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

• Published in: Journal of atmospheric and solar-terrestrial physics 2012-05, Vol.80, p.60-67
• Main Authors: Bhat, G.S., Jagannathan, R.
• Format: Article
• Language: English
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Physics of the ionosphere; Physics of the magnetosphere; Solar eclipse; Subsidence drying; Surface layer; Water vapor budget
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2012.02.025

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 2gkg−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. ► Changes observed during the annular solar eclipse of 15 January 2010 are reported. ► Around the annular phase, the skin temperature decreased by 7°C. ► The most remarkable change is observed in water vapor field. ► The lowest relative humidity during 10 day period is associated with the eclipse. ► The drying up of the surface layer is owing to enhanced subsidence.