Correlation between the spatio-temporal distributions of aerosols, sulphur dioxide, and formaldehyde using MODIS and SCIAMACHY satellite data for China

Abstract

The spatial and temporal relationship between fine-mode aerosol optical depth (AOD) observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) and tropospheric columns of SO₂ and formaldehyde (HCHO) from the Scanning Imaging Absorption Chartography (SCIAMACHY) are used to infer information on the variability of sulphate aerosol, which is a major determinant of fine-mode AOD (AOD_f) in east China. When averaging the satellite data over specific regions of China and for longer time periods (from 2005 to 2011), we find obvious similar trends between AOD_f and SO₂, HCHO columns for southern and eastern China. The results of satellite observations show the high spatial and temporal correlation between AOD_f and SO₂ over the Yangtze River Delta (R2), the Pearl River Delta (R3), and the Chongqing–Chengdu region (R4), with the coefficients of determination (R²) of 0.376, 0.438, and 0.837, respectively. These regions are performing with the huge amount of anthropogenic SO₂ emissions by traffic, industry, and domestic heating. The trend is consistent with fine-mode aerosol and SO₂ appearing in summer because AOD_f is often correlated with enhanced HCHO concentrations, reflecting the importance of secondary aerosol formation over industrialized regions in that season. Over the North China Plain, distinct maximum values of AOD_f and HCHO were observed and the minimum value for SO₂ was observed in summer. The decrease in the mean SO₂ column was 35.5%, which has been attributed to the strict security measures by the government during the 2008 Olympic Games period while there was a decrease of 46% in AOD_f at the same time. As sulphate aerosol occurs seasonally in the North China Plain, the strong correlation between anomalies of AOD_f and SO₂ can be used to estimate and analyse the distribution of sulphate aerosol. Singular value decomposition (SVD) analysis showed the same variation between AOD_f and SO₂ over eastern China and Sichuan Province, and a distinct negative value of SVD variables over comparably industrialized regions in southern and eastern China and Sichuan Province. The results for SO₄ from the Model for Ozone and Related chemical Tracers model for southern and eastern China and the Sichuan regions suggest much stronger sulphate contributions to aerosol formation than for other areas of China. We propose that the SVD variables between AOD_f and SO₂, which can be inferred from the satellite data, can be used as indicators for regional pollution control.

Additional information

Funding

Financial support for the study was provided by the NSF China Major Programme [41171324], the Funds for PhD Education [20110091110028], the fundamental research project of MOST [2005DKA32306], the National Key Project of Basic Research [2010CB4285003], the National NSF China [41101421], the Research Innovation Programme for College Graduates of Jiangsu Province [CXZZ110035], and the Programme B for Outstanding PhD candidate of Nanjing University [201301B011].