The use of QBO, ENSO, and NAO perturbations in the evaluation of GOME-2 MetOp A total ozone measurements
Authors: Eleftheratos Kostas , Zerefos Christos S. , Balis Dimitris S. , Koukouli Maria-Elissavet , Kapsomenakis John , Loyola Diego G. , Valks Pieter , Coldewey-Egbers Melanie , Lerot Christophe , Frith Stacey M. , Haslerud Amund S. , Isaksen Ivar S. A. , Hassinen Seppo 
Published: February 2019

Abstract. In this work we present evidence that quasi-cyclical perturbations in total
ozone (quasi-biennial oscillation – QBO, El Niño–Southern Oscillation –
ENSO, and North Atlantic Oscillation – NAO) can be used as independent proxies in
evaluating Global Ozone Monitoring Experiment (GOME) 2 aboard MetOp A
(GOME-2A)
satellite total ozone data, using ground-based (GB) measurements, other satellite
data, and chemical transport model calculations. The analysis is performed in
the frame of the validation strategy on longer time scales within the
European Organisation for the Exploitation of Meteorological Satellites
(EUMETSAT) Satellite Application Facility on Atmospheric Composition
Monitoring (AC SAF) project, covering the period 2007–2016. Comparison of
GOME-2A total ozone with ground observations shows mean differences of about
-0.7±1.4 % in the tropics (0–30∘), about +0.1±2.1 % in the mid-latitudes (30–60∘), and about +2.5±3.2 % and
0.0±4.3 % over the northern and southern high latitudes (60–80∘), respectively. In general, we find that GOME-2A total ozone data depict
the QBO–ENSO–NAO
natural fluctuations in concurrence with the co-located solar
backscatter ultraviolet radiometer (SBUV), GOME-type Total Ozone Essential
Climate Variable (GTO-ECV; composed of total ozone observations from GOME, SCIAMACHY – SCanning Imaging Absorption
SpectroMeter for Atmospheric CHartographY, GOME-2A, and OMI – ozone
monitoring instrument, combined into one homogeneous time series), and
ground-based observations. Total ozone from GOME-2A is well correlated
with the QBO (highest correlation in the tropics of +0.8) in agreement with
SBUV, GTO-ECV, and GB data which also give the highest correlation in the
tropics. The differences between deseazonalized GOME-2A and GB total ozone in
the tropics are within ±1 %. These differences were tested further
as to their correlations with the QBO. The differences had practically no QBO
signal, providing an independent test of the stability of the long-term
variability of the satellite data. Correlations between GOME-2A total ozone
and the Southern Oscillation Index (SOI) were studied over the tropical
Pacific Ocean after removing seasonal, QBO, and solar-cycle-related
variability. Correlations between ozone and the SOI are on the order of +0.5,
consistent with SBUV and GB observations. Differences between GOME-2A and GB
measurements at the station of Samoa (American Samoa; 14.25∘ S,
170.6∘ W) are within ±1.9 %. We also studied the impact of the NAO
on total ozone in the northern mid-latitudes in winter. We find very good
agreement between GOME-2A and GB observations over Canada and Europe as to
their NAO-related variability, with mean differences reaching the ±1 % levels. The agreement and small differences which were found between
the independently produced total ozone datasets as to the influence of the QBO, ENSO, and NAO show the importance of these climatological proxies as
additional tool for monitoring the long-term stability of satellite–ground-truth
biases.