scholarly journals Lack of vegetation exacerbates exposure to dangerous heat in dense settlements in a tropical African city

Author(s):  
Jonas Van de Walle ◽  
Oscar Brousse ◽  
Lien Arnalsteen ◽  
Chloe Brimicombe ◽  
Disan Byarugaba ◽  
...  

Abstract Both climate change and rapid urbanization accelerate exposure to heat in the city of Kampala, Uganda. From a network of low-cost temperature and humidity sensors, operational in 2018-2019, we derive the daily mean, minimum and maximum Humidex in order to quantify and explain intra-urban heat stress variation. This temperature-humidity index is shown to be heterogeneously distributed over the city, with a daily mean intra-urban Humidex Index deviation of 1.2°C on average. The largest difference between the coolest and the warmest station occurs between 16:00 and 17:00 local time. Averaged over the whole observation period, this daily maximum difference is 6.4°C between the warmest and coolest stations, and reaches 14.5°C on the most extreme day. This heat stress heterogeneity also translates to the occurrence of extreme heat, shown in other parts of the world to put local populations at risk of great discomfort or health danger. One station in a dense settlement reports a daily maximum Humidex Index of >40°C in 68% of the observation days, a level which was never reached at the nearby campus of the Makerere University, and only a few times at the city outskirts. Large intra-urban heat stress differences are explained by satellite earth observation products. Normalized Difference Vegetation Index (NDVI) has the highest (75%) power to predict the intra-urban variations in daily mean heat stress, but strong collinearity is found with other variables like impervious surface fraction and population density. Our results have implications for urban planning on the one hand, highlighting the importance of urban greening, and risk management on the other hand, recommending the use of a temperature-humidity index and accounting for large intra-urban heat stress variations and heat-prone districts in urban heat action plans for tropical humid cities.

NALARs ◽  
2019 ◽  
Vol 18 (1) ◽  
pp. 23
Author(s):  
Santi Santi ◽  
Siti Belinda ◽  
Hapsa Rianty

ABSTRAK. Fenomena UHI (Urban Heat Island) mengakibatkan suhu udara perkotaan menjadi tinggi, sehingga menurunkan kualitas lingkungan kota. Untuk dapat meningkatkan kualitas kota dan mengimbangi pertumbuhan kota, maka pemerintah menggalakkan pengembangan infrastruktur hijau perkotaan melalui pengembangan Ruang Terbuka Hijau (RTH). Kota Kendari memiliki beberapa ruang terbuka yang beberapa diantaranya merupakan pusat aktifitas dan interaksi masyarakat kota, diantaranya Taman Walikota dan Pelataran Tugu Religi. Penelitian ini merupakan penelitian deskriptif untuk mengetahui kondisi iklim mikro dan kenyamanan termal ruang terbuka. Data-data yang dikumpulkan berupa karakteristik dan nilai indikator iklim mikro yang meliputi suhu udara, kelembaban relatif, dan kecepatan angin pada sejumlah titik ukur pada siang hari. Data yang dikumpulkan dianalisis menggunakan uji Statistik Independent T Test untuk mengetahui perbedaan iklim mikro antara kedua lokasi dan analisis Temperature Humidity Index (THI) untuk mengetahui tingkat kenyamanannya. Hasil dari uji statistik menunjukkan tingkat perbedaan yang tidak sigifikan antara kedua lokasi, meliputi suhu udara (sig.=0,283); kelembaban relatif (sig.=0,115); dan kecepatan angin (sig.=0,105). Sementara itu, melalui analisia THI menunjukkan nilai index tidak nyaman hampir terjadi pada keseluruhan titik ukur. Nilai THI tertinggi pada lokasi Taman Walikota terletak pada titik A5 (THI=31,9), yaitu pada daerah memiliki kecepatan angin rendah karena posisinya pada bagian tengah kawasan. Sedangkan pada lokasi pelataran Tugu Religi, nilai terendah THI diperoleh pada titik B9 (THI=33,12), yakni titik yang sebagian besar material permukaan lahannya berupa aspal. Kata kunci: ruang terbuka, temperatur, angin, kelembaban relatif, Temperature Humidity Index ABSTRACT. The UHI (Urban Heat Island) phenomenon affected urban air temperatures become high, which decreases the quality of the city environment. To be able to improve the quality of the city and to balance the growth of the city, the government promotes the development of urban green infrastructure through the development of Green Open Space (RTH). Kendari City has several open spaces, some of which are the center of the activities and interactions of urban communities, including the Taman Walikota and the Pelataran Tugu Religi. This research is a descriptive study to determine the microclimate conditions and thermal comfort of open spaces. The data collected is in the form of characteristics and values of microclimate indicators which include air temperature, relative humidity, and wind speed at some measuring points during the day. The collected data were analyzed using the Independent T-Test Statistic Test to determine the differences in microclimate between the two locations and the Temperature Humidity Index (THI) analysis to determine the level of comfort. The results of the statistical tests show a significant level of difference between the two locations, including air temperature (sig. = 0.283); relative humidity (sig. = 0.115); and wind speed (sig. = 0.105). Meanwhile, through THI analysis, the uncomfortable index value almost occurs at the whole measuring point. The highest THI value in the location of the Taman Walikota is located at point A5 (THI = 31.9), which is in the area with low wind speed because of its position in the central part of the city. Whereas in the location of the Pelataran Tugu Religi, the lowest value of THI is obtained at point B9 (THI = 33.12), which is the point where most of the surface material in the land is asphalt. Keywords: open space, temperature, wind, relative humidity, Temperature Humidity Index 


2017 ◽  
Vol 15 (1) ◽  
pp. 57 ◽  
Author(s):  
Trinah Wati ◽  
Fatkhuroyan Fatkhuroyan

ABSTRAKFenomena iklim mempengaruhi kenyamanan fisiologis di daerah pemukiman. Analisa tingkat kenyamanan di DKI Jakarta dilakukan menggunakan THI (Temperature Humidity Index). Berdasarkan data iklim periode 1985 – 2012 stasiun Kemayoran, Tanjung Priok, Halim, Cengkareng dan Pondok Betung, hasil penelitian menunjukkan rata-rata prosentase tingkat kenyamanan harian dengan kategori tidak nyaman sebesar 22,1 % (81 hari per tahun), sebagian nyaman 71 % (259 hari per tahun) dan nyaman 7,1% (26 hari per tahun). Tingkat kenyamanan menunjukkan semakin ke tengah kota semakin besar prosentase tidak nyaman. Selama periode tersebut terjadi kecenderungan peningkatan indeks THI dengan signifikansi > 50% menunjukkan tingkat kenyamanan di DKI Jakarta cenderung semakin tidak nyaman.Kata kunci: tingkat kenyamanan, temperature humidity index, urban heat islandABSTRACTClimate phenomenon affects physiological comfortableness in residential area. Analysis of thermal comfort level in DKI Jakarta were conducted using THI (Temperature Humidity Index).  Based on climate data stations in Kemayoran, Tanjung Priok, Halim, Cengkareng dan Pondok Betung during 1985-2012 showed that the average percentage of daily thermal comfort level with categories uncomfortable were 22,1% (81 days per year), half comfortable 71 % (259 days per year) and comfortable 7,1% (26 days per year). The study showed that the greater percentage uncomfortable level, the closer into the center of the city and during 1985 to 2012 the THI index tend to increasing with significant level more than 50% meant that the thermal comfort level tend to more uncomfortable.Keywords: thermal comfort level, temperature humidity index, urban heat islandCitation: Wati, T dan Fatkhuroyan. (2017). Analisis Tingkat Kenyamanan Di DKI Jakarta Berdasarkan Indeks THI (Temperature Humidity Index). Jurnal Ilmu Lingkungan, 15(1), 57-63, doi:10.14710/jil.15.1.57-63


2021 ◽  
Vol 13 (2) ◽  
pp. 323
Author(s):  
Liang Chen ◽  
Xuelei Wang ◽  
Xiaobin Cai ◽  
Chao Yang ◽  
Xiaorong Lu

Rapid urbanization greatly alters land surface vegetation cover and heat distribution, leading to the development of the urban heat island (UHI) effect and seriously affecting the healthy development of cities and the comfort of living. As an indicator of urban health and livability, monitoring the distribution of land surface temperature (LST) and discovering its main impacting factors are receiving increasing attention in the effort to develop cities more sustainably. In this study, we analyzed the spatial distribution patterns of LST of the city of Wuhan, China, from 2013 to 2019. We detected hot and cold poles in four seasons through clustering and outlier analysis (based on Anselin local Moran’s I) of LST. Furthermore, we introduced the geographical detector model to quantify the impact of six physical and socio-economic factors, including the digital elevation model (DEM), index-based built-up index (IBI), modified normalized difference water index (MNDWI), normalized difference vegetation index (NDVI), population, and Gross Domestic Product (GDP) on the LST distribution of Wuhan. Finally, to identify the influence of land cover on temperature, the LST of croplands, woodlands, grasslands, and built-up areas was analyzed. The results showed that low temperatures are mainly distributed over water and woodland areas, followed by grasslands; high temperatures are mainly concentrated over built-up areas. The maximum temperature difference between land covers occurs in spring and summer, while this difference can be ignored in winter. MNDWI, IBI, and NDVI are the key driving factors of the thermal values change in Wuhan, especially of their interaction. We found that the temperature of water area and urban green space (woodlands and grasslands) tends to be 5.4 °C and 2.6 °C lower than that of built-up areas. Our research results can contribute to the urban planning and urban greening of Wuhan and promote the healthy and sustainable development of the city.


Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 46
Author(s):  
Reija Ruuhela ◽  
Athanasios Votsis ◽  
Jaakko Kukkonen ◽  
Kirsti Jylhä ◽  
Susanna Kankaanpää ◽  
...  

Urbanization and ongoing climate change increase the exposure of the populations to heat stress, and the urban heat island (UHI) effect may magnify heat-related mortality, especially during heatwaves. We studied temperature-related mortality in the city of Helsinki—with urban and suburban land uses—and in the surrounding Helsinki-Uusimaa hospital district (HUS-H, excluding Helsinki)—with more rural types of land uses—in southern Finland for two decades, 2000–2018. Dependence of the risk of daily all-cause deaths (all-age and 75+ years) on daily mean temperature was modelled using the distributed lag nonlinear model (DLNM). The modelled relationships were applied in assessing deaths attributable to four intensive heatwaves during the study period. The results showed that the heat-related mortality risk was substantially higher in Helsinki than in HUS-H, and the mortality rates attributable to four intensive heatwaves (2003, 2010, 2014 and 2018) were about 2.5 times higher in Helsinki than in HUS-H. Among the elderly, heat-related risks were also higher in Helsinki, while cold-related risks were higher in the surrounding region. The temperature ranges recorded in the fairly coarse resolution gridded datasets were not distinctly different in the two considered regions. It is therefore probable that the modelling underestimated the actual exposure to the heat stress in Helsinki. We also studied the modifying, short-term impact of air quality on the modelled temperature-mortality association in Helsinki; this effect was found to be small. We discuss a need for higher resolution data and modelling the UHI effect, and regional differences in vulnerability to thermal stress.


2021 ◽  
Vol 2 ◽  
Author(s):  
Véronique Ouellet ◽  
Izabella M. Toledo ◽  
Bethany Dado-Senn ◽  
Geoffrey E. Dahl ◽  
Jimena Laporta

The effects of heat stress on dry cows are profound and significantly contribute to lower overall welfare, productivity, and profitability of the dairy sector. Although dry cows are more thermotolerant than lactating cows due to their non-lactating state, similar environmental thresholds are currently used to estimate the degree of heat strain and cooling requirements. Records of dry cow studies conducted over 5 years in Gainesville, Florida, USA were pooled and analyzed to determine environmental thresholds at which dry cows exhibit signs of heat stress in a subtropical climate. Dry-pregnant multiparous dams were actively cooled (CL; shade of a freestall barn, fans and water soakers, n = 107) or not (HT; shade only, n = 111) during the last 7 weeks of gestation, concurrent with the entire dry period. Heat stress environmental indices, including ambient temperature, relative humidity, and temperature-humidity index (THI), and animal-based indices, including respiration rate, rectal temperature and daily dry matter intake were recorded in all studies. Simple correlations were performed between temperature-humidity index and each animal-based indicator. Differences in respiration rate, rectal temperature and dry matter intake between treatments were analyzed by multiple regression. Using segmented regression, temperature-humidity thresholds for significant changes in animal-based indicators of heat stress were estimated. Stronger significant correlations were found between the temperature-humidity index and all animal-based indices measured in HT dry cows (−0.22 ≤ r ≤ 0.35) relative to CL dry cows (−0.13 ≤ r ≤ 0.19). Although exposed to similar temperature-humidity index, rectal temperature (+0.3°C; P < 0.001) and respiration rate (+23 breaths/min; P < 0.001) were elevated in HT dry cows compared with CL cows whereas dry matter intake (−0.4 kg of dry matter/d; P = 0.003) was reduced. Temperature-humidity index thresholds at which respiration rate and rectal temperature began to change were both determined at a THI of 77 in HT dry cows. No significant temperature-humidity threshold was detected for dry matter intake. At a practical level, our results demonstrate that dry cow respiration rate and rectal temperature increased abruptly at a THI of 77 when provided only shade and managed in a subtropical climate. Therefore, in the absence of active cooling, dry cows should be closely monitored when or before THI reaches 77 to avoid further heat-stress related impairments during the dry period and the subsequent lactation and to mitigate potential carry-over effects on the offspring.


2021 ◽  
Author(s):  
Shihan Chen ◽  
Yuanjian Yang ◽  
Fei Deng ◽  
Yanhao Zhang ◽  
Duanyang Liu ◽  
...  

Abstract. Due to rapid urbanization and intense human activities, the urban heat island (UHI) effect has become a more concerning climatic and environmental issue. A high spatial resolution canopy UHI monitoring method would help better understand the urban thermal environment. Taking the city of Nanjing in China as an example, we propose a method for evaluating canopy UHI intensity (CUHII) at high resolution by using remote sensing data and machine learning with a Random Forest (RF) model. Firstly, the observed environmental parameters [e.g., surface albedo, land use/land cover, impervious surface, and anthropogenic heat flux (AHF)] around densely distributed meteorological stations were extracted from satellite images. These parameters were used as independent variables to construct an RF model for predicting air temperature. The correlation coefficient between the predicted and observed air temperature in the test set was 0.73, and the average root-mean-square error was 0.72 °C. Then, the spatial distribution of CUHII was evaluated at 30-m resolution based on the output of the RF model. We found that wind speed was negatively correlated with CUHII, and wind direction was strongly correlated with the CUHII offset direction. The CUHII reduced with the distance to the city center, due to the de-creasing proportion of built-up areas and reduced AHF in the same direction. The RF model framework developed for real-time monitoring and assessment of high-resolution CUHII provides scientific support for studying the changes and causes of CUHII, as well as the spatial pattern of urban thermal environments.


2021 ◽  
Vol 24 (2) ◽  
pp. 24-36
Author(s):  
Lazoumi Ouarfli ◽  
Abdelmadjid Chehma

Abstract The objective is to study the effect of heat stress on milk yield (MY) relative to milking records (n=18178) of native Holsteins (n=187), in the region of Ghardaia, according to periods of HS, using the temperature-humidity index (THI). With THI >72 during 07 months in the study area, which significantly (P<0.001) decrease the MY (-15.5% corresponding to 21.73 kg). Also, calving periods led to a significant drop (P < 0.001) in overall MY (7030.35 kg) of the order of (-14.6%), and over the lactation length (353.43 d), which explains 41% of the variations in MY. In addition, the non-significant effect (P=0.212) of the lactation range on the increase in MY, moreover, the lactation length shows a non-significant (P = 0.108) decrease (-4.68%) during heat stress (HS). Furthermore, the significant effect (P <0.001) of the interaction (Milking frequency × THI) on MY, when THI variates from < 74 to > 84, with regression of (-16.82% and -08.82%) of the MF (2X and 3X), respectively. Again, the NH cow is less sensitive to hyperthermia, so THI explains only 2% of the variation in MY levels. Thus, NH in arid regions have the ability to acclimatize to Saharan environmental conditions.


Author(s):  
A. Krtalić ◽  
A. Kuveždić Divjak ◽  
K. Čmrlec

Abstract. This study aims to assess surface urban heat islands (SUHIs) pattern over the city of Zagreb, Croatia, based on satellite (optical and thermal) remote sensing data. The spatio-temporal identification of SUHIs is analysed using the 12 sets of Landsat 8 imagery acquired during 2017 (in each month of the year). Vegetation cover within the city boundaries is extracted by using Principal Component Analysis (PCA) data fusion method on calculated three vegetation indices (VI): Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Ratio Vegetation Index (RVI) for each set of bands. The first principal component was used to compute the land surface temperature (LST) and deductive Environmental Criticality Index (ECI). As expected, the relationship between LST and all VI scores shows a negative correlation and is most negative with RVI. The environmentally critical areas and the patterns of seasonal variations of the SUHIs in the city of Zagreb were identified based on the LST, ECI and vegetation cover. The city centre, an industrial area in the eastern part and an area with shopping centers and commercial buildings in the western part of the city were identified as the most critical areas.


2019 ◽  
Vol 49 (1) ◽  
Author(s):  
Fernanda Gatti de Oliveira Nascimento ◽  
Hellen Cris Pinto Aguiar ◽  
Gustavo Moya Rodrigues ◽  
Ednaldo Carvalho Guimarães ◽  
Mara Regina Bueno de Mattos Nascimento

ABSTRACT: The aim of this study was to determine among nine temperature-humidity index (THI) equations, the one that best represents the effects of heat stress on crossbred dairy calves reared in a tropical environment. Twelve male and female calves, aged 20 to 60 days, and raised in a tropical pen were evaluated. Respiratory (RR) and heart rates (HR), rectal (RT), body surface (BST), dry bulb (Tdb) and wet bulb (Tbw) temperatures, partial vapor pressure (Pv), relative humidity (RH) and dew point temperature (Tpo) were quantified in the morning and afternoon. Nine THI equations were calculated. The highest correlation between physiological variables and this was used to select the best THI equation. Averages for nine THI equations, Tdb, Twb, Pv, Tdp, RR, HR, RT, and BST were higher in the afternoon than in the morning, whereas that for RH was the opposite. The highest values for RT occurred at temperatures above 26.4°C and when humidity was below 55.5%. The Tdb and Pv correlations with RR (0.697 and 0.707), RT (0.703 and 0.706) and BST (0.818 and 0.817) were significant and positive, whereas the RH correlations with the same physiological variables were significant and negative (-0.622, -0.590 and -0.638, respectively). The best index was the THI sensible heat-based ( T H I = 3.43 + 1.058 x T d b - 0.293 x R H + 0.0164 x T d b x R H + 35.7), which was significantly correlated with RR (r=0.668 and r²=0.446), HR (r=0.259 and r²=0.067), RT (r=0.693 and r²=0.479) and BST (r=0.807 and r²=0.650). In conclusion, the THI sensible heat-based equation best represents the effects of heat stress on crossbred dairy calves reared in a tropical environment.


2018 ◽  
Vol 57 (2) ◽  
pp. 209-220 ◽  
Author(s):  
Shaoxiu Ma ◽  
Andy Pitman ◽  
Jiachuan Yang ◽  
Claire Carouge ◽  
Jason P. Evans ◽  
...  

AbstractGlobal warming, in combination with the urban heat island effect, is increasing the temperature in cities. These changes increase the risk of heat stress for millions of city dwellers. Given the large populations at risk, a variety of mitigation strategies have been proposed to cool cities—including strategies that aim to reduce the ambient air temperature. This paper uses common heat stress metrics to evaluate the performance of several urban heat island mitigation strategies. The authors found that cooling via reducing net radiation or increasing irrigated vegetation in parks or on green roofs did reduce ambient air temperature. However, a lower air temperature did not necessarily lead to less heat stress because both temperature and humidity are important factors in determining human thermal comfort. Specifically, cooling the surface via evaporation through the use of irrigation increased humidity—consequently, the net impact on human comfort of any cooling was negligible. This result suggests that urban cooling strategies must aim to reduce ambient air temperatures without increasing humidity, for example via the deployment of solar panels over roofs or via cool roofs utilizing high albedos, in order to combat human heat stress in the urban environment.


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