The microphysics of clouds over the Antarctic Peninsula - Part 2: modelling aspects within Polar WRF

The first intercomparisons of cloud microphysics schemes implemented in the Weather Research and Forecasting (WRF) mesoscale atmospheric model (version 3.5.1) are performed in the Antarctic Peninsula using the polar version of WRF (Polar WRF) at 5 km resolution, along with comparisons to the British Antarctic Survey's aircraft measurements (presented in Part 1 of this work, Lachlan-Cope et al., 2016). This study follows previous works suggesting the misrepresentation of the cloud thermodynamic phase in order to explain large radiative biases derived at the surface in Polar WRF continent-wide, and in the Polar WRF-based operational forecast model Antarctic Mesoscale Prediction System (AMPS) over the Larsen C Ice shelf. Several cloud microphysics schemes are investigated: the WRF Single-Moment 5-class scheme (WSM5), the WRF Double-Moment 6-class scheme (WDM6), the Morrison double-moment scheme, the Thompson scheme, and the Milbrandt- Yau Double-Moment 7-class scheme. WSM5 used in AMPS struggles the most to capture the observed supercooled liquid phase mainly because of their ice nuclei parameterisation overestimating the number of activated crystals, while other micro- physics schemes (but not WSM5's upgraded version, WDM6) manage much better to do so. The best performing scheme is the Morrison scheme for its better average prediction of occurrences of clouds, and cloud phase, as well as its lowest surface radiative bias over the Larsen C ice shelf in the infrared. This is important for surface energy budget consideration with Polar WRF since the cloud radiative effect is more pronounced in the infrared over icy surfaces. However, our investigation shows that all the schemes fail at simulating the supercooled liquid mass at some temperatures (altitudes) where observations show evidence of its persistence. An ice nuclei parameterisation relying on both temperature and aerosol content like DeMott et al. (2010) (not currently used in WRF cloud schemes) is in best agreement with the observations, at temperatures and aerosol concentration characteristic of the Antarctic Peninsula where the primary ice production occurs (Part 1), compared to parame- terisation only relying on the atmospheric temperature (used by the WRF cloud schemes). Overall, a realistic ice microphysics implementation is paramount to the correct representation of the supercooled liquid phase in Antarctic clouds

The microphysics of clouds over the Antarctic Peninsula – Part 1: Observations

Observations of clouds over the Antarctic Peninsula during summer 2010 and 2011 are presented here. The peninsula is up to 2500 m high and acts as a barrier to weather systems approaching from the Pacific sector of the Southern Ocean. Observations of the number of ice and liquid particles as well as the ice water content and liquid water content in the clouds from both sides of the peninsula and from both years were compared. In 2011 there were significantly more water drops and ice crystals, particularly in the east, where there were approximately twice the number of drops and ice crystals in 2011. Ice crystals observations as compared to ice nuclei parameterizations suggest that secondary ice multiplication at temperatures around −5 °C is important for ice crystal formation on both sides of the peninsula below 2000 m. Also, back trajectories have shown that in 2011 the air masses over the peninsula were more likely to have passed close to the surface over the sea ice in the Weddell Sea. This suggests that the sea-ice-covered Weddell Sea can act as a source of both cloud condensation nuclei and ice-nucleating particles

Establishment of an economic evaluation model for urban recycled water

This study aimed at establishing an economic evaluation model to encourage continuing improvement in performance analysis and applying for any infrastructure system of urban recycled water. A thorough study towards characterization and economic performance assessment of urban water reuse scheme were carried out. An integrated evaluation technique was developed by synthesizing the quantitative and qualitative performance indicators related to the water recycled technology and urban water cycle system. Specific performance indicators and indexes were aggregated into an economic analytical modelling for effective evaluation of the water reuse scheme and technology using uniform economic performance standards. Detailed economic analyses were successfully applied to enable determination of economic lifetime of the technology and the whole water reuse scheme. This research confirmed that productivity, efficiency and reliability measurements and factors could be successfully deployed for determining the scheme performance during various life cycle stages (e.g. design development, operational and functional verification, or comparison with other reuse projects). The economic assessment model was applied to improve uniformity of analytical process and performance measure. This article demonstrates benefits associated with the application of a standardized methodology for performing economic assessment and by maintaining strong correlation between multi-parameter approach and adopted performance criteria in terms of productivity, efficiency and reliability. However, to ensure effectiveness of this assessment, the process would require systematic and perpetual inventory of the scheme performance data, consideration of variable factors such as capital and recurrent costs. © 2012 Elsevier B.V. All rights reserved

An assessment of the impact of local processes on dust lifting in martian climate models

Simulation of the lifting of dust from the planetary surface is of substantially greater importance on Mars than on Earth, due to the fundamental role that atmospheric dust plays in the former’s climate, yet the dust emission parameterisations used to date in martian global climate models (MGCMs) lag, understandably, behind their terrestrial counterparts in terms of sophistication. Recent developments in estimating surface roughness length over all martian terrains and in modelling atmospheric circulations at regional to local scales (less than O(100 km)) presents an opportunity to formulate an improved wind stress lifting parameterisation. We have upgraded the conventional scheme by including the spatially varying roughness length in the lifting parameterisation in a fully consistent manner (thereby correcting a possible underestimation of the true threshold level for wind stress lifting), and used a modification to account for deviations from neutral stability in the surface layer. Following these improvements, it is found that wind speeds at typical MGCM resolution never reach the lifting threshold at most gridpoints: winds fall particularly short in the southern midlatitudes, where mean roughness is large. Sub-grid scale variability, manifested in both the near-surface wind field and the surface roughness, is then considered, and is found to be a crucial means of bridging the gap between model winds and thresholds. Both forms of small-scale variability contribute to the formation of dust emission ‘hotspots’: areas within the model gridbox with particularly favourable conditions for lifting, namely a smooth surface combined with strong near-surface gusts. Such small-scale emission could in fact be particularly influential on Mars, due both to the intense positive radiative feedbacks that can drive storm growth and a strong hysteresis effect on saltation. By modelling this variability, dust lifting is predicted at the locations at which dust storms are frequently observed, including the flushing storm sources of Chryse and Utopia, and southern midlatitude areas from which larger storms tend to initiate, such as Hellas and Solis Planum. The seasonal cycle of emission, which includes a double-peaked structure in northern autumn and winter, also appears realistic. Significant increases to lifting rates are produced for any sensible choices of parameters controlling the sub-grid distributions used, but results are sensitive to the smallest scale of variability considered, which high-resolution modelling suggests should be O(1 km) or less. Use of such models in future will permit the use of a diagnosed (rather than prescribed) variable gustiness intensity, which should further enhance dust lifting in the southern hemisphere in particular

Evaluation of an integrated sponge - Granular activated carbon fluidized bed bioreactor for treating primary treated sewage effluent

An integrated fluidized bed bioreactor (iFBBR) was designed to incorporate an aerobic sponge FBBR (ASB-FBBR) into an anoxic granular activated carbon FBBR (GAC-FBBR). This iFBBR was operated with and without adding a new starch based flocculant (NSBF) to treat synthetic primary treated sewage effluent (PTSE). The NSBF contains starch based cationic flocculants and trace nutrients. The results indicate that the iFBBR with NSBF addition could remove more than 93% dissolved organic carbon (DOC), 61% total nitrogen (T-N) and 60% total phosphorus (T-P) at just a very short hydraulic retention time of 50min. The optimum frequency of adding NSBF to the iFFBR is four times per day. As a pretreatment to microfiltration, the iFFBR could increase 5L/m2h of critical flux thus reducing the membrane fouling. In addition, better microbial activity was also observed with high DO consumption (>66%) and specific oxygen uptake rate (>35mg O2/gVSSh). © 2010 Elsevier Ltd

Effects of sponge size and type on the performance of an up-flow sponge bioreactor in primary treated sewage effluent treatment

The effects of polyurethane sponge size and type on the performance of an up-flow sponge bioreactor were studied using different sponge cube sizes (1 × 1 × 1 cm, 2 × 2 × 2 cm and 3 × 3 × 3 cm) and types of sponge (S28-30/45R, S28-30/60R, S28-30/80R and S28-30/90R). The reactors were operated under anaerobic conditions in an early stage and an aerobic condition in a latter stage. The results indicate that there was no significant difference in the organic and nutrient removal rates between sponge types. The medium size sponge (2 × 2 × 2 cm) had the best performance in terms of both biomass growth and pollutants removal. Under anaerobic condition, the COD, TN and TP removal efficiencies were up to 70%, 45% and 55%, respectively, and significantly improved under aerobic conditions (e.g. >90% TOC, 95% COD, 65% TN and 90% TP). The external biomass grew faster under anaerobic conditions while internal biomass was dominant under aerobic condition. © 2009 Elsevier Ltd

Concepts towards a novel integrated assessment methodology of urban water reuse

Traditional supplies of large volumes of water and wastewater disposal technologies have offered a linear solution, thus intensifying environmental stress. In addition, provision of urban infrastructure especially any major augmentations are often the impractical or economically prohibitive. Urban water cycle should be viewed as an interactive and coordinated approach involving: • Available water resources, • Appropriate treatment technology producing fit for purpose water quality, and • Ascertaining long term balance between environmental, social and economic issues. Implementation of integrated water reuse scheme requires major paradigm shift within a number of technical (science, technology and knowledge) and non-technical (socio-cultural, economic, environment) dimensions. There are number of questions that arise from this scenario: • How to make decisions regarding selection, design, implementation and operation of any recycling scheme? • What knowledge is necessary to improve decision-making process? • How to assess and compare performance of the scheme? • What are the parameters for uniform evaluation process? The aim of this paper is to introduce a new concept for integrated assessment methodology that can be applied for urban water reuse schemes. The conceptual assessment methodology relies on decision that treatment technology represents a leading theme and is supported by selection of socio-economic and environmental factors, thus enabling holistic evaluation and quantification of the outcomes. © 2009 Desalination Publications

Roles of sponge sizes and membrane types in a single stage sponge-submerged membrane bioreactor for improving nutrient removal from wastewater for reuse

Sponge not only can reduce membrane fouling by means of mechanical cleaning and maintain a balance of suspended-attached microorganisms in submerged membrane bioreactor (SMBR), but also can enhance dissolved organic matter and nutrient removal. This study investigated the performance of three different sizes of sponge (S28-30/45R, S28-30/60R and S28-30/90R) associated with continuous aerated SMBR. A laboratory-scale single stage sponge-SMBR (SSMBR) showed high performance for removing dissolved organic matter (>96%) and PO4-P (>98.8), while coarse sponges such as S28-30/45R, S28-30/60R could achieve more than 99% removal of NH4-N. When three-size sponges (S28-30/45R, S28-30/60R and S28-30/90R) were mixed at a ratio of 1:1:1 and in conjunction with two kinds of membranes (0.1 μm hollow fiber and 2 μm nonwoven), the SSMBR system has proved its generic merits of superior treated effluent quality and less membrane fouling. The NH4-N and PO4-P removal were found excellent, which were more than 99.8% and over 99% respectively. Molecular weight distribution also indicated that major fractions of organic matter could be successfully removed by SSMBR. © 2009 Elsevier B.V. All rights reserved