Photochemical hazes have been suggested as candidate for the high-altitude aerosols observed in the transmission spectra of many hot Jupiters. We present 3D simulations of the hot Jupiter HD 189733b to study how photochemical hazes are transported by atmospheric circulation. The model includes spherical, constant-size haze particles that gravitationally settle and are transported by the winds as passive tracers, with particle radii ranging from 1 nm to 1 $\mu$m. We identify two general types of haze distribution based on particle size: In the small-particle regime (<30 nm), gravitational settling is unimportant, and hazes accumulate in two large mid-latitude vortices centred on the nightside that extend across the morning terminator. Therefore, small hazes are more concentrated at the morning terminator than at the evening terminator. In the large-particle regime (>30 nm), hazes settle out quickly on the nightside, resulting in more hazes at the evening terminator. For small particles, terminator differences in haze mass mixing ratio and temperature considered individually can result in significant differences in the transit spectra of the terminators. When combining both effects for HD 189733b, however, they largely cancel out each other, resulting in very small terminator differences in the spectra. Transit spectra based on the GCM-derived haze distribution fail to reproduce the steep spectral slope at short wavelengths in the current transit observations of HD 189733b. Enhanced sub-grid scale mixing and/or optical properties of hazes differing from soot can explain the mismatch between the model and observations, although uncertainties in temperature and star spots may also contribute to the spectral slope.

中文翻译：

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热木星 HD 189733b 大气中光化学雾的 3D 模拟

在许多热木星的透射光谱中观察到的高海拔气溶胶被认为是光化学雾霾的候选者。我们展示了热木星 HD 189733b 的 3D 模拟，以研究大气环流如何传输光化学雾霾。该模型包括球形、大小恒定的雾霾颗粒，它们作为被动示踪剂在重力作用下沉降并被风输送，颗粒半径范围为 1 nm 到 1 $\mu$m。我们根据颗粒大小确定了两种一般类型的雾度分布：在小颗粒区域（<30 nm）中，重力沉降并不重要，雾度积聚在两个以夜间为中心的大中纬度漩涡中，并延伸到整个早晨终结者。因此，小雾霾更集中在早晨的终结者而不是晚上的终结者。在大颗粒状态（＞30 nm）中，雾霾在夜间迅速沉降，导致在夜间终止处产生更多的雾霾。对于小颗粒，单独考虑的雾度质量混合比和温度的终止剂差异会导致终止剂的传输光谱存在显着差异。然而，当结合 HD 189733b 的两种效应时，它们在很大程度上相互抵消，导致光谱中的终止子差异非常小。在 HD 189733b 目前的过境观测中，基于 GCM 衍生的雾度分布的过境光谱无法再现短波长处的陡峭光谱斜率。增强的亚网格尺度混合和/或不同于烟灰的雾霾的光学特性可以解释模型和观察之间的不匹配，