Abstract
Given the dynamics of the atmosphere, the ozone hole is accompanied by
episodes of exchange between the polar vortex and the mid-latitudes and
the tropics (Bencherif et al., 2007). During these events, the polar
vortex is deformed and ozone-poor polar air-masses move towards the
tropics. We call these episodes of isentropic exchanges “Ozone
Secondary Effects” (OSE), and several events have been observed during
the last decade. For example, an event observed on October 14, 2012
reached the south of Brazil (Peres et al., 2017), causing 13.7%
reduction in the total columns of ozone. Recently, Bresciani et al.
(2018) reported on a major OSE event (23% reduction in TCO) and its
influence in southern Brazil and Uruguay that occurred in October 2016.
Such OSE episodes may last up to 3 weeks, causing a potential increasing
in the UV radiation levels leading to public health issues as well as
impacts on the fauna and flora, with notable risks for the biodiversity
and the agriculture. In the present study, we investigate the use of
Long Short-Term Memory recurrent neural networks to forecast OSE events,
more specifically the Causal LSTM model proposed by Wang et al. (2018),
which has been successfully applied to the analysis of video images. In
our study, however, the input data is composed by historical data for
the total column of ozone (TCO), obtained by satellites. We aim at using
the resulting forecasts to detect, monitor and classify OSE events by
isentropic levels, latitudinal bands and geographical areas. We believe
that these results can be integrated into a weather forecast workflow to
improve the accuracy of existing models. Further experiments include the
conjoint analysis of other atmospheric markers such as the potential
vorticity (PV). Together with auxiliary parameters such as cloud
fraction, aerosol optical depth, nebulosity and altitude, these
forecasts could be used to produce realistic UV-Index estimations.