  Sunspot drawings are provided on a regular basis at the Kanzelhoehe Solar
Observatory, Austria, and the derived relative sunspot numbers are reported to
the Sunspot Index Data Center in Brussels. From the daily sunspot drawings, we
derived the northern, R_n, and southern, R_s, relative sunspot numbers for the
time span 1975-2000. In order to accord with the International Sunspot Numbers
R_i, the R_n and R_s have been normalized to the R_i, which ensures that the
relation R_n + R_s = R_i is fulfilled. For validation, the derived R_n and R_s
are compared to the international northern and southern relative sunspot
numbers, which are available from 1992. The regression analysis performed for
the period 1992-2000 reveals good agreement with the International hemispheric
Sunspot Numbers. The monthly mean and the smoothed monthly mean hemispheric
Sunspot Numbers are compiled into a catalogue. Based on the derived hemispheric
Sunspot Numbers, we study the significance of N-S asymmetries and the
rotational behavior separately for both hemispheres. We obtain that about 60%
of the monthly N-S asymmetries are significant at a 95% level, whereas the
relative contributions of the northern and southern hemisphere are different
for different cycles. From the analysis of power spectra and autocorrelation
functions, we derive a rigid rotation with about 27 days for the northern
hemisphere, which can be followed for up to 15 periods. Contrary to that, the
southern hemisphere reveals a dominant period of about 28 days, whereas the
autocorrelation is strongly attenuated after 3 periods. These findings suggest
that the activity of the northern hemisphere is dominated by an active zone,
whereas the southern activity is mainly dominated by individual long-lived
sunspot groups.
