Southerly Transport Research Articles

Wave and Littoral Processes at Thengapattanam Coast, Kanyakumari District, Tamil Nadu State, SW India

The field investigations were carried out on the beach profiles, breaking wave parameters and longshore currents for a period of 25 months from December 2006 to December 2008 to study the beach dynamics of Thengapattanam coast, Kanyakumari district, Tamilnadu state, SW India. The Thengapattanam beach is well known for its long history, estuary, tourism, manmade structures and fishing activities. Monthly measurements were prepared on littoral environmental observations (LEO) and beach level variations. Longshore sediment transport rates were estimated based on the observed data. The estimated annual gross longshore sediment transport rate was higher due to recent manmade structures and the net transport was towards southerly direction . The beach profile level was lowest in July and high in April and the variation was 35 m. The total volume of sand transported was 840 m3/yr during 2007 and 710 m3/yr during 2008. The wave heights varied between 0.4 to 2.5 m during 2007 and 0.45 to 1.8 m during 2008, whereas wave period was between 8 sec to 15.5 sec and 7 sec to 21 sec for 2007 and 2008 respectively. The study concluded that the beach is experiencing significant erosion. Thengapatanam beach is being subjected to erosion phase during both monsoon seasons and get stable profiles by fair weather seasons. Longshore currents were stronger in June, July and August and steady during rest of the year. The net southerly transport was 1.2*106 m3/yr during 2007 and 0.577*106 m3/year during 2008. The volume variations of the sediments, an account of accretion/erosion were estimated considering the January 2007 profile as the base reference over which the values of other months were compared. The study area is highly vulnerable due to its erosion and other factors.

Influence of circulation types on temporal and spatial variations of ozone in Beijing

This study analyzes the impact of circulation types (CTs) on ozone (O3) pollution in Beijing. The easterly high-pressure (SWW) circulation occurred most frequently (30%; 276 day), followed by northwesterly high-pressure (AN) circulation (24.3%; 224 day). The SWW type had the highest O3 anomaly of +17.28 µg/m3, which was caused by excellent photochemical reactions, poor diffusion ability and regional transport. Due to the higher humidity and precipitation in the low-pressure type (C), the O3 increase (+8.02 µg/m3) was less than that in the SWW type. Good diffusion/wet deposition and weak formation ability contributed to O3 decrease in AN (-12.54 µg/m3) and northerly high-pressure (ESN) CTs (-12.26 µg/m3). The intra-area transport of O3 was significant in polluted circulations (SWW- and C-CTs). In addition, higher temperature, radiation and less rainfall also contributed to higher O3 in northern Beijing under the SWW type. For the clean CTs (AN and ESN CTs), precursor amount and intra-area transport played a dominant role in O3 distribution. Under the northeasterly low-pressure CT, better formation conditions and higher precursor amount combined with the intra-area southerly transport to cause higher O3 values in the south than in the north. The higher O3 in the northwestern area under the northeasterly high-pressure type was influenced by weaker titration loss and high O3 concentration in previous day. Annual variation in the CTs contributed up to 86.1% of the annual variation in O3. About 78%-83% of the diurnal variation in O3 resulted from local meteorological factors.

Wintertime Observations of Tropical Northwest Atlantic Aerosol Properties During ATOMIC: Varying Mixtures of Dust and Biomass Burning

AbstractThe Atlantic Tradewind Ocean‐Atmosphere Mesoscale Campaign (ATOMIC) took place from 7 January to 11 July 2020 in the tropical North Atlantic between the east coast of Barbados and the Northwest Tropical Atlantic Station (NTAS) mooring. Measurements of aerosol chemical, microphysical, optical, and cloud‐nucleating properties were made during boreal winter onboard the NOAA RV Ronald H. Brown from 7 January to 13 February 2020. Observed aerosol properties indicate there were distinct periods when the aerosol was typical of clean marine conditions (particle number concentrations <400 cm−3, light absorption levels <1 Mm−1, and 222Rn concentrations <500 mBq m−3) and when there were intrusions of dust mixed to varying degrees with biomass burning aerosol. In comparison to the long‐term dust record at the Barbados Atmospheric Chemistry Observatory, the fraction of samples collected during ATOMIC with dust concentrations greater than 20 μg m−3 exceeded all years of the Barbados January to February record with the exception of 1983. The degree of mixing of the dust with biomass burning aerosol was modulated by the location of the North Atlantic subtropical high. A high located to the west of Africa led to a more northerly transport route and more dust‐like (MDL) aerosol arriving at the ship. A location of the high further to the east over northern Africa led to a more southerly transport route and more biomass burning aerosol mixed with the dust. Properties for the marine, MDL, and mixed dust and biomass burning aerosol are presented.

Non-stop industries were the main source of air pollution during the 2020 coronavirus lockdown in the North China Plain.

Despite large decreases of emissions of air pollution during the coronavirus disease 2019 (COVID-19) lockdown in 2020, an unexpected regional severe haze has still occurred over the North China Plain. To clarify the origin of this pollution, we studied air concentrations of fine particulate matter (PM2.5), NO2, O3, PM10, SO2, and CO in Beijing, Hengshui and Baoding during the lockdown period from January 24 to 29, 2020. Variations of PM2.5 composition in inorganic ions, elemental carbon and organic matter were also investigated. The HYSPLIT model was used to calculate backward trajectories and concentration weighted trajectories. Results of the cluster trajectory analysis and model simulations show that the severe haze was caused mainly by the emissions of northeastern non-stopping industries located in Inner Mongolia, Liaoning, Hebei, and Tianjin. In Beijing, Hengshui and Baoding, the mixing layer heights were about 30% lower and the maximum relative humidity was 83% higher than the annual averages, and the average wind speeds were lower than 1.5 m s−1. The concentrations of NO3−, SO42−, NH4+, organics and K+ were the main components of PM2.5 in Beijing and Hengshui, while organics, K+, NO3−, SO42−, and NH4+ were the main components of PM2.5 in Baoding. Contrary to previous reports suggesting a southerly transport of air pollution, we found that northeast transport caused the haze formation.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10311-021-01314-8.

Boundary layer structure characteristics under objective classification of persistent pollution weather types in the Beijing area

Abstract. Different types of pollution boundary layer structures form via the coupling of different synoptic systems and local mesoscale circulation in the boundary layer; this coupling contributes toward the formation and continuation of haze pollution. In this study, we objectively classify the 32 heavy haze pollution events using integrated meteorological and environmental data and ERA-Interim analysis data based on the rotated empirical orthogonal function method. The thermodynamic and dynamic structures of the boundary layer for different pollution weather types are synthesized, and the corresponding three-dimensional boundary layer conceptual models for haze pollution are constructed. The results show that four weather types mainly influence haze pollution events in the Beijing area: (a) type 1 – southerly transport, (b) type 2 – easterly convergence, (c) type 3 – sinking compression, and (d) type 4 – local accumulation. The explained variances in the four pollution weather types are 43.69 % (type 1), 33.68 % (type 2), 16.51 % (type 3), and 3.92 % (type 4). In persistent haze pollution events, type 1 and type 2 surpass 80 % on the first and second days, while the other types are present alternately in later stages. The atmospheric structures of type 1, type 2, and type 3 have typical baroclinic characteristics at mid–high latitudes, indicating that the accumulation and transport of pollutants in the boundary layer are affected by coupled structures in synoptic-scale systems and local circulation. The atmospheric structure of type 4 has typical barotropic characteristics, indicating that the accumulation and transport of pollutants is primarily affected by local circulation. In type 1, southerly winds with a specific thickness and intensity prevail in the boundary layer, which is favorable for the accumulation of pollutants in plain areas along the Yan and Taihang Mountains, whereas haze pollution levels in other areas are relatively low. Due to the interaction between weak easterly winds and the western mountains, pollutants accumulate mainly in the plain areas along the Taihang Mountains in type 2. The atmospheric vertical structure is not conducive to upward pollutant diffusion. In type 3, the heights of the inversion and boundary layers are the lowest due to a weak sinking motion while relative humidity is the highest among the four types. The atmosphere has a small capacity for pollutant dispersion and is favorable to particulate matter hygroscopic growth; as a result, type 3 has the highest PM2.5 concentration. In type 4, the boundary layer is the highest among the four types, the relative humidity is the lowest, and the PM2.5 concentration is relatively lower under the influence of local mountain–plain winds. Different weather types will shape significantly different structures of the pollution boundary layer. The findings of this study allow us to understand the inherent difference among heavy pollution boundary layers; in addition, they reveal the formation mechanism of haze pollution from an integrated synoptic-scale and boundary layer structure perspective. We also provide scientific support for the scientific reduction of emissions and air quality prediction in the Beijing–Tianjin–Hebei region of China.

Hekla 1947, 1845, 1510 and 1158 tephra in Finland: challenges of tracing tephra from moderate eruptions

ABSTRACTSeveral cryptotephra layers that originate from Icelandic volcanic eruptions with a volcanic explosivity index (VEI) of ≤ 4 and tephra volumes of < 1 km3 have previously been identified in Northern Europe, albeit within a restricted geographical area. One of these is the Hekla 1947 tephra that formed a visible fall‐out in southern Finland. We searched for the Hekla 1947 tephra from peat archives within the previously inferred fall‐out zone but found no evidence of its presence. Instead, we report the first identification of Hekla 1845 and Hekla 1510 cryptotephra layers outside of Iceland, the Faroe Islands, Ireland and the UK. Additionally, Hekla 1158 tephra was found in Finland for the first time. Our results confirm that Icelandic eruptions of moderate size can form cryptotephra deposits that are extensive enough to be used in inter‐regional correlations of environmental archives and carry a great potential for refining regional tephrochronological frameworks. Our results also reveal that Icelandic tephra has been dispersed into Finnish airspace at least seven times during the past millennium and in addition to a direct eastward route the ash clouds can travel either via a northerly or a southerly transport pathway.

Regional Transport Increases Ammonia Concentration in Beijing, China

To elucidate the critical factors influencing the ammonia (NH3) concentration in Beijing, this study combined observational analyses, backward trajectory calculations, and meteorology–chemistry coupled simulations to investigate the variations in the NH3 concentration from 11 May to 24 June, 2015. A significant positive correlation was found between the NH3 and PM2.5 concentrations in Beijing. By examining the relationships between meteorological parameters and the NH3 concentration, both near-surface temperature and relative humidity showed positive correlations with the NH3 concentration. The higher NH3 concentrations were usually associated with the warming of the upper atmosphere. Distinct wind directions were noted during the days of the top and bottom 33.3% NH3 concentrations. The top 33.3% concentrations were primarily related to southwesterly winds, while the bottom ones were associated with westerly and northerly winds. Since there are strong NH3 emissions in the southern plains adjacent to Beijing, the regional transport induced by the southerly prevailing winds would increase the NH3 concentration in Beijing significantly. From 23 to 25 May, more than one third of NH3 in Beijing was contributed by the southerly transport processes. Thus, joint efforts to reduce NH3 emissions in the whole Beijing–Tianjin–Hebei region are necessary to regulate the NH3 concentration in Beijing.

Haze pollution under a high atmospheric oxidization capacity in summer in Beijing: insights into formation mechanism of atmospheric physicochemical processes

Abstract. Under a high atmospheric oxidization capacity, the synergistic effect of the physicochemical processes in the atmospheric boundary layer (ABL) caused summer haze pollution in Beijing. The southern and southwestern areas, generally 60–300 km away from Beijing, were seriously polluted in contrast to Beijing, which remained clean. Southerly winds moving faster than 20–30 km h−1 since the early morning primarily caused haze pollution initiation. The PM2.5 (particulate matter with a dynamic equivalent diameter smaller than 2.5 µm) level increased to 75 µg m−3 over several hours during the daytime, which was simultaneously affected by the ABL structure. Additionally, the O3 concentration was quite high during the daytime (250 µg m−3), corresponding to a high atmospheric oxidation capacity. Much sulfate and nitrate were produced through active atmospheric chemical processes, with sulfur oxidation ratios (SORs) up to ∼0.76 and nitrogen oxidation ratios (NORs) increasing from 0.09 to 0.26, which further facilitated particulate matter (PM) level enhancement. However, the increase in sulfate was mainly linked to southerly transport. At midnight, the PM2.5 concentration sharply increased from 75 to 150 µg m−3 over 4 h and remained at its highest level until the next morning. Under an extremely stable ABL structure, secondary aerosol formation dominated by nitrate was quite intense, driving the haze pollution outbreak. The PM levels in the southern and southeastern areas of Beijing were significantly lower than those in Beijing at this time, even below air quality standards; thus, the contribution of pollution transport had almost disappeared. With the formation of a nocturnal stable boundary layer (NSBL) at an altitude ranging from 0–0.3 km, the extremely low turbulence kinetic energy (TKE) ranging from 0 to 0.05 m2 s−2 inhibited the spread of particles and moisture, ultimately resulting in elevated near-surface PM2.5 and relative humidity (∼90 %) levels. Due to the very high humidity and ambient oxidization capacity, NOR rapidly increased from 0.26 to 0.60, and heterogeneous hydrolysis reactions at the moist particle surface were very notable. The nitrate concentration steeply increased from 11.6 to 57.8 µg m−3, while the sulfate and organics concentrations slightly increased by 6.1 and 3.1 µg m−3, respectively. With clean and strong winds passing through Beijing, the stable ABL dissipated with the potential temperature gradient becoming negative and the ABL height (ABLH) increasing to ∼2.5 km. The high turbulence activity with a TKE ranging from 3 to 5 m2 s−2 notably promoted pollution diffusion. The self-cleaning capacity of the atmosphere is commonly responsible for air pollution dispersion. However, reducing the atmospheric oxidization capacity, through strengthening collaborative control of nitrogen oxide (NOx) and volatile organic compounds (VOCs), as well as continuously deepening regional joint air pollution control, is urgent.

Transport Pathways and Potential Source Regions of PM2.5 on the West Coast of Bohai Bay during 2009–2018

Mass concentration data for particulate matter with an aerodynamic diameter less than or equal to 2.50 μm (PM2.5) combined with backward trajectory cluster analysis, potential source contribution function (PSCF), and concentration weighted trajectory (CWT) methods were used to investigate the transport pathways and potential source regions of PM2.5 on the west coast of Bohai Bay from 2009 to 2018. Two pathways responsible for the transportation of high PM2.5 levels were identified, namely a southerly pathway and a northwesterly pathway. The southerly pathway represented the major transport pathway of PM2.5 for all seasons. As a regional transport pathway, it had the greatest impact in winter, followed by autumn. The southerly transport pathway passed over the Shandong and Hebei provinces before reaching Tianjin: Air masses were transported within the boundary layer (below 925 hPa), representing a slow-moving air flow. The northwesterly pathway mostly occurred in winter and autumn and passed over desert and semidesert regions in Outer Mongolia, the sand lands of Inner Mongolia, and Hebei. The air masses associated with the northwesterly pathway represented fast-moving airflows responsible for long-range transportation of PM2.5. Two potential source regions that contributed to high PM2.5 loadings on the west coast of Bohai Bay were identified, “southerly source regions” and “northwesterly source regions”. The southerly source regions, with weighted CWT (WCWT) values in winter greater than 140.00 μg/m3, were anthropogenic source regions, including southern Hebei, western Shandong, eastern Henan, northern Anhui, and northern Jiangsu. The northwesterly source regions, with WCWT values in winter of 80.00–140.00 μg/m3, were natural source regions, encompassing central Inner Mongolia and southern Mongolia. In addition, the southerly transport pathway passed though anthropogenic source regions, while the northwesterly transport pathway passed though natural source regions. The impacts of anthropogenic source regions on PM2.5 loadings on the west coast of Bohai Bay were greater than those of natural source regions.

Observation of atmospheric new particle growth events at the summit of mountain Tai (1534 m) in Central East China

New particle formation (NPF) and growth is an important phenomenon in terms of the global particle number concentrations. However, our knowledge about NPF events at the top of the boundary layer is particularly weak in heavily polluted conditions. In this study, the aerosol size distributions, black carbon (BC), chemical components of single particles, particulate matter (PM2.5 and PM10) and meteorological data were collected from May 12 to June 8, 2017 at the summit of Mt. Tai by using a wide-range particle spectrometer (WPS), Aethalometer (AE-33), a single particle aerosol mass spectrometer (SPAMS), a β-ray continuous ambient particulate monitor and an automatic weather station. Twelve new particle growth (NPG) events occurred during the observation period, accounting for 46.2% of the total observation days. The average relative humidity (RH) was 52% on NPF days and was 11.5% lower than the value on non-NPG days. The average temperature and wind speed were 18 °C and 5.3 m s−1 on NPG days, respectively, which were 12.2% and 18.9% higher than those on non-NPG days. The PM2.5 concentration differed slightly on NPG and non-NPG days. However, the concentrations of PM10 and BC were relatively high on NPG days, with average values of 88.0 μg m−3 and 1849.9 ng m−3, respectively, which were 1.2 and 1.3 times higher than those on non-NPG days. The NPG events had major influences on the size distributions of aerosol number concentration at 10–60 nm and surface area concentrations at 100–300 nm. During the NPG events, the average formation rate (FR), growth rate (GR), condensational sink (CS), vapor source rate (Q) and condensing vapor concentration (C) were calculated to be 1.30 cm−3 s−1, 14.54 nm h−1, 3.21 × 10−2 s−1, 7.34 × 106 cm−3 s−1 and 19.92 × 107 cm−3, respectively. The NPG events were influenced mostly by foreign transport processes and less impacted by local surrounding pollutants. The meteorological factors varied with different types of NPG events. The chemical components varied greatly during different types of NPG events. Sulfate had a small influence on three types of NPG events. Nitrate and ammonium had comparatively great impacts on local and southerly transport NPG events. The organic matters contributed more significantly to the northerly transport NPG events.

Regional pollution and its formation mechanism over North China Plain: A case study with ceilometer observations and model simulations

AbstractTo investigate regional haze formation, ceilometer observations at the Beijing (BJ), Shijiazhuang (SJZ), Tianjin (TJ), and Qinhuangdao (QHD) stations were conducted from 12 October to 10 November 2014, to obtain the boundary layer height (BLH) and the attenuated backscattering coefficients (ABC). Particles at the four stations were highly correlated, whereas precursors of particles exhibited weaker correlations. By analyzing the typical haze episode between 21 and 26 October 2014, we found that warm advection at a height of 850 hPa from the Loess Plateau caused a gradual decline in the regional BLH. Moreover, water vapor transported from the southern NCP caused the column water vapor amount to increase from 0.015 kg m−2 to 0.042 kg m−2 in the boundary layer in BJ. As southerly transport prevailed during the transition period, ABC profiles in the BJ, TJ, and QHD stations showed a bilayer pattern, and the second layer was between 500 and 1000 m. As a result, the ABC integrations of BJ and TJ increased by 74.2 and 139.7%, respectively. During the polluted period, due to the weakened transport effect, the ABC integrations of the four stations decreased by 7.9, 18.2, 16.2, and 28.2%, respectively. Contributions of the secondary inorganic species (sulfate, nitrate, and ammonium) at BJ increased from 37.3% to 56.9%, and the mean particle size increased from 107.8 nm to 140.8 nm. Emissions in southern NCP should be mitigated during the transition period, whereas the inorganic precursors are the most important air pollutants during the polluted period.

Linkages between Arctic summer circulation regimes and regional sea ice anomalies

AbstractThe downward trend in overall Arctic summer sea ice extent has been substantial, particularly in the last few decades. Departures in ice extent from year to year can be very large, however, in part due to the high variability in summer atmospheric circulation patterns. Anomalies in the Pacific sector ice cover can be partially compensated by anomalies of opposite sign in the Atlantic sector. An assessment of linkages between summer atmospheric patterns and sectoral anomalies in the area of maximum open water north of 70°N demonstrates that there is asymmetry in the mechanisms. Years with low ice extent and high open water fraction are uniformly associated with positive temperature anomalies and southerly flow in both the Atlantic and Pacific sectors. However, years with high extent and low open water fraction in both sectors reveal two dominant mechanisms. Some years with anomalously low maximum open water fraction are associated with negative temperature anomalies and southerly transport—a cool summer pattern that allows ice to persist over larger areas. However, other low open water years are characterized by an “ice factory” mechanism, whereby—even when melting—ice cover is continually replenished by advection from the north.

Analysis of Low-Level Atmospheric Moisture Transport Associated with the West African Monsoon

Abstract The major objective of this study is to re-evaluate the ocean–land transport of moisture for rainfall in West Africa using 1979–2008 NCEP–NCAR reanalysis data. The vertically integrated atmospheric water vapor flux for the surface–850 hPa is calculated to account for total low-level moisture flux contribution to rainfall over West Africa. Analysis of mean monthly total vapor fluxes shows a progressive penetration of the flux into West Africa from the south and west. During spring (April–June), the northward flux forms a “moisture river” transporting moisture current into the Gulf of Guinea coast. In the peak monsoon season (July–September), the southerly transport weakens, but westerly transport is enhanced and extends to 20°N owing to the strengthening West African jet off the west coast. Mean seasonal values of total water vapor flux components across boundaries indicate that the zonal component is the largest contributor to mean moisture transport into the Sahel, while the meridional transport contributes the most over the Guinea coast. For the wet years of the Sahel rainy season (July–September), active anomalies are displaced farther north compared to the long-term average. This includes the latitude of the intertropical front (ITF), the extent of moisture flux, and the zone of strong moisture flux convergence, with an enhanced westerly flow. For the dry Sahel years, the opposite patterns are observed. Statistically significant positive correlations between the zonal moisture fluxes and Sudan–Sahel rainfall totals are most pronounced when the zonal fluxes lead by 1–4 pentads. However, although weak, they still are statistically significant at lags 3 and 4 for meridional moisture fluxes.

Longshore Sediment Transport along the Coast of Kerala in Southwest India

Accurate estimation of longshore sediment transport (LST) along the entire coastal stretch of Kerala is challenging as the sediment transport pattern varies both spatially and temporally depending on the nearshore wave climate, nearshore bedslope, shoreline orientation, coastal morphology, presence of hard structures etc. While majority of the locations show a net northerly drift, there are certain stretches of the coast which are dominated by southerly transport. For the estimation of longshore sediment transport the three commonly used formulae viz. CERC (SPM (1984)), Van Rijn (1991) and Kamphuis (2002) were considered. After detailed analysis of the computed LST results for different sectors of the coast using these formulae, the formula of Kamphuis (2002) which considers all the important parameters like the nearshore bed slope, sediment grain size and peak wave period in addition to the usual input parameters like the wave breaker height and wave breaker angle was selected as the most appropriate one. To understand the spatial and temporal variation in the LST pattern along the Kerala coast, the LST rates for eight important locations - viz. Trivandrum, Quilon, Aleppey, Andhakaranazhi, Nattika, Calicut, Kannur and Kasargod spread along the Kerala coast were computed adopting the Kamphuis (2002) formula. For computation of the LST rates for the eight locations, the one year site specific nearshore wave data derived from numerical model studies was used. For validation, the results were compared with that of the earlier estimations available in literature. It was observed that even though the net magnitude was of the same range, there were deviations in the direction. However, when the results were compared with field observations (where morphological indicators were used) a reasonable agreement could also be established for the directions. The net annual longshore sediment transport was found to vary between 0.32 x 105 m3 and 2.3 x 105 m3 along the Kerala coast and the net transport direction was pre-dominantly northerly for almost all the locations selected for the study. The maximum gross sediment transport of 12.85 x 105 m3 was obtained for Trivandrum but the net transport for this station was much less, and therefore comparable with other locations.

Will the role of intercontinental transport change in a changing climate?

Abstract. Intercontinental transport of atmospheric pollution (ITAP) can offset the impact of local emission control efforts, impact human and ecosystem health, and play a role in climate forcing. This study aims to determine the role of ITAP caused by East Asian anthropogenic emissions (EAAEs) under current and future emission and climate scenarios. The contribution from EAAEs is determined using a "brute force method" in which results from simulations with and without EAAEs are compared. ITAP from East Asia is enhanced in the future due to faster wind speeds aloft and a stronger low pressure center near eastern Russia that facilitate enhanced westerly export in the free troposphere and stronger southerly transport near the surface, increased gaseous precursor emissions, and increased temperatures. As a result, the contribution of ozone (O3) generated by EAAEs to the global average O3 mixing ratio increases by ~0.8 ppb from 1.2 ppb in 2001 to 2.0 ppb in 2050. The contribution of PM2.5 generated by EAAEs to the global PM2.5 level increases by ~0.07 μg m−3 from 0.32 μg m−3 in 2001 to 0.39 μg m−3 in 2050, despite a non-homogenous response in PM2.5 resulting from cloud and radiative feedbacks. EAAEs can increase East Asian biogenic secondary organic aerosol by 10–81%, indicating that it is largely controllable. EAAEs also increase the deposition of nitrogen, black carbon, and mercury both locally and downwind, implying that they may play a role in climate feedbacks and ecosystem health of these regions. These results show that EAAEs have a large impact on global air quality and climate, especially on downwind regions. Such impacts may be enhanced under future climate and emission scenarios, demonstrating a need to synergize global pollution control and climate mitigation efforts.

Near shore waves, long-shore currents and sediment transport along micro-tidal beaches, central west coast of India

Coastlines are undergoing constant geomorphologic changes with respect to the incident wave climate. Based on waves measured at 9 m water depth, simulation of near shore wave transformation is done using REFDIF-1 numerical model and the near shore breaker parameters are estimated at two micro-tidal beaches along central west coast of India. Model results are validated with measured values. From the breaker parameters, long-shore current and long-shore sediment transport rates (LSTR) are computed by using semi-empirical equations. Estimated long-shore current and LSTR are showing dramatic variations with respect to seasons. Predominant direction of LSTR is observed towards north since the approach waves are from south-west direction during pre-monsoon and post monsoon. During monsoon season, waves are from west south-west and resulted in southerly transport. The estimated annual net and gross LSTR by Cambridge Environmental Research Consultants (CERC) at two locations are in the same order whereas LSTR estimated by Walton & Bruno and Kamphuis equations are showing different estimations because of difference in surf-zone width and foreshore slope between the two locations. For micro-tidal beaches with length less than 6 km, Kamphuis equation is giving agreeable estimation of LSTR. Sensitivity analysis of LSTR estimate shows that coastal inclination is the prominent factor in determining LSTR than incident wave angle.

Travelling forelands: complexities in drift and migration patterns

Burningham, H., French, J.R., 2014. Travelling forelands: complexities in drift and migration patterns. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 102–108, ISSN 0749-0208.Cuspate forelands have been described from a range of shorelines around the world, but in the majority of cases, the foreland maintains a constant position relative to the neighbouring shoreline. Here, we describe the contemporary geomorphology and historical evolution of a small cuspate foreland on the Suffolk coast, UK, which has been migrating northward for several centuries. Benacre Ness, a mixed sand and gravel sedimentary accumulation, is currently located at Kessingland, 5 km to the north of Benacre, from which it gained its name when adjacent to it in the 19th century. The foreland was previously called Covehithe Ness, having been adjacent to Covehithe (3 km south of Benacre) early in the 19th century. Previous sediment transport experiments and modelling studies have demonstrated a net southerly transport direction on this coastline, yet the foreland has continued to migrate northward over several centuries. Local reversals in sediment transport direction and rates are likely responsible for the northward migration of the foreland, but substantial changes in behaviour over the last 400 years suggest a close relationship between foreland dynamics and coastal configuration.

Post-monsoon equilibrium beach profiles and longshore sediment transport rates at Candolim, Miramar and Keri beaches of Goa, India

Equilibrium profile is one of the conce pts in coastal geomorphology which is a result of the balance of destructive versus constructive forces. Two e quilibrium be ach profile models, viz. Bruun/Dean’s twothirds power mode l and modified Bodge expone ntial model were used to analyse the measured post-monsoon (winter) beach profiles from three beaches in Goa having varying coastal morphology settings. The major factors that affect the equilibrium beach profile, viz. the me dian grain size (D50) and the profile shape factor m, which are inve rsely proportional to each othe r, have been analysed for their application to the study site. Also, the variation of these two parameters with beach slope and grain size is studie d. Longshore sedime nt transport rates (LSTRs) are estimate d at these three beaches from the littoral environme ntal observations. LSTRs show that during winte r months, the net transport is of the orde r of 10.83  10 6 m 3 /year (southe rly transport) and 9.02  10 6 m 3 /year (southerly transport) respectively, at Candolim and Ke ri beaches, whe reas it is about 0.62  10 6 m 3 /year (northerly transport) at Miramar. This article discusses the methods used and results of measure me nts of beach morphology, LSTRs, analysis of equilibrium profiles and influe nce of various paramete rs relate d to equilibrium profiles.

Airborne measurements of gas and particle pollutants during CAREBeijing-2008

Abstract. Measurements of gaseous pollutants – including ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NOX = NO + NO2), carbon monoxide (CO), particle number concentrations (5.6–560 nm and 0.47–30 μm) – and meteorological parameters (T, RH, P) were conducted during the Campaigns of Air Quality Research in Beijing and Surrounding Regions in 2008 (CAREBeijing-2008), from 27 August through 13 October 2008. The data from a total 18 flights (70 h flight time) from near the surface to 2100 m altitude were obtained with a Yun-12 aircraft in the southern surrounding areas of Beijing (38–40° N, 114–118° E). The objectives of these measurements were to characterize the regional variation of air pollution during and after the Olympics of 2008, determine the importance of air mass trajectories and to evaluate of other factors that influence the pollution characteristics. The results suggest that there are primarily four distinct sources that influenced the magnitude and properties of the pollutants in the measured region based on back-trajectory analysis: (1) southerly transport of air masses from regions with high pollutant emissions, (2) northerly and northeasterly transport of less pollutant air from further away, (3) easterly transport from maritime sources where emissions of gaseous pollutant are less than from the south but still high in particle concentrations, and (4) the transport of air that is a mixture from different regions; that is, the air at all altitudes measured by the aircraft was not all from the same sources. The relatively long-lived CO concentration is shown to be a possible transport tracer of long-range transport from the northwesterly direction, especially at the higher altitudes. Three factors that influenced the size distribution of particles – i.e., air mass transport direction, ground source emissions and meteorological influences – are also discussed.

PLANNING, PRELIMINARY DESIGN, AND INITIAL PERFORMANCE OF THE NAGS HEAD BEACH NOURISHMENT PROJECT

A 3.5 million cubic meter beach nourishment project was completed along 16 kilometers of shoreline at Nags Head, North Carolina, 32 kilometers south of the US Army Corps of Engineers Field Research Facility at Duck. The project is the largest locally-funded nourishment accomplished to date in the United States. Three ocean-certified hopper dredges and one cutterhead suction dredge constructed the project between May and October 2011. This paper discusses the planning, design, and initial performance of the project. Nags Head is exposed to high waves from the northeast which generate net southerly transport over the long term. A key design issue for the project was the large gradient in erosion rates from north to south. Fill sections were varied accordingly based on documented volume erosion rates and model simulations for the area. Permitting involved over five years of environ¬mental reviews because of the need to work during fair-weather summer months in the relatively high-energy setting. The design also built on prior work in connection with a federal nourishment project scheduled for the area if and when funds become available. Two offshore areas strategically located close to south Nags Head were utilized for construction which proceeded efficiently under summer waves until late August when Hurricane Irene impacted the area. The hurricane and fall northeast storms produced rapid adjustment of the construction profile but no net loss of sand from the project area. Post-project surveys show initial profile equilibration was largely confined to the inshore zone inside the 3.7 meter (m) [âˆ'12 foot (ft) NAVD] contour. Depth of closure at decadal scales is estimated to be âˆ'7.3 m (âˆ'24 ft NAVD).