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:
- Remote Sensing instruments
The RALI platform (https://rali.aeris-data.fr/) was installed on board the aircraft. 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 (https://rali.aeris-data.fr/, Delanoë et al 2013). The radar RASTA is 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 was installed to provide reflectivity and wind components in the horizontal direction (on the right-hand side of the aircraft).
| Instrument | Measurements/ Retrieved parameters |
| RASTA (95GHz Doppler radar) | Doppler velocity, spectral width and reflectivity. Retrieved IWC and wind (Delanoë et al. 2013) |
| BASTA (95GHz Doppler radar) | Vertical Doppler velocity and reflectivity in the horizontal direction (Delanoë et al. 2016) |
| LNG (lidar) | Optical properties of clouds and aerosols. Wind. Retrieved LWC (Bruneau et al. 2015) |
2. In-situ probes
The suite of in situ probes on board the ATR42 aircraft are used to characterize the spatial distribution of cloud microphysical properties (ice crystal and liquid water droplets, scale dependent liquid-ice partition). This was investigated using the High Speed Imager (HSI), 2D-Stereo (2DS), the High Volume Precipitation Spectrometer (HVPS), the Polar Nephelometer 1 (PN), the Cloud Droplet Probes (CDP-2) and the Ultra High Sensitivity Aerosol Spectrometer (UHSAS).
These probes cover a complete size range from a few microns up to 19mm. The ice crystal morphologies and particle size distribution were measured using the combination of the 2D-S and HSI while droplets are characterized by the CDP with a typical spatial resolution of 100 to 200 m. Precipitating hydrometeors are characterized by the HVPS. Parameters such as effective size, ice and liquid water content, number concentrations, ice crystal shapes and cloud phase are derived from these instruments. The PN measurement of cloud optical properties at a wavelength of 0.8 μm is used to infer cloud phase (asymmetry parameter), cloud extinction coefficient and phase functions.
| Instrument | Measurements/ Retrieved parameters |
| High Speed Imager (HSI) | Size and images of cloud particules from 10 to 1500µm. Hydrometeor PSD, IWC, LWC. |
| 2D-Stereo (2DS) | Size and images of cloud particules from 50 to 1280µm. Individual ice crystals characteristics. Hydrometeor PSD. Mass-Diameter relation. IWC and LWC. MMD. (Lawson et al. 2006) |
| High Volume Precipitation Spectrometer (HVPS) | Size and images of cloud particules from 600µm to 19mm. Precipitating hydrometeors PSD, LWC, IWC, MMD. (Lawson et al. 1993) |
| Polar Nephelometer 1 (PN) | Scattering coefficient. Asymmetry parameter (Gayet et al. 1997) |
| Cloud Droplet Probes (CDP-2) | Droplet PSD, LWC, MMD (Lance et al. 2010) |
| Ultra High Sensitivity Aerosol Spectrometer (UHSAS) | Aerosol PSD for particules from 0.04µm to 1mm. (Cai et al. 2008) |