Long-term Climatology of Vertical Profiles of Polarimetric Variables and Ice-microphysical Retrievals at X-band. Part II: Climatology

Abstract. This two-part paper series presents a climatology of quasi-vertical profiles (QVPs) of polarimetric radar variables and ice-microphysical retrievals, including ice water content, total number concentration, and mean volume diameter. The climatology characterizes stratiform clouds and precipitation events observed with an X-band radar in Bonn, western Germany, over the period 2013–2023. It aims to improve the understanding of the processes driving precipitation formation and to provide a reference to advance bulk microphysical parameterization schemes.

While part I focuses on the calibration of reflectivity (Z_H) and differential reflectivity (Z_DR), part II examines the climatology and statistical analysis. A detailed error analysis of various ice-microphysical retrievals demonstrates promising results, by combining the linear reflectivity difference (Z_dp) or the linear Z_DR with the linear Z_H and the specific differential phase (K_DP). The total number concentration (N_t) shows the largest remaining uncertainties among the ice-microphysical retrievals inspected. The dendritic growth layer (DGL) marks the onset of aggregation and exhibits enhanced particle concentrations during summer, likely linked to more favorable conditions for primary ice formation and secondary ice production. Aggregation and riming are identified as the dominant processes in the ice phase. They occur more frequently during summer and increase the melting layer (ML) thickness due to longer melt times. Annual-cycle-adjusted correlations suggest that inside the ML, on average, a balance between aggregation and breakup processes exists. However, during the summer season, stronger aggregation and/or accretion processes, as well as higher particle concentrations, are observed.