Nowcasting Hailsizes

Figure 1 shows an range-height-indicator (RHI) of reflectivity (top panel) and cross-correlation coefficient (bottom panel) through a hail cell, observed by the BoXpol on 5 July 2015. Values of very strong reflectivity (>55dBZ) are observed up to heights of 10km. These coincide with relatively low values of correlation coefficient (0.8 to 0.9) suggesting the presence of large hail. Large hail was reported on this day around Bonn. During this day large hailstones of around 5cm in diameter have been observed in Bonn (Figure 2)
Within the extramural research program funded by the German Weather Service (DWD) an extension of standard hydrometeor classification schemes is planned, which includes a more detailed hail-size discrimination (small, moderate, giant hail stones). A reliable distinction between harmless and threatening hail sizes is key for nowcasting applications.

Figure 1: Genuine RHI (vertical cross section) measured with our polarimetric X-band radar (BoXPol) on 5 July 2015 during an intense hail storm with large hail stones. The variables shown are horizontal reflectivity Z_{H} (top panel) and cross-correlation coefficient ρ_{HV} (bottom panel).
ASCII���Hisilicon K3
Figure 2: Photographs taken in Bonn-Dottendorf on 5 July 2015 during an intense hail storm. Courtesy of Kai Mühlbauer.

radar/nowcasting_hailsizes.txt · Zuletzt geändert: 2016/05/05 17:20 von silke