Comparing Rain Gauge and Weather RaDAR Data in the Estimation of the Pluviometric Inflow from the Apennine Ridge to the Adriatic Coast (Abruzzo Region, Central Italy)

Abstract

Accurate knowledge of the rain amount is a crucial driver in several hydrometeorological applications. This is especially true in complex orography territories, which are typically impervious, thus, leaving most mountain areas ungauged. Due to their spatial and temporal coverage, weather radars can potentially overcome such an issue. However, weather radar, if not accurately processed, can suffer from several limitations (e.g., beam blocking, altitude of the observation, path attenuation, and indirectness of the measurement) that can hamper the reliability of the rain estimates performed. In this study, a comparison between rain gauge and weather radar retrievals is performed in the target area of the Abruzzo region in Italy, which is characterized by a heterogeneous orography ranging from the seaside to Apennine ridge. Consequently, the Abruzzo region has an inhomogeneous distribution of the rain gauges, with station density decreasing with the altitude reaching approximately 1500 m a.s.l. Notwithstanding, pluviometric inflow spatial distribution shows a subregional dependency as a function of four climatic and altimetric factors: coastal, hilly, mountain, and inner plain areas (i.e., Marsica). Such areas are used in this analysis to characterize the radar retrieval vs. rain gauge amounts in each of those zones. Compared to previous studies on the topic, the analysis presented the importance of an accurate selection of the climatic and altimetric subregional areas where the radar vs. rain gauge comparison is undertaken. This aspect is not only of great importance to correct biases in radar retrieval in a more selective way, but it also paves the way for more accurate hydrometeorological applications (e.g., hydrological model initialization and quantification of aquifer recharge), which, in general, require the accurate knowledge of rain amounts upstream of a basin. To fill the gap caused by the uneven rain gauge distribution, ordinary Kriging (OK) was applied on a regional scale to obtain 2D maps of rainfall data, which were cumulated on a monthly and yearly basis. Weather radar data from the Italian mosaic were also considered, in terms of rain rate retrievals and cumulations performed on the same time frame used for rain gauges. The period considered for the analysis was two continuous years: 2017 and 2018. The output of the elaborations included raster maps for both radar and interpolated rain gauges, where each pixel contained a rainfall quantity. Although the results showed a general underestimation of the weather radar data, especially in mountain and Marsica areas, they were within the 95% confidence interval of the OK estimation. Our analysis highlighted that the average bias between radar and rain gauges, in terms of precipitation amounts, was a function of altitude and was almost constant in each of the selected areas. This achievement suggests that after a proper selection of homogeneous target areas, radar retrieval can be corrected using the denser network of rain gauges typically distributed at lower altitudes, and such correction can be extended at higher altitudes without loss of generality.

Evaluation of Rain Estimates from Several Ground-Based Radar Networks and Satellite Products for Two Cases Observed over France in 2022

“…For example, Schleiss et al [69] found a underestimation of radar data compared to rain gauge of 10% in a study over northern Europe. Di Curzio et al [70] also found a general underestimation in Abruzzo and Marsica regions in Italy. In contrast, the overestimation signal estimated over the JUR area tended to be linked with the contribution of the German radars.…”

Estimating a Reliable Water Budget at a Basin Scale: A Comparison between the Geostatistical and Traditional Methods (Foro River Basin, Central Italy)

“…Also, the traditional approach could benefit from a higher number of point data. The recent developments obtained with the use of weather RaDAR data are encouraging [9,39,40] and may represent a valuable additional source of information to be integrated into the water budget estimation, especially through an advanced geostatistical approach (e.g, Multi-Collocated Co-Kriging or Kriging with External Drift). The use of weather RaDAR data would allow estimating in a more reliable way the spatial distribution of rainfall on a finer grid mesh and with a lower associated uncertainty.…”

Assessment of the Feasibility of Implementing a Flash Flood Early Warning System in a Small Catchment Area

“…Errors in the data may result from many factors, such as disturbance of the radar signal by buildings or terrain, and technological limitations. Therefore, in recent years, many researchers have sought to combine two or three of these datasets in order to maximize the advantages and minimize the disadvantages [95,96].…”