Magnitude and sign correlations in sunshine duration and diurnal temperature range records from the Sandanski weather station

In this paper we study correlation properties of the magnitude and sign of the increments of (a) diurnal temperature range (DTR) and (b) daily sunshine duration (SD) records from the Sandanski weather station. For both DTR and SD we find that the magnitude of the increments fluctuates randomly and is characterized by a value of the scaling exponent of about 0.5. Long-range temporal correlations in the fluctuations of DTR and SD are of linear character, contrary to the correlations in the temperature fluctuations in the same station and for the same period which are nonlinear. For the sign time series we find that the scaling behaviour is largely dominated by the annual periodicity for both cases of DTR and SD. The annual periodicity is most likely superimposed on random fluctuations.