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 (H2O) and nitrogen dioxide (NO2) 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 NO2 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 NO2. Variability of total H2O is not significantly correlated with the QBO. The effects of ENSO on total H2O are clearly seen in the tropics, while the effect of NAO is evident in the northern midlatitudes. Variability in total H2O 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 NO2 and H2O 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 NO2 and H2O 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.