  Up to now, only a very small number of dwarf novae have been studied during
their outburst state (~30 per cent in the Northern hemisphere). In this paper
we present the first comprehensive atlas of outburst spectra of dwarf novae. We
study possible correlations between the emission and absorption lines seen in
the spectra and some fundamental parameters of the binaries. We find that out
of the 48 spectra presented, 12 systems apart from IP Peg show strong HeII in
emission: SS Aur, HL CMa, TU Crt, EM Cyg, SS Cyg, EX Dra, U Gem, HX Peg, GK
Per, KT Per, V893 Sco, IY UMa, and 7 others less prominently: FO And, V542 Cyg,
BI Ori, TY Psc, VZ Pyx, ER UMa, and SS UMi. We conclude that these systems are
good targets for finding spiral structure in their accretion discs during
outburst if models of Smak (2001) and Ogilvie (2001) are correct. This is
confirmed by the fact that hints of spiral asymmetries have already been found
in the discs of SS Cyg, EX Dra and U Gem.
