Minimum Time Lags Research Articles

Comparison between Satellite Derived Solar-Induced Chlorophyll Fluorescence, NDVI and kNDVI in Detecting Water Stress for Dense Vegetation across Southern China

In the context of global climate change and the increase in drought frequency, monitoring and accurately assessing the impact of hydrological process limitations on vegetation growth is of paramount importance. Our study undertakes a comprehensive evaluation of the efficacy of satellite remote sensing vegetation indices—Normalized Difference Vegetation Index (MODIS NDVI product), kernel NDVI (kNDVI), and Solar-Induced chlorophyll Fluorescence (GOSIF product) in this regard. Initially, we applied the LightGBM-Shapley additive explanation framework to assess the influencing factors on the three vegetation indices. We found that Vapor Pressure Deficit (VPD) is the primary factor affecting vegetation in southern China (18°–30°N). Subsequently, using Gross Primary Productivity (GPP) estimates from flux tower sites as a performance benchmark, we evaluated the ability of these vegetation indices to accurately reflect vegetation GPP changes during drought conditions. Our findings indicate that SIF serves as the most effective surrogate for GPP, capturing the variability of GPP during drought periods with minimal time lag. Additionally, our study reveals that the performance of kNDVI significantly varies depending on the estimation of different kernel parameters. The application of a time-heuristic estimation method could potentially enhance kNDVI’s capacity to capture GPP dynamics more effectively during drought periods. Overall, this study demonstrates that satellite-based SIF data are more adept at monitoring vegetation responses to water stress and accurately tracking GPP anomalies caused by droughts. These findings not only provide critical insights into the selection and optimization of remote sensing vegetation product but also offer a valuable framework for future research aimed at improving our monitoring and understanding of vegetation growth status under climatic changes.

A label-setting algorithm for the truck driver scheduling problem in accordance with European Community social legislation

In this paper, a label-setting algorithm is proposed in order to efficiently solve the weekly Truck Driver Scheduling Problem (TDSP), which can be seen as a single-machine problem that minimizes the completion time of a fixed sequence of jobs with release and due times and break periods. A focus is made on the night working rule that has only partially been considered in the literature. In the wide literature dedicated to Vehicle Routing Problems, some published heuristics and exact algorithms include constraints related to break/rest periods. But the night working rule defined by the European Community Social Legislation is only considered in some simplified and sub-optimal versions. This constraint is of interest, since it has a direct impact on the practical applicability of routes. Moreover, from a scheduling point of view, the night working rule enforces minimum and maximum time lag constraints, which makes challenging the development of an efficient solution algorithm. The method is benchmarked with a mixed integer linear programming model. Computational experiments show the efficiency of the proposed methods and the effect of the night working constraint on the feasibility of the schedules.

Carbon reduction decisions in green technology collaborative R&D and spillover time lag effects

The time lag of green technology spillovers affects emissions reduction decisions and environmental policies. In this study, we model two competitive manufacturers sharing a common supplier. We investigate their optimal decisions in cooperative and non-cooperative R&D circumstances, considering the presence or absence of a cap-and-trade policy. Findings indicate that the time lag effect of green technology spillovers slows the carbon reductions without a cap-and-trade policy. However, the time lag effect is only emphasized under low carbon trading prices with a cap-and-trade policy. Excessive time lag decreases emission reductions for non-cooperative spillover free-riders. Intra-cooperative spillovers appear more advantageous for both parties involved in the spillover than non-cooperative spillovers. Manufacturers achieve carbon neutrality only at a limited market scale, and collaborative R&D can expand this market scale threshold. Furthermore, we identify the minimum time lag thresholds for manufacturers and supplier to meet the carbon allowance. Collaboration is more conducive to fulfilling carbon allowance in a low-priced carbon trading market.

Increasing yield of in vitro transcription reaction with at-line high pressure liquid chromatography monitoring.

The COVID-19 pandemic triggered an unprecedented rate of development of messenger ribonucleic acid (mRNA) vaccines, which are produced by in vitro transcription reactions. The latter has been the focus of intense development to increase productivity and decrease cost. Optimization of in vitro transcription (IVT) depends on understanding the impact of individual reagents on the kinetics of mRNA production and the consumption of building blocks, which is hampered by slow, low-throughput, end-point analytics. We implemented a workflow based on rapid at-line high pressure liquid chromatography (HPLC) monitoring of consumption of nucleoside triphosphates (NTPs) with concomitant production of mRNA, with a sub-3 min read-out, allowing for adjustment of IVT reaction parameters with minimal time lag. IVT was converted to fed-batch resulting in doubling the reaction yield compared to batch IVT protocol, reaching 10 mg/ml for multiple constructs. When coupled with exonuclease digestion, HPLC analytics for quantification of mRNA was extended to monitoring capping efficiency of produced mRNA. When HPLC monitoring was applied to production of an anti-reverse cap analog (ARCA)-capped mRNA construct, which requires an approximate 4:1 ARCA:guanidine triphosphate ratio, the optimized fed-batch approach achieved productivity of 9 mg/ml with 79% capping. The study provides a methodological platform for optimization of factors influencing IVT reactions, converting the reaction from batch to fed-batch mode, determining reaction kinetics, which are critical for optimization of continuous addition of reagents, thus in principle enabling continuous manufacturing of mRNA.

Packing-based branch-and-bound for discrete malleable task scheduling

This paper addresses the problem of scheduling chain-like structures of tasks on a single multiprocessor resource. In fact, sub-tasks of unit-time length and predefined size are aggregated to composite tasks that have to be scheduled without preemption, but subject to flexibility concerning resource allocation. This setting most closely resembles the problem of malleable task scheduling, with sub-tasks being the smallest atomic unit of allocation. The specific type of malleability is realized using precedence constraints with minimum and maximum time lags. A bin packing model is established for this scheduling problem and a corresponding, dedicated branch-and-bound algorithm is devised, alongside problem-specific bound tightening, symmetry breaking and dominance concepts. The efficacy of the solution approach is demonstrated based on extensive computational experiments, including randomized instances, adapted benchmark instances from the literature, and a small real-world data set. In comparison to mixed-integer and constraint programming formulations, the new method is able to achieve a considerably higher percentage of optimal solutions at computation times that are up to orders of magnitude smaller.

A Survey of Retracted Articles by Turkish Authors

Background: Not all manuscripts that are accepted and published in scientific journals have retained their status as published articles, and some of them are retracted after publication. There are various reasons for retraction that are usually grouped into a scientific error, such as statistical flaws, and research misconduct such as plagiarism. Nowadays the number of scientific publications are a source of career advancement and respect in the scientific community. To attain these, the focus of researchers is towards increasing the number of publications per year which sometimes compromises the quality of publications. Aim: The current study aimed to investigate the characteristics of retracted publications that were contributed by Turkish authors to scientific databases. Methods: We searched PubMed, Scopus, and Web of Science databases. The search strategies were based on a combination of MeSH terms relevant to “retracted publication” and “Turkey.” The databases were searched on 23rd October 2021, without any restrictions on the search period. The inclusion criteria were: (i) retracted publication and, (ii) any authors of the study having affiliation with an institution in Turkey. The titles, authors' affiliations, and abstracts of the search results were screened and bibliographic information was extracted. Results: After removing duplicates and irrelevant studies, our search retrieved a total of 147 publications. The oldest retracted article was published in 1996; thereafter an increasing trend of retracted publications was evident. Regarding access to full-text status, 106 (72.1%) of full-texts were available. Overall 127 scientific journals have published these articles. Biochemical Genetics was the most frequent publisher with five publications. From the institutional point of view, Hacettepe University was the main university, contributing seven papers. The most common reason for retractions was duplication = 50 (34%), and most retracted notices have been issued by the editor-in-chief = 63 (42.9% of papers). The majority of publications were from Medical Science = 93 (63.3% of papers). Among the Medical Science publications, the highest number, 44, were from surgery and allied fields. Turkish authors had international collaborations with 20 countries. Sixteen papers have international collaborations with researchers from Iran. Only 10 of the retracted publications have received funding. Five of the first authors have submitted more than one retracted publication. Citation analysis indicates that the median number of citations received by retracted publications was two (IQR 0-7). The minimum time lag between publication and retraction was less than one year and the maximum was 13 years. Conclusion: The publish or perish pressure in academia sometimes leads to intentional and unintentional research misconduct. Although the number of retracted publications is fewer, their trend is increasing. To overcome the problem, it can be suggested that research methodology and research ethics training are essential in the under- and post-graduate curriculum.

A constructive branch-and-bound algorithm for the project duration problem with partially renewable resources and general temporal constraints

This paper deals with the resource-constrained project scheduling problem with partially renewable resources and general temporal constraints with the objective to minimize the project duration. The consideration of partially renewable resources allows to integrate the decision about the availability of a resource for a specific time period into the scheduling process. Together with general temporal constraints, which permit to establish minimum and maximum time lags between activities, even more aspects of real-life projects can be taken into account. We present a branch-and-bound algorithm for the stated problem that is based on a serial schedule-generation scheme. For the first time it is shown how a dominance criterion can be applied on the associated generation scheme to reduce the start times in each scheduling step. To improve the performance of the solution procedure, we integrate consistency tests and lower bounds from the literature and devise new pruning techniques. In a comprehensive experimental performance analysis we compare our exact solution procedure with all available branch-and-bound algorithms for partially renewable resources. Additionally, we investigate a directly derived priority rule-based approximation method from our new enumeration scheme. The results of the computational study demonstrate the efficiency of our branch-and-bound algorithm and reveal that the derived approximation method is only suited to solve small- and medium-sized instances.

Assessment of Various Scheduling and Load Balancing Algorithms in Integrated Cloud-Fog Environment

Background: It is required to design a suitable scheduling algorithm that enhances the timely execution of goals such as load distribution, cost monitoring, and minimal time lag to react, increased security awareness, optimized energy usage, dependability, and so on. In order to attain these criteria, a variety of scheduling strategies based on hybrid, heuristic, and meta-heuristic techniques are under consideration. Objective: IoT devices and a variety of network resources make up the integrated cloud-fog environment. Every fog node has devices that release or request resources. A good scheduling algorithm is required in order to maintain the requests for resources made by various IoT devices. Method: This research focuses on analysis of numerous scheduling challenges and techniques employed in a cloud-fog context. This work evaluates and analyses the most important fog computing scheduling algorithms. Results: The survey of simulation tools used by the researchers is done. From the compared results, the highest percentage in the literature has 60% of scheduling algorithm which is related to task scheduling and 37% of the researchers have used iFogSim simulation tool for the implementation of the proposed algorithm defined in their research paper. Conclusion:: The findings in the paper provide a roadmap of the proposed efficient scheduling algorithms and can help researches to develop and choose algorithms close to their case studies.

Study of social tension based on electronic social networks big data

The article presents a methodology for assessing the level of social tension according to the data of electronic social networks. The calculation of the level of social tension according to the specified method is carried out automatically using software tools and requires the participation of the researcher only at the level of an analytical conclusion. An approach to identifying the dissatisfaction of the population at the level of the simplest actions of social network accounts has been described in detail. The necessity of identifying certain spheres of public life for the identification of population discontent has been substantiated, the indicated spheres have been highlighted and described. An indicator has been developed that makes it possible to calculate the level of social tension within each of the identified spheres of public life, taking into account the level of negative messages (posts and comments) and the discussion of each topic. A generalising indicator of the level of social tension has been developed, combining individual indicators of tension by topic. The calculation of the generalising indicator makes it possible to identify the level of social tension in a region or other territorial entity and track its dynamics in any perspective, including retrospectively.The proposed methodology for assessing social tension based on data from electronic social networks differs significantly from existing sociological and statistical approaches. Its main advantage lies in the minimal time lag between the dynamics of social tension, reflected in the social network, and its identification, which expands the possibilities of a prompt response to the growth of negative moods in society. Another difference of the proposed approach is the possibility of multiple repetitions of calculations with minimal, in contrast to the sociological method, the cost of additional resources for each subsequent iteration of the calculation of the indicator value.

Lost Data and Transmition Speed Analysis on Incubator Analyzer Based IoT Technology

The importance of the readiness of the baby incubator for critical infant patients who are treated intensively encourages health technicians to carry out regular maintenance and calibration to overcome the problem of equipment malfunctions. Critical infant patients are babies who are treated in the NICU (Neonatal Intensive Care Unit) due to premature birth or babies using incubators are diagnosed with abnormalities or diseases, this situation makes babies need tools for survival, especially in the first month. Calibrating temperature control is very necessary for the incubator. In addition to temperature, it is necessary to control humidity so that the baby's respiratory system is in optimal condition. In addition, it is also equipped with a noise sensor to ensure that the noise in the baby incubator room is appropriate. From the above problems, a tool for temperature testing was made using a DHT22 sensor with five measurement points, humidity with a level of 30% RH - 60% RH and noise with a range of 30dB-60db to ensure the tool functions properly equipped with a lost data testing system and delivery speed. using internet access with thingspeak display. This research resulted in the design of a calibration tool with three parameters, namely the temperature setting at 33ºC the smallest error percentage is 0% and the largest error is 0.96%, and at the temperature setting 35ºC the smallest error percentage is 0.28% and the largest error is 4 .1%, humidity with an error percentage of 0.82% and noise with an error percentage of 0.93%. The drawback in using the Thingspeak application is that there is a limit on the channel ID, which can only display 8 readings, while the minimum time lag is 20 seconds. For the MAX4466 noise sensor, there are shortcomings, namely the accuracy in readings is not good.

Mixed Integer Linear Programming Model for Open Pit Mine Scheduling

An open-pit mines consist of the accumulation of ore layers with different chemical characteristics and aims to extract ores from the surface. Based on a geological discretization of the deposit, the ore body model is represented as a three-dimensional array of blocks divided into two subsets; ore blocks, which can be extracted and processed profitably, and waste blocks, which include all the remaining blocks. The extraction process results from the iteration of a sequence of elementary operations performed on blocks by specialized or multipurpose machines. Short-term planning of the ore extraction process in open-pit mines is a complex undertaking that necessitates the identification of the best spatio-temporal machinery affectation. All of this is constrained by several factors: operations sequencing, machines compatibility, machines availability, machines motions, and priorities of layers (urgency of obtaining certain qualities). In this study, a Mixed Integer Linear Programming model (MILP) is used to generate the short-term extraction schedule. The MILP is based on the well-known flexible job-shop theoretical problem with generic minimal time-lags between operations. A simple example is used to clearly explain the model and the solution obtained.

A partition-based branch-and-bound algorithm for the project duration problem with partially renewable resources and general temporal constraints

The concept of partially renewable resources provides a general modeling framework that can be used for a wide range of different real-life applications. In this paper, we consider a resource-constrained project duration problem with partially renewable resources, where the temporal constraints between the activities are given by minimum and maximum time lags. We present a new branch-and-bound algorithm for this problem, which is based on a stepwise decomposition of the possible resource consumptions by the activities of the project. It is shown that the new approach results in a polynomially bounded depth of the enumeration tree, which is obtained by kind of a binary search. In a comprehensive experimental performance analysis, we compare our exact solution procedure with all branch-and-bound algorithms and state-of-the-art heuristics from the literature on different benchmark sets. The results of the performance study reveal that our branch-and-bound algorithm clearly outperforms all exact solution procedures. Furthermore, it is shown that our new approach dominates the state-of-the-art heuristics on well known benchmark instances.

The Positive Rhinovirus/Enterovirus Detection and SARS-CoV-2 Persistence beyond the Acute Infection Phase: An Intra-Household Surveillance Study

We aimed to assess the duration of nasopharyngeal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA persistence in adults self-confined at home after acute infection; and to identify the associations of SARS-CoV-2 persistence with respiratory virus co-detection and infection transmission. A cross-sectional intra-household study was conducted in metropolitan Barcelona (Spain) during the time period of April to June 2020. Every adult who was the first family member reported as SARS-CoV-2-positive by reverse transcription polymerase chain reaction (RT-PCR) as well as their household child contacts had nasopharyngeal swabs tested by a targeted SARS-CoV-2 RT-PCR and a multiplex viral respiratory panel after a 15 day minimum time lag. Four-hundred and four households (404 adults and 708 children) were enrolled. SARS-CoV-2 RNA was detected in 137 (33.9%) adults and 84 (11.9%) children. Rhinovirus/Enterovirus (RV/EV) was commonly found (83.3%) in co-infection with SARS-CoV-2 in adults. The mean duration of SARS-CoV-2 RNA presence in adults’ nasopharynx was 52 days (range 26–83 days). The persistence of SARS-CoV-2 was significantly associated with RV/EV co-infection (adjusted odds ratio (aOR) 9.31; 95% CI 2.57–33.80) and SARS-CoV-2 detection in child contacts (aOR 2.08; 95% CI 1.24–3.51). Prolonged nasopharyngeal SARS-CoV-2 RNA persistence beyond the acute infection phase was frequent in adults quarantined at home during the first epidemic wave; which was associated with RV/EV co-infection and could enhance intra-household infection transmission.

Retracted papers by Iranian authors: causes, journals, time lags, affiliations, collaborations

This study aims to analyze 343 retraction notices indexed in the Scopus database, published in 2001-2019, related to scientific articles (co-)written by at least one author affiliated with an Iranian institution. In order to determine reasons for retractions, we merged this database with the database from Retraction Watch. The data were analyzed using Excel 2016 and IBM-SPSS version 24.0, and visualized using VOSviewer software. Most of the retractions were due to fake peer review (95 retractions) and plagiarism (90). The average time between a publication and its retraction was 591 days. The maximum time-lag (about 3,000 days) occurred for papers retracted due to duplicate publications; the minimum time-lag (fewer than 100 days) was for papers retracted due to ''unspecified cause'' (most of these were conference papers). As many as 48 (14%) of the retracted papers were published in two medical journals: Tumor Biology (25 papers) and Diagnostic Pathology (23 papers). From the institutional point of view, Islamic Azad University was the inglorious leader, contributing to over one-half (53.1%) of retracted papers. Among the 343 retraction notices, 64 papers pertained to international collaborations with researchers from mainly Asian and European countries; Malaysia having the most retractions (22 papers). Since most retractions were due to fake peer review and plagiarism, the peer review system appears to be a weak point of the submission/publication process; if improved, the number of retractions would likely drop because of increased editorial control.

Towards Finding Robust Execution Strategies for RCPSP/max with Durational Uncertainty

Resource Constrained Project Scheduling Problems with minimum and maximum time lags (RCPSP/max) have been studied extensively in the literature. However, the more realistic RCPSP/max problems — ones where durations of activities are not known with certainty – have received scant interest and hence are the main focus of the paper. Towards addressing the significant computational complexity involved in tackling RCPSP/max with durational uncertainty, we employ a local search mechanism to generate robust schedules. In this regard, we make two key contributions: (a) Introducing and studying the key properties of a new decision rule to specify start times of activities with respect to dynamic realizations of the duration uncertainty; and (b) Deriving the fitness function that is used to guide the local search towards robust schedules. Experimental results show that the performance of local search is improved with the new fitness evaluation over the best known existing approach.

Multiobjective optimization for complex flexible job-shop scheduling problems

In this paper, we are concerned with the resolution of a multiobjective complex job-shop scheduling problem stemming from semiconductor manufacturing. To produce feasible and industrially meaningful schedules, this paper extends the recently proposed batch-oblivious approach by considering unavailability periods and minimum time lags and by simultaneously optimizing multiple criteria that are relevant in the industrial context. A novel criterion on the satisfaction of production targets decided at a higher level is also proposed. Because the solution approach must be embedded in a real-time application, decision makers must express their preferences before the optimization phase. In addition, a preference model is introduced where trade-off is only allowed between some criteria. Two a priori multiobjective extensions of Simulated Annealing are proposed, which differ in how the simultaneous use of a lexicographic order and weights is handled when evaluating the fitness. A known a posteriori approach of the literature is used as a benchmark. All the metaheuristics are embedded in a Greedy Randomized Adaptive Search Procedure. The different versions of the archived GRASP approach are compared using large industrial instances. The numerical results show that the proposed approach provides good solutions regarding the preferences. Finally, the comparison of the optimized schedules with the actual factory schedules shows the significant improvements that our approach can bring.

Integer Linear Programming Formulations for the RCPSP considering Multi-Skill, Multi-Mode, and Minimum and Maximum Time Lags

The project scheduling problem is essential both in the theoretical part, as in the field of operational research, and practice, with the project management in corporate environments. Integer linear programming formulations indexed on time are studied for the Resource-Constrained Project Scheduling Problem (RCPSP). Moreover, the multi-skill, multiple modes, and time lag constraints are taken into consideration. The objective of the RCPSP is to minimize the makespan. The formulations are solved with the default branch-and-cut algorithm of the solver Gurobi Optimizer. The formulations and solver are analyzed concerning the runtime, the number of optimal solutions, and the gap on the resolution of more than 2000 instances. Results indicate the solver can have better performance when instances with up to 50 activities are solved. Then, to develop models to handle hard instances of this problem is a challenge. Moreover, it can bring significant advantages to the corporate environment, helping managers to make accurate decisions and reduce costs.

An Injectable Sustained Release Lipid Based in situ Gel System of Aripiprazole for the Management of Schizophrenia

<p style="text-align: justify;"><strong>Objectives:</strong> Development and evaluation of aripiprazole (AP) loaded lipid based<em> in situ </em>gel system (AP-LIGS) which could maintain the release of drug throughout period circumventing the need of oral therapy. <strong>Materials and Methods: </strong>AP possesses oral bioavailability (~87%) and biological half-life (~75 h) and undergoes extensive first-pass metabolism. Available AP long term injectable preparations have drawback of simultaneous administration of AP tablets orally for first few weeks, leading to patient non-compliance and making the therapy less effective. AP-LIGS was formulated using phospholipid E80, medium chain triglyceride and ethanol. Optimization was done by evaluating the effect of water content on viscosity of prepared AP-LIGS and % cumulative drug release (% CDR) at day 1. <strong>Results: </strong>Optimized AP-LIGS showed rapid gelation with minimum lag time and <em>in vitro</em> drug release profile upto 6 weeks. <em>In vivo </em>depot formation was confirmed by gamma scintigraphy after subcutaneous injection of liquid state of AP-LIGS. Histopathological study revealed its safety and biocompatibility with surrounding tissues since no alteration or any inflammation was observed at the injection site even after 45 days of subcutaneous administration. <em>In vivo </em>neurobehavioral assessment was done for assessing the efficacy of AP-LIGS system using Morris water Maze (MWM) test. MK-801 (Dizocilpine) model was used for inducing schizophrenia in Sprague-Dawley rats. All three parameters escape latency, time spent in target quadrant and total distance travelled was significantly improved (<em>p </em>&lt;0.001) in AP-LIGS group when compared to MK-801 group at all time points. <strong>Conclusion: </strong>Developed novel AP-LIGS system is safe and may be used as a promising approach for sustained drug release and effectively manage schizophrenia. <p style="text-align: justify;"><strong>Key words: </strong> Aripiprazole, Gamma scintigraphy, Injectable, In-situ gel, Phospholipid E80, Schizophrenia.

Improving Bioavailability of Cefpodoxime Proxetil by Increasing Retention Time in Stomach with the Help of Natural Polymer: Formulation and Evaluation

Background: Cefpodoxime proxetil is an orally administered, extendedspectrum, semi-synthetic antibiotic of the cephalosporin class. Cefpodoxime proxetil has a short elimination half-life and also possesses high solubility, chemical, enzymatic stability and absorption profiles in acidic pH which makes Cefpodoxime proxetil suitable candidate for formulating it as a gastro retentive dosage form for improved bioavailability. Methods: The formulation of floating tablets of Cefpodoxime proxetil was prepared by the direct compression technique using Pomegranate peel powder as release retarded material. The floating tablets of Cefpodoxime proxetil are prepared by applying design of experiment in that 32 Factorial Design was selected. In vivo gastro-retention of the optimized floating formulation was determined by X-ray imaging studies on healthy rabbits. Results: The F3 Formulation containing Pomegranate peel powder peel powder of 50mg and sodium bicarbonate 100 mg has shown sustained release for 24 hr. The Floating lag time of all the prepared batches was found to be from 49±0.5 to 57±0.5 in sec. The minimum lag time was 49 sec. The in vitro release data of optimized formulation was treated with mathematical equations and was concluded that drug release followed zero-order kinetics with anomalous transport mechanism. In vivo Gastro retention of the optimized formulation F3 determined by X-ray imaging studies on healthy rabbits shows retention of the tablet in stomach for sufficient period of time. Conclusion: The prepared gastro retentive floating tablet formulation using Pomegranate peel powder as rate control polymer shows betterfloating properties and effective gastro retention when Pomegranate peel powder and drug is used in the ration of 1:2.5. Hence CFP floating tablet formulation can be a suitable alternative to immediate release CFP tablets to increase gastric residence time and thereby improving its bioavailability.

Evaluation of Atmospheric Correction Algorithms for Sentinel-2-MSI and Sentinel-3-OLCI in Highly Turbid Estuarine Waters

The present study assesses the performance of state-of-the-art atmospheric correction (AC) algorithms applied to Sentinel-2-MultiSpectral Instrument (S2-MSI) and Sentinel-3-Ocean and Land Color Instrument (S3-OLCI) data recorded over moderately to highly turbid estuarine waters, considering the Gironde Estuary (SW France) as a test site. Three spectral bands of water-leaving reflectance ( R h o w ) are considered: green (560 nm), red (655 or 665 nm) and near infrared (NIR) (865 nm), required to retrieve the suspended particulate matter (SPM) concentrations in clear to highly turbid waters (SPM ranging from 1 to 2000 mg/L). A previous study satisfactorily validated Acolite short wave infrared (SWIR) AC algorithm for Landsat-8-Operational Land Imager (L8-OLI) in turbid estuarine waters. The latest version of Acolite Dark Spectrum Fitting (DSF) is tested here and shows very good agreement with Acolite SWIR for OLI data. L8-OLI satellite data corrected for atmospheric effects using Acolite DSF are then used as a reference to assess the validity of atmospheric corrections applied to other satellite data recorded over the same test site with a minimum time difference. Acolite DSF and iCOR (image correction for atmospheric effects) are identified as the best performing AC algorithms among the tested AC algorithms (Acolite DSF, iCOR, Polymer and C2RCC (case 2 regional coast color)) for S2-MSI. Then, the validity of six different AC algorithms (OLCI Baseline Atmospheric Correction (BAC), iCOR, Polymer, Baseline residual (BLR), C2RCC-V1 and C2RCC-V2) applied to OLCI satellite data is assessed based on comparisons with OLI and/or MSI Acolite DSF products recorded on a same day with a minimum time lag. Results show that all the AC algorithms tend to underestimate R h o w in green, red and NIR bands except iCOR in green and red bands. The iCOR provides minimum differences in green (slope = 1.0 ± 0.15, BIAS = 1.9 ± 4.5% and mean absolute percentage error (MAPE) = 12 ± 5%) and red (slope = 1.0 ± 0.17, BIAS = −9.8 ± 9% and MAPE = 28 ± 20%) bands with Acolite DSF products from OLI and MSI data. For the NIR band, BAC provides minimum differences (slope = 0.7 ± 0.13, BIAS = −33 ± 17% and MAPE = 55 ± 20%) with Acolite DSF products from OLI and MSI data. These results based on comparisons between almost simultaneous satellite products are supported by match-ups between satellite-derived and field-measured SPM concentrations provided by automated turbidity stations. Further validation of satellite products based on rigorous match-ups with in-situ R h o w measurements is still required in highly turbid waters.