Zha, Y; Gao, J; Jiang, JJ; Lu, H; Huang, JZ (2012). Normalized difference haze index: a new spectral index for monitoring urban air pollution. INTERNATIONAL JOURNAL OF REMOTE SENSING, 33(1), 309-321.
Haze is an undesirable meteorological and environmental phenomenon that can cause enormous harm to the environment, people's lives and health, and economic activities. This study focuses on Nanjing, Yangzhou and Suzhou in the lower reaches of the Yangtze River valley, China, which have suffered from the adverse effects of hazy weather in recent years. The spectral influence of haze on surface features was determined through analysis of the spectral variations of surface covers between hazy and haze-free days. On the basis of the established relationship, a new index called the normalized difference haze index (NDHI) was derived using moderate resolution imaging spectroradiometer (MODIS) data from winter 2008-2009. Correlation analysis of the derived NDHI with in situ observed PM(10) (particulate matter with diameter < 10 mu m) data reveals that NDHI over water bodies has a coefficient of 0.74, 0.57 and 0.67 with PM(10) for Nanjing, Yangzhou and Suzhou, respectively. It is concluded that NDHI is a reliable indicator of air pollution. It can be used as a new method of effectively monitoring air pollution from remotely sensed data.