Main Results of Grossversuch IV

Radar-based hail detection

“…The weighting functions (Witt et al, 1998) assign weights to the values between 0°C and − 20°C for temperature and between 40 dBZ and 50 dBZ for reflectivity. The weighting function for reflectivity was used by Federer et al (1986) when calculating the flux of hail kinetic energy but with higher reflectivity threshold values of 55 and 65 dBZ. The SHI is primarily sensitive to high reflectivity values at temperatures near − 20°C or colder, where most hail growth occurs.…”

“…Witt et al (1998) noted that the default values cannot be treated as fixed. Because they are lower than those used by Federer et al (1986), we also tested values of 45 dBZ and 55 dBZ. POSH method: the Probability of Severe Hail (POSH) is determined from the SHI and the warning threshold value WT.…”

Weather Modification: Finding Common Ground

“…The evidence that hail suppression is effective is quite compelling (Mesinger and Mesinger 1992;Rudolph et al 1994;Smith et al 1997;Dessens 1998) (Renick 1975) in the 1970s and 1980s. In Switzerland the Grossversuch hail experiment was run for five years during this period and produced many research papers (Federer et al 1986;Lacaux et al 1985). can be modified by the specific demands exacted by prevailing conditions.…”

The Zurich Ice Nucleation Chamber (ZINC)-A New Instrument to Investigate Atmospheric Ice Formation

“…While there is now a good understanding of particle properties that affect CCN activation, there is still a lack of understanding as to which intrinsic properties of aerosol particles determine their ice nucleation capabilities (Szyrmer and Zawadzki 1997;Cantrell and Heymsfield 2005). While ice nucleation was studied intensely in the 1970s in the scope of weather modification programs (Bruintjes 1999;Federer et al 1986;Willoughby et al 1985), contem-porary interest focuses more on the climate impact of natural and anthropogenic ice nuclei through the so-called aerosol indirect effect. The indirect effect traditionally refers to an increase in cloud droplets due to anthropogenic aerosols (Baker 1997).…”