Trace pollutant fluctuations observed in Calicut city, India, during the annular solar eclipse on 26 December 2019

Özet

Atmospheric boundary layer perturbations were monitored during an annular solar eclipse event on December26, 2019 to understand its impact on the meteorological parameters (temperature, relative humidity, windspeed, and wind direction) and trace gas concentrations (O3, NO, NO2, NH3, CO, and HONO) at Calicut (11.24°N, 75.78° E), a tropical city along the coastal belt of Arabian Sea in the southwest coast of Indian Subcontinent.The solar eclipse started at 8:05 IST (5.5 h ahead of UTC), reached to a maximum coverage of 93.28% at 09:27IST and ends at 11:07 IST. Eclipse day data were compared with the nearby days' records from this site. Therapid fall in the irradiance caused cooling of the surface air by ~0.7 °C and weakened the wind speed, whereasthe relative humidity, as expected, was increased by 5.1%. A gradual decrease in the surface O3 along with thereduction in solar irradiance was observed during the eclipse, due to the decreased efficiency in the photochemical formation of ozone. There was a decrease in mixing ratios of NO2 during the eclipse period, which wasa result of the fall in ozone concentrations. No significant variation was observed in HONO levels, whereasvariations in concentrations of NO and NH3 have followed the night time chemistry. The NO3 radical mixingratios were below the detection limit during the eclipse event.