  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 hazes particles that gravitationally settle and are transported
by the winds as passive tracers, with particle radii ranging from 1 nm to 300
$\mu$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 centered
on the night side 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 HD189733b, 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. Differing optical properties of
hazes, hotter temperatures at low pressures because of heating by hazes,
enhanced sub-grid-scale mixing, or star spots might explain the mismatch
between the model and observations.
