Abstract
AbstractA statistical analysis of simultaneous observations of more than 800 hailstorms over the continental United States performed by the Global Precipitation Measurement (GPM) Dual-Frequency Precipitation Radar (DPR) and the ground-based Next Generation Weather Radar (NEXRAD) network has been carried out. Several distinctive features of DPR measurements of hail-bearing columns, potentially exploitable by hydrometeor classification algorithms, are identified. In particular, the height and the strength of the Ka-band reflectivity peak show a strong relationship with the hail shaft area within the instrument field of view (FOV). Signatures of multiple scattering (MS) at the Ka band are observed for a range of rimed particles, including but not exclusively for hail. MS amplifies uncertainty in the effective Ka reflectivity estimate and has a negative impact on the accuracy of dual-frequency rainfall retrievals at the ground. The hydrometeor composition of convective cells presents a large inhomogeneity within the DPR FOV. Strong nonuniform beamfilling (NUBF) introduces large ambiguities in the attenuation correction at Ku and Ka bands, which additionally hamper quantitative retrievals. The effective detection of profiles affected by MS is a very challenging task, since the inhomogeneity within the DPR FOV may result in measurements that look remarkably like MS signatures. The shape of the DPR reflectivity profiles is the result of the complex interplay between the scattering properties of the different hydrometeors, NUBF, and MS effects, which significantly reduces the ability of the DPR system to detect hail at the ground.
Highlights
The launch of the Global Precipitation Measurement (GPM) mission core satellite in February 2014 offers an unprecedented opportunity to explore the three-dimensional structure of precipitating systems from space (Hou et al 2014)
The mission carries on the legacy of the Tropical Rainfall Measuring Mission (TRMM), thoroughly described by Kummerow et al (1998), with the goals of mapping global precipitation and of better understanding the structure of precipitating systems
The analysis shows that the conditional probability of hail occurrence in the column is very small even for strong Ku reflectivity echoes; that is, approximately 41% of all profiles exceeding the 40-dBZ measured Ku reflectivity threshold have no hail in the column
Summary
The launch of the Global Precipitation Measurement (GPM) mission core satellite in February 2014 offers an unprecedented opportunity to explore the three-dimensional structure of precipitating systems from space (Hou et al 2014). Several studies (Cecil 2009, 2011; Cecil and Blankenship 2012; Ferraro et al 2015; Mroz et al 2017; Ni et al 2017) have tried to identify thresholds of brightness temperatures at the different frequencies for the detection of hail embedded in a precipitating system identified by a precipitation feature (Nesbitt et al 2000), that is, contiguous areas occupied by clouds and rain Such measurements can be combined with ground validation to statistically establish optimal detection thresholds.
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