Influence of urbanization on the thermal environment of meteorological station: Satellite-observed evidence

You

Intl Journal of Climatology

et al. 2018

This study uses the daily maximum and minimum temperature data sets of 48 meteorological stations to assess the observed changes in temperature extremes over China–Pakistan Economic Corridor (CPEC) during 1980–2016. The nonparametric Mann–Kendall, Sen's slope estimator, least squares method, and two‐tailed simple t‐test methods were used to assess the trend in nine temperature extreme indices. The results of the study indicated that the trends in annual mean anomalies of cold nights, cold days, and frost days significantly decreased at the rates of −1.09, −1.58, and −1.05 day/decade, respectively. The number of warm nights, warm days, and summer days exhibited significant positive trends at the rates of 1.49, 1.04, and 4.32 day/decade, respectively. In addition, the trends of the warmest day and coldest day also increased significantly at the rates of 0.45 and 0.51 °C/decade, respectively. The trend of diurnal temperature range decreased significantly with −0.35 °C/decade. The spatial distribution of temperature extreme indices indicated that the number of cold nights, cold days, and diurnal temperature range have been decreased, while the trends of warm nights, warm days, summer days, warmest day, and coldest day have been increased over the whole country. Large‐scale atmospheric circulation changes derived from ERA‐Interim reanalysis show that a weak (strong) wind pressure, increasing (decreasing) geopotential height, and rapid warming (cooling) over the northern (southern) region have contributed to the changes in temperature extremes in Pakistan to some extent. With respect to elevation‐dependent warming (EDW), the trends of cold nights, warm days, summer days, warmest day, and diurnal temperature range showed significant positive correlations with increasing elevation. However, the trends of cold days, warm nights, frost days, and coldest day showed significant negative relationships with increasing elevation. The findings of this study will be helpful in the adaptation of climate change and mitigation of climatological disasters in the region. The study recommends that future studies should investigate the natural and anthropogenic drivers of temperature extremes and the possible mechanism of EDW in the CPEC region.

Section: Resultsmentioning

confidence: 97%

Observed changes in temperature extremes over China–Pakistan Economic Corridor during 1980–2016

You

Intl Journal of Climatology

et al. 2018

“…Because of the variability and uncertainty of local climate/surface conditions, it is not appropriate to directly compare the characteristics of different thermal environments using LST values [62][63][64]. Hence, we first normalized and standardized the retrieved LST values of each city using a range between 0 and 1 (Equation (2)) and then removed the extreme LST values.…”

Section: Thermal Environment Mappingmentioning

confidence: 99%

Impacts of Land Cover/Use on the Urban Thermal Environment: A Comparative Study of 10 Megacities in China

et al. 2020

Satellite-derived land surface temperature (LST) reveals the variations and impacts on the terrestrial thermal environment on a broad spatial scale. The drastic growth of urbanization-induced impervious surfaces and the urban population has generated a remarkably increasing influence on the urban thermal environment in China. This research was aimed to investigate land surface temperature (LST) intensity response to urban land cover/use by examining the thermal impact on urban settings in ten Chinese megacities (i.e., Beijing, Dongguan, Guangzhou, Hangzhou, Harbin, Nanjing, Shenyang, Suzhou, Tianjin, and Wuhan). Surface urban heat island (SUHI) footprints were scrutinized and compared by magnitude and extent. The causal mechanism among land cover composition (LCC), population, and SUHI was also identified. Spatial patterns of the thermal environments were identical to those of land cover/use. In addition, most impervious surface materials (greater than 81%) were labeled as heat sources, on the other hand, water and vegetation were functioned as heat sinks. More than 85% of heat budgets in Beijing and Guangzhou were generated from impervious surfaces. SUHI for all megacities showed spatially gradient decays between urban and surrounding rural areas; further, temperature peaks are not always dominant in the urban core, despite extremely dense impervious surfaces. The composition ratio of land cover (LCC%) negatively correlates with SUHI intensity (SUHII), whereas the population positively associates with SUHII. For all targeted megacities, land cover composition and population account for more than 63.9% of SUHI formation using geographically weighted regression. The findings can help optimize land cover/use to relieve pressure from rapid urbanization, maintain urban ecological balance, and meet the demands of sustainable urban growth.

“…(a) Firstly, long-term observation [38] of meteorological data [39,40], climate factors [41], and remote sensing images [42] during the period 1980-2016 were applied and analyzed. For this purpose, raster maps of Wuhan City (8573 km 2 ) at ten-yearly intervals from 1980 to 2016 were established and carefully analyzed using specified raster information.…”

Section: Long-term and Mobile Observational Study Using Srst And Gis mentioning

confidence: 99%

The Interactive Impact of Building Diversity on the Thermal Balance and Micro-Climate Change under the Influence of Rapid Urbanization

Makvandi

Elsadek

et al. 2019

Sustainability

Numerous cities face the serious problems of rapid urbanization and climate change, especially in recent years. Among all cities, Wuhan is one of the most affected by these changes, accompanied by the transformation of water surfaces into urban lands and the decline of natural ventilation. This study investigated the impact of surface urban heat island enlargement (SUHI) and block morphology changes in heat balance. Accordingly, the interactive impact of building diversity with major building forms (low-rise, mid-rise, and high-rise) on thermal balance and microclimate changes under the influence of urban land expansion at the residential block scale was studied. To investigate the heat balance changes by air temperature intensification and air movement reduction, a long-term and field observational analysis (1980–2018) coupled with computational fluid dynamic simulation (CFD) was used to evaluate the impact of building diversity on thermal balance. Outcomes show that urban heat island intensity (UHII) increased by 2 ℃ when water surfaces in urban areas decreased; consequently, there was a deterioration in the air movement to alleviate UHII. Thus, the air movement declined substantially with UHII and SUHI enlargement, which, through increased urban surfaces and roughness length, will become worse by 2020. Furthermore, the decline in air movement caused by the transformation of urban water bodies cannot contribute to the heat balance unless reinforced by the morphology of the urban blocks. In the design of inner-city blocks, morphological indicators have a significant impact on microclimate and heat balance, where increasing building density and plot ratio will increase UHII, and increasing water surfaces will result in an increase in urban ventilation. Lastly, a substantial correlation between air temperature and relative humidity was found, which, together with the block indicators, can help control the air temperature and adjust the urban microclimate.