The total solar eclipse of December 14, 2020 in southern South America and its effects on atmospheric variables

• Published in: Quarterly journal of the Royal Meteorological Society Vol. 147; no. 737; pp. 2547 - 2561
• Main Authors: Piscitelli, Franco M., Saurral, Ramiro I.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-04-2021; Wiley Subscription Services, Inc
• Subjects: Advection; Air temperature; Cloud cover; Cloudiness; Cold front; cold‐air advection; incoming solar radiation; Radiation; radiative cooling; Solar eclipses; Solar radiation; Surface temperature; Surface wind; Temperature effects; Temperature variations; total solar eclipse; Weather; Weather conditions; Winds; South America
• ISSN: 0035-9009; 1477-870X
• DOI: 10.1002/qj.4040

A total solar eclipse affected southern South America on December 14, 2020. Its occurrence close to the summer solstice in the Southern Hemisphere and around noon brought almost ideal conditions to study the effects of the sudden reduction in incoming solar radiation on different atmospheric variables. Interestingly, the astronomical phenomenon moved over a region that at that time was being affected by a cold front accompanied by significant cloudiness and cold air advection to the area. Therefore, the actual drop in surface temperature over the umbra region resulted from a combination of the radiative effect (i.e., the reduction in solar radiation due to the eclipse itself) and a circulation effect related to the injection of colder air. A quantification of both effects on the full temperature variation is provided, along with a discussion on the underlying mechanisms and the related effects on surface winds derived from the cooling. Results show that temperature drops associated with total solar eclipses in areas far away from the umbra can be as high as (or even higher than) those within the umbra, depending on the prevailing weather conditions.
A total solar eclipse affected South America on December 14, 2020. The phenomenon occurred over a region that was being affected by a cold front with significant temperature advection and cloudiness. The drop in surface temperature over the umbra region was a combination of the radiative and advective effects. Results show that temperature drops associated with solar eclipses in areas far away from the umbra can be as high as (or even higher than) those within the umbra, depending on the prevailing weather conditions.