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X-band dual-polarization radar-based hydrometeor classification for Brazilian tropical precipitation systems

Preprint published in 2018 by Jean-François Ribaud, Luiz A. T. Machado, Thiago Biscaro
This paper is available in a repository.
This paper is available in a repository.

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Preprint: policy unknown
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Postprint: policy unknown
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The dominant hydrometeor types associated with Brazilian tropical precipitation systems are identified via research X-band dual-polarization radar deployed in the vicinity of the Manaus region (Amazonas) during both the GoAmazon2014/5 and ACRIDICON-CHUVA field experiments. The present study is based on an Agglomerative Hierarchical Clustering (AHC) approach that makes use of dual polarimetric radar observables (reflectivity at horizontal polarization Z H , differential reflectivity Z DR , specific differential phase K DP , and correlation coefficient ρ HV ) and temperature data inferred from sounding balloons. The sensitivity of the agglomerative clustering scheme for measuring the inter-cluster dissimilarities (linkage criterion) is evaluated through the wet season dataset. Both the weighted and Ward linkages exhibit better abilities to retrieve cloud microphysical species, whereas clustering outputs associated with the centroid linkage are poorly defined. The AHC method is then applied to investigate the microphysical structure of both the wet and dry seasons. The stratiform regions are composed of five hydrometeor classes: drizzle, rain, wet snow, aggregates, and ice crystals, whereas convective echoes are generally associated with light rain, moderate rain, heavy rain, graupels, aggregates and ice crystals. The main discrepancy between the wet and dry seasons is the presence of both low- and high-density graupels within convective regions, whereas the rainy period exhibits only one type of graupel. Finally, aggregate and ice crystal hydrometeors in the tropics are found to exhibit higher polarimetric values compared to those at mid-latitudes.

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