Instruments

The ATR42 aircraft will be equipped with remote sensing instruments and in-situ microphysics probes in addition to the usual sensors on board the aircraft:

  • The RALI platform will be installed on board the aircraft (Fig. 4). RALI consists of a combination of the multi beam 95 GHz Doppler radar RASTA (RAdar SysTem Airborne) and the lidar LNG (Leandre New Generation). Both instruments were developed at LATMOS and DT-INSU (http://rali.projet.latmos.ipsl.fr/, Delanoë et al 2013). The radar RASTA will be equipped with 6 antennas, 3 looking up and 3 looking down) to retrieve the 3 components of the wind in the aircraft’s referential frame. These three components can be converted into Earth referential frame with horizontal wind components (U, V). Once the Doppler velocity is unfolded and corrected from aircraft’s motion and the reflectivity calibrated it is possible to retrieve both dynamical and microphysical cloud properties. The LEANDRE New Generation (LNG) airborne Lidar system is based on a two-wave interferometry [Mach–Zehnder Interferometer (MZI)] to provide both the determination of optical parameters of aerosol and clouds as well as along-sight wind in the troposphere (Bruneau et al., 2003, 2015). LNG operates at three wavelengths (355 nm, 532 nm, 1064 nm), including depolarization at 355 nm. Additionally, the bi-static 95 GHz Doppler radar BASTA will be installed to provide reflectivity and wind components in the horizontal direction (on the right-hand side of the aircraft).
  • The suite of in situ probes on board the ATR42 aircraft will be used to characterize the spatial distribution of cloud microphysical properties (ice crystal and liquid water droplets, scale dependent liquid-ice partition). This will be investigated using the Polar Nephelometer (PN), the Cloud droplet probe (CDP), the 2D-S stereo imaging probe (or CIP) and the Precipitating Imaging Probe (PIP). These probes cover a complete size range from a few microns up to 6mm. The ice crystal morphologies and particle size distribution will be measured using the combination of the 2D-S and PIP while droplets will be characterized by the CDP with a typical spatial resolution of 100 to 200 m. Parameters such as effective size, ice and liquid water content, number concentrations, ice crystal shapes and cloud phase will be derived from these instruments. The PN measurement of cloud optical properties at a wavelength of 0.8 μm will be used to infer cloud phase (asymmetry parameter), cloud extinction coefficient and phase functions.

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