Distance Inland Research Articles

The origin of solutes in groundwater in a hyper-arid environment: A chemical and multi-isotope approach in the Atacama Desert, Chile

The major ion and the multi-isotopic composition (87Sr/86Sr, δ11B, δ34S(SO4) and δ18O(SO4)) of groundwater from the Central Depression in northern Chile is investigated to identify the origin of groundwater solutes in the hyper-arid core of the Atacama Desert. The study area is between the Cordillera de Domeyko and the Central Depression, at latitudes 24–25°S, and is characterized by near-zero air moisture conditions, rare precipitation and very limited runoff. Groundwater composition varies from Ca-HCO3 to Ca, Na-SO4 type below elevations of 3400 m a.s.l. The rCl/rBr ratio of meteoric waters and groundwater overlap, but significantly increase in the aquifer as salinity goes up due to evapoconcentration far from the Domeyko Cordillera. The wind-displaced dust originating in the Central Depression (87Sr/86Sr: 0.706558–0.710645; δ34S(SO4): 0 to +4‰) affects the precipitation composition in the highest parts of the Domeyko Cordillera (87Sr/86Sr: 0.706746–0.709511; δ34S(SO4): +1 to +6‰), whose δ34S(SO4) and δ11B values are greatly different from marine aerosols, discarding its contribution to dust at this distance inland. Sr and S isotopic values in groundwater indicate a strong relation with three main geological units: i) Paleozoic rocks contribute high radiogenic strontium isotope ratios to groundwater (0.707011–0.714862), while sulphate isotopic composition is probably acquired from atmospheric dust (>− 1.4‰), ii) Jurassic marine limestones contribute low-radiogenic strontium isotopic ratios to groundwater (<0.70784), while sulphate can be related to oxidized sulphides that change the isotopic signatures of sulphur (<−1.2‰), and iii) mixed salts in the Atacama Gravels contribute lower radiogenic strontium isotopic ratios and sulphate to groundwater (87Sr/86Sr: <0.707324; δ34S(SO4): +0.1 to +7.7).These three processes reflect water-rock interactions. The δ11B of groundwater generally up to +13‰, does not increase along the regional groundwater flow path, discarding fractionation by interaction with clays. These results improve the understanding of the groundwater evolution in hyper-arid systems through a new conceptual model.

Impacts of transport connections on port hinterlands

ABSTRACTThis paper examines the spatial distribution of freight flows between the French NUTS-3 regions and West European ports. It focuses on the impacts of the quality of inland and maritime connections on the scope of hinterlands. The results of a spatial interaction analysis reveal that the inland distance constraint is significantly lower when intermodal connections such as regular barge or rail services are available. A case study focused on East Asian trade confirmed that factors related to maritime connectivity, such as the frequency of services at ports and their ability to accommodate large vessels, also contribute to limit the distance impedance. However, these effects vary considerably depending on the value density of the cargo.

Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica

Abstract. Antarctic ice core nitrate (NO3-) can provide a unique record of the atmospheric reactive nitrogen cycle. However, the factors influencing the deposition and preservation of NO3- at the ice sheet surface must first be understood. Therefore, an intensive program of snow and atmospheric sampling was made on a traverse from the coast to the ice sheet summit, Dome A, East Antarctica. Snow samples in this observation include 120 surface snow samples (top ∼ 3 cm), 20 snow pits with depths of 150 to 300 cm, and 6 crystal ice samples (the topmost needle-like layer on Dome A plateau). The main purpose of this investigation is to characterize the distribution pattern and preservation of NO3- concentrations in the snow in different environments. Results show that an increasing trend of NO3- concentrations with distance inland is present in surface snow, and NO3- is extremely enriched in the topmost crystal ice (with a maximum of 16.1 µeq L−1). NO3- concentration profiles for snow pits vary between coastal and inland sites. On the coast, the deposited NO3- was largely preserved, and the archived NO3- fluxes are dominated by snow accumulation. The relationship between the archived NO3- and snow accumulation rate can be depicted well by a linear model, suggesting a homogeneity of atmospheric NO3- levels. It is estimated that dry deposition contributes 27–44 % of the archived NO3- fluxes, and the dry deposition velocity and scavenging ratio for NO3- were relatively constant near the coast. Compared to the coast, the inland snow shows a relatively weak correlation between archived NO3- and snow accumulation, and the archived NO3- fluxes were more dependent on concentration. The relationship between NO3- and coexisting ions (nssSO42-, Na+ and Cl−) was also investigated, and the results show a correlation between nssSO42- (fine aerosol particles) and NO3- in surface snow, while the correlation between NO3- and Na+ (mainly associated with coarse aerosol particles) is not significant. In inland snow, there were no significant relationships found between NO3- and the coexisting ions, suggesting a dominant role of NO3- recycling in determining the concentrations.

Mesoscale precipitation characteristics near the Western Ghats during the Indian Summer Monsoon as simulated by a high‐resolution regional model

This study investigates (i) the role of orography in precipitation along and upstream of the Western Ghats (WG) and (ii) a diurnal cycle of precipitation in western India during the summer monsoon, using a high‐resolution meteorological model and a network of surface rain‐gauges over the WG. The Weather Research and Forecasting model (WRF‐ARW) was used to simulate the 2008, 2009 and 2010 summer monsoons at 5 km horizontal grid spacing and allows resolved convection, with initial and boundary conditions provided by ERAInterim. The highest daily mean precipitation is found immediate to the WG escarpment and coastal plain between 11.5° and 18°N, but areas receiving the most rainfall do not necessarily receive it most frequently. The greatest percentage of rainy days occurs over the escarpment of the WG and slightly inland, corresponding to the topography, and high percentages (over 75%) of rainy days occur along the coast, along the coastal plain and the WG. These findings are in agreement with several recent studies using high spatial resolution Tropical Rainfall Measuring Mission (TRMM) precipitation data. Analysis of WRF output at time increments of 30 min reveals a clear diurnal pattern of rainfall, with an early morning maximum offshore and afternoon maxima over inland regions that occur later in the day with distance inland. A weak land breeze circulation is observed, as nocturnal cooling of the land surface results in deceleration of westerly flow upstream of the WG. Offshore moisture convergence and destabilization of low‐level air results in the offshore morning maximum. Rainfall maxima over inland regions indicate that, while orography is the primary impetus for lift, rainfall is also convectively driven. Analysis of convective parameters and landsurface variables such as soil moisture and latent and sensible heat fluxes supports this weak land–sea breeze circulation embedded in prevailing westerly monsoonal flow.

Quantitative roundness analysis of coastal boulder deposits

The sedimentology of coastal boulder deposits (CBD) is little known. These deposits, and especially the largest clasts within them—which commonly weigh many 10s of tonnes—are of increasing interest because they attest to extreme energy wave events acting well above the high-tide mark (in some cases >40m above high water and >100m inland). Recent observations have made clear that storm waves (rather than tsunami) are important in both creating and activating these deposits; but beyond that we know little about their hydrodynamics, or the relative frequency of boulder movement, and how this might vary with topographic setting.Roundness is a first-order characteristic that preserves a record of deposit reworking. It can tell us whether clasts move around much after they have been created from bedrock, or whether they are emplaced into CBD with little or no subsequent transport. But because roundness has historically been difficult to measure, most roundness estimates in the literature are based on qualitative visual assessment, and are therefore of limited analytical value. Fully reproducible roundness measurements are possible, however, and in the case of boulders they can be acquired quite easily using the Kirkbride (2005) device in combination with a trigonometric formula presented here.CBD at locations in Ireland and Scotland provide a test case, demonstrating the utility of quantitative boulder roundness measurements. The 567 clasts we measured are generally angular, but a substantial proportion shows some degree of rounding. Most importantly, there are demonstrable, consistent patterns relating topography and roundness. There is a strong and unsurprising inverse correlation between clast roundness and deposit elevation. There is no first-order relationship between roundness and inland distance, but there is a power-law inverse relationship between rounding and steepness (ratio of elevation to distance inland). The greatest degree of rounding is found in CBD located at the back of gentle coastal platforms with gradual slopes. These relationships provide new insights into CBD sedimentology, which we hope will be probed and tested in future studies.

Modal choice preferences in short-distance hinterland container transport

Short distance inland container transport to Western European seaports provides opportunities for additional modal shift to intermodal transport, thanks to the concentration of transport flows transported to the immediate hinterland of these ports. The literature on modal choice behavior, however, fails to explain the (relatively low) success of this market segment. In this paper, a choice-based conjoint experiment is conducted to increase the insight on the preferences of modal choice decision-makers in Belgium, active in the considered market segment. The findings of the experiment suggest that, to enhance a further modal shift, operators should try to provide daily services at a competitive price, with a focus on providing more reliable services than road transport. Additional efforts should be made to correctly inform decision-makers on the available intermodal services.

The integrated impacts of human activities and rising sea level on the saltwater intrusion in the east coast of the Yucatan Peninsula, Mexico

Saltwater intrusion is a major hazard to coastal communities as it causes degradation of fresh water resources. The impact of rising sea level on the saltwater intrusion into coastal aquifers has been studied for decades, but how human activities affect the extent of saltwater intrusion is poorly understood. Human activities are known to influence groundwater availability indirectly by affecting precipitation patterns and directly by extracting groundwater and reducing recharge. In this paper the authors investigated the integrated impacts of human activities and rising sea level on aquifer recharge in Quintana Roo, Mexico, by incorporating anthropogenic impacts on groundwater recharge into an analytical saltwater intrusion model. The impact of human activities on groundwater extraction was firstly calculated; then, the resulting groundwater recharge was used in a Ghyben–Herzberg analytical model to determine the inland distance of saltwater intrusion. The analytical model tested six scenarios stemming from different combinations of human development patterns, hydrological settings, hydraulic conditions and rising sea level to obtain the range of possible inland movement of saltwater intrusion. Our results indicate that the groundwater recharge will decrease to 32.6 mm year−1 if human activities increase by 50 % more. With 1-m sea level rise, inland saltwater intrusion distance is estimated to be up to 150 and 1 km under head-controlled and flux-controlled scenarios, respectively. A sensitivity analysis of the model reveals that the large hydraulic conductivity of the Quintana Roo aquifer (0.26–68.8 m s−1) is the most important factor in determining saltwater intrusion distance. Therefore, in this aquifer, the response to human activities is greatly exceeded by natural hydrogeological conditions.

Determining flow patterns and emplacement dynamics from tsunami deposits with no visible sedimentary structure

AbstractIn the absence of eyewitness reports or clear sedimentary structures, it can be difficult to interpret tsunami deposits or reconstruct tsunami inundation patterns. The emplacement dynamics of two historical tsunami deposits were investigated at seven transects in Okains Bay, New Zealand, using a combined geospatial, geomagnetic and sedimentological approach. The tsunami deposits are present as layers of sand and silt intercalated between soils and become finer and thinner with distance inland. The deposits are attributed to the 1960 and possibly the 1868 tsunamis, based on radiometric dating and correlation with historical records. Measurements of Magnetic Fabric (MF: Anisotropy of Magnetic Susceptibility) and particle size were used to reconstruct the evolution of flow dynamics laterally and vertically. A combination of statistical methods, including spatial autocorrelation testing, Spearman's rank order correlation, Principal Component Analysis (PCA) and K‐means cluster analysis, was applied to examine relationships between MF parameters and sediment texture, and infer depositional hydrodynamics. Flow patterns deduced from MF show the estuary channel acted as a conduit for inundation, with flow commonly aligned sub‐perpendicular to the estuary bed. MF and sediment data suggest deposition occurred from settling during laminar flow. Evidence of both uprush and backwash deposition, as well as wave reflection from infrastructure, was found. Statistical analysis of data showed significant relationships between grain size parameters and MF parameters associated with flow speed and magnetic fabric type. PCA and cluster analysis differentiated samples into two primary hydrodynamic groups: (1) samples deposited from laminar flow; and (2) samples deposited close to the limit of inundation, which includes samples deposited further inland, those affected by flow convergence, and those in the upper part of tsunami deposits. This approach has potential as a tool for reconstructing hydrodynamic conditions for palaeotsunamis and by combining spatial and statistical analyses, large‐scale investigations can be more easily performed. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Continental-scale variation in chloride/bromide ratios of wet deposition

Chlorine and bromine play crucial roles in atmospheric element cycles and are important environmental tracers in catchment investigations, so understanding their distribution at the Earth's near-surface is imperative for deciphering their behaviour. This study presents the first continental-scale analysis of Cl− and Br− concentrations of wet deposition, based on six and half years of weekly samples collected across North America. A recently developed imputation algorithm was applied to estimate the high proportion of censored Br− values, as well as the other eight analytes, based on the multivariate relationships of nine analytes. The results are consistent with previous studies that have found that the concentrations of these two ions in wet deposition, and the Cl−/Br− ratios of wet deposition decrease with distance inland. Close to the coast, Cl−/Br− ratios of wet deposition are similar to the ratio found in seawater (~288 by mass), rapidly decrease to approximately a third of the seawater ratio at ~200km inland, and then decrease at a much lesser rate to reach mass-ratios of 20 to 10 at ~1500km inland, following a logarithmic regression. The Niagara Falls and the Great Salt Lake are identified as localised sources of atmospheric solutes based on elevated Cl−/Br− ratios of wet deposition at proximal sites. Our observations provide further confidence in the findings presented in previous studies that have shown that Cl−/Br− ratios systematically decrease with increasing distance from the coast, despite the potential confounding impact of other processes, such as weather patterns, chemical behaviour and anthropogenic activity. Our results provide improved estimates of Cl−/Br− ratios of wet deposition source water in the absence of site-specific data.

Characterizing large-scale glaciotectonic sediment deformation using electrical resistivity methods

Large-scale sediment deformation structures formed by glaciotectonic processes have been identified south of Ludington, USA. Here, several apparent clay diapirs rise from below beach level to near the top of an approximately 60 m high bluff along the eastern shore of Lake Michigan. Throughout the area, the surface topography and locations of springs indicate a complicated subsurface structure and a preferred pattern of groundwater drainage. Since public borehole information is sparse, it is not known whether the structures exposed in the bluff are true diapirs or ridges, and if the latter, what is their orientation. In this paper we present the results of field, laboratory, and modeling studies to characterize the inland extent and orientation of these deformation structures using galvanic-source electrical geophysical methods. We exploit the large electrical contrast between a sandy sedimentary layer and an underlying clayey silt sedimentary layer in which the deformation occurred. Constant-spread traverses and multi-electrode tomographic data demonstrate that at least one of the narrow structures extends a significant distance inland.

High Resolution Deterministic Prediction System (HRDPS) Simulations of Manitoba Lake Breezes

ABSTRACTThe Effects of Lake Breezes On Weather–Manitoba (ELBOW-MB) field project, conducted around Lakes Manitoba and Winnipeg in July 2013, was the first in-depth field study of lake breezes in Manitoba, Canada. Using observational data collected during ELBOW-MB and output from the 2.5 km Canadian High Resolution Deterministic Prediction System (HRDPS), comparisons were made between HRDPS output and observational data to determine whether the HRDPS can simulate Manitoba lake breezes. The model comparisons considered various lake-breeze characteristics, such as depth, inland penetration distance, and initiation and dissipation time. In addition, cross-sections of lake-breeze circulations were analyzed. The results show that the HRDPS was able to correctly simulate lake breezes, or lack thereof, in 78% of cases on Lake Winnipeg and 68% of cases on Lake Manitoba. Modelled lake-breeze initiation and dissipation times were found to be too early in some cases and too late in others when compared with observations. Overall, it was found that the HRDPS was able to simulate most aspects of lake breezes, although inland penetration distance was one characteristic that the HRDPS was not able to simulate realistically.

Distribution of tritium in precipitation and surface water in California

Summary The tritium concentration in the surface hydrosphere throughout California was characterized to examine the reasons for spatial variability and to enhance the applicability of tritium in hydrological investigations. Eighteen precipitation samples were analyzed and 148 samples were collected from surface waters across California in the Summer and Fall of 2013, with repeat samples from some locations collected in Winter and Spring of 2014 to examine seasonal variation. The concentration of tritium in present day precipitation varied from 4.0 pCi/L near the California coast to 17.8 pCi/L in the Sierra Nevada Mountains. Concentrations in precipitation increase in spring due to the ‘Spring Leak’ phenomenon. The average coastal concentration (6.3 ± 1.2 pCi/L) in precipitation matches estimated pre-nuclear levels. Surface water samples show a trend of increasing tritium with inland distance. Superimposed on that trend, elevated tritium concentrations are found in the San Francisco Bay area compared to other coastal areas, resulting from municipal water imported from inland mountain sources and local anthropogenic sources. Tritium concentrations in most surface waters decreased between Summer/Fall 2013 and Winter/Spring 2014 likely due to an increased groundwater signal as a result of drought conditions in 2014. A relationship between tritium and electrical conductivity in surface water was found to be indicative of water provenance and anthropogenic influences such as agricultural runoff. Despite low initial concentrations in precipitation, tritium continues to be a valuable tracer in a post nuclear bomb pulse world.

Groundwater Flow Modeling in Coastal Aquifers: The Influence of Submarine Groundwater Discharge on the Position of the Saltwater-Freshwater Interface

An investigation of the impact of submarine groundwater discharge on the position of saltwater-freshwater interface is presented in this manuscript. Two conceptualizations were considered and analyzed using both analytic and numerical techniques, for comparison purposes. The first conceptualization assumes that the tip of the saltwaterfreshwater interface occurs at the shoreline, and the second conceptualization allows for the tip to extend off-shore. Analytic solutions exist for both conceptualizations. Results from both analytic and numeric analysis for the two conceptualizations are presented. Results from the first conceptualization were found to overestimate the inland distance to the interface toe, compared to the second conceptualization, for it ignores the influence of submarine groundwater discharge on the interface location. Moreover, results from the analytic solutions as a whole were found to overestimate the interface location compared to the numerical modeling results, for analytic solutions are based on the sharp interface approximations. Therefore, an empirically derived dispersion factor should be used to correct the analytic solution results so as to compare them with the numerically simulated values. Furthermore, offshore model extents should be incorporated when modeling coastal aquifer systems to include the influence of submarine groundwater discharge on the saltwater-freshwater interface position.

The Evolution of Lake-Effect Convection during Landfall and Orographic Uplift as Observed by Profiling Radars

Abstract A pronounced snowfall maximum occurs about 30 km downwind of Lake Ontario over the 600-m-high Tug Hill Plateau (hereafter Tug Hill), a region where lake-effect convection is affected by mesoscale forcing associated with landfall and orographic uplift. Profiling radar data from the Ontario Winter Lake-effect Systems field campaign are used to characterize the inland evolution of lake-effect convection that produces the Tug Hill snowfall maximum. Four K-band profiling Micro Rain Radars (MRRs) were aligned in a transect from the Ontario coast onto Tug Hill. Additional observations were provided by an X-band profiling radar (XPR). Analysis is presented of a major lake-effect storm that produced 6.4-cm liquid precipitation equivalent (LPE) snowfall over Tug Hill. This event exhibited strong inland enhancement, with LPE increasing by a factor of 1.9 over 15-km horizontal distance. MRR profiles reveal that this enhancement was not due to increases in the depth or intensity of lake-effect convection. With increasing inland distance, echoes transitioned from a convective toward a stratiform morphology, becoming less intense, more uniform, more frequent, and less turbulent. An inland increase in echo frequency (possibly orographically forced) contributes somewhat to snowfall enhancement. The XPR observations reproduce the basic vertical structure seen by the MRRs while also revealing a suppression of snowfall below 600 m AGL upwind of Tug Hill, possibly associated with subcloud sublimation or hydrometeor advection. Statistics from 29 events demonstrate that the above-described inland evolution of convection is common for lake-effect storms east of Lake Ontario.

Maximum-recorded overland run-ups of major nearfield paleotsunamis during the past 3000 years along the Cascadia margin, USA, and Canada

Maximum-recorded run-up estimates of six major nearfield paleotsunamis, dating from 0.3 to 2.8 ka, are compiled from reported studies at 12 reliable localities distributed over a north–south distance of 1000 km in the Cascadia subduction zone. The run-up estimates are based on surveyed elevations and positions of terminal sand sheet layers that were deposited by the dated paleotsunamis. Maximum terminal deposit elevations from open-coastal sites range from 3 to 12 m NAVD88. Paired proximal and distal run-up sites at four localities demonstrate landward vertical attenuation gradients (−2.5 to −4.2 m km−1) of decreasing terminal sand deposit elevation with increasing distance inland. An averaged attenuation gradient is reversed (3.0 m km−1) to project paleotsunami run-up elevations to adjacent ocean shorelines. The run-up projections are further adjusted by paleotsunami age and relative sea level curves to estimate shoreline inundation elevations under modern sea level conditions. The tsunami shoreline inundation elevations range from 3 ± 2 to 15 ± 2 m NAVD88, with the largest values occurring along the central Cascadia margin and the smallest values occurring in the eastern Juan de Fuca Strait. Contradictory to some numerical tsunami modeling assumptions, there is no apparent correlation between duration of interseismic strain accumulation or estimated upper-plate elastic flexure and corresponding paleotsunami run-up heights on the central Cascadia margin. The short duration since the last Cascadia megathrust rupture (0.3 ka) cannot be used to imply smaller run-up values for a near-future Cascadia tsunami. Coastal communities should plan for the maximum paleotsunami run-ups as recorded at the nearest reliable run-up localities.

Spatiotemporal variations of monocarboxylic acids in snow layers along a transect from Zhongshan Station to Dome A, eastern Antarctica

The spatiotemporal distributions of formate and acetate in snow layers along a transect from Zhongshan Station to Dome A are presented here. The mean concentrations of mono-carboxylic acids in summer surface snow layers were 2.93±1.72ngg−1 and 10.07±5.87ngg−1 for formate and acetate, respectively. In the snow pit samples, the concentrations varied between 0.47±0.14ngg−1 and 3.12±4.24ngg−1 for formate and between 5.31±1.55ngg−1 and 13.29±4.64ngg−1 for acetate. Spatially, the concentrations of both acids featured negative trends with increasing elevation and distance inland for the initial 600km of the transect, which implies that marine sources from the coastal oceans dominate the acid supply. Different distribution styles of the acids in the interior section (600–1248km) suggest that different source region and transporting mechanism may be responsible for the acid deposition in the interior regions. Seasonal variations in the amounts of acid in a coastal snow pit (29-A) indicate higher values in the summer and lower amounts in the winter. An enlarged source region and intensified production and transport mechanisms were primarily responsible for the higher values in summer. Longer records from the interior snow pits (29-L and 29-M) indicate elevated values in the 1970s and lower values in the 1980s and early 1990s. The increases in the mono-carboxylic acids since 1999 in snow pit 29-L and since 2005 in snow pit 29-M were temporally coincident with Chinese expedition activities in the area, suggesting that human activities were responsible for the increases in the acid load during recent decades.

Meteorological factors controlling low-level continental pollutant outflow across a coast

Abstract. Coastal outflow describes the horizontal advection of pollutants from the continental boundary layer (BL) across a coastline. The outflow can ventilate polluted continental BLs and thus regulate air quality in highly populated coastal regions. This paper investigates the factors controlling coastal outflow and quantifies their importance as a ventilation mechanism. Tracers in the Met Office Unified Model (MetUM) are used to examine the magnitude and variability of coastal outflow over the eastern United States during summer 2004. Over the 4 week period examined, ventilation of tracer from the continental BL via coastal outflow occurs with the same magnitude as vertical ventilation via convection and advection. The relative importance of tracer decay rate, cross-coastal advection rate, and a parameter based on the relative continental and marine BL heights on coastal outflow is assessed by reducing the problem to a time-dependent box model. The ratio of the advection rate and decay rate is a dimensionless parameter which determines whether tracers are long-lived or short-lived. Long- and short-lived tracers exhibit different behaviours with respect to coastal outflow. Short-lived tracers exhibit large diurnal variability in coastal outflow but long-lived tracers do not. For short-lived tracers, increasing the advection rate increases the diurnally averaged magnitude of coastal outflow, but this has the opposite effect for very long-lived tracers. By using the box-model solutions to interpret the MetUM simulations, a land width is determined which represents the distance inland over which emissions contribute significantly to coastal outflow. A land width of between 100 and 400 km is found to be representative for a tracer with a lifetime of 24 h.

The composition and physiognomy of forest types are strongly linked to distance inland along the northern California coast

The composition and physiognomy of forest types are strongly linked to distance inland along the northern California coast

Spatial distribution of marine chemicals along a transect from Zhongshan Station to the Grove Mountain area, Eastern Antarctica

This study investigates the regional distribution of marine aerosol originated species (Na+, Cl−, nss-SO4 2− and MSA) in the snow pits (or firn cores) collected along a transect between Zhongshan Station and the Grove Mountain area (450 km inland) on the eastern side of the Lambert Glacier Basin. Concentrations of Na+ and Cl− decrease exponentially with distance from the coast to 100 km inland (i.e., 1500 m a.s.l.). Statistical results demonstrate that distance from the coast inland and elevation affect the concentration of sea-salt originated ions in inland areas significantly. Increase of Cl-/Na+ ratio and higher variability in its standard deviation suggest that there are other sources of ions in addition to sea-salt in inland areas of the Antarctic continent. The concentrations of Na+ and Cl− from nine sampling sites in the Grove Mountain area are relatively higher than those from sites along CHINARE transect, although all sites are at similar distance inland. This phenomenon indicates that the barrier effect of the mountain may be the most important factor influencing ion deposition. In addition, nss-SO4 2− and MSA vary differently, with nss-SO4 2− decreasing with distance more significantly. This implies that sources and transporting pathways influence the deposition of the two sulfur compounds considerably, being supported by the spatial pattern of correlation coefficients between the nss-SO4 2− and MSA.

Evolution of Stratocumulus Over Land: Comparison of Ground and Aircraft Observations with Numerical Weather Prediction Simulations

Forecasting of low cloud continues to challenge numerical weather prediction. With this in mind, surface and airborne observations were made over East Anglia, UK, during March 2011 to investigate stratus and stratocumulus advecting from the sea over land. Four surface sites were deployed at various distances inland aligned approximately along the flow. In situ data include cloud-droplet measurements from an aircraft operating off the coast and a tethered balloon 100 km inland. Comparisons of thermodynamic and cloud properties are made with Met Office operational model simulations at horizontal resolutions of 4 and 1.5 km. The clouds contained droplet concentrations up to 600 cm $$^{-3}$$ within polluted outflow off Europe. These measurements were compared to three different model schemes for predicting droplet concentration: two of them perform well at low to moderate concentrations but asymptote to 375 cm $$^{-3}$$ . Microwave radiometers at the ground sites retrieved liquid water paths that reduced with distance inland and were generally below 200 g m $$^{-2}$$ . The modelled water path performs well upstream but more erratically far inland. Comparisons of thermodynamic profiles are made within both Lagrangian and Eulerian frameworks and show the model predicted changes in equivalent potential temperature generally within 1 K, with occasional errors of 2 K or more. The modelled cloud-top temperatures were in good agreement with the observations down to $$-$$ 7 $$^{\circ }$$ C, but the magnitude of the temperature inversion, although good at times, was too small by on average 1.6 K. The different simulations produced different cloud-top water contents due to a combination of resolution and scientific upgrades to the model, but they generally underestimate the amount of cloud water. Major changes, such as the mesoscale temporary cloud breaks on 2 March 2011 and the complete clearance on 4 March, were seemingly predicted by the model for the correct reasons.