Application of radar polarimetry to estimate rainfall from the bright band

Radar measurement of precipitation is impaired in systems where the melting layer is close to the ground. This paper explores how to infer rainfall on the ground from measurements in the bright band. Criteria how to identify the beginning of beam penetration into the bright band and exit are based on the correlation coefficient ρhv, presence of signal, and some continuity in range. These are tested on cases obtained with the newly upgraded dual polarization WSR-88D radars. Assumption of water flux conservation between the bright band and rain immediately below is made to appropriately transform a R(Z) relation from one medium to the other. The relation gradually changes as the beam penetrates the bright band to account for the beam weighting and filling effects. It is demonstrated that multiplication of R_b(Z) by a coefficient linearly dependent on penetration depth can significant improve rain rate estimation. The slope of the linear relation is allowed to vary and so is the maximum value of the correction. Measurements in the bright band and immediately below, simulations and geometrical considerations are used to define the linear slopes and the maximum values. Comparisons of rainfall measured in cases of pronounced bright band with rain gauges indicate skill in the methodology as well as paths toward further improvements.Comparisons of rainfall measured in cases of pronounced bright band with rain gauges indicate skill in the methodology as well as paths toward further improvements.