The influence of meteorological parameters and atmospheric pollutants on lightning, rainfall, and normalized difference vegetation index in the Indo-Gangetic Plain

Variation of lightning flash distribution, rain, and normalized difference vegetation index (NDVI) and their dependency on meteorological parameters were studied along the Indo-Gangetic Plain from 21°N to 35°N, dividing it into four regions of equal area (R ₁, R ₂, R ₃ and R ₄). Time series and correlation analysis were used to study the variations and relations among the parameters. Maximum lightning flashes were observed in region R ₁ where rain, surface temperature, convective available potential energy (CAPE), cloud cover, water vapour, and NDVI were found to be minimum. Lightning flashes and rain are positively correlated with surface temperature, CAPE, and aerosol optical depth (AOD), on both an annual and seasonal basis, over the whole region. Seasonal variation in NDVI showed a double-peak distribution, which can be understood by considering its dependence on water vapour, soil moisture, accumulated rain and surface temperature, and their variation from season to season and region to region. The effects of the atmospheric pollutants (AOD, carbon dioxide (CO ₂), nitrogen dioxide (NO ₂), and ozone (O ₃)) on NDVI showed a mixed response. A small variation in atmospheric CO ₂ showed no statistically significant impact in any season or region. AOD had a negative effect in general except that a small positive tendency was observed in R ₃ and R ₄ during summer months. NO ₂ showed a negative impact in all regions and seasons. O ₃ had a negative effect in R ₃ and R ₄ during the monsoon months and in R ₂–R ₄ during the summer months, and a positive effect in the other regions and seasons. When all four regions are merged, correlation analysis on an annual basis showed that the effects in localized regions are lost and the impact from the larger area predominates. To understand the regional localized effect, analysis of the smaller regions seems to be important.