Urbanization and heterogeneous surface warming in eastern China

Wu, Kai; Yang, Xiu‐Qun

doi:10.1007/s11434-012-5627-8

Cited by 66 publications

(50 citation statements)

References 35 publications

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“…The maximum T 2 changes are usually found in the city centers of the PRD region, with typical increments of over 1.1 • in January and of over 0.5 • in July. These findings are comparable to the values estimated for other cities (Fan and Sailor, 2005;Ferguson and Woodbury, 2007;Zhu et al, 2010;Menberg et al, 2013;Wu and Yang, 2013;Bohnenstengel et al, 2014;Yu et al, 2014;Xie et al, 2016) and can be confirmed by similar research in South China (Meng et al, 2011;Feng et al, 2012Feng et al, , 2014. Figure 4e and f present the vertical changes in air temperature from the surface to the 800 hPa layer along the line AB (shown in Fig.…”

Section: Changes In Surface Energy and Air Temperaturesupporting

confidence: 89%

“…Anthropogenic heat (AH) can increase turbulent fluxes in sensible and latent heat (Oke, 1988), implying that it can modulate local and regional meteorological processes (Ichinose et al, 1999;Block et al, 2004;Fan and Sailor, 2005;Ferguson and Woodbury, 2007;Zhu et al, 2010;Feng et al, 2012Feng et al, , 2014Menberg et al, 2013;Ryu et al, 2013;Wu and Yang, 2013;Bohnenstengel et al, 2014;Chen et al, 2014a;Meng et al, 2011;Yu et al, 2014;Xie et al, 2016) and thereby exert an important influence on the formation and the distribution of ozone (Ryu et al, 2013;Yu et al, 2014;Xie et al, 2016) as well as aerosols (Yu et al, 2014;Xie et al, 2016).…”

mentioning

confidence: 99%

“…Sometimes, the fluxes might exceed the value of 100 W m −2 (Iamarino et al, 2012;Quah and Roth, 2012;Lu et al, 2016;Xie et al, 2016), with the extreme value of 1590 W m −2 in the densest part of Tokyo at the peak of air-conditioning demand (Ichinose et al, 1999). With regard to their effects, the researchers found that AH fluxes can cause urban air temperatures to increase by several degrees (Fan and Sailor, 2005;Ferguson and Woodbury, 2007;Zhu et al, 2010;Feng et al, 2012Feng et al, , 2014Menberg et al, 2013;Wu and Yang, 2013;Bohnenstengel et al, 2014;Chen et al, , 2014aYu et al, 2014;Xie et al, 2016), induce the atmosphere to be more turbulent and unstable, change the urban heat island circulation, strengthen vertical air movement (Ichinose et al, 1999;Block et al, 2004;Fan and Sailor, 2005;Feng et al, 2012Feng et al, , 2014Bohnenstengel et al, 2014;Yu et al, 2014;Xie et al, 2016), enhance the convergence of water vapor in cities, and change the regional precipitation patterns (Feng et al, 2012(Feng et al, , 2014Xie et al, 2016). In spite of meteorology conditions and air quality being inextricably linked, however, few investigations have paid attention to how the air quality is altered by the changes in regional meteorology induced by anthropogenic heat.…”

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confidence: 99%

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Changes in regional meteorology induced by anthropogenic heat and their impacts on air quality in South China

et al. 2016

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Abstract. Anthropogenic heat (AH) emissions from human activities can change the urban circulation and thereby affect the air pollution in and around cities. Based on statistic data, the spatial distribution of AH flux in South China is estimated. With the aid of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem), in which the AH parameterization is developed to incorporate the gridded AH emissions with temporal variation, simulations for January and July in 2014 are performed over South China. By analyzing the differences between the simulations with and without adding AH, the impact of AH on regional meteorology and air quality is quantified. The results show that the regional annual mean AH fluxes over South China are only 0.87 W m −2 , but the values for the urban areas of the Pearl River Delta (PRD) region can be close to 60 W m −2 . These AH emissions can significantly change the urban heat island and urban-breeze circulations in big cities. In the PRD city cluster, 2 m air temperature rises by 1.1 • in January and over 0.5 • in July, the planetary boundary layer height (PBLH) increases by 120 m in January and 90 m in July, 10 m wind speed is intensified to over 0.35 m s −1 in January and 0.3 m s −1 in July, and accumulative precipitation is enhanced by 20-40 % in July. These changes in meteorological conditions can significantly impact the spatial and vertical distributions of air pollutants. Due to the increases in PBLH, surface wind speed and upward vertical movement, the concentrations of primary air pollutants decrease near the surface and increase in the upper levels. But the vertical changes in O 3 concentrations show the different patterns in different seasons. The surface O 3 concentrations in big cities increase with maximum values of over 2.5 ppb in January, while O 3 is reduced at the lower layers and increases at the upper layers above some megacities in July. This phenomenon can be attributed to the fact that chemical effects can play a significant role in O 3 changes over South China in winter, while the vertical movement can be the dominant effect in some big cities in summer. Adding the gridded AH emissions can better describe the heterogeneous impacts of AH on regional meteorology and air quality, suggesting that more studies on AH should be carried out in climate and air quality assessments.

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Section: Changes In Surface Energy and Air Temperaturesupporting

confidence: 89%

mentioning

confidence: 99%

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confidence: 99%

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Changes in regional meteorology induced by anthropogenic heat and their impacts on air quality in South China

et al. 2016

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“…A spatial filtering method described by Wu and Yang (2013) is applied to isolate the heterogeneous climatic forcing of urbanization. More specifically, for each grid a spatial anomaly is defined as the departure from the average value over a region centered at each grid.…”

Section: Model Evaluationmentioning

confidence: 99%

“…It covers an area of 9.96 × 10 4 km 2 , with a total urban area of 4.19 × 10 3 km 2 . Observations have shown that the urban land-use expansion in this region has induced a remarkable warming due to the significant UHI effect (Du et al, 2006;Wu and Yang, 2013;Wang et al, 2015). The annual mean warming reached up to 0.16 • C/10 yr based on station measurements in large cities (Ren et al, 2008), which accounted for 47.1 % of the overall warming during the period of 1961-2000.…”

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confidence: 99%

Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta region of China

et al. 2017

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Abstract. The WRF-Chem model coupled with a singlelayer urban canopy model (UCM) is integrated for 5 years at convection-permitting scale to investigate the individual and combined impacts of urbanization-induced changes in land cover and pollutant emissions on regional climate in the Yangtze River Delta (YRD) region in eastern China. Simulations with the urbanization effects reasonably reproduced the observed features of temperature and precipitation in the YRD region. Urbanization over the YRD induces an urban heat island (UHI) effect, which increases the surface temperature by 0.53 • C in summer and increases the annual heat wave days at a rate of 3.7 d yr −1 in the major megacities in the YRD, accompanied by intensified heat stress. In winter, the near-surface air temperature increases by approximately 0.7 • C over commercial areas in the cities but decreases in the surrounding areas. Radiative effects of aerosols tend to cool the surface air by reducing net shortwave radiation at the surface. Compared to the more localized UHI effect, aerosol effects on solar radiation and temperature influence a much larger area, especially downwind of the city cluster in the YRD.Results also show that the UHI increases the frequency of extreme summer precipitation by strengthening the convergence and updrafts over urbanized areas in the afternoon, which favor the development of deep convection. In contrast, the radiative forcing of aerosols results in a surface cooling and upper-atmospheric heating, which enhances atmospheric stability and suppresses convection. The combined effects of the UHI and aerosols on precipitation depend on synoptic conditions. Two rainfall events under two typical but different synoptic weather patterns are further analyzed. It is shown that the impact of urban land cover and aerosols on precipitation is not only determined by their influence on local convergence but also modulated by large-scale weather systems. For the case with a strong synoptic forcing associated with stronger winds and larger spatial convergence, the UHI and aerosol effects are relatively weak. When the synoptic forcing is weak, however, the UHI and aerosol effects on local convergence dominate. This suggests that synoptic forcing plays a significant role in modulating the urbanization-induced land-cover and aerosol effects on individual rainfall event. Hence precipitation changes due to urbanization effects may offset each other under different synoptic conditions, resulting in little changes in mean precipitation at longer timescales.

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Seasonality in anthropogenic aerosol effects on East Asian climate simulated with CAM5

Jiang

Yang

Liu

2015

J. Geophys. Res. Atmos.

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This study investigates the seasonality in anthropogenic aerosol optical depth (AOD) distributions and their effects on clouds and precipitation in East Asia with the Community Atmospheric Model version 5. The differences between the model experiments with and without anthropogenic emissions exhibit a northward shift of the maximal AOD change in East Asia from March to July and then a southward withdrawal from September to November, which are induced by East Asian monsoon circulation. Associated with the shift, the direct and semidirect effects of the anthropogenic aerosols are the most pronounced in spring and summer, with a maximum center in North China during summer and a secondary center in South China during spring. The cloud liquid water path and shortwave cloud forcing changes, however, are the weakest in North China during summer. The indirect effect is the strongest in South China during spring, which is related to the large amount of middle-low level clouds in cold seasons in East China. A positive feedback between aerosol induced surface cooling and low-level cloud increase is identified in East China, which acts to enforce the aerosol indirect effect in spring. Accordingly, the climate response to the anthropogenic aerosols is also characterized by a northward shift of reduced precipitation from spring to summer, leading to a spring drought in South China and a summer drought in North China. The spring drought is attributed to both direct and indirect effects of the anthropogenic aerosols, while the summer drought is primarily determined by the aerosols' direct effect.

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Urbanization and heterogeneous surface warming in eastern China

Cited by 66 publications

References 35 publications

Changes in regional meteorology induced by anthropogenic heat and their impacts on air quality in South China

Changes in regional meteorology induced by anthropogenic heat and their impacts on air quality in South China

Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta region of China

Seasonality in anthropogenic aerosol effects on East Asian climate simulated with CAM5

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