Problems regarding the tropospheric O3 residual method and its interpretation in Fishman et al. (2003)
Other literature type
Laat, A. D. J.
(issn: 1680-7324, eissn: 1680-7324)
In this article we will show that the Total Ozone Residuals (TOR) method as presented
by Fishman et al. (2003) contains an erroneous assumption, due to which the TOR as
presented in this article reflects mainly a tropospheric O<sub>3</sub> climatology (Logan, 1999),
scaled to the layer between the surface and the tropopause height, rather than a satellite
measured TOR. We will show that it is possible to obtain a tropospheric O<sub>3</sub>
column that is very similar to what is being presented in Fishman et al.
(2003), solely based on the Logan (1999) tropospheric O<sub>3</sub> climatology and an estimate for the tropopause heights
without using satellite data. Furthermore, we will show that one of the interpretations of
observed O<sub>3</sub> variability (high TOR values over Southeast Asia) is not the result of
pollution, but primarily of tropopause height variations. We suggest adjusting the method
in such a way that the final retrieved TOR product becomes independent of the actual
values of the Logan (1999) O<sub>3</sub> climatology. The proposed adjustments are also more in
line with the original methodology suggested by Fishman and Balok (1999) in a previous
paper. We furthermore show that the assumption that the stratospheric O<sub>3</sub>
column is nearly constant within a 5-day period is not always valid. This can introduce errors in the
final TOR product, although we recognize that these errors may become small when
averaging the TOR product over longer periods of time. However, we feel that a detailed
study on this assumption is also needed.