Project Details
Projekt
Investigation of Convective Evolution towards stratiform Precipitation using simulatiOns and poLarimetric radar observations at C- and Ka-band (IcePolCKa - Phase 2)
Applicants
Dr. Florian Ewald; Dr. Tobias Zinner
Subject Area
Atmospheric Science
Term
since 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 408027579
Current weather models struggle to capture the spatial structure of precipitation created by convective cloud systems which biases the prediction of rainfall intensity and duration. This project aims to investigate how ice cloud microphysics influence the development of stratiform precipitation regions within convective cloud systems. To that end we propose to exploit the synergy of two polarimetric radars, the C-band POLDIRAD at DLR, Oberpfaffenhofen, and the Ka-band MIRA-35 at LMU, Munich to constrain hydrometeor properties in the convective- stratiform transition. On the one hand, we will shed new light on ice particle properties using an enhanced remote sensing technique. On the other hand, we will follow individual cell track motions using the operational DWD weather radar network to capture the temporal and horizontal evolution of cells. The spatial structure in the observed cases will be compared to high-resolution weather model runs (WRF) using different microphysics schemes. To advance the scientific understanding why most current models still overestimate radar reflectivity in convective regions and underestimate stratiform rainfall, we will consolidate our observational insights with the cell tracking perspective in model runs and operational DWD weather radar data. In phase 1 of this project, we have proven the feasibility of coordinated C- and Ka-band measurements at the two locations and developed an ice microphysics retrieval. We also developed an in-depth understanding of the remaining ambiguities and limitations which are connected to the unknown ice particle bulk density. We have performed WRF runs of the numerous observation days with five different microphysics schemes to analyze the variability of classical parameters (e.g. cell number, height and distribution of cell cores) between the schemes using a tracking approach. By extending our methods developed in Phase 1, we intend to capture previously unaccounted parameters like the ice particle density and the spatial structure of the convective and stratiform region at large. We aim to deepen the scientific understanding how microphysical processes like riming and aggregation modify hydrometeor properties which influence their detrainment from convective into stratiform regions. To this end, we plan to augment our existing retrieval with fall speed and linear depolarization measurements to further constrain hydrometeor properties. These time-height measurements will be systematically contextualized with the tracked cells in the DWD network data to compile an aggregated statistic of the convective to stratiform transition during 100 convective days. The analysis of cell characteristics will be extended to include surrounding stratiform precipitation regions to analyze the development and the interaction of related regions over time. This combination of the horizontal and vertical perspective will be a major novelty of our approach compared to previous studies.
DFG Programme
Priority Programmes
Co-Investigators
Dr. Silke Groß; Dr. Martin Hagen; Dr. Fabian Hoffmann; Professor Dr. Bernhard Mayer
