Characteristics of Convective Organizations in Radar Measurements

摘要

Previous studies suggested that organization of clouds in clusters can modify the mean state of the atmosphere. The increase in outgoing longwave radiation can result in a negative feedback on the surface temperature. This raised the question whether convective organizations can also impact the climate and how climate predictions are affected by the current negligence of such representation in the climate models. Since recent studies show diverging results regarding the question whether convective clouds have a tendency to organize in clusters, our goal in this study is to investigate how convection and precipitation cores organize in a typical mid latitude region. We identified and characterized convection in reflectivity fields of C-band radar composites for Germany every 30 minutes from April to September in the years 2014 and 2015. The identified objects are characterized by means of organization indices which provide information on the spatial arrangements, the number of objects, their shapes and the rainfall produced. The climatology of organization indices indicate some degree of organization in about 98 % of the time. In the remaining 2 % of the time the objects are either random or regularly arranged in space. Organized spatial arrangements presented a larger amount of rainfall than the random and the regular arrangements. This is associated with the fact that more precipitation cores prevail in organizations than in non-organized arrangements.