Simulation of radiometric and attenuation measurements along Earth‐satellite links in the 10‐ to 50‐GHz band through horizontally finite convective rain cells

Abstract

Abstract.An iterative solution is illustrated of the three-dimensional radiative transfer equation for a horizontally finite and vertically inhomogeneous precipitating cloud. The method is applied to modeling a convective rain cell of cylindrical shape, characterized by spherical raindrops having a negative-exponential drop size distribution. The realistic model also takes into account the presence of a cloud and an ice layer above the rain cell itself. The simulated brightness temperature, the mean radiative temperature, and the path attenuation are evaluated in a three-dimensional geometry from a surface observation point in order to simulate a ground-based station with a beacon receiver and a multichannel radiometer. Numerical results are shown to illustrate the potential of the proposed model for different sets of frequency channels, observation geometries, cloud sizes and types, and precipitation intensities. After generating a large data set by varying the relevant rain cell parameters, regression analysis is applied to derive a statistical estimation of the total path attenuation from surface rain rate and ground-based radiometric measurements together with the frequency scaling factors for cumuliform clouds in the 10-to 50-GHz band. IntroductionTropospheric attenuation due to precipitating clouds has a strong impact on terrestrial and satellite links in the microwave and millimeter-wave bands.For the usual elevation angles (5ø-40 ø ) and for carrier frequencies greater than 10 GHz, strong path atten-

Neural-network approach to ground-based passive microwave estimation of precipitation intensity and extinction

“…Note that the latter hypothesis is behind the radiative transfer model applied to vertically-stratified atmosphere. This problem may be removed by resorting to the local homogeneity within the beamwidth and by carrying out a modified radiative transfer computation along the inclined path (Marzano et al, 1999b). Moreover, by utilizing the scanning information, there might be the opportunity to develop new algorithms to retrieve the gross vertical profiles of hydrometeors.…”

“…The major drawback is the representativeness of its microphysics and electromagnetic description which needs to be carefully adapted to a large variety of scenarios (e.g., Marzano and Bauer, 2001). The radiative transfer theory (RTT) offers a suitable theoretical model to characterize the down-welling brightness temperature, measured by a microwave radiometer and due to clouds and precipitation (Marzano et al, 1999b;Czekala et al, 2001;Smith et al, 2002). The rainfall radiative model, adopted in this paper, is here briefly summarized in order to give a physical understanding of the retrieval results.…”

Numerical investigation of intense rainfall effects on coherent and incoherent slant-path propagation at K-band and above

“…If the specific intensity is assumed to be uniform within the antenna beamwidth, for highly directive antennas (19) yields , which is the approximation used in [22]. Notice that we do not model here the antenna noise temperature due to rainfall along the path [36], [38].…”

“…The solution of (8b) is not an easy task, especially if considering a three-dimensional geometry of the scattering medium [36]- [38]. Under the assumption of a plane-parallel medium (horizontally stratified), the RT equation can be simplified and expressed using the coordinates (distance), (zenithal angle), and (azimuthal angle).…”

Evaluation of radiative transfer schemes for mesoscale model data assimilation: a case study

“…This mapping is easily obtained in clear sky or non rainy conditions (Faccani et al, 2005 1 ), but it becomes complex in rainfall conditions (Amerault and Zou, 2003). The computation of the atmospheric microwave radiance in cloudy and rainy conditions is a critical task for radiative transfer models, as it has to include multiple scattering effects (Marzano et al, 1999a(Marzano et al, , 1999bDi Michele et al, 2005). To accurately compute T B in previous conditions, it is necessary to use a hydrometeor profiles such as liquid water droplets, raindrops, ice crystals, snow and graupel particles.…”