Abstract
AbstractDual‐frequency dual‐polarization radar observations of the melting of two ice populations in a stratiform rainfall event are presented. The observed phenomenon occurs as a two‐layer linear depolarization ratio (LDR) signature in a single radar bright band. Doppler spectra observations show that the upper LDR layer is caused by the melting of ice needles, potentially generated by the rime‐splintering process, while the lower one is mainly due to the melting of background ice particles formed at the cloud top. The melting signal of small needles acts as a unique benchmark for detecting the onset of melting and is used to verify the current methods for the identification of melting layer boundaries. The radar‐derived characteristics of the melting layer are found to be dependent on the radar variable and frequency used. The implications of the presented findings for radar‐based studies of precipitation properties in and above the melting layer are also discussed.
Highlights
The majority of rainfall in middle to high latitudes over land originates from ice clouds (Field & Heymsfield, 2015; Mülmenstädt et al, 2015)
Doppler spectra observations show that the upper linear depolarization ratio (LDR) layer is caused by the melting of ice needles, potentially generated by the rime‐splintering process, while the lower one is mainly due to the melting of background ice particles formed at the cloud top
The vertically pointing C‐ and W‐band radars recorded two layers of enhanced LDR inside a single radar bright band. These two layers were caused by the melting of two populations of ice particles, namely, ice needles, generated in the region favorable to Hallett‐Massop secondary ice production, and background ice formed at the cloud top
Summary
The majority of rainfall in middle to high latitudes over land originates from ice clouds (Field & Heymsfield, 2015; Mülmenstädt et al, 2015). There are no reports on how multiple ice particle populations modify the properties of the ML This is important given that more and more efforts being devoted to developing sophisticated models that attempt to explain dual‐polarization and multifrequency radar observations of the ML and how it is impacted by ice microphysics (Carlin & Ryzhkov, 2019; Johnson et al, 2016; Ori & Kneifel, 2018; Russchenberg & Ligthart, 1996; Tyynelä et al, 2014). These observations are supplemented by the National Centers for Environmental Prediction (NCEP) reanalysis data set to provide information on the atmospheric state
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