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MAPM (Mapping Air Pollution eMissions) is a project whose goal is to develop a method to infer airborne particulate matter (PM) emissions maps from in situ PM concentration measurements. In support of MAPM, a winter field campaign was conducted in New Zealand in 2019 (June to September) to obtain the measurements required to test and validate the MAPM methodology. Two different types of instruments measuring PM were deployed: ES-642 remote dust monitors (17 instruments) and Outdoor Dust Information Nodes (ODINs; 50 instruments). The measurement campaign was bracketed by two intercomparisons where all instruments were co-located, with a permanently installed tapered element oscillating membrane (TEOM) instrument, to determine any instrument biases. Changes in biases between the pre- and post-campaign intercomparisons were used to determine instrument drift over the campaign period. Once deployed, each ES-642 was co-located with an ODIN. In addition to the PM measurements, meteorological variables (temperature, pressure, wind speed, and wind direction) were measured at three automatic weather station (AWS) sites established as part of the campaign, with additional data being sourced from 27 further AWSs operated by other agencies. Vertical profile measurements were made with 12 radiosondes during two 24 h periods and complimented measurements made with a mini micropulse lidar and ceilometer. Here we present the data collected during the campaign and discuss the correction of the measurements made by various PM instruments. We find that when compared to measurements made with a simple linear correction, a correction based on environmental conditions improves the quality of measurements retrieved from ODINs but results in over-fitting and increases the uncertainties when applied to the more sophisticated ES-642 instruments. We also compare PM2.5 and PM10 measured by ODINs which, in some cases, allows us to identify PM from natural and anthropogenic sources. The PM data collected during the campaign are publicly available from https://doi.org/10.5281/zenodo.4542559 (Dale et al., 2020b), and the data from other instruments are available from https://doi.org/10.5281/zenodo.4536640 (Dale et al., 2020a).

Southern Ocean (SO) shortwave (SW) radiation biases are a common problem in contemporary general circulation models (GCMs), with most models exhibiting a tendency to absorb too much incoming SW radiation. These biases have been attributed to deficiencies in the representation of clouds during the austral summer months, either due to cloud cover or cloud optical thickness being too low. The problem has been the focus of many studies, most of which utilised satellite datasets for model evaluation. We use multi-year ship based observations and the CERES spaceborne radiation budget measurements to contrast cloud representation and SW radiation in the atmospheric component Global Atmosphere (GA) version 7.0 and 7.1 of the HadGEM3 GCM and the MERRA-2 reanalysis. We find that MERRA-2 is biased in the opposite direction to GA (reflects too much SW radiation). In addition, MERRA-2 performs better in terms of absolute SW bias than nudged runs of GA7.0 and GA7.1 in the 60–70° S latitude band. GA7.1 reduces the SO SW radiation biases relative to GA7.0, but significant errors remain at up to 20 W m−2 between 60 and 70° S in the austral summer months. Using ship-based ceilometer observations, we find low cloud below 2 km to be predominant in the Ross Sea and the Indian Ocean sector of the SO. Utilising a novel surface lidar simulator developed for this study, derived from an existing COSP-ACTSIM spaceborne lidar simulator, we find that GA7.0 and MERRA-2 both underestimate low cloud occurrence relative to the ship observations by 18–25 % on average, though the cloud cover in MERRA-2 is closer to observations by about 7 %. Based on radiosonde observations, we also find the low cloud to be strongly linked to boundary-layer atmospheric stability and the sea surface temperature. GA7.0 and MERRA-2 agree well with observations in terms of boundary-layer stability, suggesting that subgrid-scale parametrisations do not generate enough cloud in response to the thermodynamic profile of the atmosphere and the surface temperature. Our analysis shows that MERRA-2 has a much greater proportion of cloud liquid water in the SO in January than GA7.0, a likely key contributor to the difference in SW radiation. We show that boundary-layer stability and relative humidity fields are very similar in GA7.0 and MERRA-2, and unlikely to be the cause of the different cloud representation, suggesting that subgrid-scale parametrisations are responsible for the difference between the models.

Analysis of Coupled Model Intercomparison Project Phase 6 (CMIP6) models has focused on their higher equilibrium climate sensitivity (ECS) relative to CMIP5 simulations, with higher ECS values attr...

We demonstrate that the relationship between the abundance of particulate surface area observed at sea-level and measurements of backscattered light by a ceilometer can be used to classify the mixi...

The 2B-CLDCLASS-LIDAR R05 (2BCL5) and the raDAR/liDAR (DARDAR) satellite retrievals of cloud occurrence are compared as a function of altitude and latitude. The largest disparities are observed at ...

We studied sulfate aerosols over the Southern Ocean using the atmosphere-only climate model HadGEM3-GA7.1. The model contains biases in the aerosol seasonal variability over the Southern Ocean (40°S to 60°S), which cascade to uncertainties in aerosol-cloud interactions. Aerosols over the Southern Ocean are primarily natural in origin, such as sea spray aerosol and sulfate aerosol formed by phytoplankton-produced dimethyl sulfide (DMS).The current sulfate chemistry scheme implemented in the model simplifies the oxidation pathways for DMS, which has been identified as a major source of the seasonal bias present. The simulations performed here incorporate a comprehensive sulfate scheme in both the gas and aqueous-phase. An intermediate complexity biogeochemical dynamic model, MEDUSA, simulated a global climatology of seawater DMS, which is compared with a seawater DMS observational dataset from 2011. We compared the seasonality of sulfate aerosols over the Southern Ocean, and the global distribution using the two seawater DMS climatologies. Simulated aerosols over the Southern Ocean were evaluated against satellite and in-situ observations. The results show the impact of seawater DMS on sulfate aerosols and their influence on cloud formation.

Weather and climate models are challenged by uncertainties and biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation, and radiative processes, and their interactions. Projects between 2016 and 2018 used in situ probes, radar, lidar, and other instruments to make comprehensive measurements of thermodynamics, surface radiation, cloud, precipitation, aerosol, cloud condensation nuclei (CCN), and ice nucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase clouds common to this pristine environment. Data including soundings were collected from the NSF–NCAR G-V aircraft flying north–south gradients south of Tasmania, at Macquarie Island, and on the R/V Investigator and RSV Aurora Australis. Synergistically these data characterize boundary layer and free troposphere environmental properties, and represent the most comprehensive data of this type available south of the oceanic polar front, in the cold sector of SO cyclones, and across seasons. Results show largely pristine environments with numerous small and few large aerosols above cloud, suggesting new particle formation and limited long-range transport from continents, high variability in CCN and cloud droplet concentrations, and ubiquitous supercooled water in thin, multilayered clouds, often with small-scale generating cells near cloud top. These observations demonstrate how cloud properties depend on aerosols while highlighting the importance of dynamics and turbulence that likely drive heterogeneity of cloud phase. Satellite retrievals confirmed low clouds were responsible for radiation biases. The combination of models and observations is examining how aerosols and meteorology couple to control SO water and energy budgets.

We demonstrate that the temporal correlation between the abundance of particulate surface area at sea-level and measurements of ceilometer backscatter can be used to quantify boundary layer mixing....

With low concentrations of tropospheric aerosol, the Southern Ocean offers a "natural laboratory" for studies of aerosol–cloud interactions. Aerosols over the Southern Ocean are produced from biogenic activity in the ocean, which generates sulfate aerosol via dimethylsulfide (DMS) oxidation, and from strong winds and waves that lead to bubble bursting and sea spray emission. Here, we evaluate the representation of Southern Ocean aerosols in the Hadley Centre Global Environmental Model version 3, Global Atmosphere 7.1 (HadGEM3-GA7.1) chemistry–climate model. Compared with aerosol optical depth (AOD) observations from two satellite instruments (the Moderate Resolution Imaging Spectroradiometer, MODIS-Aqua c6.1, and the Multi-angle Imaging Spectroradiometer, MISR), the model simulates too-high AOD during winter and too-low AOD during summer. By switching off DMS emission in the model, we show that sea spray aerosol is the dominant contributor to AOD during winter. In turn, the simulated sea spray aerosol flux depends on near-surface wind speed. By examining MODIS AOD as a function of wind speed from the ERA-Interim reanalysis and comparing it with the model, we show that the sea spray aerosol source function in HadGEM3-GA7.1 overestimates the wind speed dependency. We test a recently developed sea spray aerosol source function derived from measurements made on a Southern Ocean research voyage in 2018. In this source function, the wind speed dependency of the sea spray aerosol flux is less than in the formulation currently implemented in HadGEM3-GA7.1. The new source function leads to good agreement between simulated and observed wintertime AODs over the Southern Ocean; however, it reveals partially compensating errors in DMS-derived AOD. While previous work has tested assumptions regarding the seawater climatology or sea–air flux of DMS, we test the sensitivity of simulated AOD, cloud condensation nuclei and cloud droplet number concentration to three atmospheric sulfate chemistry schemes. The first scheme adds DMS oxidation by halogens and the other two test a recently developed sulfate chemistry scheme for the marine troposphere; one tests gas-phase chemistry only, while the second adds extra aqueous-phase sulfate reactions. We show how simulated sulfur dioxide and sulfuric acid profiles over the Southern Ocean change as a result and how the number concentration and particle size of the soluble Aitken, accumulation and coarse aerosol modes are affected. The new DMS chemistry scheme leads to a 20% increase in the number concentration of cloud condensation nuclei and cloud droplets, which improves agreement with observations. Our results highlight the importance of atmospheric chemistry for simulating aerosols and clouds accurately over the Southern Ocean.

This study investigates the impacts of strong wind events on the sea ice concentration within polynya regions, with a focus on the Ross Sea Polynya (RSP). In particular, this work quantifies the sensitivity of sea ice concentrations to surface winds and whether there are threshold wind speeds required for regions of the polynya to open up with subsequent impacts on air-sea heat fluxes. To analyse these processes, we examine version 3.1 of the Bootstrap sea ice concentration (SIC) satellite data set derived from SSM/I brightness temperatures and how they are connected to the surface winds from the ERA5 reanalysis over the period 1979 to 2018. While we examine these relationships around the entire Antarctic continent, we focus on the RSP and low-level jets in the Ross Sea. In particular, we examine how strong wind events which impact SIC in the RSP are linked to Ross Ice Shelf Air Stream events (strong low-level jets in the region). The hypothesis that the increase in Ross Ice Shelf Air Stream events, associated with a strengthening of the Amundsen Sea Low, has contributed to trends in sea ice production in this region is examined.

Asymmetry in the Southern Hemisphere stratospheric ozone hole is important due to both direct radiative heating and its effect on dynamics. It is also a strong indicator of the underlying quality of the stratospheric dynamics of a climate model. We investigate the simulation of the zonal asymmetry in ozone in the NIWA-UKCA atmosphere–ocean chemistry–climate model using elliptical diagnostics, a methodology used for the first time in this subject area. During spring, the region most depleted in ozone is displaced from the pole toward South America based on ERA-Interim and the model output. The model correctly simulates the direction of this displacement but significantly underestimates its magnitude. The model shows that as ozone becomes increasingly depleted over the late 20th century this asymmetry in the ozone distribution moves west, before moving east as polar ozone recovers over the course of the 21st century. Comparison with model runs in which ozone-depleting substances are held fixed at pre-ozone-hole levels shows that this shift is primarily a function of the magnitude of ozone depletion, although increases in greenhouse gases also have some effect.

We examine the effects of non-linear interactions between surface albedo, water vapor and cloud cover (referred to as climate variables) on amplified warming of the polar regions, using a new energy balance model. Our simulations show that the sum of the contributions to surface temperature changes due to any variable considered in isolation is smaller than the temperature changes from coupled feedback simulations. This non-linearity is strongest when all three climate variables are allowed to interact. Surface albedo appears to be the strongest driver of this non-linear behavior, followed by water vapor and clouds. This is because increases in longwave radiation absorbed by the surface, related to increases in water vapor and clouds, and increases in surface absorbed shortwave radiation caused by a decrease in surface albedo, amplify each other. Furthermore, our results corroborate previous findings that while increases in cloud cover and water vapor, along with the greenhouse effect itself, warm the polar regions, water vapor also significantly warms equatorial regions, which reduces polar amplification. Changes in surface albedo drive large changes in absorption of incoming shortwave radiation, thereby enhancing surface warming. Unlike high latitudes, surface albedo change at low latitudes are more constrained. Interactions between surface albedo, water vapor and clouds drive larger increases in temperatures in the polar regions compared to low latitudes. This is in spite of the fact that, due to a forcing, cloud cover increases at high latitudes and decreases in low latitudes, and that water vapor significantly enhances warming at low latitudes.

Location information from long-duration super-pressure balloons flying in the Southern Hemisphere lower stratosphere during 2014 as part of X Project Loon are used to assess the quality of a number of different reanalyses including National Centers for Environmental Prediction Climate Forecast System version 2 (NCEP-CFSv2), European Centre for Medium-Range Weather Forecasts (ERA-Interim), NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA), and the recently released MERRA version 2. Balloon GPS location information is used to derive wind speeds which are then compared with values from the reanalyses interpolated to the balloon times and locations. All reanalysis data sets accurately describe the winds, with biases in zonal winds of less than 0.37 m s−1 and meridional biases of less than 0.08 m s−1. The standard deviation on the differences between Loon and reanalyses zonal winds is latitude-dependent, ranging between 2.5 and 3.5 m s−1, increasing equatorward. Comparisons between Loon trajectories and those calculated by applying a trajectory model to reanalysis wind fields show that MERRA-2 wind fields result in the most accurate simulated trajectories with a mean 5-day balloon–reanalysis trajectory separation of 621 km and median separation of 324 km showing significant improvements over MERRA version 1 and slightly outperforming ERA-Interim. The latitudinal structure of the trajectory statistics for all reanalyses displays marginally lower mean separations between 15 and 35° S than between 35 and 55° S, despite standard deviations in the wind differences increasing toward the equator. This is shown to be related to the distance travelled by the balloon playing a role in the separation statistics.

Model evaluation is difficult and generally relies on analysis that can mask compensating errors. This paper defines new metrics, using clusters generated from a machine learning algorithm, to estimate mean and compensating errors in different model runs. As a test case, we investigate the Southern Ocean shortwave radiative bias using clusters derived by applying self‐organizing maps to satellite data. In particular, the effects of changing cloud phase parameterizations in the MetOffice Unified Model are examined. Differences in cluster properties show that the regional radiative biases are substantially different than the global bias, with two distinct regions identified within the Southern Ocean, each with a different signed bias. Changing cloud phase parameterizations can reduce errors at higher latitudes but increase errors at lower latitudes of the Southern Ocean. Ranking the parameterizations often shows a contrast in mean and compensating errors, notably in all cases large compensating errors remain.

In this study, a dynamic water budget model is developed for the Emirate of Abu Dhabi (EAD) in the United Arab Emirates (UAE). The model, called Abu Dhabi Water Budget Model (ADWBM), accounts for a number of drivers such as population growth, economic growth, consumption pattern and climatic factors. Model formulation, calibration, validation as well as simulation results for two future situations are presented in this paper. The two water simulations discuss demand-side options in response to different future water conditions until 2050. The first simulation, namely, baseline (BL) simulation examined water balance in the emirate assuming no change in both water production and consumption. BL simulation results highlight the expected shortages in water resources assuming no modification in the supply side. The second simulation, a more conservative and practical simulation considering water conservation options and sustainable improvements to the supply side was developed to achieve a balanced water budget by reducing the baseline consumption rates. The results show that a significant demand reduction is needed in all demand sectors, reaching 60% in the potable sectors and above 70% in non-potable sectors. Overall, results show that the ADWBM can be used as a numerical tool to produce accurate figures of water supply and demand for the sake of planning and decision making in the water sector of the EAD until 2050.

Study region Abu Dhabi, United Arab Emirates (UAE) Study focus Water demand in the Emirate of Abu Dhabi (EAD) has increased significantly over the last few decades. Hence, a main challenge for the EAD water policy makers is to develop long-term resilient water resources strategies. This study evaluates future water supply-demand condition in the EAD and identifies water management strategies that support a sustainable future. A dynamic water budget modelling framework is used to evaluate future water demand as affected by population growth, economic growth, proposed water related policies, consumption patterns, and climate change. The Abu Dhabi Dynamic Water Budget Model (ADWBM) is used to construct future water scenarios and assess the status of the EAD water system until 2050 in terms of water supply-demand balance. This study presents four suites of water scenarios, namely: Business as Usual (BAU), Policy First (PF), Sustainability by Conservation (SC), and Rainfall Enhanced Sustainability (RES) scenarios. New hydrological insights Simulation results indicate that both SC and RES scenarios achieved balanced water budget without any shortage throughout the entire period until 2050. The RES scenario is recommended for adoption because of the reasonable and achievable proposed consumption reductions needed in the different demand sectors. The obtained results should be valuable for devising appropriate strategies to prevent potential future water shortages in the Emirate.

This study is concerned with blocking events (BEs) in the Southern Hemisphere (SH), their past variability, and future projections. ERA-Interim (ERA-I) is used to compare the historical output from four general circulation models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5); the output of the representative concentration pathway 4.5 and 8.5 (RCP4.5 and RCP8.5) projections are also examined. ERA-I shows that the higher latitudes of the South Pacific Ocean (SPO) are the main blocking region, with blocking occurring predominantly in winter. The CMIP5 historical simulations also agree well with ERA-I for annual and seasonal BE locations and frequencies. A reduction in BEs is observed in the SPO in the 2071–2100 period in the RCP4.5 projections, and this is more pronounced for the RCP8.5 projections and occurs predominantly during the spring and summer seasons. Preliminary investigations imply that the southern annular mode (SAM) is negatively correlated with blocking activity in the SPO in all seasons in the reanalysis. This negative correlation is also observed in the GCM historical output. However, in the RCP projections this correlation is reduced in three of the four models during summer, suggesting that SAM may be less influential in summertime blocking in the future.

Anthropogenic emissions of greenhouse gases and ozone-depleting substances are expected to continue to affect concentrations of ozone in the stratosphere through the 21st century. While a range of estimates for when stratospheric ozone is expected to return to unperturbed levels is available in the literature, quantification of the spread in results is sparse. Here we present the first probabilistic study of latitudinally resolved years of return of stratospheric ozone to 1960 levels. Results from our 180-member ensemble, simulated with a newly developed simple climate model, suggest that the spread in return years of ozone is largest around 40°N/S and in the southern high latitudes and decreases with increasing greenhouse gas emissions. The spread in projections of ozone is larger for higher greenhouse gas scenarios and is larger in the polar regions than in the midlatitudes, while the spread in ozone radiative forcing is smallest in the polar regions.

A cluster analysis-based synoptic classification scheme, known as the Kidson types, was applied to reanalyses and Coupled Model Inter-comparison Project phase 3 (CMIP3) general circulation model (GCM) output over New Zealand to identify the potential for future changes in regional circulation. Results indicate that a number of GCM 20th century control runs reproduce the type frequencies observed in reanalysis data. Application to future scenario runs for the periods 2046–2065 and 2081–2100 displays little variation in the annual frequency of the synoptic types relative to the 20th century, especially when uncertainty associated with the model ensemble is considered. This is surprising in the context of previous work on possible future movements in jet position and subsequent impacts on weather patterns. A sensitivity analysis that mimics the movement of the jet position was performed, revealing that the annual type frequencies are relatively insensitive to change. To determine whether this is a problem with the synoptic typing scheme, a correlation-based classification technique was also used, but showed similar results. This work highlights issues with applying synoptic classification schemes to GCM output and indicates that if such schemes are to be used they should be designed and tested with this application in mind.

This study describes SNOW-WEB, a distributed system of atmospheric sensors, which is cost-effective and can be efficiently deployed in Antarctica. The system supports traditional atmospheric sensors and has built-in redundancy as many units can be deployed in a relatively small area for a similar cost to one conventional weather station. Furthermore, each unit is equipped with wireless mesh-networking capabilities and so is able to share information with those units in its direct vicinity. This allows for the ferrying of collected information to a manned observation station and hence the ability to monitor data in real-time. GPS hardware installed on each unit also allows for high-resolution glacier or ice shelf tracking. As a testing study, eighteen such weather stations were deployed in the vicinity of Scott Base, Ross Island, Antarctica over the 2011/12 summer season. This paper reports on the successful development and deployment of the system, results from the testing period and challenges encountered during the experiment. Collected data is validated against automatic weather stations already operating in the region and an intercomparison is performed between SNOW-WEB data and forecast output from the Antarctic Mesoscale Prediction System. A high degree of agreement is found between data sources. We conclude that SNOW-WEB data is suitable for use in studies of mesoscale meteorology.

Kennicutt, M.C. et. al.-- 17 pages, 3 figures, The Antarctic Roadmap Challenges (ARC) project identified critical requirements to deliver high priority Antarctic research in the 21st century. The ARC project addressed the challenges of enabling technologies, facilitating access, providing logistics and infrastructure, and capitalizing on international co-operation. Technological requirements include: i) innovative automated in situ observing systems, sensors and interoperable platforms (including power demands), ii) realistic and holistic numerical models, iii) enhanced remote sensing and sensors, iv) expanded sample collection and retrieval technologies, and v) greater cyber-infrastructure to process ‘big data’ collection, transmission and analyses while promoting data accessibility. These technologies must be widely available, performance and reliability must be improved and technologies used elsewhere must be applied to the Antarctic. Considerable Antarctic research is field-based, making access to vital geographical targets essential. Future research will require continent- and ocean-wide environmentally responsible access to coastal and interior Antarctica and the Southern Ocean. Year-round access is indispensable. The cost of future Antarctic science is great but there are opportunities for all to participate commensurate with national resources, expertise and interests. The scope of future Antarctic research will necessitate enhanced and inventive interdisciplinary and international collaborations. The full promise of Antarctic science will only be realized if nations act together, The authors recognize the financial support that made the Scan and ARC possible. The Council of Managers of National Antarctic Programs (COMNAP), the Tinker Foundation and the Scientific Committee on Antarctic Research (SCAR) provided the majority of the funding for this project including the costs of travel and participation of invited, non-COMNAP workshop attendees. In-kind support was provided by many COMNAP-Member national Antarctic programmes including Dirección Nacional del Antártico (DNA, Argentina), Australian Antarctic Division (AAD, Australia), Programa Antártico Brasileiro (PROANTAR, Brazil), Instituto Antártico Chileno (INACH, Chile), Polar Research Institute of China (PRIC, China), Instituto Antártico Ecuatoriano (INAE, Ecuador), Institut Polaire Français Paul Emile Victor (IPEV, France), Alfred Wegener Institute (AWI, Germany), National Institute of Polar Research (NIPR, Japan), Korea Polar Research Institute (KOPRI, Republic of Korea), Antarctica New Zealand (New Zealand), Arctic and Antarctic Research Institute (AARI, Russia), Spanish Polar Committee (CPE, Spain), British Antarctic Survey (BAS, UK), and the US National Science Foundation (NSF, USA)

Summary Peatland water table depth is an important control on runoff production, plant growth and carbon cycling. Many peatlands have been drained but are now subject to activities that might lead to their restoration including the damming of artificial drains. This paper investigates water table dynamics on intact, drained and restored peatland slopes in a blanket peat in northern England using transects of automated water table recorders. Long-term (18 month), seasonal and short-term (storm event) records are explored. The restored site had drains blocked 6 years prior to monitoring commencing. The spatially-weighted mean water table depths over an 18 month period were −5.8 cm, −8.9 cm and −11.5 cm at the intact, restored and drained sites respectively. Most components of water table behaviour at the restored site, including depth exceedance probability curves, seasonality of water table variability, and water table responses to individual rainfall events were intermediate between that of the drained and intact sites. Responses also depended on location with respect to the drains. The results show that restoration of drained blanket peat is difficult and the water table dynamics may not function in the same way as those in undisturbed blanket peat even many years after management intervention. Further measurement of hydrological processes and water table responses to peatland restoration are required to inform land managers of the hydrological success of those projects.

This study compares the spatial and temporal variability of water colour for fifteen sub-catchments of the River Nidd, northeast England, in 1986 and 2006/2007. Between 1986 and 2006/2007, mean annual water colour increased in all the sub-catchments. However, there was considerable variation in the increase, which ranged from 22 to 155%. Statistical analysis revealed that the sub-catchments could be split into two ‘types’ based on water chemistry and therefore dominant source of runoff; type 1 where flow was dominated by runoff from peat and type 2 where a greater contribution of flow appears to originate from mineral soil horizons, as indicated by the higher silicon, base cation concentrations and pH values. Largest proportional increases in water colour were observed in the sub-catchments that had the smaller mean annual water colour values in 1986 which were, in general, the type 2 sub-catchments. The higher rate of water colour increase in the type 2 catchments, in comparison to the type 1 catchments, may be related to changes in adsorption of dissolved organic carbon (DOC) within the mineral horizons of the organo-mineral soils on the lower catchment slopes possibly as a result of changes in acid sulphur deposition.

Peatlands are important terrestrial carbon stores but their environmental degradation has led to concerns of increased carbon loss. Many peatlands have been drained using open ditches and this practice has been associated with enhanced dissolved organic carbon loss and water discolouration. Recent peatland restoration schemes have therefore included the blocking of peatland drains as a strategy for environmental improvement. However, it is not clear whether drain-blocking consistently reduces dissolved organic carbon loads and water discolouration because many peats undergo significant physical and chemical change when they are disturbed. Previous studies investigating the impact of drain-blocking on water colour and dissolved organic carbon have been restricted to a limited spatial and temporal research framework. This study combines an extensive UK-wide survey of blocked and unblocked drains across 32 study sites and intensive monitoring of a peat drain system that has been blocked for 7 years. Dissolved organic carbon concentrations and water discolouration were significantly lower in blocked drains: the mean dissolved organic carbon concentration of water sampled from blocked drains was 28% less than that sampled from unblocked drains. However, this pattern was not consistent at all sites. At the intensive monitoring site no significant differences could be observed in total dissolved organic carbon flux from the fully instrumented blocked and unblocked drains: the blocked drain exported 31,592 kg km2 yr1 and the unblocked drain 30,123 kg km2 yr1. Results from bi-weekly grab samples from other drains at the intensively monitored site, however, did conform to the general national pattern of lower dissolved organic carbon and discolouration in blocked drains. The results demonstrate that drain-blocking can be an effective management strategy for reducing DOC loss and water discolouration in disturbed peat catchments. The caveat remains, however, that there will be a number of sites where no significant change will occur.

A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs). POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm. A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (TNAT), shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed. Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses). For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to TNAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically associated with the Antarctic Peninsula; a known mountain wave "hotspot". The latitudinal variation of POAM III observations means that we only observe this region in June–July, and thus the true pattern of enhanced PSC production may continue operating into later months. The analysis has shown that early in the Antarctic winter stratospheric background temperatures are close to the TNAT threshold (and PSC formation), and are thus sensitive to temperature perturbations associated with mountain wave activity near the Antarctic peninsula (40% of PSC formation). Later in the season, and at latitudes away from the peninsula, temperature perturbations associated with gravity waves contribute to about 15% of the observed PSC (a value which corresponds well to several previous studies). This lower value is likely to be due to colder background temperatures already achieving the TNAT threshold unaided. Additionally, there is a reduction in the magnitude of gravity waves perturbations observed as POAM III samples poleward of the peninsula.

Residuum lodges comprise small dams constructed on feeder streams immediately before they enter a reservoir, behind which ponds form, where sediment is deposited. Despite their construction on many impoundment reservoirs (IRE) and catchwaters, little research has previously investigated their efficacy at removing sediments from feeder streams. The current pilot study has, therefore, been carried out at an IRE supplying Halifax, West Yorkshire, UK, where a residuum lodge was recently cleaned out. Sediment concentrations reaching the reservoir were reduced by up to 42% although no certain impacts were noted on the other water quality variables that were measured. Moreover, it was found that the clearance operation did not result in the release of excessive quantities of sediment into the reservoir. It was estimated that the cleared residuum lodge would take 12 years to refill. A survey of other residuum lodges in the Yorkshire region showed there to be considerable differences in their remaining capacities.

Summer sampling of storm runoff generated from areas of roofs and hardstanding situated on four dairy/beef farms has provided novel information regarding its microbiological and chemical quality. All farm hardstandings generated runoff that was contaminated with respect to those pollutants (faecal coliforms, FC, and faecal streptococci, FS, major nutrients, organic carbon) that are ubiquitously associated with faecal matter and urine. The separate analysis of roof runoff indicated that these can contribute significant concentrations of FS, phosphorus (P) and potentially toxic elements such as zinc (Zn), and suggests a level of 'background' contamination originating from wash-off of bird droppings and in the case of Zn galvanised surfaces. On average hardstanding runoff showed enhanced concentrations of >4 orders of magnitude for FC and 2-3 for major nutrients and carbon relative to roof runoff. Organic forms of nitrogen (N) and P contributed significantly (averaging >40%) to the total dissolved fraction in both roof and hardstanding runoff. Part of the substantial variability in composition of runoff samples could be attributed to differences between farms as well as the timing of sample collection during individual storms. Where situations allowed, a comparison of water upstream and downstream of the farmyard demonstrated they acted as a source of multiple contaminants not only during hydrologically active storm events but also during dry periods. Contamination pathways included a combination of both point (e.g., septic overflows) and non-point (e.g., seepage from livestock housing) sources. Farmyards situated within intensive livestock farming areas such as SW Scotland, would be expected to have significant local and accumulated downstream impacts on the aquatic environment. Localised impacts would be particularly important for headwaters and low order streams.

The European Water Framework Directive requires the integrated management of point and diffuse pollution to achieve 'good' water quality in 'protected areas'. These include bathing waters, which are regulated using faecal indicator organisms as compliance parameters. Thus, for the first time, European regulators are faced with the control of faecal indicator fluxes from agricultural sources where these impact on bathing water compliance locations. Concurrently, reforms to the European Union (EU) Common Agricultural Policy offer scope for supporting on-farm measures producing environmental benefits through the new 'single farm payments' and the concept of 'cross-compliance'. This paper reports the first UK study involving remedial measures, principally stream bank fencing, designed to reduce faecal indicator fluxes at the catchment scale. Considerable reduction in faecal indicator flux was observed, but this was insufficient to ensure bathing water compliance with either Directive 76/160/EEC standards or new health-evidence-based criteria proposed by WHO and the European Commission.

Parallel policy developments driven in the USA by the Clean Water Act and in Europe by the Water Framework Directive have focused attention on the need for quantitative information on the fluxes of faecal indicator bacteria in catchment systems. Data are required on point and diffuse source loadings, fate and transport of these non-conservative parameters, on the land surface, within soil systems, in groundwater, streams, impoundments and nearshore waters. This new information is needed by regulators to inform Total Maximum Daily Load estimates in the USA and Programmes of Measures in Europe both designed to prevent impairment of water quality at locations where compliance is assessed against health-based standards for drinking, bathing or shellfish harvesting. In the UK, the majority of catchment-scale activity in this field has been undertaken by physical geographers although microbial flux analysis and modelling has received much less attention from the research and policy communities than, for example, the nutrient parameters. This paper charts the policy drivers now operative and assesses the evidence base to support current policy questions. Finally, gaps and priority research questions are identified.

Peatlands are an important terrestrial carbon store. However, heightened levels of degradation in response to environmental change have resulted in an increased loss of dissolved organic carbon (DOC) and an associated rise in the level of discolouration in catchment waters. A significant threat to peatland sustainability has been the installation of artificial drainage ditches. However, recent restoration schemes have pursued drain blocking as a possible strategy for reducing degradation, fluvial carbon loss and water discolouration. This paper investigates the effect of open cut drainage and the impact of drain blocking on DOC and colour dynamics in blanket peat soil-water solutions. Three treatments (intact peat, drained peat and drain-blocked peat) were monitored in an upland blanket peat catchment in the UK. DOC and colour values were significantly higher on the drained slopes compared with those of the intact peat, which in turn had greater DOC and colour values than the drain-blocked slopes. Consequently, drain blocking is shown to be a highly successful technique in reducing both the DOC concentration and level of discolouration in soil waters, even to values lower than those observed for the intact site, which suggests a process of store exhaustion and flushing may operate. The colour per carbon unit (C/C) ratio was significantly higher at the drain-blocked site than either the intact or the drained treatments, while the E4/E6 ratio (fulvic acid/humic acid) was significantly lower at the blocked site compared to the two other treatments. The high C/C and low E4/E6 ratios indicate that drain blocking also modifies the composition of DOC, such that darker-coloured humic substances become more dominant compared to the intact site. This implies disturbance to DOC production and/or transportation processes operating within the peat.

The Ribble drainage basin is the single UK sentinel study area chosen for examining the implementation of the EU Water Framework Directive (WFD 20/60/EC). The study which has generated the data for this paper was initiated to quantify ‘catchment-derived’ fluxes of faecal indicators originating from both point and diffuse sources to inform the competent authorities on the potential for, and prioritization of, further options for reducing the faecal indicator loadings to this crucial coastal environment. It represents the first UK drainage basin-scale ‘profile’ of faecal indicator sources as recommended by WHO [1999 . Health Based Monitoring of Recreational Waters: The Feasibility of a New Approach; the “Annapolis Protocol”. World Health Organisation Geneva, Switzerland; 2003. Guidelines for Safe Recreational-Water Environments Volume 1: Coastal and Fresh-Waters. World Health Organisation Geneva, Switzerland] and incorporated into current drafts of the revised Bathing Water Directive [ Anon, 2004 . Council of the European Communities Amended proposal for a Directive of the European Parliament and of the Council concerning the management of bathing water quality. Brussels 23rd June]. This paper focuses on the relationships between land use and faecal indicator organism concentrations in surface waters within this very large drainage basin (1583 km2) containing some extensive urban areas. A geographical information system comprising readily available digital elevation, remotely sensed land cover and digital map data was used to generate the land use variables for subcatchments draining to 41 locations across the study area. Presumptive concentrations of coliforms, Escherichia coli and enterococci (colony forming unit (cfu) 100 ml−1) were measured at each location on at least 20 occasions over a 44-day period within the 2002 bathing season. The sampling programme targeted hydrograph events. Hydrometric records were used to allocate results as either base flow or high flow. At each site, geometric mean faecal indicator organism concentrations were significantly elevated at high flow compared to base flow. Stepwise regression modelling produced statistically significant models predicting geometric mean base and high-flow faecal indicator organism concentrations from land use variables ( r 2 : 49.5–68.1%). The dominant predictor variable in each case was the proportion of built-up land in subcatchments, suggesting that this land use type, with associated sewage-related inputs, is a critical source of faecal indicator organisms in this drainage basin.

Intestinal enterococci are the principal 'health-evidence-based' parameter recommended by WHO for the assessment of marine recreational water compliance. Understanding the survival characteristics of these organisms in nearshore waters is central to public health protection using robust modelling to effect real-time prediction of water quality at recreation sites as recently suggested by WHO and the Commission of the European Communities Previous models have more often focused on the coliform parameters and assumed two static day-time and night-time T90 values to characterise the decay process. The principal driver for enterococci survival is the received dose of irradiance from sunlight. In the water column, transmission of irradiance is determined by turbidity produced by suspended material. This paper reports the results of irradiated microcosm experiments using simulated sunlight to investigate the decay of intestinal enterococci in relatively turbid estuarine and coastal waters collected from the Severn Estuary and Bristol Channel, UK. High-turbidity estuarine waters produced a T90 value of 39.5 h. Low-turbidity coastal waters produced a much shorter T90 value of 6.6 h. In experiments receiving no irradiation, high-turbidity estuarine waters also produced a longer T90 of 65.1 h compared with corresponding low-turbidity coastal waters, T90 24.8 h. Irradiated T90 values were correlated with salinity, turbidity and suspended solids (r0.8, p0.001). The results suggest that enterococci decay in irradiated experiments with turbidity200 NTU is similar to decay observed under dark conditions. Most significantly, these results suggest that modelling turbidity and or suspended solids offers a potential means of predicting T90 values in 'real-time' for discrete cells of a hydrodynamic model.

A small number of studies have indicated that reductions in the signal strength of clear air returns can be observed at low altitudes in regions of precipitation. This study uses data from the NERC MST radar facility in Aberystwyth (52.4° N, 4.1° W) and co-located tipping bucket rain gauge data to determine whether this effect can be observed for all periods where high rainfall rates were observed at the ground. The period selected for examination includes all of the days where a peak rainfall rate of 6mm h-1 was exceeded in 2001. A statistical examination of VHF radar signal power during periods with and without surface rainfall suggests that the returned power is reduced by the presence of precipitating clouds. The corrected spectral width of the Doppler spectra is also significantly wider during periods of precipitation. The process which causes the decrease in the VHF signal power seems to be associated with a reduction in Fresnel reflection within precipitating clouds. This, in turn, may be due to a reduction of humidity gradients in clouds. UHF wind profiler data is also used to show that there is a relationship between enhanced UHF returns (signifying precipitation) and reduced VHF returns. To clarify the processes and effects observed we examine three case studies which show typical relationships between the VHF signal power and surface rainfall or enhanced UHF signal-to-noise ratios. The effect of precipitation on the signal processing scheme's derivation of signal power and spectral width is explored using individual Doppler spectra.

Knowledge of the hydrochemical dynamics of the trace metal manganese (Mn) in upland catchments is required for water quality management. Stream water Mn and other solutes and flow were monitored in two upland catchments in northern England with different soils: one dominated by peat (HS7), the other by mineral soils (HS4). Maximum Mn concentration s occurred at different times in the two catchments: in summer baseflow at HS4 and during late summer storm events at HS7. A two- component chemical mixing model was used to identify the hydrological processes controlling Mn concentration s in stream water. This approach was more successful for HS4 than HS7, probably because of different processes of Mn release in the two catchments and also difficulties in selecting conservative solutes. Factor analysis of the stream water chemistry data set for each catchment was more useful in identifying the controls on Mn release into runoff. The factors indicate that the main source of Mn at HS4 is the hydrological pathway supplying summer baseflow, whereas at HS7 Mn is released during the rewetting of dried peat soils. Manganese concentrations in stream water in upland catchments appear to depend on soil type and antecedent moisture conditions. This has implications for the design of sampling strategies in upland catchments and also for managing the quality of water supplies from such areas.

The ARBRE (ARable Biomass Renewable Energy) project, the first large-scale wood-fueled electricity generating plant in the U.K., represents a significant development in realising British and European policy objectives on renewable energy. The plant is fueled by a mix of wood from short rotation coppice (SRC) and forest residues. Where feasible, composted/conditioned sewage sludge is applied to coppice sites to increase yields and improve soil structure. In the Yorkshire Water region, typical total N:P:K composition of composted/conditioned sludge is 2.9:3.8:0.3, respectively. Sludge application is calculated on the basis of total nitrogen (N) content to achieve 750 kg N ha-1, for 3 years’ requirement. Willow coppice forms a dense, widely spaced, root network, which, with its long growing season, makes it an effective user of nutrients. This, in combination with willow’s use as a nonfood, nonfodder crop, makes it an attractive route for the recycling of sewage sludge in the absence of sea disposal, banned under the EC Urban Waste Water Treatment Directive (UWWTD). Further work is required on the nutritional requirements of SRC in order to understand better the quantities of sludge that can be applied to SRC without having a detrimental impact on the environment. This paper suggests the source of N rerouting under the UWWTD and suggests the likely expansion of SRC as an alternative recycling pathway.

The non-market nature of water quality improvement in rivers hinders the use of traditional cost-benefit analysis (CBA) to measure the efficiency of investments. Substantial investments have been made to clean up contaminated river water with little comparison of the costs or environmental impact (EI) with future benefits. Water quality impact models are used in this study to predict the impact of discharges on downstream water quality. Contingent valuation (CV) is used to measure the total value, including use and non-use, of river water quality improvement. This provides the benefit side of the cost-benefit equation. The method outlined provides a tool to evaluate investment on environmental improvement integrating EI and CV in CBA.

This work presents an investigation of the forest information content of spectral vegetation indices including the SR, NDVI, PVI, SAVI, TSAVI, and GEMI. The results were derived from two separate reflectance models including a geometric–optical and a Monte Carlo ray-tracing model, assuming nadir viewing. The effects of the atmosphere on the indices were also examined, using the 6S atmospheric code, and a short section is devoted to an analysis of Landsat Thematic Mapper data. Overall, the indices were not linear with respect to forest cover and, in many situations, an index did not have a unique value for a given cover. The general form of the indices’ responses to changes in cover could be explained by shadowing effects, linked to the heterogeneous nature of forest. The indices were also significantly affected by perturbations including solar zenith angle, background reflectance, stand structure, and leaf-area index. The relative importance of these perturbations depended on both the cover and on the particular spectral index tested. Existing indices should be selected according to the characteristics of the site under investigation, since no single index performed well over all covers. At low covers, GEMI performed best, where a decrease in the value of GEMI corresponded to an increase in crown cover. There was some evidence that the soil-adjusted indices (PVI, SAVI, TSAVI, and GEMI) partially reduced background reflectance effects in the data, although the reductions were not always associated with increased sensitivity to crown cover. At high covers, SAVI and TSAVI were found to perform best, since these indices had large dynamic ranges and small susceptibility to atmospheric perturbations. Further work is required to develop spectral indices specifically for conifer forests.

Nuisance cyanobacterial blooms are an important environmental problem. Toxins released by cyanobacteria can kill animals and cause illness in humans. The sustainable manage ment of toxic cyanobacteria would increase the conservation and amenity value of affected water bodies, and decrease on-site water treatment costs. Methods are available to kill or to prevent blooms but often the expense is prohibitive or the agent used is detrimental to desirable lake organisms. Different management strategies are therefore considered within the context of the current state of the UK water industry. Particular reference is made to the potential impact of the 1994 Ofwat-determined water-price increase limits on environmental policy and prioritization.

The relationship between the distribution of naturally occurring discoloured water and catchment characteristics is determined for an upland catchwater system in North Yorkshire, U.K. Primary non-point sources of colour are identified as areas of Winter Hill peat with slopes

Water regulation world-wide is moving to a new and challenging paradigm characterised by integrated assessment and management of multiple pollution loadings within drainage basins. This is seen in the European Water Framework Directive and the United States Clean Water Act. Implementation lessons of the latter suggest the principal water quality concern at the continental scale is microbial pollution by faecal indicators and pathogens. This presents a major new challenge to the microbiological community and presents major opportunities of joint working with catchment scientists, modellers, engineers and the farming community. To date, very little catchment-scale science has addressed microbial flux measurement, modelling and prediction when compared to other parameters such as the nutrients, oxygen demand and sediments. The engineering community has made excellent progress on point-source pollution control from sewage works but, parallel progress on agricultural best management practices to limit diffuse-source pollution from agriculture is less evident and the science evidence-base for the efficacy of such measures remains equivocal. This contribution presents a clear set of research challenges and management priorities designed to stimulate further involvement by the microbiological community in this emerging area.

Microbial indicators of water quality are used to quantify the risk derived from faecally contaminated surface and drinking waters. The historical focus in this area has centred on human-derived sewage contamination of bathing, shellfish and drinking waters. However, emerging catchment-scale water legislation in North America and Europe, in particular, is driving a more holistic approach in which quantification of microbial pollution from all sources is undertaken, to inform and prioritise appropriate remedial action designed to ensure health risk is minimised. This involves integrated management of agricultural livestock-derived pollution alongside sewage effluents to ensure compliance of impacted sites with appropriate regulatory standards. The evidence-base for the design of best management practices by farmers which will remove and/or attenuate microbial flux from catchment systems is very limited when compared to the chemical parameters associated with ecological impairments, such as phosphorus and nitrogen. However, early empirical investigations do suggest the potential to realise very significant water quality benefits from simple interventions, such as stock exclusion fencing of stream banks and well-designed constructed wetland systems. Further process-based investigation of these areas is underway and this research effort is becoming imperative as emerging experience of catchment-scale legislation strongly suggests the importance of microbial pollution as the principal reason for non-compliance with water quality standards in North America.

The input of fecal coliform bacteria to the River Skell stream from a small, approximately 0.5 ha, instrumented research site on Pateley Moor in the Yorkshire Dales was investigated. Bacterial concentrations were determined for a total of 433 water samples collected between October and December 1984 from 31 stream bank sites representing three types of near-surface water flow: matrix through flow, nonmatrix through flow, and overland flow. Bacterial concentrations in matrix through flow were found to be very low, but much higher input rates were found in both nonmatrix through flow and overland flow. Overland flow sites were the most important group for the input of bacteria to the channel, both between and during storm events. The rate of fecal coliform input was found to increase during storm events, and there was a strong, positive correlation between bacterial input rate and stream stage height.

This paper examines the discolouration of water by dissolved organic matter under controlled conditions. Winter hill association (raw peat) is subjected to prolonged natural drying to induce a range of moisture deficits. This peat is then subjected to rainfall simulation. Throughflow colour relates to drought duration and near surface water loss and rewetting. Attention is paid to the role of pore spaces in colour generation and removal. The implications for moorland management and the long term pattern of water discolouration are considered.

The levels of total coliform and Escherichia coli bacteria were determined within the surface soils of two upland catchments in North Yorkshire. The results indicated that enteric bacteria can survive for a sufficient period outside parent faecal material to provide a semi-permanent land store that might then be capable of contaminating upland waters following transport by hydrological processes. Significant differences in bacterial counts were found between broadly wet and dry soil moisture/vegetation zones in both catchments. This was explained by the more favourable survival conditions found where the soil moisture content was high enough to prevent the rapid desiccation and death of enteric bacteria. Significant differences were also found between the counts of total coliform and Escherichia coli bacteria in surface soils. It was concluded that the use of the total coliform group alone, as an indicator of the degree of sanitary bacterial contamination of soils, may over-estimate the true extent of contamination.

The faecal coliform concentration of overland flow and streamwater within a small catchment in the Yorkshire Dales was monitored over a 2 year period. Strong and consistent seasonal trends in bacterial concentration were found. During the height of summer (mid June to the end of August), faecal coliform concentrations in streamwater were found to be significantly higher than at other times of year. Consistently low concentrations were found during winter months. These trends closely followed those identified for semi-permanent overland flow, suggesting a direct causal link between streamwater quality and the bacterial concentration of overland flow entering the stream channel. The seasonal trends identified were explained with respect to long term changes in the size of the store of enteric bacteria existing in the surface soils of the catchment. Changes in land store size were related to seasonal changes in the frequency and amount of rainfall input to the catchment. The implications of the research findings for the management of upland catchments used for water supply or recreation are discussed.