EUREC4A, closer to the trade-winds cumulus

About the mission of the SAFIRE ATR42

It flies a series of low-level legs either within the sub-cloud layer, and within the cloud layer, especially just above cloud base (around 1 km). The legs are about 100 km long and spaced by about 20 km, and sample the cloud field within the area encompassed by HALO circles. A particularity of the aircraft instrumentation is that it includes sideways and vertical-pointing lidar and radars that probe the atmosphere horizontally and vertically, aiming at measuring the cloud fraction at cloud base. The legs below cloud level aim at characterizing :

turbulence structures within the subcloud-layer, both cross-wind and along-wing,
the thermodynamic properties of the subcloud-layer,
temperature at the sea surface,
and radiative fluxes.

Given the mean science speed of the aircraft (about 100 m/s) and the endurance expected for the envisioned payload, the ATR-42 makes two four-hour flights per day bracketed by the daily nine-hour flight of HALO.

Read the data-paper of the ATR42 campaign

January 26: first scientific flight

With only 6 days behind the most optimistic forecast, while the transformation work started with 2 months more than expected, while the plane left more than 20 days late, the ATR carried out this January 26, its first scientific flight to Barbados. It should be followed by several others, grouped by "pair" of 4 hours each. A decisive step was taken this Thursday, January 23 with the success of the EMI test flight, the last link in a series of checks that aimed at verifying that the on-board scientific instrumentation does not disturb the proper functioning of the aircraft's systems: our plane is therefore now available to the EUREC⁴A experiment. The first scientific flight, coordinated with the other planes participating in the experiment, is now scheduled for Sunday. Today Friday, January 24, the Safire team and the scientists of the participating laboratories worked hard to eliminate the breakdowns and faults detected, inevitably after an integration, all the more if this is new and some instruments having remained stored since the fall. A test of the scientific instruments is scheduled in flight this Saturday, January 25 in the morning.

An unusual trip, meticulously prepared on a historic route

To get there, a long preparation has been necessary for more than one year, in our base at Francazal Airport as well as in the laboratories. The launching of operations in Barbados was the high point of this preparation: container finally delivered, equipment installed ... After a forced stop in Cayenne, spending a night in Guyana, the flying laboratory has arrived at Bridgetown airport on Sunday January 19 at 12.40 p.m. to participate in the EUREC4A scientific mission. It was the last one missing, the ATR42 had taken off from Fortaleza for Bridgetown the day before in just over 8:30, at the limits of its endurance. Headwinds stronger than expected decided otherwise and the crew had to land in Rochambeau Airport to refuel. On Thursday 16, the Safire crew had conducted the ATR42 to South America.After 8 hours of flight, the plane landed in Fortaleza, Brazil, after taking off from Prahia (Cape Verde). The previous steps had been Tenerife-Prahia (Cape Verde Islands) in 4:15 on January 15, and on January 14 Toulouse - Tenerife in 6:45.

The aircraft has been especially prapared for an unusually long flight, on the path of the "Aéropostale" pioneers. The crew involves two pilots and a flight-engineer.

In Bridgetown, a five-persons team was already there to prepare all so that, at the arrival of the aircraft, the integration of the scientific instruments and all in-board equipments (cabin seats, work stations, second lifeboat ...) could be done in order to perform the first scientific flight as soon as possible. This has started as soon as 19/01 afternoon, by reinstalling the cabin.

Some facts

The EUREC⁴A project is funded by ERC. Other aircraft involved are the jet HALO opated by DLR, the Twin-Otter of the BAS. The Orion-WP3D of NOAA is also involved but as a part of the US project "ATOMIC" concomitant to EUREC⁴A.

For this project, the SAFIRE ATR42 team highly appreciates the support provided by :

the barbadian government and its administrations including CAA (civil aviation)
the RSS (Regional Security Service - hosting the SAFIRE ATR42),
the CIMH (Caribbean Institute For Météorology and Hydrology),
the French Consulate.

See the CNRS press release here

PI/Contact:

Sandrine Bony (LMD), Julien Delanoë (LATMOS) and Cyrille Flamant (LATMOS)

Instruments of the Aircraft

Thermodynamics and turbulence:	Temperature, pressure and wind will be measured at high frequency. Humidity will be measured both by a Licor-7500 sensor (2-3 Hz) and by two KH-20 sensors (10 Hz). These measurements will make it possible to characterize the turbulent structure of the subcloud-layer. (SAFIRE, CNRM/TRAMM, PI: Marie Lothon, LA )
Microphysics:	The aerosol and droplet size distributions will be characterized by UHSAS (60 nm to 1μm), FSSP 300 (0.3 to 20 μm), CDP/FCDP (2-50 μm) and 2D-S (10-1280 μm) measurement probes. The total and liquid water content will be directly measured by two instruments (a Nevzorov for the total water content and a LWC300), and indirectly calculated from droplet size distributions. (SAFIRE, CNRM/TRAMM, PI: Alfons Schwarzenboeck, LAMP)
RASTA Radar:	Upward and downward looking 95 GHz Doppler pulsed cloud radar with four antennas (three above the aircraft and one below the aircraft) for the characterization of cloud microphysics and dynamics. The system allows us to retrieve the 3D wind above the aircraft, to detect updrafts, downdrafts and the presence of precipitation. (PI: Julien Delanoë, LATMOS)
BASTA Radar:	Side looking bistatic FMCW 95 GHz Doppler cloud radar will derive the cloud fraction at the altitude of the aircraft and (depending on flight plans) the vertical cloud mask. Additional cloud properties will be retrieved, such as liquid water content. BASTA and AliAS will team up to make the most of the radar-lidar synergy, combining the high sensitivity of the lidar and the capability of penetrating optically thick clouds of the radar (lidar more sensitive to the concentration of the hydrometeors and radar to the particle size). (PI: Julien Delanoë, LATMOS)
AliAS Lidar:	Lightweight eye-safe backscatter lidar operating at 355 nm and detecting parallel and perpendicular polarization. The system will be deployed in sidewards looking mode to monitor the aerosol and hydrometeor distributions and dispersions in the lower troposphere with an along the line of sight resolution of 30 m and full overlap beyond 200 m. AliAS will allow detecting clouds up to 10 km. The across line of sight resolution will depend on the sampling strategy. (PI: Patrick Chazette, LSCE)
CLIMAT CE332:	Three channel downward staring measurements of infrared irradiance at 8.7, 10.8, and 12.0 μm to measure sea-surface temperature. (SAFIRE, CNRM/TRAMM, PI: Gérard Brogniez, LOA)
Pyrgeometer and Pyranometer:	Hemispheric broadband upwelling and downwelling longwav (4.5 µm– 42 µm) and shortwave (200 nm – 3600 nm) radiative fluxes. (SAFIRE, CNRM/TRAMM, PI: Gérard Brogniez, LOA)
Camera VIS	A high-resolution VIS-camera (Prosilica GT 1930) VIS-camera installed and looking through one of the aircraft window, next to the horizontally-looking lidar and radar. This camera will be used to characterize the environment of lidar/radar measurements, and to reconstruct the vertical structure of the cloud side surface by stereography. (PI: Céline Cornet, LOA)
Picarro:	Cavity Ring-down laser spectrometric measurements of the stable water isotopic composition will made on-board the aircraft using a custom-made flight Picarro L2130. It will measure the isotopic ratios of Oxygen-18 and Deuterium. (PI: Aemisegger Franziska, ETH)