Differences in the Same OMI/MLS AuraTropospheric Ozone Data Set PublishedBefore and After January 2013

Abstract

On the website “NASA Goddard Homepage for Tropospheric Ozone”, global data of tropospheric
ozone obtained from observations of OMI and MLS Aura satellite instruments, are reported. In mid-2013, the
data was covering the period between October 2004 and January 2013. Subsequently, in early 2014, the time
series was extended until December 2013. At present time, the published series has been extended to
December 2014. Analysing this new series, we observed that the data already published to January 2013 had
been replaced; not only the missing months of 2013 were added but all the values published since 2004 were
recalculated. We present the detected differences in the comparison between common data to both time series
(the original, before January 2013, and the new one, currently published on the website). These differences are
important considering that they represent the result of the same satellite observation and should be considered
when comparing results before/after January 2013, especially when adopting a certain confidence level in the
spectral analysis of these data to intraseasonal scale. A warn of caution is suggested in the use of these
observations and intercomparison with other values of these and other instruments, because of possible
recurrent problems of instrumental calibration.