Transport of Pollutants by the Sea Breeze in São Paulo under the South Atlantic High

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.

Estimation of the effective zone of sea/land breeze in a coastal area

The aim of this work is to determine the interaction in terms of ozone transport between two metropolitan regions of São Paulo State: The Metropolitan Region of Campinas (MRC) and Metropolitan Region of São Paulo (MRSP), with different characteristics and dimensions. In order to describe the interaction between both regions, 3-D Eulerian photochemical CIT model was used with a new approach for São Paulo regions since most previous studies deal with individual areas considering the contribution of other areas only as boundary conditions. The results from the photochemical simulations showed that the ozone concentration in the MRC is associated to local emissions and the transport of ozone and its precursors from the MRSP, demonstrating the significant impact of a megacity in its neighborhood and the importance of meteorological and topography conditions in the transport of air pollutants from the local source to distant regions.

Simulation of sea-land breezes and a discussion of their implications on the transport of air pollution during a multi-day ozone episode in the Pearl River Delta of China

Main properties of the Low-Level Jet (LLJ) in the metropolitan region of São Paulo (MRSP) are numerically simulated with the WRF (Weather Research Forecasting) model for two 10-day field campaigns of the MCITY BRAZIL Project, carried out in February 19-28 (Summer) and August 6-15 (winter) 2013. The WRF model was able to simulate 66.6% of the observed LLJ events, displaying a high degree of agreement with the observed main properties. These modeling results confirmed that the presence of an Upper Tropospheric Cyclonic Vortex northeast MRSP during summer and South Atlantic Subtropical High circulation in the MRSP during winter favor the LLJ formation. On average, the simulated LLJ is 2.9 m s-1 more intense in the rural area and 189 m higher in the urban area. The direction of the LLJ does not vary much between the urban and rural areas. These differences can be attributed to the urban- rural contrast in the roughness and thermal properties at the surface, which together influence the intensity of turbulence in the urban boundary layer. The simulations indicated that LLJ is part of a shallow flow reminiscent of the daytime sea-breeze circulation produced by shallow baroclinicity associated by the daytime land-ocean thermal contrast. The WRF-model simulation indicates that the LLJ observed in the MRSP spreads westward for more than 300 km over the interior of the State of São Paulo, becoming more intense. The behavior of the rural LLJ can be explained in terms of the mechanical blocking effect produced by the Serra de Cantareira high hills to the easterly flow from ocean caused by a combination of sea breeze and large-scale circulations in the MRSP.

A detailed study of the hourly variations of refractivity has been made from the meteorological data for a number of years at stations along the coasts of the Arabian Sea and the Bay of Bengal, during the clear months October to May. The prevailing winds and sea surface temperatures have also been taken into consideration when drawing inferences on the occurrence of anomalous propagation associated with the land and sea breezes.Ducting conditions over the coastal land areas will be absent in the sea breeze during the day when convection is active, but will be experienced from about the evening when the land cools and the temperature inversion begins to form and prevents convection. The ducting increases in intensity till the land breeze begins to flow. With the remaining sea-breeze moisture and the strong inversion, while there may be a fall in refractivity near the surface, ducting conditions will prevail. After sunrise, during the land breeze, there will be an increase in the intensity of the ducting due to the evaporation of moisture in the ground. However, with the increased convectional mixing with the upper layers, the ducting conditions will disappear. Later the warm land breeze which flows over the adjacent sea will cause conditions suitable for anomalous propagation over the sea. Thus, a shifting of the ducting conditions from the land areas to the sea takes place during the warm forenoon till the sea breeze sets in. it is expected that normal propagation conditions will prevail from the time of onset of the sea breeze till about sunset.Along the Arabian sea coast, from October to February, the pattern of ducting conditions changes wi h latitude. The times of onset and duration of the sea breeze undergo changes. However, from March to May, there is an appreciable change due to the altered conditions over the Arabian sea. An anticyclone develops near about the middle regions of the sea and air from the warmer areas flows over colder areas to the west of the anticyclone and later strike the west coast as a westerly over Bombay and to its northern latitudes. As a result anomalous propagation and ducting extends over a large area of the Arabian sea with little diurnal variation, particularly over the latitudes to the north of Bombay. During these months, ducting will be absent only over the land when convection is largest. Normal propagation will prevail all along the coasts of the Arabian sea during the monsoon months.Along the coasts of the Bay of Bengal, the conditions during October to February are different from those on the Arabian Sea. There is no common feature among Madras, Visakhapatnam and Calcutta. The sea breeze is practically absent at Calcutta, it is observed to occur at Visakhapatnam, and the northeast monsoon influences the land and sea breezes at Madras during October and November. However, from March to May, there is a large change in the prevailing conditions due to the variation in the distribution of the sea surface temperature and wind circulation over the Bay of Bengal, and are similar to those on the Arabian Sea. Ducting conditions prevail most of the time along the coasts in March-April and extend over the whole Bay in May when warmer air from the land flows over the cooler sea. During this minth, the large-scale ducting condition over the sea is accentuated near the coasts by the prevailing land breeze which is warmer than the sea most of the day and even night.An interesting feature over the Bay of Bengal coast is observed during the monsoon. While normal propagation prevails over most of the country, the land and sea breezes are strongest and prominent at Madras in this season and ducting conditions are experienced to the south of Madras.

The Central Japan has notable topographical features such that high mountains of the Japanese Alps exist at its center, large plains extend in its coastal area, and it is bounded with complex coast lines at the south and north sides facing to the Pacific Ocean and the Sea of Japan, respectively. Thus various types of local flows develop in summer season. In this situation, medium range transport of air pollutants from highly developed urban area to mountainous rural area has attracted concern of many people in applied meteorology and atmospheric environment in Japan, since it occurs in an interesting combination of several types of local winds such as land and sea breezes, mountain and valley winds, and plain-plateau winds, and the transport repeated in summer season probably causes severe damage to eco-systems in the mountainous area. Kurita et al. (1985) pointed out that the pollutants discharged in Tokyo Bay area migrate to the mountains in central Japan, i.e. the travel distance of about 150 km within one day. The distance far exceeded what was expected in simple sea breeze situation in mid-latitudes, and thus the phenomena suggested importance of combined effects of sea breeze, valley wind, and plain to plateau wind for the transport. Later Kondo (1990) numerically verified using meso-scale meteorological model that the presence of the high mountains in the central Japan, which are taller than 2000 m, is a key for the formation of the flow resulting in the medium range transport of pollutants. Kitada et al. (1998) also discussed dominant role of the high mountains of the central Japan in temporal variation of sea breezes over coastal plain area in the Pacific Ocean side, i.e., the Nohbi Plain. It was made clear more than 10 years ago, as noted above, that the pollutants released from huge urban areas in the coastal Japan such as Tokyo can be transported more than 150 km within 12 hours mostly during the daytime and reach to the mountains.

The main features of low‐level jet (LLJ) in the metropolitan region of São Paulo (MRSP), Brazil, are assessed using rawinsondes carried out: (a) every 3‐hr during 10‐consecutive days in summer and winter field campaigns of the MCITY BRAZIL Project in 2013, (b) at 0900 and 2100 local time, from September 2009 to August 2013. These observations indicate that the LLJ is a typical feature of the MRSP, observed in 85% of the 20 days of the field‐campaigns and 77.6% of the 1,446 days of regular rawinsonde period. The fine temporal and spatial resolution soundings indicate that most of the LLJs occur during nighttime and early in the morning, with mean intensity of 8.5 ± 0.3 m s−1, height of 539 ± 26 m, and mostly (52.5%) from east and north. The coarse resolution soundings indicate the LLJ display a seasonal variation with maximum intensity in October (8.6 ± 0.3 m s−1) and a minimum in February (7.1 ± 0.2 m s−1), a maximum height in March (703 ± 151 m) and a minimum in June (577 ± 151 m). During MCITY campaigns about 76.4% of LLJ events show inertial oscillation and 35.3% of them are combined with sea breeze. Only 17.6% of LLJ events are associated with cold fronts and post‐frontal high pressure system. The urban heat island intensity, surface inversion layer strength, particulate matter 2.5 and carbon monoxide concentrations are negatively correlated with the LLJ intensity, suggesting the jet‐induced turbulent mixing may contribute to reduce them.

Sea and land breezes represent fundamental types of coastal mesoscale meteorological phenomena. They result from the uneven heating of land and sea, which induces mesoscale pressure and therefore circulation oscillations between day and night. The onshore sea breeze occurs by day, peaking in afternoon, and the offshore land breeze occurs nocturnally, peaking near sunrise. The Florida peninsula has a double-sea breeze—from both the Atlantic Ocean and the Gulf of Mexico. Analogous processes occur when the water body is a large lake, in which case, the lake breeze occurs during afternoon hours. When well-organized along a homogeneous coastline, the sea breeze can form a sea-breeze front. The shape of a coastline also has a major impact on the timing and location of convergence associated with the sea breeze and the sea-breeze front. In order for a land or sea breeze circulation to develop, there must be a temperature difference between the land and the adjacent sea.

One of the most prominent mesoscale phenomena in the coastal zone is the sea-breeze/land-breeze circulation. The pattern and its implications for the weather in coastal areas are well described, and with mesoscale-resolving operational NWP models the circulation can be captured. In this study, a straightforward method to identify sea and land breezes based on the change in wind direction in the column above a grid point on the coastline is presented. The method was tested for southern Sweden using archived output from the HARMONIE-AROME model with promising results, describing both the seasonal and diurnal cycles well. In areas with a complex coastline, such as narrow straits, the concept of the land–sea breeze becomes less clear, and several ways to address this problem for the suggested method are discussed. With an operational index of the sea and land breezes, the forecaster can better understand and express the weather situation and add value for people in the coastal zone. Further, the indices can be used to study systematic biases in the model and to create climatologies of the sea and land breezes. Significance Statement A wind pattern that is frequently occurring in the coastal zone is the sea-breeze/land-breeze circulation, and the purpose of this study is to test a new method to automatically identify sea breezes and land breezes in weather forecasts. Knowing if a sea breeze or a land breeze is occurring is helpful for the operational weather forecaster in understanding the weather situation. It can also be used to study systematic model behavior, for example, errors in the forecast temperature during sea-breeze conditions. The method has been tested for seven coastal sites in Sweden and shows promising results both in case studies and multiyear statistics.

The Magnificent Frigatebird Fregata magnificens (MAFR) has the largest area of occurrence of any species in the Fregatidae family, with a large nesting colony in Southeast Brazil. However, studies with birds that occur on the coastal plain and in other areas of the continent are lacking. We organized information obtained in the field, from the literature, and from online ornithological platforms, and we evaluated the occurrence of MAFR on the plateau of the Metropolitan Region of São Paulo (MRSP), the largest urban area in South America. A total of 31 records were obtained dating back to 1960. Twelve of the records are concentrated near large reservoirs. The records indicate homogeneous seasonality over the years and occasional occurrence in a little-known extra-marine domain on the MRSP plateau. This occurrence has been detected in medium- and long-term field studies and by both photographers and bird watchers. Occurrence can be attributed to the proximity of this region to the coast and to the high flight capacity of these birds, in addition to the female and juvenile behavior of flying great distances, although these hypotheses need to be tested with new information.

Factors influencing atmospheric visibility (VIS) in coastal areas are more complex than those for inland and far oceans owing to the complex circulation and aerosol sources. This study analyzed the factors influencing VIS under sea-land breeze circulation (SLBC) for different external aerosol sources based on field survey data in southern Chinese coastal areas. First, SLBC characteristics observed during the experiment period showed that on SLBC days, sea breeze occurs more frequently (∼50%) than land breeze (∼27%), and the wind speed (WS) is generally small, with a mean sea and land breeze WSs of ∼2.18 m/s and ∼2.38 m/s, respectively. Then, analysis of factors influencing VIS was conducted for different land/sea breeze conditions and external aerosol source conditions indicated by the HYSPLIT4 model simulations. Results showed that the aerosol particle number concentration (PNC) and relative humidity (RH) both had negative correlations with VIS, while only very weak relationships between WS and VIS were found, possibly due to small WSs on SLBC days or because local aerosols were not pure marine aerosols. Further two-factor analysis of VIS showed that the power-law function relating VIS with PNC in each RH bin ranges from ∼-0.3 to ∼-1.5, and VIS exhibited sharper exponential decline with increasing PNC under high RH. A new method of retrieving aerosol-extinction hygroscopic growth factor (fext) with the measured VIS, RH, and PNC was developed to investigate the optical hygroscopic growth property of aerosols. Results show that aerosols in the study area have similar fext under different land/sea breeze and external aerosol source conditions; the deliquescence RH of aerosols is ∼60%, suggesting that mainly polluted marine aerosol was observed during experiments in this area.

Features of sea and land breezes, surface fluxes and drag coefficient over Cochin are studied using more than 300 daily observations of air temperature, wind speed and direction data. The duration and intensity of sea breeze circulation vary with the rain or cloud as it reduces the differential heating. Onset of sea breeze is early in summer season for the near equatorial station compared to winter season. Cessation is almost same for all seasons and is around 1900 hours. The sea breeze circulation is almost westerly and land breeze circulation is almost easterly in all the seasons. It is found that in most of the cases, the temperature and wind speed decreases at the time of onset of sea breeze and turning of wind direction with height becomes counter clockwise (backing) during the transition period from land breeze to sea breeze. In all seasons, the momentum flux is directed downward. High values of momentum flux were found during the presence of sea breeze in pre-monsoon season. Average sensible heat flux is directed upward during the entire period and during nighttime it is almost zero in the winter and monsoon seasons. The intensity of momentum flux decreases during onset and cessation of sea breeze for all the cases. The cold air advection associated with the sea breeze results in the decrease of sensible heat flux at the time of onset of sea breeze. Averaged surface momentum and sensible flux patterns resemble closely to the instantaneous pattern for all the seasons. Generally, sea breeze is stronger than land breeze in all the seasons. Accordingly, the drag coefficient power relationship with wind is different for sea breeze and land breeze circulations.Key words – Sea breeze circulation, Monsoon boundary layer, Surface fluxes, Drag coefficient, Diurnal variation.

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

A combination of observations and a numerical model revealed the meso‐scale structure of the near‐surface atmospheric conditions over the Persian Gulf. Low‐level winds were dominated by a single, coherent, perennial land–sea breeze circulation (LSBC) that varied seasonally and diurnally. In summer the sea breeze was deeper and wider than in winter. At night the core of the LSBC over the Gulf was confluent with uplift, whereas in daytime it was difluent with subsidence. Sensitivity tests with the model revealed the influence on the LSBC of the land–sea distribution, orography and the ambient wind. The latter resulted in different conditions over the north, east, south and west coasts. Over the north coast, where the opposing ambient wind created a sea breeze front, landward penetration was very limited; over the south coast it was over 250 km. The thermal effect of the Iranian mountains accentuated the depth and penetration, landward and seaward, of the LSBC, thus influencing the duration of the land and sea breezes over the east coast. From spring to autumn the marine boundary layer over the Gulf was shallow, cool, moist and stable, with strong vertical gradients of temperature and humidity at its top. Its depth increased in the ambient flow from northwest to southeast and also, in daytime, from west to east, because of different magnitudes of the subsidence in the sea breeze circulation over the west and east coasts. Copyright © 2004 Royal Meteorological Society