Abstract. In this study we compare measured and simulated O₄ absorptions for conditions of extremely low aerosol optical depth (between 0.034 to 0.056 at 360 nm) on one day during a ship cruise in the tropical Atlantic. For such conditions, the uncertainties related to imperfect knowledge of aerosol properties don't significantly affect the comparison results. We find that the simulations underestimate the measurements by 15 % to 20 %. Even for simulations without any aerosols the measured O₄ absorptions are still systematically higher than the simulation results. The observed discrepancies can not be explained by uncertainties of the measurements and simulations and thus indicate a fundamental inconsistency between simulations and measurements.

中文翻译：

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在热带大西洋上极低的气溶胶负荷下，一天中测量和模拟的O ₄吸收量的定量比较

摘要。在这项研究中，我们比较了在热带大西洋上航行的一天中，在极低的气溶胶光学深度（360 nm处介于0.034至0.056之间）的条件下测量和模拟的O ₄吸收。在这种情况下，与气溶胶特性知识不完善相关的不确定性不会显着影响比较结果。我们发现，模拟将测量值低估了15％至20％。即使对于没有任何气溶胶的模拟，测得的O ₄吸收值仍会系统地高于模拟结果。观测到的差异无法通过测量和模拟的不确定性来解释，因此表明了模拟和测量之间的根本矛盾。