Abstract
Abstract. Accurate, timely, and reliable precipitation observations are mandatory for hydrological forecast and early warning systems. In the case of convective precipitation, traditional rain gauge networks often miss precipitation maxima, due to density limitations and the high spatial variability of the rainfall field. Despite several limitations like attenuation or partial beam blocking, the use of C-band weather radar has become operational in most European weather services. Traditionally, weather-radar-based quantitative precipitation estimation (QPE) is derived from horizontal reflectivity data. Nevertheless, dual-polarization weather radar can overcome several shortcomings of the conventional horizontal-reflectivity-based estimation. As weather radar archives are growing, they are becoming increasingly important for climatological purposes in addition to operational use. For the first time, the present study analyses one of the longest datasets from fully operational polarimetric C-band weather radars; these are located in Estonia and Italy, in very different climate conditions and environments. The length of the datasets used in the study is 5 years for both Estonia and Italy. The study focuses on long-term observations of summertime precipitation and their quantitative estimations by polarimetric observations. From such derived QPEs, accumulations for 1 h, 24 h, and 1-month durations are calculated and compared with reference rain gauges to quantify uncertainties and evaluate performances. Overall, the radar products showed similar results in Estonia and Italy when compared to each other. The product where radar reflectivity and specific differential phase were combined based on a threshold exhibited the best agreement with gauge values in all accumulation periods. In both countries reflectivity-based rainfall QPE underestimated and specific differential-phase-based product overestimated gauge measurements.
Highlights
Detailed surface rainfall information is of great importance in many fields, for agricultural or hydrological applications
The main aim of this study is to evaluate the potential of using polarimetric weather radar quantitative precipitation estimation (QPE) on long-term warmseason datasets in various climatological environments
Radar QPE products are compared with singlelocation gauge measurements of selected short periods from Estonia and Italy
Summary
Detailed surface rainfall information is of great importance in many fields, for agricultural or hydrological applications. In the recent past the COST 717 Action entitled “Use of radar observations in hydrological and NWP models” investigated the assimilation of weather-radar-based precipitation in numerical weather prediction (NWP; Macpherson, 2004). Latent heat nudging was the most popular technique (Gregorcet al., 2000), while researchers have recently moved towards volume reflectivity assimilation techniques: for example, Schraff et al (2016) proposed the KENDA (ensemble Kalman filter for convective-scale data assimilation) operator to assimilate reflectivity volume data in the COSMO (COnsortium for Small-scale MOdelling) model. Gauge networks have provided the best reference datasets. The E-OBS 50-year daily European gridded interpolated dataset has been widely used in climatological studies (Cornes et al, 2018). Gauge-based datasets have well-known shortcomings in their low spatial resolution and to a lesser degree temporal resolution.
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