sea breezes occur essentially every day. Land breezes start just after sunset but last many hours after sunrise and reach their maximum speed almost halfway through their median 15-h duration. These properties vary intraseasonally and seasonally. Sea breezes begin around 1000 LT and are much shorter and stronger than land breezes. ERA5 does a reasonable job capturing many characteristics of the land–sea breeze circulation but underestimates the maximum wind speed in both cases.

A pilot investigation of PM10-bound atmospheric microplastics over a protected mangrove ecosystem: Role of land-sea breeze circulation in marine and terrestrial inputs.

WRF-UCM simulations of urbanization impacts on land–sea breeze circulations during three heatwaves in Colombo, Sri Lanka

Abstract This study investigates the impact of the interaction between large‐scale and local‐scale forcings in regulating rainfall patterns and their propagation over coastal areas of Northeast (NE) Australia using a convective‐scale regional model run for 180 days. Over the coastal areas, spatially heterogeneous rainfall patterns are evident in both radar observations and model simulations. By classifying the characteristics of three distinct rainfall groups, we found that the rainfall propagation modulates the average rainfall patterns. Modelling results suggest that the large‐scale background wind and local‐scale land–sea breeze circulations are two important factors driving rainfall propagation. Offshore rainfall propagation, which is frequently observed in coastal regions in the tropics, occurs during the days with weak easterlies near the surface and strong upper‐and mid‐level westerlies. Rainfall is triggered during the afternoon by convergence driven by the sea breeze and then propagates offshore during the nighttime with the land breeze density current and large‐scale background westerlies. In contrast, onshore rainfall propagation is observed during days with strong background easterlies from the surface to upper levels. For the No‐Propagation group, rainfall occurs during the afternoon due to the convergence of sea breezes and low‐level background westerlies, and it persists over land during the nighttime with low‐ and mid‐level easterlies. Our results also suggest that the background wind regimes associated with different phases of intraseasonal variability modulate the direction and strength of rainfall propagation, leading to different coastal rainfall patterns.

Understanding the interactions between air pollutants and vegetation is essential for developing effective air quality management strategies, particularly in forest-rich regions. This study investigates the spatial and temporal characteristics of air pollution in Gangwon Province, South Korea, from 2019 to 2023, focusing on pollutant concentrations, emissions, and their relationships with vegetation. We utilized data from the national air quality monitoring network, including PM10, PM2.5, and O3 concentrations, along with emissions data from the Clean Air Policy Support System (2019–2021) and NDVI data derived from MODIS satellite observations. Our analysis revealed that PM concentrations were highest in inland cities such as Chuncheon, Hongcheon, and Wonju, largely due to atmospheric stagnation and topographical confinement, while coastal areas exhibited lower levels owing to maritime dispersion. O? levels were elevated in coastal and mountainous regions, influenced by land-sea breeze circulation. Emissions varied regionally, with traffic and fugitive dust dominating in urban inland areas, biomass burning in Gangneung, and industrial emissions in Donghae. Seasonal patterns showed PM peaking in spring and winter, while O3 peaked in summer. NDVI exhibited a consistent negative correlation with PM, particularly PM2.5, indicating the potential mitigating effect of vegetation. In contrast, O3-NDVI correlations varied regionally, showing positive associations in some western areas. These findings emphasize the importance of region-specific air quality policies, including green space expansion for PM control and precursor emission management for O3, along with continued monitoring of external pollutant inflows and meteorological stagnation.

Characteristics of sea-land breeze circulation in coastal-urban regions of China

Hot–wet compound events, the sequential occurrence of humid hot days followed by extreme rainfall, can cause catastrophic consequences, often exceeding the impacts of the isolated occurrence of each event. The urban-coastal microclimate is confounded by complex interactions of land–sea breeze circulations, urban effects of convection and rainfall, and horizontal advection of moisture, which can favor the hot–wet compound occurrence. We present the first observational assessment (1951–2022) of summertime hot–wet compound events across global coastal megacities. We find a significant (P < 0.001) increase in the frequency of hot–wet compound events in both hemispheres: on average, ~3 events in the 1950s to 43 events in the 2020s. Cities with upward trends in the frequency of hot–wet compound events are situated < 30 km from coasts, with cities in the southern hemisphere showing faster hot-to-wet transition times (<3 days) than cities in the northern hemisphere. Further, 26 out of 29 sites show increased extreme precipitation, reaching 153%, when humid heat amplitude rises from the 50th to 90th percentiles. Understanding hot–wet compound interactions over the world’s coasts is highly relevant for climate change impact assessment and informing climate adaptation.

The ambient levels of NO2 in urban areas in China in recent years have generally shown a downward trend, but high NO2 concentrations still exist under certain conditions, and the causes for such phenomenon and its impact on air quality remain unclear. Taking Dongying, a typical petrochemical city in the Bohai Bay of China, as an example, this paper analyzed the influence of NO2 on urban air quality and investigated the causes for the formation of NO2 with high concentrations. The results indicated that higher daily NO2 concentrations (>40 μg/m3) mainly occurred during January-April and September-December each year, and higher hourly NO2 concentrations mainly occurred during the nighttime and morning rush hour in Dongying from 2017 to 2023. With the increase in daily NO2 concentrations, the daily air pollution levels showed a general increasing trend from 2017 to 2023. The occurrence of high NO2 values in Dongying was affected by the combination of unfavorable meteorological conditions, local emissions and regional transports, and localized atmospheric chemical generation. High-pressure and uniform-pressure weather patterns in 2017-2022, along with land-sea breeze circulation in 2022, contribute to high NO2 concentrations in Dongying. Boundary layer heights (BLH) in spring (-0.43) and winter (-0.36), wind direction in summer (0.21), and temperature in autumn (-0.46) are the primary meteorological factors driving NO2-HH (High hourly NO2 values), while BLH (-0.47) is the main cause for NO2-HD (High daily NO2 values). The titration reaction between NO with O3 is the main cause for NO2-HH in spring, summer and autumn, and photochemical reactions of aromatics have a significant influence on NO2-HD. NOx emissions from the thermal power and petrochemical industry in Dongying and air pollution transports from western and southwestern Shandong Province (throughout the year) and from the Bohai Sea (during spring and summer) had serious adverse impact on high NO2 values in 2022. The results of the study could help to provide a scientific basis for the control of NO2 and the continuous improvement of air quality in Dongying and similar petrochemical cities.

In recent years, ground-level-ozone（O3） pollution in urban areas in the Bohai Rim has attracted wide attention. Based on the analysis of the spatiotemporal distribution characteristics of O3 concentration in Dongying, a representative city in the Bohai Rim from 2017 to 2022, the effects of meteorological factors and sea-land breeze circulation on O3 concentration were evaluated. The results showed that： ① From 2017 to 2022, the annual assessment value of O3 concentration in Dongying showed a fluctuating upward trend, and the pollution days with O3 as the primary pollutant increased. O3 pollution mainly occurred in spring, summer, and autumn, with the most severe O3 pollution episodes typically occurring in May and June, and the duration of O3 pollution season tended to be longer. The monthly variation in the daily maximum 8-h average ozone （MDA8 O3） presented a bimodal distribution, with significant increases in the 5th and 25th percentiles, and the spatial distribution was "high in the north and south, low in the middle." In addition, the nocturnal O3 concentration in recent years in Dongying also showed a significant increase trend. ② Meteorological factors greatly influenced O3 concentration in Dongying. When the temperature was greater than 30℃, the relative humidity was less than 50%, and the wind direction was south-southwest or east-northeast, a high O3 value was more likely to occur. Meteorological factors contributed 30% of the MDA8 O3 variation in Dongying during the study period. In the case of moderate and severe O3 pollution, the contribution of meteorological factors to the change in MDA8 O3 could be as high as 40%. ③ To some extent, sea-land breeze contributed to the occurrence of MDA8 O3 exceeding the secondary standard limit value of the National Ambient Air Quality Standard. In the afternoon, the hourly concentration of O3 during the sea-land breeze days was approximately 20 μg·m-3 higher than that during the non-sea-land breeze days. On the days of moderate and severe O3 pollution, the O3 concentration during the sea-land breeze days from 10：00 to 16：00 was higher than that during non-sea-land breeze days, and the O3 concentration was also at a high level from 20：00 to 23：00 on sea-land breeze days. In the O3 pollution season, the sea-land breeze could significantly affect the O3 level in coastal cities, which could bring significant challenges for O3 pollution prevention and control in this region. In the future, cities in the Bohai Rim need to further strengthen regional joint prevention and control of O3 pollution and increase emission reduction efforts of nitrogen oxides and volatile organic compounds. This strategy could effectively lower pollutant concentrations within the land breeze air mass, consequently reducing the impact of the sea breeze air mass on air quality in cities in the Bohai Rim.

Recirculated transport mechanism aggravates ozone pollution over the mountainous coastal region: Increased contribution from vertical mixing

Influences of daily solar radiation intensity on the sea-land breeze and pollutant dispersion in coastal areas

Abstract To understand how coastal precipitation is controlled by the low-level background wind, we performed comprehensive analysis using the 17-yr observations of the TRMM PR over the entire region of the tropics. We classified the data according to the direction (onshore or offshore) and strength of the cross-shore wind. Under weak winds, the contribution of the diurnal cycle to total precipitation is large, indicating that thermally forced precipitation with a symmetrical propagation pattern with opposite sign across the coastline is dominant. As the background wind strengthens, the contribution of the diurnal cycle reduces owing to the predominance of mechanical forcing; however, the effect of the diurnal cycle remains nonnegligible with an asymmetrical propagation pattern across the coastline. Using the linear theory of the sea–land-breeze circulation, we demonstrated that the difference in propagation is attributable to gravity waves excited by the land–ocean surface heating difference. Under weak winds, symmetrical diurnal phase propagation is caused by the two symmetrical modes of landward and seaward gravity waves. Under stronger background winds, in addition to the Doppler-shifted landward and seaward modes, waves propagating toward the upwind side in the flow-relative frame but with slow group velocity are advected to the downwind near the coastline, forming another mode that moves slowly in the downwind direction. The superposition of the three modes leads to asymmetrical propagation of precipitation with varying phase speed depending on the distance from the coastline.

As the main anthropogenic source in open seas and coastal areas, ship emissions impact the climate, air quality, and human health. The latest marine fuel regulation with a sulfur content limit of 0.5% went into effect globally on January 1, 2020. Investigations of ship emissions after fuel switching are necessary. In this study, online field measurements at an urban coastal site and modeling simulations were conducted to detect the impact of ship emissions on air quality in the Greater Bay Area (GBA) in China under new fuel regulation. By utilizing a high mass-resolution single particle mass spectrometer, the vanadium(V) signal was critically identified and was taken as a robust indicator for ship-emitted particles (with relative peak area > 0.1). The considerable number fractions of high-V particles (up to 30-40% during ship plumes) indicated that heavy fuel oils via simple desulfurization or blending processes with low-sulfur fuels were extensively used in the GBA to meet the global 0.5% sulfur cap. Our results showed that ship-emitted particulate matter and NOx contributed up to 21.4% and 39.5% to the ambient, respectively, in the summertime, significantly affecting the air quality in the GBA. The sea-land breeze circulation also played an important role in the transport pattern of ship-emitted pollutants in the GBA.

Few studies have explored the details of climatology in the Gulf of California (GoC) coastal zone, a region characterized by robust land–sea breeze circulation that results from land heating on both coasts of the GoC. Using hourly historical observations from automatic weather stations (AWSs) from 2008 to 2018, we performed harmonic and empirical orthogonal function analyses to describe the climatology of several characteristics that are regularly monitored in the GoC coastal zone. The characteristics included air temperature (°C), relative humidity (%), atmospheric pressure (hPa), wind intensity (m s−1), and wind direction (°). The National Water Commission (CNA) provided records for stations located along the coast of the GoC. The results revealed an intense annual and, to a lesser extent, interannual signal for all characteristics. The presence of synoptic patterns forces seasonal and intraseasonal variations to occur. In summer, tropical systems increase the seasonal variability, mainly at the eastern mouth of the GoC. Some stations display this increase until the cold season arrives with the passage of winter systems. Finally, we found that interannual variability could be associated with El Niño–Southern Oscillation events.

Performance of summertime temperature and wind fields under different background winds in Kowloon, Hong Kong