Atmospheric boundary layer response sequence to the 2019 annular solar eclipse over a tropical rural terrain

Abstract

ABSTRACT Transient alterations in the surface meteorological parameters and atmospheric boundary layer (ABL) due to annual solar eclipse occurred on 26 December 2019 have been investigated using collocated ground-based remote-sensing and in situ measurements over a tropical rural station, Gadanki (13.5 ºN, 79.2 ºE). This event had provided an opportunity to assess the eclipse effect on atmospheric parameters as it occurred during initial hours of the boundary layer evolution (between 08:07 IST and 11:15 IST with peak at 09:32 IST over Gadanki). As eclipse commenced, the observations showed a dramatic reduction in the incoming shortwave radiation and consequent changes in air temperature and wind patterns throughout the ABL. Nevertheless, the amplitude of the changes in various parameters is not analogous to the obscuration proportions but is significantly dictated by the background meteorological conditions such as prevalence of dense fog and cloudiness during the eclipse timings. Ceilometer and wind profiler observations have provided the high-resolution continuous signatures of clouds and fog, strong subsidence, thick layers above the ABL, and a clear change in ABL height (ABLH) during the eclipse epoch. Interestingly, the delay in the evolution of ABL due to the eclipse is clearly manifested. The ABLH, which remained shallow even after the eclipse peak, has shown a rapid increase by more than 1000 m within a short span of an hour just before and after the eclipse culmination. However, significant delay (of about 2 hours after the eclipse) is observed in the surface variables to fall in the range of their climatological values. The observations elusively suggest that commence and termination phases of eclipse analogously influenced the surface and boundary layer parameters in descending sequence (eclipse effect is subtly seen first in Ceilometer and wind profiler attributes followed by surface state variables).