A near-sunset atmospheric sounding during the 14 October 2023 annular solar eclipse over Natal

Abstract. Solar eclipses are transient atmospheric events that cause rapid localized reduction in solar radiation, which produces complex changes associate with the vertical coupling of the layers. This study investigates the vertical response of the neutral atmosphere to the 14 October 2023 annular solar eclipse over Natal, Brazil (5.79° S, 35.2° W). This event presented a unique configuration as the maximum obscuration of ∼ 88.5 % occurred near sunset in a region of transition between land an ocean. A stratospheric balloon sounding launched immediately before the umbra reached Natal was used. The balloon collected atmospheric profiles (temperature, pressure, relative humidity, and ozone concentration) for over 1.45 hours, with the umbra passing over the balloon at ∼ 22.35 km altitude for 3 min and 36 s. Comparison with average October profiles and model data revealed significant vertical structures: (i) A notable cooling of 4–5 K was observed in the tropopause region (14 km altitude); (ii) Vertical fluctuations in temperature were enhanced, particularly above 14 km; (iii) atmospheric pressure decreased by 0.2–0.7 hPa above 12 km; (iv) ozone concentration showed strong vertical oscillation and an enhancement of up to 1 ppm above 20 km altitude; (v) relative humidity increased between 5 and 21 km altitude compared to control profiles. These observations of complex, small-scale fluctuations and clear responses in the vertical atmospheric field are consistent with previous reports and theoretical expectations of solar eclipse effects, confirming the importance of even an annular eclipse as a significant driver of localized atmospheric dynamics.