SAFIRE ATR42: Turbulence Data 25 Hz

During the EUREC4A field experiment, the French ATR 42 environmental research aircraft of SAFIRE was dedicated to the exploration of the cloud amount and of the subcloud layer structure within a larger scale circle jointly described by the German HALO research aircraft. The SAFIRE ATR42 aircraft was equipped with a 5-hole nose radome, and several temperature and humidity sensors, for measurements of the three wind components, temperature and humidity at fast rate (25 Hz). Those high frequency measurements allow us to estimate the turbulent moments and to study the turbulence structure of the subcloud layer, as well as the fine thermodynamical structure of the cloud base level.

The turbulence moments are calculated on stabilized legs, (i) after detrending and (ii) after high-pass filtering at cut-off wavelength of approximately 5 km. The two kinds of calculation give access to the homogeneity of the sample and to random and systematic sampling errors.
For all stabilized legs of all processed flights, a set of turbulence moments or characteristics are available, as well as the high rate fluctuations.

The dataset includes two kinds of data:
- Turbulent moments, calculated over each segment, from filtered and unfiltered series. Those are supplied in netcdf files, with one file per flight, for the two sets of shorter (30 km) or longer (60 km) segments.
- The fluctuations over each segment are also made available (detrended and high-pass filtered series), for the three sets of shorter (30 km), longer (60 km) and longest segments (as long as possible on each leg, i.e. composed of segments of different lengths from 60 to 125 km). For this, each flight directory includes a set of netcdf files associated with all segments or legs, with one file per segment.

For those two types of data, two levels of data processing are considered:
- Level 2: Complete files of turbulent moments and fluctuations, using both humidity sensors and both temperature sensors (all moments calculated with individual sensors are available), together with a quality flag.
- Level 3: `Best estimates' of turbulent moments and fluctuations, , and corresponding quality flag (for each segment, the moments and fluctuations are computed from the sensor that has the best quality flag).