Evaluation of variability in GOME-2 total water vapor and nitrogen dioxide columns associated with natural oscillations

Abstract This study presents the variability of total water vapor (H 2 O) and nitrogen dioxide (NO 2 ) columns associated with natural oscillations (QBO, ENSO, NAO), based on monthly GOME-2 Level-3 trace gas column data produced under the ACSAF project. The periods studied are 01/2007-12/2018 for GOME-2A, 01/2013-05/2025 for GOME-2B and 01/2019-05/2025 for GOME-2C. The QBO-type periodicity in total NO 2 is strongest in the tropics with a measurable amplitude of a few percent. Going from low to mid-latitudes, there is a phase shift in the QBO impact seen in total NO 2 . Variability of total H 2 O is not significantly correlated with the QBO. The effects of ENSO on total H 2 O are clearly seen in the tropics, while the effect of NAO is evident in the northern midlatitudes. Variability in total H 2 O from GOME-2 in regions affected by ENSO and NAO is compared with that from CAMS reanalysis and ECHAM/MESSy Atmospheric Chemistry (EMAC) model results, and good agreement is found between the datasets. Overall, our results show that the total column NO 2 and H 2 O data from GOME-2 capture well the variability associated with large-scale natural fluctuations in the recent past, supporting that QBO/ENSO/NAO–tracer correlations can serve as a diagnostic tool for model and reanalysis evaluations. This provides confidence that data from the newer versions of the GOME-2 instrument (GOME-2B, GOME-2C) can be quite useful for monitoring the response of NO 2 and H 2 O to potential anomalies in the QBO/ENSO/NAO signals in the near future and can significantly help in evaluating the representation of these natural cycles in climate model simulations of trace gases in the coming years.