Numerical Modeling System Research Articles

Deformation rule and mechanical characteristic analysis of subsea tunnel crossing weathered trough

It is difficult to comprehend the deformation rule and mechanical characteristics in the construction process of subsea tunnel crossing weathered trough owing to the complex tunnel structure and unfavorable geological conditions. In this study, a geomechanical model test and a numerical model system for the excavation of subsea tunnel were developed based on Haicang Subsea Tunnel to investigate the characteristics of the tunnel displacement, stress, and seepage. After subsea tunnel excavation, the displacement, stress, and hydraulic pressure distribution of surrounding rocks were similar, with the release of stress and lower hydraulic pressure often accompanied with the growth of its displacement. Generally, multiple-physical monitoring information was interactional. In addition, the influence of seawater on the weathering trough was mainly concentrated in an area approximately twice the diameter of the hole, and the influence of water on the vault was greater than that of the sidewall. These results could serve as reference for the construction of subsea tunnel crossings and warning mechanisms of weathered trough.

China’s Policy Choices and Effects in Response to the Economic Impact of CPTPP

The Comprehensive and Progressive Agreement for Trans-Pacific Partnership（CPTPP）has officially entered into force and is in the expansion stage. It will have a profound impact on the Asia-Pacific economic and trade structure and global economic and trade investment rules in the future.Outside of CPTPP, China needs to take active measures to respond, build or join more regional trading systems, and expand the “friend circle” of economic and trade cooperation. China’s measures to deal with the economic impact of CPTPP can be divided into three categories: One is China’s policy choice for directly responding to CPTPP, the other is China’s policy choice for joining CPTPP, and the third is China’s policy choice for responding to the U.S. returning to CPTPP.This paper constructs a large-scale general equilibrium numerical model system to simulate the effects of different measures in China’s response to CPTPP. The value chain and value-added trade are embedded in the model, and the imbalanced trade structure of “inside money” is introduced to optimize the stability of the model. In terms of data, the model parameters are calibrated and estimated using the latest 2018 data, a numerical model system is constructed, and the effects of the three types of response measures are quantitatively simulated.The simulation results find that the policy effects of China’s unilateral measures to cope with the impact of CPTPP, from high to low, are in order: construction of a China-Japan-Korea free trade zone, implementation of RCEP, no measures, and further opening up. Under the two scenarios of China joining CPTPP, the measures to join the agreement together with the first batch of countries to expand the capacity will be more effective. After the U.S. returns to CPTPP, under the three scenarios of China’s policy choices, the policy effects from high to low are optimizing the business environment, not taking measures, and joining CPTPP with the U.S. Among the three different options, the economic effect of actively joining CPTPP is the best; the effect of unilateral measures to deal with CPTPP is the second; and once the U.S. returns to CPTPP, it will have an adverse impact on China. The effective measure to deal with is to optimize the business environment to reduce trade costs.The results of the analysis enlighten China in terms of policies to accelerate the development of free trade agreement and expand the scope of the economic and trade “friend circle”. At the same time, we should speed up domestic reform and opening up, optimize the business environment, and promote domestic system reform with new international economic and trade rules. In addition, we should actively consider joining CPTPP in an appropriate way to further promote domestic reforms and opening up to the outside world, and promote win-win cooperation and economic development in the Asia-Pacific region. The research of this paper will provide decision-making reference for China’s policy choices in response to CPTPP.

Impact of Arctic Oscillation anomalies on winter PM2.5 in China via a numerical simulation.

The impact of Arctic Oscillation (AO) anomalies on winter PM2.5 variability in China was investigated using a numerical modeling system (WRF-CUACE). The model results showed that the influence of AO anomalies on winter PM2.5 concentration was mainly concentrated in eastern China, especially in Central China (CEN), Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD), and Pearl River Delta (PRD) and was mostly consistent with the conclusions of a previous analysis using haze data. Winter PM2.5 concentrations in CEN and BTH increased under abnormally high AO and decreased under abnormally low AO due to the subsequent changes in specific meteorological conditions, such as temperature, wind speed, and boundary layer height. Winter PM2.5 decreased in the YRD and PRD in both abnormally high and low AO years due to more favorable vertical transport conditions and regional transport capacity compared with those of other regions. In addition to meteorological factors, AO anomalies also impacted PM2.5 depositions in winter, with more apparent effects in southern China. It is found that AO had a larger impact on dry deposition than on wet deposition, and dry deposition was a dominant factor affecting PM2.5 concentrations in CEN.

Variability of USA East Coast surface total alkalinity distributions revealed by automated instrument measurements

Seawater total alkalinity (TA) is one important determinant used to monitor the ocean carbon cycle, whose spatial distributions have previously been characterized along the United States East Coast via discrete bottle samples. Using these data, several regional models for TA retrievals based on practical salinity (S) have been developed. Broad-scale seasonal or interannual variations, however, are not well resolved in these models and existing data are highly seasonally biased. This study reports findings from the first long duration deployment of a new, commercially available TA titrator aboard a research vessel and the continuous underway surface TA measurements produced. The instrument, operated on seven East Coast USA cruises during six months in 2017 and for two months in 2018 on the summertime East Coast Ocean Acidification survey (ECOA-2), collected a total of nearly 11,000 surface TA measurements. Data from these efforts, along with a newly synthesized set of more than 11,000 regional surface TA observations, are analyzed to re-examine distributions of TA and S along the United States East Coast. Overall, regional distributions of S and TA generally agreed with prior findings, but linear TA:S regressions varied markedly over time and deviated from previously developed models. This variability is likely due to a combination of biological, seasonal, and episodic influences and indicates that substantial errors of ±10–20 μmol kg−1 in TA estimation from S can be expected due to these factors. This finding has likely implications for numerical ecosystem modeling and inorganic carbon system calculations. New results presented in this paper provide refined surface TA:S relationships, present more data in space and time, and improve TA modeling uncertainty.

Clean air in cities: Impact of the layout of buildings in urban areas on pedestrian exposure to ultrafine particles from traffic

Traffic-related pollutant concentrations are typically much higher in near-roadway microenvironments, and pedestrian and resident exposures to air pollutants can be substantially increased by the short periods of time spent on and near roadways. The design of the built environment plays a critical role in the dispersion of pollutants at street level; after normalizing for traffic, differences of a factor of ~5 have been observed between urban neighborhoods with different built environment characteristics. We examined the effects of different built environment designs on the concentrations of street-level ultrafine particles (UFP) at the scale of several blocks using the Quick Urban and Industrial Complex (QUIC) numerical modeling system. The model was capable of reasonably reproducing the complex ensemble mean 3D air flow patterns and pollutant concentrations in urban areas at fine spatial scale. We evaluated the effects of several built environment designs, changing building heights and spacing while holding total built environment volumes constant. We found that ground-level open space reduces street-level pollutant concentrations. Holding volume/surface area constant, tall buildings clustered together with larger open spaces between buildings resulted in substantially lower pollutant concentrations than buildings in rows. Buildings arranged on a ‘checkerboard’ grid with smaller contiguous open spaces, a configuration with some open space on one of the sides of the roadway at all locations, resulted in the lowest average concentrations for almost all wind directions. Rows usually prohibit mixing for perpendicular and oblique wind directions, even when there are large spaces between them, and clustered buildings have some areas where buildings border both sides of the roadways, inhibiting mixing. The model results suggest that pollutant concentrations drop off rapidly with height in the first 10 m or so above the roadways. In addition, the simulated vertical concentration profiles show a moderate elevated peak at the roof levels of the shorter buildings within the area. Model limitations and suggestions both for urban design are both discussed.

The impact of WTO reform on china’s economy: some numerical simulation results

Using a global general equilibrium numerical model system with endogenous trade imbalance, this paper simulates the potential economic impacts of different WTO reform scenarios on China. The simulation results show that ending China’s ‘special and differential treatment’ (SDT) alone would have a negative impact on China’s social welfare and GDP, but the impact on manufacturing employment and foreign trade would be positive. The results of a simultaneous withdrawal of SDT from China, Brazil, India, and South Africa would be in line with the effect of China’s separate exit, but China’s damage would be lessened. If all developing countries were to withdraw from SDT, China’s losses would be further reduced. If the WTO reform goals were to promote and achieve a new round of global trade liberalisation, China’s welfare, output, manufacturing employment, and foreign trade would all improve significantly.

Emission source-based ozone isopleth and isosurface diagrams and their significance in ozone pollution control strategies

In the past decade, ozone (O3) pollution has been continuously worsening in most developing countries. The accurate identification of the nonlinear relationship between O3 and its precursors is a prerequisite for formulating effective O3 control measures. At present, precursor-based O3 isopleth diagrams are widely used to infer O3 control strategy at a particular location. However, there is frequently a large gap between the O3-precursor nonlinearity delineated by the O3 isopleths and the emission source control measures to reduce O3 levels. Consequently, we developed an emission source-based O3 isopleth diagram that directly illustrates the O3 level changes in response to synergistic control on two types of emission sources using a validated numerical modeling system and the latest regional emission inventory. Isopleths can be further upgraded to isosurfaces when co-control on three types of emission sources is investigated. Using Guangzhou and Foshan as examples, we demonstrate that similar precursor-based O3 isopleths can be associated with significantly different emission source co-control strategies. In Guangzhou, controlling solvent use emissions was the most effective approach to reduce peak O3 levels. In Foshan, co-control of on-road mobile, solvent use, and fixed combustion sources with a ratio of 3:1:2 or 3:1:3 was best to effectively reduce the peak O3 levels below 145 ppbv. This study underscores the importance of using emission source-based O3 isopleths and isosurface diagrams to guide a precursor emission control strategy that can effectively reduce the peak O3 levels in a particular area.

ROMS Based Hydrodynamic Modelling Focusing on the Belgian Part of the Southern North Sea

The North Sea is a shallow sea that forms a complex physical system. The nonlinear interaction of the astronomical tides, varying wind fields and varying pressure systems requires appropriate approaches to be described accurately. An application based on the advanced numerical model Regional Ocean Modeling System (ROMS) was newly developed by the authors, tailored to simulate these hydrodynamic processes in the North Sea and the Belgian Continental Shelf, which is the area of particular interest in the present study. The purpose of this work is to develop and validate a state-of-the-art three-dimensional numerical model to form the basis of a compound operational and forecasting tool for the Belgian coastal zone. The model was validated with respect to water levels and temperature. Validation for astronomical tides was accomplished through the comparison of the principal constituents between the model results and observations at a number of tidal gauges in Belgium and other countries. A statistical analysis of the results showed that the model behaves as expected throughout the North Sea. The model response to the varying meteorological conditions was also validated using hindcast data for 2011 as input. In this case, the comparison between observed and modelled water levels showed a good agreement with average RMSE in Belgium 9.5 cm. Overall, the added value of this work is the development of an independent model for validation and comparison with other models and which can be used as an efficient tool for operational and forecasting purposes.

An Assessment of the Hydrological Trends Using Synergistic Approaches of Remote Sensing and Model Evaluations over Global Arid and Semi-Arid Regions

Drylands cover about 40% of the world’s land area and support two billion people, most of them living in developing countries that are at risk due to land degradation. Over the last few decades, there has been warming, with an escalation of drought and rapid population growth. This will further intensify the risk of desertification, which will seriously affect the local ecological environment, food security and people’s lives. The goal of this research is to analyze the hydrological and land cover characteristics and variability over global arid and semi-arid regions over the last decade (2010–2019) using an integrative approach of remotely sensed and physical process-based numerical modeling (e.g., Global Land Data Assimilation System (GLDAS) and Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS) models) data. Interaction between hydrological and ecological indicators including precipitation, evapotranspiration, surface soil moisture and vegetation indices are presented in the global four types of arid and semi-arid areas. The trends followed by precipitation, evapotranspiration and surface soil moisture over the decade are also mapped using harmonic analysis. This study also shows that some hotspots in these global drylands, which exhibit different processes of land cover change, demonstrate strong coherency with noted groundwater variations. Various types of statistical measures are computed using the satellite and model derived values over global arid and semi-arid regions. Comparisons between satellite- (NASA-USDA Surface Soil Moisture and MODIS Evapotranspiration data) and model (FLDAS and GLDAS)-derived values over arid regions (BSh, BSk, BWh and BWk) have shown the over and underestimation with low accuracy. Moreover, general consistency is apparent in most of the regions between GLDAS and FLDAS model, while a strong discrepancy is also observed in some regions, especially appearing in the Nile Basin downstream hyper-arid region. Data-driven modelling approaches are thus used to enhance the models’ performance in this region, which shows improved results in multiple statistical measures ((RMSE), bias (ψ), the mean absolute percentage difference (|ψ|)) and the linear regression coefficients (i.e., slope, intercept, and coefficient of determination (R2)).

Source-Receptor Relationship Revealed by the Halted Traffic and Aggravated Haze in Beijing during the COVID-19 Lockdown.

The COVID-19 outbreak greatly limited human activities and reduced primary emissions particularly from urban on-road vehicles but coincided with Beijing experiencing “pandemic haze,” raising the public concerns about the effectiveness of imposed traffic policies to improve the air quality. This paper explores the relationship between local vehicle emissions and the winter haze in Beijing before and during the COVID-19 lockdown based on an integrated analysis framework, which combines a real-time on-road emission inventory, in situ air quality observations, and a localized numerical modeling system. We found that traffic emissions decreased substantially during the COVID-19 pandemic, but its imbalanced emission abatement of NOx (76%, 125.3 Mg/day) and volatile organic compounds (VOCs, 53%, 52.9 Mg/day) led to a significant rise of atmospheric oxidants in urban areas, resulting in a modest increase in secondary aerosols due to inadequate precursors, which still offset reduced primary emissions. Moreover, the enhanced oxidizing capacity in the surrounding regions greatly increased the secondary particles with relatively abundant precursors, which was transported into Beijing and mainly responsible for the aggravated haze pollution. We recommend that mitigation policies should focus on accelerating VOC emission reduction and synchronously controlling regional sources to release the benefits of local traffic emission control.

Quantifying uncertainty sources in extreme flow projections for three watersheds with different climate features in China

Extreme flow projections are of considerable necessity for flood and drought disaster prevention and sustainable water resources management to adapt to future climate change. However, these projections are usually associated with large uncertainties arising from different sources. A numerical modeling system including three emission scenarios (ESs), four climate models (CMs), four statistical downscaling (SD) methods, four hydrological modeling (HM) schemes, and four probability distribution (PD) functions was established in this study to project future extreme flow changes at basin scales. This modeling system was employed in the following three watersheds with different climatic and topographical characteristics in China: The Upper Ganjiang River basin (UGRB) in the humid region, the Laoha River basin (LRB) in the semi-arid region, and the Yellow River source region (YRSR) in the semi-humid region. Subsequently, the analysis of variance approach (ANOVA) was used to quantify the contribution of different uncertainty sources in extreme flow projections. Results show that extreme high flow was projected to increase in all basins. By contrast, extreme low flow would decrease in UGRB, and inconsistent change signals were found in LRB and YRSR. The ANOVA-based assessment reveals that CM is generally the dominant uncertainty source for mean monthly streamflow and extreme low flow projections. ES explains a large proportion of total uncertainty for extreme low flow projection in the 2060s in UGRB because of the large difference in non-precipitation frequency projected under different ESs. SD is the main uncertainty source in extreme high flow projection in UGRB where extreme precipitation events frequently occur. Compared with other basins, HM produces relatively high uncertainty in LRB due to its inferior performance in historical streamflow simulations. PD contributes a low percentage of uncertainty in extreme flow projections. Interactions among uncertainty sources even produce larger uncertainties than most individual sources. Although future extreme flow projections are associated with non-negligible uncertainties, the projected remarkable changes in extreme high and low flows indicate that stakeholders should take certain measures to mitigate flood risks in the three basins and alleviate drought risks in UGRB

Reefing Viability Index for Rigs-to-Reefs (R2R) in Malaysia.

Decommissioning of the offshore platform as an artificial reef, known as Rigs-to-Reefs (R2R), has become a sustainable approach for oil companies. The platform was reused to serve the underwater ecosystem as an artificial reef for a new marine ecosystem which helps to tackle food security issue. This paper presents the findings of the formulation of the reefing viability index to recognize an offshore region that can be used for R2R projects within the South China Sea. The combined effects of spatial data, numerical modelling, and geographic system (GIS) are proposed to study the relationship of spawning ground coral reefs, diversity, and planula larvae in the process of colonization to establish a map of the reef potential environment. Coral connectivity and spawning behaviour were studied to determine the possible source of coral seedling released during the spawning season, twice a year. A geographic reef viability index was established consisting of seven parameters which are coral larval density, pelagic larval length, sea currents, temperature, chlorophyll-a, depth, and substrate availability. The ocean hydrodynamic model was designed to resemble the pattern of larval scattering. By using the simulations and rankings, there were 95 (21%) sites which could probably be used for in situ reefing, whereas 358 (79%) sites were likely ideal for ex situ reefing. Validation of the viability index was carried out using media footage assessment of remotely operated vehicle (ROV).

Identification of close relationship between atmospheric oxidation and ozone formation regimes in a photochemically active region

Understanding ozone (O3) formation regime is a prerequisite in formulating an effective O3 pollution control strategy. Photochemical indicator is a simple and direct method in identifying O3 formation regimes. Most used indicators are derived from observations, whereas the role of atmospheric oxidation is not in consideration, which is the core driver of O3 formation. Thus, it may impact accuracy in signaling O3 formation regimes. In this study, an advanced three-dimensional numerical modeling system was used to investigate the relationship between atmospheric oxidation and O3 formation regimes during a long-lasting O3 exceedance event in September 2017 over the Pearl River Delta (PRD) of China. We discovered a clear relationship between atmospheric oxidative capacity and O3 formation regime. Over eastern PRD, O3 formation was mainly in a NOx-limited regime when HO2/OH ratio was higher than 11, while in a VOC-limited regime when the ratio was lower than 9.5. Over central and western PRD, an HO2/OH ratio higher than 5 and lower than 2 was indicative of NOx-limited and VOC-limited regime, respectively. Physical contribution, including horizontal transport and vertical transport, may pose uncertainties on the indication of O3 formation regime by HO2/OH ratio. In comparison with other commonly used photochemical indicators, HO2/OH ratio had the best performance in differentiating O3 formation regimes. This study highlighted the necessities in using an atmospheric oxidative capacity-based indicator to infer O3 formation regime, and underscored the importance of characterizing behaviors of radicals to gain insight in atmospheric processes leading to O3 pollution over a photochemically active region.

Development and validation of a storm surge forecasting/hindcasting modelling system for the extensive Río de la Plata Estuary and its adjacent Continental Shelf

The Rio de la Plata (RdP) Estuary is affected by significant surges several times per year. This phenomenon has historically caused catastrophic water-level enlargements of up to 4.44 m, threatening and claiming human lives and producing major economic and material damages. The negative surges are less frequent, but when they do occur, inhibit the access to the principal harbors and waterways and disable the drinking water intakes of the Metropolitan Area of Buenos Aires (the Capital City of Argentina) with a population of more and 16 million people. Recent works suggest that the number and strength of the surge events have been increasing with time. Nevertheless, a state-of-the-art system for the forecast of those events is not available yet. In this work, the implementation of a numerical modelling system for the forecast/hindcast of storm surges and the associated currents in the RdP and the adjacent continental shelf are presented and validated. This pre-operational system is based on an adaptation of the CROCO community ocean model to solve the dynamics associated with the surge. The model was implemented using a set of routines written in open-source programming language (Linux and Python) to be cheap and efficient and to ensure an easy future transfer to the services responsible for the alerts. For a better representation of the regional atmospheric dynamics, wind speed and sea-level pressure used to force the simulations were corrected using direct observations collected at an oceanographic buoy anchored at the estuary. The model system performance in hindcast mode was quantified by comparison with observations from tidal gauges and current meters at several locations of the estuary and the adjacent shelf. Percent errors for water level over the whole estuary and currents in the intermediate and exterior estuary drove to average results of 8 and 13%, respectively. The skill scores resulted, on average, of 0.90 and 0.80, respectively. The model performance in both hindcast and forecast modes was evaluated during historical extreme storm surges. Results support the good performance of the model to simulate even extreme events with average skill scores of 0.97 and 0.92, respectively. Results are encouraging, particularly taking into account the limitations in the atmospheric forcing for the region, where only a relatively small number of direct observations are assimilated by the reanalysis and forecast models.

Impact of Altika Sea Level Anomaly Data on a Variational Assimilation System

Imranali, M.M.; Mitra, A.K.; Waters, J.; Martin, M.J., and Rajagopal, E., 2020. Impact of Altika Sea Level Anomaly data on variational assimilation system. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 46-51. Coconut Creek (Florida), ISSN 0749-0208.Altimeter data provide measurements of dynamic topography over the global ocean and is useful for the constraining numerical ocean modeling systems through data assimilation. In this study, sensitivity experiments are carried out to understand the relative impact of Sea Level Anomaly (SLA) extracted from satellite data on a variational assimilation system for the month of August 2013. A first experiment, without assimilation of SLA observations is called CNTR while a second experiment assimilating Ka band Altika SLA into the variational assimilation system is called ALTK. Both experiments assimilated all other observations such as surface and in situ observations of temperature and salinity as well as sea ice concentration. To understand the impact of altimeter observations, we computed the root mean square difference (RMSD) of analyzed temperature from both experiments and showed that the maximum impact is over the Indian Ocean, North Atlantic Ocean and tropical Pacific Ocean regions due to the large displacement change applied to the thermocline depth in the ALTK experiment. We also note that the impact of altimeter on analyzed temperature is over different depths. Finally, the analyzed SSH has less root mean square error (RMSE) with respect to the altimeter observations for ALTK experiment than CNTR experiment over the global ocean and shallow water over the Indian Region (60-105°E, 5-40°N).

Flood Hazard Risk Matrix for Urbanization Control Area of Flood Plain

Identification and understanding the potential flood risk area are important elements in disaster risk reduction through development planning control plan. The development growth in Merlimau area causes demand for new urbanization area for residential, commercial and public infrastructure. Therefore, the risk of flood should evaluate to identify the possible future flood hazard-risk area based on future land use in Merlimau. This paper describes an approach to produce flood hazard and risk matrix and map using a combination of flood numerical modelling and Geographical Information System (GIS) analysis in Merlimau River Basin. The result from this study is a flood hazard risk map that provides information on flood risk level in Merlimau basin, which further can contribute to future development planning. This matrix and map identified as the risk areas that suggested being an Urbanization Control Area (UCA) to control future development. Six locations identified as the UCA that involved about 26.27 hectares. The analysis also shows almost 80% or 21.03 hectares of UCA already been planned for residential area and about 18% or 4.78 hectares for industrial area. There are only about 2% or 0.46 hectare of UCA remain in the future development plan.

Study of ice cover impact on hydrodynamic processes in the Curonian Lagoon through numerical modeling

Summary In this study, we present an analysis of the hydrodynamic processes under ice cover in the largest lagoon in Europe – the Curonian Lagoon. By applying a finite element numerical modelling system (SHYFEM) and remote sensing ice cover data, the residual circulation, water fluxes through specific areas of the lagoon, saltwater intrusions, and water residence time (WRT) were investigated. The results, taken over an 11 year period, show that ice cover affects the circulation patterns in the lagoon by forming and shifting different gyre systems. Different circulation patterns are observed throughout all the meteorological seasons of the year. Since ice decreases circulation, water fluxes also decrease, especially in a cross-section in the middle of the lagoon, where the ice-cover suppressed wind-stress has a higher impact on the water movement rather than it has in the north. The presence of ice cover also decreases the salinity of the water in the northern part of the lagoon. In general, the salinity in the water column averaged over different periods is vertically uniform, however, a slight increase of salt concentration can be observed at the bottom layers in the Klaipėda Strait, where the difference of >1 PSU between bottom and top layers shows up on average 130 hours per year. The ice cover also decreases the saltwater intrusions into the lagoon by nearly 14 days per year. The increase of WRT is most prominent after long ice cover periods, away from the river inlets, especially in the southern part of the lagoon, where without the help of the wind action, water takes a longer time to renew than in the northern part.

On the origin of the shift between vertical excitation and band maximum in molecular photoabsorption

The analysis of the photoabsorption spectra of molecules shows that the band maximum is usually redshifted in comparison to the vertical excitation. We conducted a throughout analysis of this shift based on low-dimensional analytical and numerical model systems, showing that its origin is rooted in the frequency change between the ground and the excited states in multidimensional systems. Moreover, we deliver a benchmark of ab initio results for the shift based on a comparison of vertical excitations and band maxima calculated with the nuclear ensemble approach for the 28 organic molecules in the Mülheim molecular dataset. The mean value of the shift calculated over 60 transitions is 0.11 ± 0.08 eV. The mean value of the band width is 0.32 ± 0.14 eV.Graphical abstract.

Advances in Urban Meteorological Research in China

Over the past decades, a large number of studies have been carried out in the field of urban meteorology in China. This paper summarizes the main progress in urban meteorology research from four aspects: urban meteorological observation network and field campaign, multi-scale model of urban meteorology, interaction between urban meteorology and atmospheric environment, and the impacts of urbanization on weather and climate. Major advances are as follows. China’s major cities have established or are improving comprehensive urban meteorological observation networks characterized by multi-platform, multi-variable, multi-scale, multi-link, and multi-function. Beijing, Nanjing, Shanghai, and other cities carried out urban meteorological field campaigns, which were included in the WMO research demonstration project. Wind tunnel experiments and scale-model outdoor experiments were successfully conducted. Multi-scale urban meteorological and air quality prediction numerical model systems have been developed and put into operational use. The urban heat island effect; urban impacts on precipitation, regional climate, and air quality; urban planning; and interaction between urban meteorology and atmospheric environment are extensively investigated. Finally, efforts to improve observational technology, data assimilation, and urban system modeling, to explore the impacts of urbanization on environment and human health, and to provide integrated urban hydro-meteorological climate and environmental services are planned ahead.

Multiscale modelling of cage effects on the transport of effluents from open aquaculture systems.

Most Atlantic salmon mariculture operations use open sea cages for the grow out phase. The ultimate fate and effects of the effluents and the possibilities of disease transfer between fish farms are major concerns for farmers, governance and the general public alike. Numerical model systems applied to studying and managing effluents and disease transfer in mariculture must realistically resolve the hydrodynamics in the vicinity of the fish farms. In the present study, the effects of the aquaculture structures on the current patterns were introduced in the ocean model system SINMOD. The drag parameters for the ocean model were determined by comparing the simulation results from the ANSYS Fluent ® software suite and SINMOD in an idealized channel setting with uniform currents. The model was run for a number of realistic scenarios in high horizontal resolution (∼30 m) with sea cages influencing the flow field. Comparisons between extensive current measurements and the simulation results showed that the model system reproduced the current local current field well. By running simulation scenarios with and without the effects of the sea cages on the flow field, it was possible to assess the importance of such effects for numerical dispersal models and aquaculture environment interactions simulations and hence for assessment of environmental impacts.