Abstract
Abstract. The study examined the spatio-temporal variability, validation and climatological trend of MODIS Terra and Aqua level-2 Dark Target retrieval algorithms 3-km AOD over India region during 2001–2017. Analysis reveal the MODIS AOD shows significant variability in spatial extent; Indo-Gangetic plane having high aerosol loading and Southern peninsula shows relatively low aerosol loading in all seasons. The climatological zonal averaged (throughout India) AOD500 are 0.401 ± 0.23 and 0.324 ± 0.64 for Terra and Aqua respectively whereas the ground measured all stations averaged AOD500 is 0.43 ± 1.2 during study period. For validation we obtained daily AOD data from nine ground network stations across India. MODIS 3-km AOD shows good agreement with ground measurements. A total of 5646 and 4920 data points are utilized for validation of MODIS Terra and Aqua AODs respectively and the overall correlation coefficients and RMSE values are 0.94 & 0.08 and 0.72 & 0.17 for Terra and Aqua over the Indian region. However, during monsoon season, both the MODIS AODs are highly overestimated because of atmospheric noise and turbidity. Trend slopes and significances were calculated using Mann-Kendell test at nine selected stations and whole region. AOD shows a significant positive trend (99.9% confidence level) over India with an increasing rate of 2.35 yr−1 and 2.03 yr−1 for Terra and Aqua respectively. All stations annual AODs shows the increasing trend with different significance levels except Patiala. This study reveals the potential applications of the 3-km AOD product in aerosol climatology over Indian region.
Highlights
The knowledge of spatial and temporal distribution of aerosols on regional scale is essential to understand the dynamics of aerosol and its associated effects on regional and global climatic conditions (Morel et al 2018)
The present study aims to develop an integrated picture of the spatial and temporal distribution of aerosol loading over the Indian region based on ModerateResolution Imaging Spectroradiometer (MODIS) Terra and Aqua Dark Target (DT) algorithm 3-km Aerosol optical depth (AOD) data for a period of 17 years and evaluate the accuracy and feasibility of MODIS aerosol products with ground based network (ARFINET, AERONET & SKYRADNET) datasets
As observed from figure 2, during winter both MODIS Aqua and Terra (AOD550nm) show high aerosol loading over northern India, over Central and eastern Indo Gangetic Plain (IGP) (AOD from 0.5 to 0.7) because of cold surface conditions coupled with the abundance of cold air, which produces dense fog, mist, and haze, through condensation of water vapor on carbonaceous aerosols
Summary
The knowledge of spatial and temporal distribution of aerosols on regional scale is essential to understand the dynamics of aerosol and its associated effects on regional and global climatic conditions (Morel et al 2018). The observations of aerosols is geographically limited, and their impacts on climate changes still remain uncertain (IPCC 2013) In this context, satellite remote sensing has the advantage of generating spatial and temporal distribution of aerosol optical properties. The present study aims to develop an integrated picture of the spatial and temporal distribution of aerosol loading over the Indian region based on MODIS Terra and Aqua Dark Target (DT) algorithm 3-km AOD data for a period of 17 years and evaluate the accuracy and feasibility of MODIS aerosol products with ground based network (ARFINET, AERONET & SKYRADNET) datasets. The daily-averaged Level 2.0 AOD products (final cloud-screened and quality assured products) are taken from five AERONET stations i.e., Jaipur (26.90 N, 75.80 E), New Delhi (28.63 N, 77.17 E), Nainital (29.35 N, 79.45 E), Kanpur (26.51 N, 80.23 E) and Gandhi College (25.87 N, 84.12 E)
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