Journal Article

Backscatter Differential Phase—Estimation and Variability

Trömel, Silke, Ryzhkov, Alexander V., Kumjian, Matthew R., Diederich, Malte, Simmer, Clemens

2013

Overview

On the basis of simulations and observations made with polarimetric radars operating at X, C, and S bands, the backscatter differential phaseδhas been explored;δhas been identified as an important polarimetric variable that should not be ignored in precipitation estimations that are based on specific differential phaseK DP, especially at shorter radar wavelengths. Moreover,δbears important information about the dominant size of raindrops and wet snowflakes in the melting layer. New methods for estimatingδin rain and in the melting layer are suggested. The method for estimatingδin rain is based on a modified version of the “ZPHI” algorithm and provides reasonably robust estimates ofδandK DPin pure rain except in regions where the total measured differential phase ΦDPbehaves erratically, such as areas affected by nonuniform beam filling or low signal-to-noise ratio. The method for estimatingδin the melting layer results in reliable estimates ofδin stratiform precipitation and requires azimuthal averaging of radial profiles of ΦDPat high antenna elevations. Comparisons with large disdrometer datasets collected in Oklahoma and Germany confirm a strong interdependence betweenδand differential reflectivityZ DR. Becauseδis immune to attenuation, partial beam blockage, and radar miscalibration, the strong correlation betweenZ DRandδis of interest for quantitative precipitation estimation:δandZ DRare differently affected by the particle size distribution (PSD) and thus may complement each other for PSD moment estimation. Furthermore, the magnitude ofδcan be utilized as an important calibration parameter for improving microphysical models of the melting layer.

• Publisher: American Meteorological Society
• Subject: Atoms & subatomic particles / Backscattering / Earth, ocean, space / Estimates / Estimating / Estimation methods / Exact sciences and technology / External geophysics / Geophysics. Techniques, methods, instrumentation and models / Hydrometeorology / Melting / Meteorology / Meteors / Precipitation / Radar / Radar beams / Rain / Raindrops / Studies / Superhigh frequencies / Water in the atmosphere (humidity, clouds, evaporation, precipitation) / Wavelengths