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

摘要

Anthropogenic heat (AH) emissions from human activities can change the urbancirculation and thereby affect the air pollution in and around cities. Basedon statistic data, the spatial distribution of AH flux in South China isestimated. With the aid of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem), in which the AHparameterization is developed to incorporate the gridded AH emissions withtemporal variation, simulations for January and July in 2014 areperformed over South China. By analyzing the differences between thesimulations with and without adding AH, the impact of AH on regionalmeteorology and air quality is quantified. The results show that theregional annual mean AH fluxes over South China are only0.87 W m, but the values for the urban areas of the PearlRiver Delta (PRD) region can be close to 60 W m. These AH emissionscan significantly change the urban heat island and urban-breeze circulationsin big cities. In the PRD city cluster, 2 m air temperature rises by1.1° in January and over 0.5° in July, the planetary boundarylayer height (PBLH) increases by 120 m in January and 90 m in July, 10 mwind speed is intensified to over 0.35 m s in January and0.3 m s in July, and accumulative precipitation is enhanced by20–40 % in July. These changes in meteorological conditions cansignificantly impact the spatial and vertical distributions of airpollutants. Due to the increases in PBLH, surface wind speed and upwardvertical movement, the concentrations of primary air pollutants decrease near the surface and increase in the upper levels. But the vertical changes in Oconcentrations show the different patterns in different seasons. The surfaceO concentrations in big cities increase with maximum values of over2.5 ppb in January, while O is reduced at the lower layers andincreases at the upper layers above some megacities in July. This phenomenoncan be attributed to the fact that chemical effects can play asignificant role in O changes over South China in winter, while thevertical movement can be the dominant effect in some big cities in summer.Adding the gridded AH emissions can better describe the heterogeneous impactsof AH on regional meteorology and air quality, suggesting that more studieson AH should be carried out in climate and air quality assessments.