Recently, aerosol optical depth (AOD) study has become more important in the field of atmosphere sciences. AOD datasets retrieved from satellites are widely used in multiple fields because of their wide coverage and low cost. However, the integrity of AOD spatial coverage can be easily influenced by clouds, rain, haze and other weather phenomena. Fortunately, the full coverage AOD images are producible by employing the data fusion algorithm and ancillary methods. Based on AOD data derived from MODIS and OMI with meteorological parameters on November 18, 2013 over the East China, this study combined the universal kriging with stepwise regression and second-order polynomial fitted to extend the coverage of MODIS AOD at 550 nm. Results showed that stepwise regression method is efficient to infer the MODIS AOD by using the OMI AOD and meteorological parameters. The wind speed, relative humidity, pressure and solar radiation have significant impacts on the spatial and temporal distributions of AOD. The mean prediction error of universal kriging prediction model is 0.0047 in this paper, indicating that the universal kriging is an effective and accurate interpolation method for AOD data fusion. The methods employed in this paper can provide the data source of AOD for studies in climate and other related fields, effectively compensating the non-full coverage shortcoming of satellite AOD datasets.
Aerosol optical depth (AOD) is a key indicator of atmospheric environment. Aerosol remote sensing is the most efficient way to obtain the temporal and spatial distributions of AOD. In this paper, the data from Environment Satellite (HJ-1) CCD camera were employed to retrieve AOD by using deep blue algorithm over the Yangtze River Delta. The third band (in blue) was firstly extracted from the MODIS land surface reflectance product (MOD09) and then converted to the first band of CCD/HJ-1. According to the characteristics of the study area and CCD data, a multi-dimension look up table was then built by the Second Simulation of the Satellite Signal in the Solar Spectrum (6S). AOD over the Yangtze River Delta were finally retrieved from the radiance of the first band of CCD/HJ-1. After the retrieved AOD were validated by the MODIS AOD product (MOD04), the correlation coefficient (R) is 0.64 by regression of all cloud screened pixels (1147). The retrieved AOD has a higher spatial resolution than the MODIS AOD and thus can provide more detailed information. Compared with the AERONET ground observation data, the retrieved AOD is closer to the ground-based data than the MODIS AOD.
Recently, the air quality has been continuing to deteriorate and threaten public health in the Pearl River Delta. China, the host country for the 2010 Asian Games, faced the great challenge of air quality issues, particularly in the Pearl River Delta, where the Asian Games were held. The major aim of this study is to reveal the spatial and temporal characteristics of NO2 in the Pearl River Delta during October 2004 to December 2010. The long-term characteristics and variations of the NO2 column concentration before and during the 2010 Asian Games were analyzed by using the NO2 product OMNO2e from the Ozone Monitoring Instrument (OMI). Results show that the annual average of the NO2 column concentration has a significant downward trend from 2005 to 2010 in the Pearl River Delta: the total column concentration of NO2 (TotNO2) in the atmosphere decreased from 9.207×1015 molec/cm2 to 8.173×1015 molec/cm2, with an average annual rate of -2.247%; the tropospheric column concentration of NO2 (TropNO2)decreased from 6.685×1015 molec/cm2 to 5.646×1015 molec/cm2, with an average annual rate of -3.109%. The ratio TropNO2/TotNO2 indicating the amount of NO2 exhausted by human activities also decreased from 0.726 in 2005 to 0.691 in 2010. During the 2010 Asian Games, the weekly average of the TropNO2 in Pearl River Delta was maintained at a low level. The NO2 average distribution in the Pearl River Delta is characterized by the maximum in the geometric center, outwardly smaller, and the shrinking areas with high TropNO2 concentration from 2005 to 2010. Foshan, Jiangmen and Kwangchowan were severely polluted cities during the Games. However, the air quality of the Pearl River Delta was improved compared to its historical periods due to governmental preventive/control measures during the 2010 Asian Games.
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