Efficacy of different antifouling treatments for seawater cooling systems

In an industrial seawater cooling system, the effects of three different antifouling treatments, viz. sodium hypochlorite (NaClO), aliphatic amines (Mexel1432) and UV radiation, on the characteristics of the fouling formed were evaluated. For this study a portable pilot plant, as a side-stream monitoring system and seawater cooling system, was employed. The pilot plant simulated a power plant steam condenser, having four titanium tubes under different treatment patterns, where fouling progression could be monitored. The nature of the fouling obtained was chiefly inorganic, showing a clear dependence on the antifouling treatment employed. After 72 days the tubes under treatment showed a reduction in the heat transfer resistance (R) of around 70% for NaClO, 48% for aliphatic amines and 55% for UV, with respect to the untreated tube. The use of a logistic model was very useful for predicting the fouling progression and the maximum asymptotic value of the increment in the heat transfer resistance (DRmax). The apparent thermal conductivity (l) of the fouling layer showed a direct relationship with the percentage of organic matter in the collected fouling. The characteristics and mode of action of the different treatments used led to fouling with diverse physicochemical properties

Evaluation of bias correction methods for a multivariate drought index: case study of the Upper Jhelum Basin

Bias correction (BC) is often a necessity to improve the applicability of global and regional climate model (GCM and RCM, respectively) outputs to impact assessment studies, which usually depend on multiple potentially dependent variables. To date, various BC methods have been developed which adjust climate variables separately (univariate BC) or jointly (multivariate BC) prior to their application in impact studies (i.e., the component-wise approach). Another possible approach is to first calculate the multivariate hazard index from the original, biased simulations and bias-correct the impact model output or index itself using univariate methods (direct approach). This has the advantage of circumventing the difficulties associated with correcting the inter-variable dependence of climate variables which is not considered by univariate BC methods. Using a multivariate drought index (i.e., standardized precipitation evapotranspiration index – SPEI) as an example, the present study compares different state-of-the-art BC methods (univariate and multivariate) and BC approaches (direct and component-wise) applied to climate model simulations stemming from different experiments at different spatial resolutions (namely Coordinated Regional Climate Downscaling Experiment (CORDEX), CORDEX Coordinated Output for Regional Evaluations (CORDEX-CORE), and 6th Coupled Intercomparison Project (CMIP6)). The BC methods are calibrated and evaluated over the same historical period (1986–2005). The proposed framework is demonstrated as a case study over a transboundary watershed, i.e., the Upper Jhelum Basin (UJB) in the Western Himalayas. Results show that (1) there is some added value of multivariate BC methods over the univariate methods in adjusting the inter-variable relationship; however, comparable performance is found for SPEI indices. (2) The best-performing BC methods exhibit a comparable performance under both approaches with a slightly better performance for the direct approach. (3) The added value of the high-resolution experiments (CORDEX-CORE) compared to their coarser-resolution counterparts (CORDEX) is not apparent in this study.</p

Climate change scenarios in use: heat stress in Switzerland

Under hot conditions the human body is able to regulate its core temperature via sweat evaporation, but this ability is reduced when air humidity is high. These conditions of high temperature and high humidity invoke heat stress which is a major problem for humans, in particular for vulnerable groups of the population and people under physical stress (e.g. heavy duty work without appropriate cooling systems). It is generally expected that the frequency, duration and magnitude of such unfavorable conditions will increase with further climate warming. In this respect, climate services play a crucial role by putting together climatological information and adaptation solutions to reduce future heat stress. We here assess the recently developed CH2018 scenarios for Switzerland (https://www.climate-scenarios.ch) in terms of heat stress conditions including their future projections. For this purpose, we characterize future extreme heat conditions with the use of climate analogs. By doing so, we attempt to produce more accessible climate information which might foster the use and understanding of regional-scale climate scenarios. Here heat stress is expressed through the Wet Bulb Temperature (TW), which is a relatively simple proxy for heat stress on the human body and which depends non-linearly on temperature and humidity. It is assessed in terms of single-day events and heat stress spells. Projections based on the CH2018 scenarios indicate increasing heat stress over Switzerland, which is accentuated towards the end of the century. High heat stress conditions might be about 3?5 times more frequent for an emission scenario without mitigation (RCP 8.5) than for the mitigation scenario (RCP 2.6) by the end of the 21st century. The projected increase of heat stress results in more and longer heat stress spells, thus highlighting the importance of timely and precise prevention strategies in the context of heat-health action plans. Spatial climate analogs based on heat stress spells in Switzerland greatly vary depending on the emission scenario and are found in Central Europe under a mitigation scenario and in southern Europe under unmitigated warming.Financial support for this work is provided by the HEAT-SHIELD Project (European Commission HORIZON 2020, research and innovation programme under the grant agreement 668786). A.C. acknowledges support from Project COMPOUND (TED2021-131334A-I00) funded by MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR

Regional assessment of the Jenkinson-Collison weather types classification and observational uncertainty based on different reanalyses over the Mediterranean region

Ponencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022.[ES]El algoritmo de clasificación en tipos de tiempo de Jenkinson y Collison (JC-WT, Jenkinson and Collison 1977) es una técnica de agrupamiento usada para clasificar la circulación atmosférica en un número reducido de patrones de presión a nivel del mar. Esta metodología se basa en el cálculo de 6 parámetros intermedios relacionados con las características del flujo del viento. Este método ha tenido numerosas aplicaciones, siendo una de ellas la caracterización objetiva de la circulación atmosférica tanto a nivel global como regional, esencial para la evaluación de modelos climáticos y para su aplicabilidad en regionalización dinámica y estadística. La primera definición del método JC-WT centraba el estudio sobre las Islas Británicas pero puede ser, en principio, aplicado en latitudes medias-altas (Jones et al., 2013). El presente estudio examina la aplicabilidad la metodología JC-WT sobre la región Mediterránea y explora las diferencias entre cinco reanálisis a la hora de representar las características de los 27 JC-WT (sus frecuencias relativas y las probabilidades de transición entre tipos). Los resultados muestran diferencias importantes entre los distintos catálogos, sobre todo en verano. Además, se analizan estas diferencias entre reanálisis a nivel de los 6 parámetros intermedios de JC-WT con el fin de arrojar luz sobre la naturaleza sinóptica de las mismas. Estas discrepancias pueden comprometer la robustez de los estudios relacionados con la evaluación de modelos basada en procesos para esta región y desaconsejan el uso de un único reanálisis como referencia.[EN]The Jenkinson-Collison Weather Type (JC-WT; Jenkinson and Collison, 1977) classification is a clustering method used to classify the regional atmospheric circulation into a reduced number of typical recurrent sea-level pressure patterns. This methodology is a function of six parameters related to wind-flow characteristics. Originally developed for the British Isles, the method since then has seen many applications. One of its applications is serving for an objective characterization of either global or regional atmospheric circulation, a key feature for the assessment of climate models and their suitability for driving dynamical and statistical modeling experiments. Encouraged by the estimate that the JC-WT approach can in principle be applied to any mid-to-high latitude region (Jones et al, 2013), this study assesses the general application of JC-WT over the Mediterranean region, extending from the Iberian Peninsula in the west to the Levant in the east. We also explore to what extent the JC-WT features (such as frequencies of the 27 weather types and transition probabilities between pairs of types) obtained from five distinct reanalysis products agree with each other. Our results unveil important discrepancies among reanalyses, accentuated in summer. We furtherly explore these discrepancies deepening on the JC-WT base parameters in order to shed some light on the synoptic nature of these inconsistencies, that may compromise the robustness of circulation-based model assessments relying on a single reanalysis in these regions.The authors acknowledge funding from the R+D+i projects CORDyS (PID2020- 116595RB-I00) and ATLAS (PID2019-111481RB-I00), funded by MCIN/AEI/10.13039/501100011033. J.A.F. acknowledge funding from grant PRE2020-094728 funded by MCIN/AEI/10.13039/501100011033

Analysis of platelets from a diet-induced obesity rat model: elucidating platelet dysfunction in obesity

Obesity is one of the main health problems in industrialized countries. The contribution of multiple factors developed in obesity can hardly be modeled in vitro. In this context, the development of animal models mimicking human obesity could be essential. The aim of the present study was to compare platelets from a diet-induced obesity (DIO) rat model with their lean control group in order to elucidate platelet dysfunction mechanisms in obesity and correlate the results with previous data from morbid obese patients. In parallel, we also established a blood collection and platelet isolation methodology to study the DIO rat model at biochemical and functional level. Optimal blood collection was obtained from vena cava and platelet isolation was based on a serial of centrifugations avoiding platelet activation. Our results show that the DIO rat model simulate obesity pathologically since weight gain, fasting glucose and platelet counts are increased in obese rats. Interestingly, platelet levels of the active form of Src (pTyr(419)) showed a tendency to increase in DIO rats pointing towards a potential dysfunction in Src family kinases-related signalling pathways in obesity. Moreover, platelets from DIO rats adhere more to collagen compared with the control group, pointing towards Glycoprotein VI (GPVI) as one of the dysregulated receptors in obesity, in agreement with our recent studies in humans. These results confirm that obesity, in line with human studies, present a platelet dysregulation, and highlight the relevance of considering novel antithrombotic drug targets in these patients, such as GPVI