The effects 9of inhomogeneous drop size distributions (DSDs) in a radar volume, vertical structure and spectral modes of DSDs

• Applicant: Dr. Gerhard Peters
• Subject Area: Atmospheric Science
• Term: from 2005 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5448365

MRR data obtained during a time period of several years will be analyzed, in order to answer basic questions raised in section 4 of the overview. The fine spatial resolution of the MRR data relative to weather radars as well as its disdrometer functionality with much finer temporal resolution as compared with conventional disdrometers allow to investigate the effects of instationarity and inhomogeneity of drop distributions on Z-R-relations in a quantitative sense. The height-resolved information provided by MRRs will be used to establish characteristics of height profiles of drop size distributions. These results provide a novel data base for relating radar observable reflectivity patterns, analyzed in other co-projects of this proposal, to the micro physical properties of precipitation. In addirion the data will help to validate advanced microphysical models. The MRR data will be also analyzed to obtain statistical data about frequency, intensity, height and extension of the bright band, in order to assess the general impact of this feature on radar-based QPE. In addition, case studies shall reveal how reliably and with which fidelity the bright band can be captured by weather radars in their operational mode. The analysis of vertical precipitation structure includes also the question, how often and with which intensity shallow precipitation occurs at the MRR sites; i.e. precipitation profiles with too small vertical extension to be detectable by weather radar. In a special experimental effort using arrays of MRRs we will attempt to track individual rain cells in order to observe the temporal development of drop size distributions within a rain cell. In addition, the transformation of drop size distributions on the fall path will be analyzed. These observations will provide a unique handle to assess the realism of spectral rain models and of their description of microphysical processes governing the formation of drop size distributions. This ambitious goal shall be achieved in a joint special observation period together with various synchronized auxiliary measurements as described in more detail in the work plan. In order to utilize the results for improved weather radar rainfall estimates, statistical or physically based relations will be searched between the finescale MRR observations and characteristic pattern features of simultaneously measured weather radar reflectivity fields, as analyzed in other AQUARADAR sub-projects.

• DFG Programme: Research Grants