Mediterranean Outdoor Comfort Index Research Articles

Effect of heatwaves on urban sea breeze, heat island intensity, and outdoor thermo-hygrometric comfort in Rome (Italy)

The purpose of this study is to investigate the impact of heatwaves on sea breeze, urban heat island intensity, and outdoor thermo-hygrometric comfort analysing ground-based remote sensing and in-situ meteorological measurements collected in a Mediterranean coastal metropolitan area (Rome, Italy) during the summer of 2022. The dataset (01 May - 31 August 2022) has been divided into heatwaves and not-heatwaves days to highlight the distinctive features of extreme heat episodes. Furthermore, the year 2022 was compared to 2020, the latter having been characterised by temperatures in line with the last two-decades.The heatwaves do not significantly affect the onset time and the duration of sea breeze, while its cooling effect intensifies during the heatwaves. The urban heat island intensity (UHII) is evaluated by computing the hourly-averaged air temperature difference between two stations, one in the urban centre and the other in rural surroundings. Although the daily-averaged UHII does not show significant differences among the years under investigation and the subsets, marked differences can be identified in the urban heat island daily cycle. In fact, during daytime the highest temperatures are detected in rural inland areas while, at night, the city experiences higher temperatures, especially during the heatwaves. Finally, the Mediterranean outdoor comfort index suggests that a heatwave seems to be a not sufficient condition for human thermo-hygrometric stress, even if stronger discomfort is experienced during heatwaves.

Evaluation of effectiveness and resources consumption of water mist spray systems in Mediterranean areas by predictions based on LSTM Recurrent Neural Networks

To counter the increasing urban overheating, climate adaptation solutions are proposed. Among them, water mist spray recently acquired particular attention, due to its efficiency, cost-effectiveness, and versatility. However, spray devices require a large amount of water and energy to cool even limited areas, thus their environmental costs/benefits ratio should be carefully evaluated. This study analyses cooling benefits and resources consumption of mist devices in 11 cities within 3 climate contexts, through Recurrent Neural Networks (RNNs) trained with experimental data. RNNs predict the expected time series of thermal benefits and of energy and water consumptions, also considering different design solutions of devices. Results show that when sun/wind shielding is used in the sprayed area, or the height of nozzles is limited, higher cooling results are obtained. However, energy and water consumption are extremely high if misting systems are perennially active during the day. Considering all simulated conditions, the predicted average daily energy to obtain a unitary variation of the Mediterranean Outdoor Comfort Index is 4,17 Wh/m2, while the corresponding average daily volume of water is 0,56 l*h/m2. These results confirm the need for applications managed by control logics based on the acquisition of real-time climatic data to reduce the environmental loads.

On the association between high outdoor thermo-hygrometric comfort index and severe ground-level ozone: A first investigation

According to the European Environment Agency, the year 2015 was the warmest on record to that point, with a series of heat waves from May to September resulted in high levels of tropospheric ozone. The implications of such a year on the human well-being and health are therefore of multiple nature and can be quantified referring to the exceedances of the corresponding thresholds. This work focused on the analysis of the May–September period of 2015 in the city of Milan (Italy) in terms of Mediterranean Outdoor Comfort Index (MOCI) and ozone concentrations, recorded by monitoring stations and modeled through the Weather Research and Forecasting model. Main findings show that thermo-hygrometric stress events (periods of at least six consecutive days characterized by daily maximum values of the MOCI higher than 0.5) are characterized by daily ozone higher than the guideline level of the World Health Organization (equal to 100 μgm−3). This means that thermo-hygrometric stress conditions are added up to poor air quality conditions, with severe risks for human health. Moreover, a daily MOCI-daily ozone correlation coefficient equal to 0.6 was found for the whole period. The degree of correspondence between ozone events (defined according to the European Air Quality Directive) and MOCI events was also investigated pointing out that 86% and 95% of days during ozone events are correctly predicted by events of recorded and modeled MOCI respectively, with a corresponding false alarm rate of 3% and 9%.

High albedo materials to counteract heat waves in cities: An assessment of meteorology, buildings energy needs and pedestrian thermal comfort

Climatological data show that the frequency of Heat Waves (HWs) has increased since the 1950s and that it will continue to increase. These phenomena exasperate the urban heat island (UHI) phenomenon. In this study, we investigated the impact of a HW on the UHI in Milan (Italy); we also analyzed the effects of the application of high albedo materials on the vertical and horizontal urban built surfaces. We performed numerical experiments with the Weather Research and Forecasting model, whose output were used as input for the EnergyPlus software and the computation of the Mediterranean Outdoor Comfort Index (MOCI). Our results showed that the HW induces a maximum increase of about 4 °C in the temperature at 2 m height and that the use of high albedo materials covering all urban surfaces only partially counteracts this increase. The wind speed decreases due to the HW and the introduction of high albedo materials leads to its further decrease. The cooling energy consumption for a building located in the city doubles in the presence of HW and high albedo materials have a negligible positive effect when applied to the surrounding urban environment. The HW brings an increase up to about 0.7 of the MOCI and the use of high albedo materials further worsens thermal sensation. Therefore, this mitigation strategy leads to considerable benefits in terms of temperature and energy, while it determines a penalization of the well-being of the pedestrian. Its application requires a careful evaluation of benefits and side effects.

Dressed for the season: Clothing and outdoor thermal comfort in the Mediterranean population

Outdoor comfort, as perceived by the average person, is linked to a wide variety of parameters. Microclimatic, physiological and psychological factors influence the perception of each individual and more generally, that of the local population, given the acclimatization phenomenon with respect to local climate. One of the few mechanisms available to protect ourselves from the outdoor climate to achieve thermal comfort is choosing adequate thermal insulation in our clothing. Each individual can easily implement this protection mechanism to adjust her/his own thermal sensation. In order to quantitatively evaluate the comfort provided by thermal insulation of clothing, the following parameters must be considered: (i) outdoor thermal conditions, such as air and mean radiant temperature, relative humidity and wind speed; (ii) the individuals' genders and ages; and (iii) their expressions of thermal comfort, with reference to the specific local climate to which each subject is usually exposed (acclimatization). This work aims at analyzing these factors, by means of an experimental investigation, with particular reference to a statistically relevant sample of the Mediterranean population. To this end, thermal comfort is expressed by means of the Mediterranean Outdoor Comfort Index (MOCI), which was specifically created to describe the thermal comfort of the Mediterranean population. Results allow defining the preferred clothing's thermal resistance “ICL,med” for Mediterranean people, evidencing the different preferences as a function of gender and age. A slight tendency towards higher thermally-insulated clothing has been assessed with increasing age of the interviewees and among female interviewees.

On the outdoor thermal perception and comfort of a Mediterranean subject across other Koppen-Geiger's climate zones

The climatic conditions characterizing the troposphere affect the outdoor activities of the population which, in turn, characterize the anthroposphere. Over the past years recent studies examined a possible analytical definition of the outdoor thermal comfort for different types of population acclimatized to their specific residency area. Thanks to the use of the MOCI (Mediterranean Outdoor Comfort Index: an index used to predict the thermal perception of the Mediterranean population in an outdoor environment), the present study aimed at analyzing the psychophysiological response of a Mediterranean subject with respect to climatic conditions different from the original ones after having experienced a quick change. Indeed, thermal stress and discomfort might affect deeply the ability of the subject to carry out outdoor activities. This condition determines the necessity of possessing useful information to plan the best period to perform a journey in distant places and/or perform useful actions that will make the outdoor activity as much comforting as possible (choosing the proper clothes with the right thermal insulation). For this reason, the worldwide environmental conditions during an average year were examined. To be more specific, this study focused its attention on the editing of seasonal spatial maps with the MOCI level curves and on the temporal analysis of the MOCI values characterizing those 6 different cities (one for each continent) reporting the higher number of foreign arrivals.

Complying with the demand of standardization in outdoor thermal comfort: a first approach to the Global Outdoor Comfort Index (GOCI)

Over the past ten years the number of studies regarding outdoor thermal comfort has been progressively increasing. However, the existing works are characterized by a certain variety of instruments and methods. An example can be found in the indexes and evaluation scales used to estimate thermal perception. This is why this paper proposes the Global Outdoor Comfort Index (GOCI), which is obtained thanks to the combination of the empirical relations provided by the existing literature. Its independent variables are: air temperature (according to the reported F test value it is the most significant influencing parameter in the new proposed index), mean radiant temperature, relative humidity, wind velocity, latitude, mean annual temperature, mean temperatures of the hottest and coldest months. The index performances were compared to those of the Predicted Mean Vote (PMV), the Physiological Equivalent Temperature (PET), the Mediterranean Outdoor Comfort Index (MOCI) and the Universal Thermal Climate Index (UTCI) by means of an experimental field survey carried out in Rome (Italy). The GOCI reported a total percentage of correct predictions of 27.8%, higher than the PMV (27.7%), PET (25.4%) and UTCI (23.0%) but lower than the MOCI (32.2%). The higher predictive ability of this last index is due to the fact that it was specifically meant for the Mediterranean population. According to Spearman's rho measure of correlation and symmetrical measure of association Gamma calculations, the GOCI was the most sensitive index and it can be used to predict outdoor thermal comfort in areas devoid of studies about specific indexes.

Implications of climate and outdoor thermal comfort on tourism: the case of Italy

Whether a journey is pleasant or not usually depends on the climatic conditions which permit to perform outdoor activities. The perception of climatic conditions, determined by physiological and psychological factors, can vary according to different adaptation phenomena related to the person involved and the weather conditions of the place where they live. Studying the bioclimatology of a country characterized by a high flux of tourism, as e.g. Italy, can provide some important information about where and when is it better to visit a place. Some differences have to be specified though, like the local tourism, which is used to that type of climate, and international tourism, which is formed by people coming from countries with different types of climates. Therefore this paper examined the climatic conditions and outdoor thermal comfort through the Mediterranean Outdoor Comfort Index (MOCI) for local tourism and through the predicted mean vote (PMV) for international tourism. The cities examined were three (Venice, Rome and Palermo located in the North, Centre and South of Italy, respectively), where average information were collected every week for an entire year. Finally, a map of the entire Italian territory reporting the seasonal average values of these indexes was also reported.

Relating microclimate, human thermal comfort and health during heat waves: An analysis of heat island mitigation strategies through a case study in an urban outdoor environment

Over the past years the concern of the international scientific community towards the study of the Urban Heat Island (UHI) phenomenon has been growing. Such issue is particularly important in cities as Rome, where it is possible to experience intense heat stress conditions especially when heat waves intensify this phenomenon. Therefore this study wants to examine different mitigation strategies of the urban microclimate by taking into consideration the campus of the Sapienza University of Rome. It was carried out through the software ENVI-met V 3.1 which gave the possibility to reproduce the model of the site (experimentally calibrated) and examine, in terms of MOCI (Mediterranean Outdoor Comfort Index), the different mitigation strategies implemented. This index was also related to the Apparent Temperature and to the health risk. Among the main results provided through this study, it is possible to notice how the solution combining cool roofs, urban vegetation and cool pavement leads, with respect to the current configuration of the site, to a mean and maximum decrease in the MOCI of −2.5 and −3.5. Finally it is able to determine a decrease of about 60% in the health risk for those who are exposed.

Thermal Perception in the Mediterranean Area: Comparing the Mediterranean Outdoor Comfort Index (MOCI) to Other Outdoor Thermal Comfort Indices

Outdoor thermal comfort is an essential factor of people’s everyday life and deeply affects the habitability of outdoor spaces. However the indices used for its evaluation were usually developed for indoor environments assuming still air conditions and absence of solar radiation and were only later adapted to outdoor spaces. For this reason, in a previous study the Mediterranean Outdoor Comfort Index (MOCI) was developed, which is an empirical index able to estimate the thermal perception of people living in the Mediterranean area. In this study it was compared numerically (by using the data obtained through a field survey) with other selected thermal indices. This comparison, performed in terms of Spearman’s rho correlation coefficient, association Gamma, percentage of correct predictions and cross-tabulation analysis, led to identify the MOCI as the most suitable index to examine outdoor thermal comfort in the interested area. As a matter of fact it showed a total percentage of correct predictions of 35.5%. Good performances were reported even in thermophysiological indices as the Physiological Equivalent Temperature (PET) and Predicted Mean Vote (PMV). Moreover it was revealed that adaptation and acclimatization phenomena tend to have a certain influence as well.

Outdoor thermal comfort in the Mediterranean area. A transversal study in Rome, Italy

This paper examines the outdoor thermal comfort in the Mediterranean area. A transversal field survey has been conducted in Rome and, during an entire year, over 1000 questionnaires were filled and combined with micrometeorological measurements. In the first part of the questionnaire, the interviewees answered to personal questions, whereas in the second they evaluated their thermal perception and preference through the ASHRAE 7-point scale and the McIntyre scale respectively. Regression lines were obtained by elaborating the thermal perception votes and determining a PET (Physiological Equivalent Temperature) value for each questionnaire. These regression lines gave the possibility to calculate the neutral PET values: 26.9 °C for the hot season and 24.9 °C for the cold one. Differently, the votes concerning the thermal preference were related to the corresponding PET values through a logistic curve model with the probit function: for the hot season a preferred PET value of 24.8 °C was calculated, whereas for the cold season 22.5 °C. This shows the influence of thermal adaptation. Then since the thermal comfort interval should correspond to the range −0.5÷0.5 of the ASHRAE 7-point scale, a PET comfort range of 21.1÷29.2 °C was obtained. Finally two indexes were determined: the first, called MOCI (Mediterranean Outdoor Comfort Index), is based on the ASHRAE 7-point scale and predicts the mean value of the votes Mediterranean people might give to judge the thermal qualities of an environment; the second is the adaptation of the PPD (Predicted Percentage of Dissatisfied) relation to the Mediterranean population.