Planet Boundary Layer sulfur dioxide (PBL-SO<sub>2</sub>) derived from Ozone Monitoring Instrument (OMI) are compared with
in-situ measurements from Differential Optical Absorption Spectroscopy (DOAS) and gas analyzer observations at three
sites in Beijing (Jan-Dec, 2007) and Hebei province (Jan-May, 2007). We use an Air Mass Factor (AMF) lookup table,
which was calculated via Linearized Discrete Ordinate Radiative Transfer (LIDORT) model, to convert OMI PBL-SO<sub>2</sub>
slant column density to vertical column density. Co-locate Lidar (UV) aerosol extinction profiles are used to correct the
effect of aerosol. Results show that, AMF decreases less than 3% with the increasing solar zenith angle from 0° to 45°,
AMF is more sensitive to surface albedo and the viewing zenith angle. AMF reduces by 6% with the increasing Ozone density from 275DU to 325DU. Normally, absorption aerosol reduces AMF and scattering aerosol increases AMF, aerosol profiles are critical to AMF estimation. Under very clear conditions, from winter to later spring, OMI observed SO<sub>2</sub> values are underestimated by 3.6ppbv to 20ppbv, but in reasonable agreement with in-situ measurements. Because
of the effects of Sub-pixel cloud contamination, long slant path (higher solar zenith angles or viewing zenith angles),
differences in aerosol types and large Aerosol Optical Depth (AOD), direct comparisons between the OMI retrieval and
the in situ measurements show that the correlation is low and the differences vary with months, while averaging over half
a month can significantly reduces the bias.
Band division is an important basis in radiative calculations, and the configuration of band divisions for various research purposes directly influences the accuracy and speed of radiative transfer computations. We explore four band-division schemes and their impacts on computed radiative fluxes and cooling rates. We explain that discrepancies in solar radiation at the surface that exist between radiation models and observations under clear-sky conditions arise partly from ignoring minor gases and weak absorption bands for major gases.