Spatiotemporal trends in sunshine hours over India during three decades from 1988 to 2018

This study delves the trends of sunshine reaching the earth surface, both temporally and spatially, across nine geographically diverse regions including 20 stations in India, spanning the years 1988 to 2018. The monthly sunshine hours (SSH) analysis concluded significant increment from October to May followed by significant drops from June to July in six regions, except northern inland and Himalayan region that showed comparatively opposite monthly trends. The trend analysis depicted annual negative trend in all geographical regions with different rate (east coast: - 4.88 h/year; west coast: - 8.62 h/year; northern inland - 13.15 h/year; central inland: - 4.71 h/year; Deccan plateau: - 3.05 h/year; north eastern region: - 1.33 h/year; Himalayan region: - 9.47 h/year; island location Arabian Sea: - 5.72 h/year and Bay of Bengal - 6.10 h/year). Seasonal trends were found significant decline, but due to regional meteorological variation, accompanying Twomey effect may lead levelling off in SSH over north east region during monsoon and post-monsoon season. Analogous to annual SSH trend, intra-annual anomaly results were also depicting consistent decline in all geographical locations of India. The study reveals persistent decline of SSH in Indian subcontinent on all temporal scales excluding north eastern region where mild seasonal levelling off was found.