Dependence of Umkehr Ozone Profile Retrieval From Model of Light Scattering
Abstract
Umkehr measurements at networks of Dobson and Brewer spectrophotometers are source for determination of ozone vertical distributions. Standard Umkehr retrieval algorithm uses approximative scheme to account multiple scattering of light. A mul- tiple scattering correction is subtracted from measured intensities, but the standard algorithm uses weighting functions calculated for single scattering. Authors proposed earlier a new extended Umkehr algorithm for Brewer instrument to overcome some shortage of the standard one. For second stage of its modernization they developed a radiative transfer model, called MCC++, which take into account multiple scatter- ing. MCC++ code implement Monte Carlo method of conjugate walk for spherical atmosphere. MCC++ model is used in the extended Umkehr algorithm of stage 2 to calculate both intensities and weighting function. Authors compare accuracy of retrieval, which take into account only single scattering, with retrieval based on all orders of scattering for calculation of weighting functions. Intensity is calculated for multiple scattering in both cases. It is shown that more accurate radiative transfer model (with multiple scattering) gives better result not only bellow 15-20 km, where multiple scattering is significant, but at all altitudes, as well as for estimation of total ozone content. The extended Umkehr algorithm is more sensitive to radiative transfer model in comparison with standard one. However, when model with multiple scattering is used, errors of extended algorithm are less then errors of standard algorithm. Moreover the extended algorithm reduces errors by a factor of 1.5-2 below 20 km.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.2068P