Round-the-clock measurements of aerosol optical thickness over Antarctica made using a Dual Imager System during January-February 2017

Antarctica provides an opportunity to study natural forcing and background values of various constituents in the atmosphere, in particular, aerosols. In a recent effort during the 36th Indian Scientific Expedition to Antarctica (36th ISEA), a Dual Imager System was installed at Indian station Bharati (69.4 degrees S, 76.18 degrees E) to study round-the-clock variations of aerosol optical thickness (AOT). The data reveal a weak diurnal pattern in the AOT variability and the values vary from 0.07 to 0.10 during daytime while they reach0.12 during nighttime. The daytime (solar zenith angle <70 degrees) results compare well with collocated sun photometer as well as space based estimates, while the higher solar zenith angle (>70 degrees) AOT values are reported for the first time over Antarctica. The observed higher AOT values at higher zenith angles, i.e. during nighttime are suggested to be due to variations in wind speed and temperature.