Testing six wet snow models by 30 years of observations in Bulgaria

Six simple wet snow accretion models are applied for simulations of well documented historical severe wet snow events in Bulgaria for the period 1969-1998. The data base consists of information about the diameters andmasses, and thereof about the densities, of wet snow depositions in cases of damages on power lines. These measurements were taken soon after each of the damage. For all cases is checked if the meteorological conditions correspond to the wet snow accretion criterion of Makkonen. The models used in this study are: the model of Admirat and Sakamoto (Admirat et al., 1986a,b, Admiratand Sakamoto, 1988a), the model of Finstad et al. (1988), two model suggestions of Sakamoto and Miura (1993), the model of Makkonen (1989) and its improvement (Makkonen and Wichura, 2010) and one with the latest suggestion for the sticking efficiency by Nygaard et al. (2013). The estimated density of the wet snow depositions varied between 700 and 400 kg/m³ and these measured values are used in the calculations instead of the experimental relationships proposed in some of the models. Working with known densities allows us to make conclusions for the approximations of the sticking efficiency and the snow concentration in air. The models are tested with two data sets – the original one consisting of standard three and six hourly synoptic measurements and its transformation into hourly values. The sensitivity of some of the models to the meteorological parameters is also demonstrated.