Moisture depletion in the surface layer in response to an annular solar eclipse

Abstract

Eclipse provides a rare occasion to study the interactions between radiation, land and atmosphere under a solar forcing distinctly different from normal conditions. An opportunity came during the annular solar eclipse of 15 January 2010, the longest annular eclipse of the millennium where parts of India experienced up to 92% obscurity in early afternoon hours. Detailed measurements were carried out in the surface layer during 8–18 January at a land station located close to the central line of the eclipse. The focus of this study is on the effect of the annular eclipse on water vapor concentration, an aspect neglected in the past studies. During the entire 11-day study period, the lowest value in relative humidity occurred towards the end of the eclipse. Specific humidity decreased by 2 g kg−1 during the eclipse and continued to decrease for few more hours. It recovered to the pre-eclipse values in the following afternoon. Humidity decrease is attributed to increased subsidence of drier air during and after the eclipse.