Aircraft – NAWDIC

Two aircraft will be deployed:

Coordinated virtual flights for ATR42 (green) and for Cessna F406 (orange) on 18 Feb 2022 12 UTC targeting the mesoscale inhomogeneities of the DI. Vertical cross section along common leg showing wind speed perpendicular to the flight track (black contours in m s^-1 ) and frozen hydrometeor content (shading) based on ERA5. Coloured cones denote areas where conditions for measurements with instruments on board are met.

The ATR42, operated by SAFIRE, will be deployed from Shannon (Ireland). It usually flies in middle troposphere (~5 km) up to 7.5 km, it has an endurance of about 3h30 and a range of 1300 km with the planned payload. It will be equipped of a Radar/lidar platform (RALI), in-situ microphysics probes and lidar ALIAS.

The Cessna F406, operated by the TU Braunschweig, will be deployed from Brest (France). The Cessna F406 is a twin-engine turboprop aircraft and can accommodate two pilots plus two scientists. Its typical endurance is 4 h at a cruising speed of 140 knots with flight altitudes between 100-6000 m.

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ATR42 payload

Schematic of the Safire ATR42 aircraft configuration and payload: (left) in situ microphysical probes are shown in red, and (right) remote sensing instruments (positions of BASTA and RASTA radars and LNG lidar are indicated in green, black, and blue, respectively). Also included the ALIAS lidar and the water isotope analyzer PICARRO.

The ATR42 will be deployed with a very large payload including both remote sensing and in-situ measurements of aerosols, clouds and precipitation properties (see figure above). The aircraft will carry the RALI (Radar-lidar) and PMA (Airborne in-situ Measurement Platform) platforms, both labeled “National Instrument Facility” by CNRS-INSU. They will be accompanied by the ALiAS lidar and the water isotope analyzer PICARO. This configuration will allow us to document cloud and precipitation microphysics and dynamics.

Instruments / Objectives	Aerosols	Clouds precipitation	Wind	Turbulence	Surface	Humidity
LNG lidar (UV, 532, 1064 nm)	yes	yes	C/A	C/A	yes
Multiview Doppler cloud radar RASTA (95GHz)		yes	C/P	C/P	yes
Sideward Doppler cloud radar BASTA (95 GHz)		yes	C/P	C/P
Sideward Backscatter Lidar ALiAS (UV)	yes	yes
PMA probes	yes	yes
Aircraft baseline information			yes	yes		yes
CLIMAT, Pyrano- & pyrgeometers	yes	yes			yes
PICARRO		isotopes				isotopes

Payload of the ATR42. Labels indicate targets: A: Aerosols, C: Clouds, P: Precipitation

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Cessna F406 payload

The Cessna F406 is equipped with a nose-boom which incorporates a 100 Hz in-situ turbulence probe (3-D wind vector, temperature, humidity). Thus, the aircraft can perform measurements of the sensible and latent heat flux, as well as the momentum fluxes, inside the boundary layer. Further, the aircraft also carries radiation and surface temperature sensors as well as a VIS camera system, establishing a link between the observed fluxes and the land- or sea-surface characteristics.

The new AIRflows system installed in the TUBS Cessna F406 (call sign D-ILAB). The main rack contains the five laser units, the data acquisition unit is placed to the left.

Besides the in-situ turbulence probe the Cessna F406 will carry a novel fixed-beam airborne Doppler lidar (ADL) system, which allows to measure wind below the aircraft at 100 m resolution (https://www.imk-tro.kit.edu/english/12875.php). The novel ADL has been developed at KIT in a project termed AIRflows (AIRborne fixed-beam lidar for wind measurements). Instead of a single Doppler lidar with a scanner, used by all previously existing ADL systems, the new AIRflows system uses five small and lightweight Doppler lidars with fixed beam directions. The simultaneous availability of multiple viewing directions brings advantages: Simulation results and first observations have demonstrated that a multi-lidar system can achieve approximately one order of magnitude improved spatial wind measurement resolution as well as higher accuracy, compared to existing scanning systems.

Exemplary wind measurements at 100 m resolution, obtained with AIRflows during a flight below cloud base inside the boundary layer. Shown are (a) wind speed, (b) wind direction, (c) vertical wind and (d) carrier-to-noise ratio. The TUBS Cessna F406 in-situ measurements are shown as a thin line at flight level, the curtain below the flight path is provided by AIRflows.

Synchronizing the flight paths of the ATR42 and Cessna F406, with their sophisticated instrumentation on-board, allows us to investigate the relationship between in-cloud dynamics and microphysics and boundary layer conditions such as wind shear, turbulent fluxes and wind variances in unique ways. The measurements will provide detailed insight into the role of wind shear, meso-scale wind features, (evaporating) clouds and differences in surface characteristics on momentum and energy transport during DI situations. Besides improved physical understanding, extensive cross-validation of remote sensing retrievals will become possible due to the synergistic aircraft measurements.

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