Modeling of apparent radar reflectivity due to convective clouds at attenuating wavelengths

Abstract

[1] Spaceborne precipitation radars are usually designed to operate at attenuating wavelengths, mostly at X, Ku and Ka band. At these frequencies and above, convective rainfall can cause severe attenuation. Moreover, raindrops and precipitating ice can give rise to appreciable multiple scattered radiation which apparently tends to enhance the nominal attenuated reflectivity. In order to properly describe radar observations in such conditions, apparent reflectivity has to be modeled taking into account both path attenuation and incoherent effects. To this aim, a general definition of volume radar reflectivity is introduced, and a Monte Carlo model of backscattered specific intensity is implemented. The numerical model is applied to synthetic profiles, extracted from a mesoscale cloud-resolving model simulation and representing intense and heavy convective precipitation at a developing and mature stage. Realistic appearance of these average profiles is argued by resorting to radar measurements available in literature. Spaceborne apparent reflectivity due to multiple scattering is shown to be significantly different from the attenuated one for the near-surface layers of mature convection at Ku band and even for growing convection at Ka band. A discussion about this discrepancy is carried out at Ku band showing its possible impact for estimated rain rate profiles. If precipitation incoherent effects are formally treated as perturbation factors of the specific attenuation model, constrained single-frequency inversion techniques are shown to be suitable to minimize rain rate retrieval errors due to multiple scattering phenomenon.

Hail storm hazard in urban areas: identification and probability of occurrence by using a single-polarization X-band weather radar

“…Processing chain has been focused on some systematic errors that include biases and range-dependent effects, as ground clutter residuals, backscatter from sea surface, beam blocking by surrounding topography and beam attenuation along the path (Capozzi et al, 2014). The latter could be important in heavy rain or hail at X-band (Marzano et al, 2003). 5…”

Relation between weather radar equation and first-order backscattering theory

“…it can take into account multiple scattering effects to any order of scattering, being the apparent radar reflectivity related to specific intensity solution of the radiative transfer equation (Marzano et al, 2000(Marzano et al, , 2003; 2. it includes, as a particular case, the modified radar equation if the apparent reflectivity factor is expressed in terms of the equivalent reflectivity factor Z e and the binaveraged extinction factor f b , i.e. :…”

“…In order to do this, the backscattered specific intensity, incident on the radar antenna, can be expressed by means of the apparent radar reflectivity of the considered range bin (Marzano et al, 2000;Marzano et al, 2003).…”

“…This means that the contribution of first and successive orders of scattering can be appreciable in determining the radar received power. A careful analysis of the validity of the classical radar equation could be obtained only if the radar equation itself is framed within a more general theory which can include the effects of incoherent scattering phenomena (Marzano et al, 2003).…”

Evaluation of radar multiple scattering effects in Cloudsat configuration

“…Previous studies at lower frequencies (Marzano et al, 2003;Battaglia et al, 2005;Kobayashi et al, 2005) have shown that multiple scattering (MS) effects become relevant in space-borne configuration at 35 GHz at high scattering optical thickness (defined as the columnar integral of the scattering coefficient), e.g. associated with large amounts of highdensity ice particles.…”