Diploma Thesis: Developing mechanism of convergence linesMarkus Übel and Andreas Bott
A convergence line is an aligned area of a convergent wind field near the surface without a discontinuity in temperature which leads to rising air masses, convective cloud formation and precipitation. Especially in summer convergence lines are often observed in the warm air or the warm sector and primarily in the leading area of cold fronts. These convergence lines induce fronts of severe thunderstorms orientated at this line with heavy rain, large hail and destructive gust fronts. But also in winter convergence lines exist in the cold air region behind frontal cloud bands and initiate bands of snow or graupel showers.
In this diploma thesis the dynamic and thermodynamic mechanisms which force the convergence lines of the warm air case in summer will be investigated by studying series of convergence lines under synoptic considerations. After that case studies of actual convergence lines will be performed with the COSMO model of the German Weather Service in order to better understand the different processes which are responsible of forming convergence lines. To compare the model simulations with synoptic measurements, the model output will be verified with various products of the NinJo system, an excellent program of visualizing meteorological data.