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Urban heat island effect and its contribution to observed temperature increase at Wuhan station, Central China
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Based on an in-homogeneity adjusted dataset of the monthly mean temperature, minimum and maximum temperature, this paper analyzes the temporal characteristics of Urban Heat Island (UHI) intensity at Wuhan Station, and its impact on the long-term trend of surface air temperature change recorded during 1961-2015 by using an urban-rural method. Results show that UHI effect is obvious near Wuhan Station in the past 55 years, especially for minimum temperature. The strongest UHI intensity occurs in summer and the weakest in winter, on the contrary to the seasonal variation of northern cities. For the period 1961-2004, UHI intensity undergoes a significant increase near the urban station, with the increase especially large for the period 1988-2004, but a significant decrease is registered for the last 10 years, with the decrease in minimum temperature more significant than that of maximum temperature. The annual mean urban warming and its contribution to overall temperature increase are 0.18 C/10yr and 48.8% respectively for the period 1961-2015, with a more significant and larger urbanization effect seen in T min than T max. A large proportion warming, about half of the overall increase in annual mean temperature, as observed at the urban station, thus can be attributed to the rapid urbanization in the past half a century.
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... The population density shows an increase of 61% in 2015 compared to 1990, and the urban land use ratio has tripled from 1980 to 2018. Additionally, a significant UHI has been found over the past few decades using both annual and seasonal mean Surface Air Temperature (SAT) time series at the Wuhan station from the basic national meteorological observation network of China [46,47]. Furthermore, the land surface temperature in urban areas has increased ...
... The population density shows an increase of 61% in 2015 compared to 1990, and the urban land use ratio has tripled from 1980 to 2018. Additionally, a significant UHI has been found over the past few decades using both annual and seasonal mean Surface Air Temperature (SAT) time series at the Wuhan station from the basic national meteorological observation network of China [46,47]. Furthermore, the land surface temperature in urban areas has increased [48,49]. ...
Increasing of evidence suggests that rapid urbanization modifies precipitation and increases atmospheric instability in urban areas mainly due to urban heat island (UHI)-induced thermal effects and urban building-induced dynamic effects. However, few studies focus on the impact of urbanization on the diurnal variations in urban rainfall in terms of initiating time, frequency, amount, and intensity. Here, six years of hourly data from a relatively dense meteorological observation network in the Wuhan area in central China are used to quantify the issue of urbanization-induced diurnal variations in hourly rainfall and short-duration rainfall (SDR) events by comparing urban and surrounding rural stations during the summer dry period (13 July to 4 August), corresponding to hot weather with little rainfall and high evaporation. The results indicate that: (i) A higher frequency of hourly rainfall appears during night-time and afternoon over urban areas as compared to rural areas. The urban rainfall is more concentrated during the night-time; (ii) More and stronger urban SDR events are triggered during the night-time over urban areas, especially in terms of amount and intensity of rainfall events. A greater diurnal urban–rural difference in SDR events is detected than that in hourly mean rainfall; (iii) There is an enhancement in the night-time and afternoon urban SDR events when UHI intensity increases before they are initiated, and this is detectable in the frequency, amount, and intensity of SDR events. It is also found that the UHI-induced thermal effects are the main reason for the stronger nocturnal SDR events in Wuhan during the summer dry period, which is caused by increases in the convection current and water vapor flux convergence in the urban areas.
... Peterson, 2003;Weng and Yang, 2004;于 淑 秋 等 , 2005;陈正洪等, 2007;Ren et al., 2007Ren et al., , 2008唐国利 等, 2008;Bian et al., 2015;丁硕毅 等, 2015;刘伟东等, 2016;Jia et al., 2019;Tysa et al., 2019)，研究指出城市热岛效应在单个城市或区域 尺度上对城市气象站气温观测趋势有显著的高估作 用，且对日最低气温趋势估计的影响最为明显。 Ren et al.(2008) Bian et al., 2017;Jia et al., and Ren, 2011;杨元建等, 2011;He et al., 2013) ...
... ，研究指出城市热岛效应在单个城市或区域 尺度上对城市气象站气温观测趋势有显著的高估作 用，且对日最低气温趋势估计的影响最为明显。 Ren et al.(2008) Bian et al., 2017;Jia et al., and Ren, 2011;杨元建等, 2011;He et al., 2013) ...
The spatial distribution and temporal variation of the Urban Heat Island Intensity (UHII) are analyzed. We use the hourly surface air temperature (SAT) data from the observational networks of automatic weather stations during September 2012−August 2014 and January 2016−December 2017 over four cities, Changchun, Beijing, Wuhan and Guangzhou, and a proved method to classify observational sites into urnan and rural stations. The results show that the annual mean UHII in built-up areas of these cities (Changchun, Beijing, Wuhan and Guangzhou) are 0.96°C, 1.06°C, 0.91°C, and 0.78°C, respectively. The UHII in northern cities is higher in autumn and winter than in spring and summer due to calm and inversion weather and higher anthropogenic heat release. In southern cities, autumn UHII is the most obvious, because the clear sky and crisp air are conducive to the development of heat island, followed by the UHII of winter and summer. The diurnal variation of UHII in each city is characterized by a stronger UHII at night than during the day, with UHII beginning to decline (rise) in the early morning (afternoon). The amplitude of UHII diurnal variation is the largest in Wuhan due to the synchronous diurnal effect of the lakes with UHI in the urban areas, and the smallest in Guangzhou probably because of more anthropogenic heat release at daytime in the tropical climate. For the UHII diurnal variations, the steadily strong (weak) UHII period at night (day) is longer (shorter) in autumn and winter in the northern cities than in the southern cities. The UHII difference between north and south climate zones as revealed in this paper has practical significance for urban planning and management of eastern China.
... In this study, we calculated the simple urbanization process index K based on the relevant data from 1993 to 2020 and explored the relationship between urban development and urban mean temperature change (Figure 9). Not only in Nanchong, Jia et al. [56] pointed out that a large proportion of the warming in Wuhan can be attributed to the rapid urbanization in the past half-century. However, some studies have pointed out that the heat island effect brought about by urbanization does not directly cause an increase in maximum temperature, but only affects the average temperature [57]. ...
It is necessary to alleviate the high temperatures and heat wave disasters in cities in southwest China that are beginning to occur because of global warming. During this study, the spatial and temporal characteristics of heat waves in Nanchong from 1961 to 2022 are analyzed by using the signal smooth method and mutation test. Based on the meteorological data and socioeconomic statistics, the entropy value method is used to obtain the indicator weights to construct a heat wave social vulnerability evaluation index system and conduct vulnerability assessments and classifications. The results show that: ① The heat wave indicators in Nanchong show an increasing trend, although there is a low period of heat waves from 1980 to 1995. Additionally, there are significant mutations in the number of days, frequency, and intensity of high-temperature heat waves from 2009 to 2011, which may be caused by the abnormal high-pressure belt in the mid-latitude. ② The distribution of exposure, sensitivity, and adaptability in Nanchong City, under high temperatures, is uneven in space. Generally, the indicators in the north are lower than those in the south. ③ The high-vulnerability counties are mainly distributed in the east and west of Nanchong, the proportion of the medium social vulnerability index areas are more than a half, while the dominant factor in the distribution pattern is natural factors. ④ The Western Pacific Subtropical High (WPSH) anomaly directly led to the extremely high temperature in Nanchong in the summer of 2022, and the urbanization process index shows a significant positive correlation with the trend of high temperatures and heat waves in Nanchong.
... The tourism and the marine industry in Pingtan's main island had achieved remarkable development from 2013 to 2018 (Linhong 2018). The degree of human disturbance and ecological sensitivity are the key factors affecting ecological vulnerability (Tables 6 and 7, Figure 3): (1) Although different land-use types areas had different ecological pressures, they were generally high; (2) The micro degree area was often forest or its central area; (3) Mild, moderate, and severe vulnerability area were mostly distributed in grassland, forest land, agricultural land, unused land, and other areas; (4) The severe vulnerability area was distributed in the area with a large degree of soil erosion, including the tourism area and parts of the port; (5) Most of the extremely fragile areas were related to reclamation and port areas which were greatly disturbed by human activities, and frequent human activities often contribute to the urban heat island effect and make the land surface temperature increase (Wenqian et al. 2019). The ecological sensitivity distribution pattern is roughly consistent with the land surface temperature distribution, and ecological pressure is affected by the factors of construction land, thus most of the crowded construction sites are extremely fragile areas. ...
Despite the recent progress on Ecological Vulnerability studies by developing index models, similar studies on the coastal areas are still rare. Pingtan’s main island of Fujian Province in China and the coastal area of Nile Delta in Egypt, have witnessed unprecedented development associated with fragile coastal areas. SRP model is a comprehensive model, utilized to evaluate the ecological vulnerability to provide a solid reference for the development of SRP model development. Research results indicated that the ecological vulnerability of the coastal areas of Nile Delta was slightly better than that of Pingtan’s main island in 2018, the former was almost at a micro level, while the latter was almost at a mild level (micro and mild vulnerable area accounted for 65.99%). Pingtan’s main island, showed a slight deterioration trend from west to east, and the characteristics of massive regional distribution, with a slight deterioration of the overall ecological environment of the planning area from 2013 to 2018. For the coastal area of Nile Delta, the ecological vulnerability was gradually increasing from the middle of the basin to the periphery, and the extremely vulnerable area was mainly distributed in the northern coastal area and the arid desert areas from 2018 to 2019. Moreover, according to the statistics results about the maximum weight of ecological pressure was 0.4989 on Pingtan’s main island and 0.4960 in the coastal area of Nile Delta, ecological sensitivity and pressure played a vital role in ecological vulnerability and spatial pattern of two study areas, which contain climate (mainly involving temperature, precipitation), vegetation, and human activities (mainly involving land-use, economy, and population). The current study not only confirmed the close relationship between ecological vulnerableity, natural attributes, and human activities, also showed the strong applicability of SRP model in the coastal ecological fragile area.
Applying surface air temperature (2-m) data observed from automatic weather stations from September 2017 to August 2019 and the long-term surface air temperature data from 1960 to 2019, we analyzed spatial and temporal characteristics of urban heat island intensity (UHII) in Xiamen city, southern China, and urbanization effect on trends of surface air temperature at two urban stations. The results showed that high-value areas of the UHII were primarily distributed in central to northern parts of the urban area, with UHIIs >0.60 ℃. Affected by sea breeze, the UHII center tended to be inland during daytime and on the coast and islands at night. The UHII during daytime was greater than at nighttime, and the amplitude of UHII diurnal variation in the mainland urban areas was greater than that on the Xiamen Island. Seasonally, the UHII during spring and summer was typically higher than that of autumn and winter. The two long-sequence urban observational stations at Xiamen and Tongan (national stations with their historical data series used in studies of regional climate change) have recorded obvious enhancement of the UHII around the observational sites during the past 60 years, with the trend of annual mean UHII at Xiamen station reaching 0.13 ℃/10 yr, which has contributed at least 38.8% to the overall warming observed at the station.
Whether the urban heat island (UHI) is affected by air pollution in urban areas has attracted much attention. By analyzing the observation data of automatic weather stations and environmental monitoring stations in Beijing from 2016 to 2018, we found a seasonally dependent interlink of the UHI intensity (UHII) and PM2.5 concentration in urban areas. PM2.5 pollution weakens the UHII in summer and winter night, but strengthens it during winter daytime. The correlation between the UHI and PM2.5 concentration has been regulated by the interaction of aerosol with radiation, evaporation and planetary boundary layer (PBL) height. The former two change the surface energy balance via sensible and latent heat fluxes, while the latter affects atmospheric stability and energy exchange. In summer daytime, aerosol-radiation interaction plays an important role, and the energy balance in urban areas is more sensitive to PM2.5 concentration than in rural areas, thereby weakening UHII. In winter daytime, aerosol-PBL interaction is dominant, because aerosols lower the PBL height and stabilize atmosphere, weaken the heat exchange with the surrounding, with more heat accumulated in the urban areas and the increased UHII. Changes in evaporation and radiation strengthen the relationship. At night, the change of UHII more depends on the energy stored in the urban canopy. Aerosols effectively reduce the incident energy during daytime, and the long-wave radiation from the buildings of urban canopy at night becomes less, leading to a weakened UHII. Our analysis results can improve the understanding of climate-aerosols interaction in megacities like Beijing.
Based on the homogeneity test and correction of the relative humidity series, climatological characteristics and long-term trend of relative humidity in the urban area of Wuhan are analyzed. The results showed that: (1) The non-homogeneity deviation caused by relocated stations in the relative humidity series is prodigious, and the deviation caused by relocation of Wuhan station in 2010 is 8%. (2) Annual average relative humidity in the urban area of Wuhan remains high, and the values vary between 75%−85% with the highest value occurring at Wuhan station. (3) The relative humidity gradually increases from January to June, and then begins to decrease slowly after reaching its peak value in June. Monthly differences are pretty small with the values within 0.1%−2.5%. Seasonal characteristics of relative humidity in the urban area of Wuhan show that the RH is the highest in the summer and lowest in the winter during the whole year. (4) From 1961 to 2015, the average relative humidity in the urban area of Wuhan urban area exhibited a long-term decreasing trend, and the linear trend was accelerated after the 1990s. (5) In the past 55 years, time series of average relative humidity in the spring, autumn, and winter all show declining trends in varied degrees, of which the trend in the spring is more obvious, and a significant rising trend is found in the summer. However, the annual and seasonal means are showing a significant downward trend after 1991.
Using a data set of monthly mean air temperature from 20 stations, the effect of urban heat island magnitude on mean surface air temperature (SAT) records of the last 40 years in Beijing area was analyzed. Two stages, a short cooling period between 1961-1969 and a significant warming period after 1969, were observed for both urban and rural annual mean SAT in Beijing area, and an obvious warming trend for each station was detected. The warming rate in winter is much higher than in any other seasons. It was also noted that the SAT anomaly series as calculated using the data from Beijing Station and the national basic/reference stations of the study area are significantly impacted by urban warming, especially for the last 20 years. Although the positive tendency of SAT anomalies is much greater in winter than in other seasons, the urban warming is generally stronger in warm seasons. By analyzing the difference of SAT change rates between the basic/reference stations and the rural stations, we could further obtain the warming rate induced by urbanization, and could calculate the relative contribution of urban warming to the total change in the mean SAT anomalies series. The urbanization contribution to the annual mean SAT change of the basic/reference stations in Beijing area reaches to 48.5 % for period 1979-2000 and 71.1 % for period 1961-2000. It is also obvious that the urbanization contribution generally increases from winter and spring to summer and autumn. During 1961-2000, the recorded warming in summer and autumn at the basic/reference stations can be entirely accounted for by the urbanization effect. Overall, these results indicate the essentiality to pay more attention to the effect of the increased urban heat island magnitude on long-term mean SAT data series at least on regional scale.
The radiance lights data in 2006 from the Na-tional Oceanic and Atmospheric Administration Air Force Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) and authoritative energy data distributed by the United State Energy Information Administration were applied to estimate the global distri-bution of anthropogenic heat flux. A strong linear rela-tionship was found to exist between the anthropogenic heat flux and the DMSP/OLS radiance data. On a global scale, the average value of anthropogenic heat flux is ap-proximately 0.03 W m 2 and 0.10 W m 2 for global land area. The results indicate that global anthropogenic heat flux was geographically concentrated and distributed, fundamentally correlating to the economical activities. The anthropogenic heat flux concentrated in the eco-nomically developed areas including East Asia, Europe, and eastern North America. The anthropogenic heat flux in the concentrated regions, including the northeastern United States, Central Europe, United Kingdom, Japan, India, and East and South China is much larger than global average level, reaching a large enough value that could affect regional climate. In the center of the concen-trated area, the anthropogenic heat flux density may ex-ceed 100 W m 2 , according to the results of the model. In developing areas, including South America, Central and North China, India, East Europe, and Middle East, the anthropogenic heat flux can reach a level of more than 10 W m 2 ; however, the anthropogenic heat flux in a vast area, including Africa, Central and North Asia, and South America, is low. With the development of global economy and urban agglomerations, the effect on climate of an-thropogenic heat is essential for the research of climate change.
On the premise that urban heat islands are strongest in calm conditions but are largely absent in windy weather, daily minimum and maximum air temperatures for the period 1950–2000 at a worldwide selection of land stations are analyzed separately for windy and calm conditions, and the global and regional trends are compared. The trends in temperature are almost unaffected by this subsampling, indicating that urban development and other local or instrumental influences have contributed little overall to the observed warming trends. The trends of temperature averaged over the selected land stations worldwide are in close agreement with published trends based on much more complete networks, indicating that the smaller selection used here is sufficient for reliable sampling of global trends as well as interannual variations. A small tendency for windy days to have warmed more than other days in winter over Eurasia is the opposite of that expected from urbanization and is likely to be a consequence of atmospheric circulation changes.
Shanghai is the biggest and most important industrial and commercial center in China. Multiple observations show that the urban area is nearly always warmer. During the maximum development of an urban heat island, the temperature field often induces a 'country breeze'. There are more thunderstorm days, and heavy rainy days in Shanghai city compared with its nearby counties due to the rising current above the heat island. The mean temperature value of the coldest month, the hottest month and the annual are higher in urban districts compared to the rural areas on average. -after English summary
The global warming hiatus during 1998-2012 has aroused a great public interest in past several years. Based on the air temperature at 622 meteorological stations in China, the response of temperature to global warming hiatus was analyzed on national and regional scales. The main results were as follows: (1) The trend magnitude of air temperature in China was -0.221 ℃/10 a during 1998-2012, which was lower than the long-term trend during 1960-1998 by 0.427 ℃/10 a. There was a warming hiatus in China that was more obvious than the global mean. Winter played a dominant role (contribution rate was 74.13%) in the nationwide warming hiatus, and the contribution of summer was the least among the four seasons. (2) The warming hiatus was spatial incoherent in different climate backgrounds in China. Among the three natural zones in China (the monsoon region of eastern China, the arid region of northwestern China and the high frigid region of Tibetan Plateau), there was a significant cooling in the eastern and northwestern China, especially the eastern China with a contribution rate of 53.79%. In the eastern China, the trend magnitudes were 0.896 ℃/10 a in winter and 0.134 ℃/10 a in summer, respectively. In the Tibetan Plateau, the air temperature has increased by 0.204 ℃/10 a without significant warming hiatus. (3) The warming hiatus in China may be associated with the negative phase of PDO as well as the reduction of sunspot numbers and total solar radiation. (4) Although warming hiatus occurred in China during 1998-2012, the air temperature has rapidly increased after 2012 and is likely to be continuously warming in the next few years.
Wetland is one of the three most valuable ecosystems in the world. Blessed with numerous lakes, Wuhan has enjoyed the reputation of "City with hundreds of lakes&", and "Lake&"is the important name card of Wuhan. Based on the Landsat TM images of the year of 2000, 2005, and 2010, we get the lakes variation characteristics from year 2000 to year 2010 of central Wuhan with the method of NDWI to extract prominent information of lakes and then create the vector layers of the lakes data of the three years, which are used to calculate the Shrinking Rate of the lakes, fractal dimension of lake patches and the degree of fragmentation of lake landscape. The study shows that: (1) All the lakes have shrunk, and there are different shrinking rates of different lakes, which are mainly decided by which loop are these lakes in and policy factors. (2) fractal dimensions of these lake patches are range from 1 to 1.3, and are increasingly close to 1. It shows that the lakes are becoming regularly shaped under human activity influence. (3) There is an increase in the number of lake patches. With their decrease in area, the lakes become fragmented at the same time due to the traffic construction. When a lake is fragmented, it is easier to be polluted for the reduction of its self-purification capacity and probably to be filled in at last. In one word, the landscape environment of lakes proceeds in a negative direction. Stricter policies should be put forward for administration and protection of the lakes of Wuhan City.