Beschreibung:
<jats:p>Measured and modeled stratospheric filter sensitivity weighted ultraviolet/visible (UV/vis) actinic fluxes—approximating the NO<jats:sub>2</jats:sub> photolysis rate coefficients <jats:sup>(j</jats:sup>NO<jats:sub>2</jats:sub>)— are compared. The measurements were performed with two calibrated 2π‐actinometers assembled on the azimuth angle‐controlled LPMA/DOAS (Laboratoire de Physique Moléculaire et Applications/Differential Optical Absorption Spectroscopy) gondola during a series of balloon flights. Since the actinometer's spectral sensitivity curve did not exactly match the actinic spectrum of NO<jats:sub>2</jats:sub> and the skylight's spectrum shape changes with atmospheric height and solar illumination, only proxies (proxy‐<jats:sup>)j</jats:sup>NO<jats:sub>2</jats:sub> rather than true <jats:sup>j</jats:sup>NO<jats:sub>2</jats:sub> values were monitored during balloon ascents (0–30 km) for solar zenith angle (SZA) 75° < SZA < 86°, and at balloon float altitude during solar occultation (86° < SZA < 95°). The measured direct and diffuse total proxy<jats:sup>‐j</jats:sup>NO<jats:sub>2</jats:sub> values compare excellently with radiative transfer (RT) modeling. That finding allows us to rule out uncertainties in computing UV/vis actinic fluxes as a significant factor in the still insufficient modeling of stratospheric NO<jats:sub>2</jats:sub> at large SZAs.</jats:p>