Abstract
The detection and characterisation of the radar Bright Band (BB) are essential for many applications of weather radar quantitative precipitation estimates, such as heavy rainfall surveillance, hydrological modelling or numerical weather prediction data assimilation. This study presents a new technique to detect the radar BB levels (top, peak and bottom) for Doppler radar spectral moments from the vertically pointing radars applied here to a K-band radar, the MRR-Pro (Micro Rain Radar). The methodology includes signal and noise detection and dealiasing schemes to provide realistic vertical Doppler velocities of precipitating hydrometeors, subsequent calculation of Doppler moments and associated parameters and BB detection and characterisation. Retrieved BB properties are compared with the melting level provided by the MRR-Pro manufacturer software and also with the 0 °C levels for both dry-bulb temperature (freezing level) and wet-bulb temperature from co-located radio soundings in 39 days. In addition, a co-located Parsivel disdrometer is used to analyse the equivalent reflectivity of the lowest radar height bins confirming consistent results of the new signal and noise detection scheme. The processing methodology is coded in a Python program called RaProM-Pro which is freely available in the GitHub repository.
Highlights
The atmospheric layer where this process takes place is known as the melting layer and may produce a characteristic radar signature, the so-called radar Bright Band, a term originated from the local maxima caused by high reflectivity values visible in the equivalent reflectivity vertical profile [4]
The Bright Band (BB) is caused by differences in the dielectric constants, shape and terminal fall speeds of liquid and solid hydrometeor precipitating particles, which lead to abrupt changes of the radar backscattered power within the BB
The most evident BB signatures are produced under stratiform cold rain conditions [5,6] as updrafts, and vertical mixing present in convective precipitation do not provide the proper conditions for BB formation
Summary
Precipitating hydrometeors undergo various processes as they fall, including water vapour condensation, coalescence, break-up or evaporation for liquid water and ice nucleation, riming, aggregation or accretion for the solid phase [1]. The atmospheric layer where this process takes place is known as the melting layer and may produce a characteristic radar signature, the so-called radar Bright Band (hereafter BB), a term originated from the local maxima caused by high reflectivity values visible in the equivalent reflectivity vertical profile [4]. The BB is caused by differences in the dielectric constants, shape and terminal fall speeds of liquid and solid hydrometeor precipitating particles, which lead to abrupt changes of the radar backscattered power within the BB. The most evident BB signatures are produced under stratiform cold rain conditions [5,6] as updrafts, and vertical mixing present in convective precipitation do not provide the proper conditions for BB formation
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