Abstract
Abstract. The aim of this paper is to present the Monte Carlo code McRALI that provides simulations under multiple-scattering regimes of polarized high-spectral-resolution (HSR) lidar and Doppler radar observations for a three-dimensional (3D) cloudy atmosphere. The effects of nonuniform beam filling (NUBF) on HSR lidar and Doppler radar signals related to the EarthCARE mission are investigated with the help of an academic 3D box cloud characterized by a single isolated jump in cloud optical depth, assuming vertically constant wind velocity. Regarding Doppler radar signals, it is confirmed that NUBF induces a severe bias in velocity estimates. The correlation of the NUBF bias of Doppler velocity with the horizontal gradient of reflectivity shows a correlation coefficient value around 0.15 m s−1 (dBZ km-1)-1, close to that given in the scientific literature. Regarding HSR lidar signals, we confirm that multiple-scattering processes are not negligible. We show that NUBF effects on molecular, particulate, and total attenuated backscatter are mainly due to unresolved variability of cloud inside the receiver field of view and, to a lesser extent, to the horizontal photon transport. This finding gives some insight into the reliability of lidar signal modeling using independent column approximation (ICA).
Highlights
Spaceborne atmospheric lidar and radar are suitable tools to investigate vertical properties of clouds on a global scale
For total and particulate ATB, we can note that independent column approximation (ICA) biases are larger whatever the vertical position in the cloud, whereas PP biases are smaller in the upper part of the cloud due to multiple scattering, which becomes more significant as the field of view (FOV) increases; this latter behavior is coherent with Eq (B7)
This paper presents the Monte Carlo code McRALI-FR that provides simulations of range-resolved z and frequencyresolved f Stokes parameters S(z, f ) = (I, Q, U, V ) recorded by different kinds of monostatic polarized highspectral-resolution lidars and Doppler radars from a 3D cloudy atmosphere and/or precipitation fields
Summary
Spaceborne atmospheric lidar (light detection and ranging) and radar (radio detection and ranging) are suitable tools to investigate vertical properties of clouds on a global scale. Lidar and/or radar simulators are steadily advancing, allowing us to explore direct and inverse problems in a cost-effective way In this Introduction, published works restricted to the case when multiple scattering was taken into account are briefly discussed. As for lidar and radar measurements, we can refer to the EarthCARE simulator (ECSIM) that is a modular multi-sensor simulation framework, wherein a fully 3D Monte Carlo forward model can calculate the spectral polarization state of ATLID lidar signals (Donovan et al, 2008; Donovan et al, 2015). Two illustrative applications (i.e., ATLID lidar and CPR radar of the EarthCARE mission) of the developed simulator are presented.
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