README file for the field experiment in Grand Colon from February 12th to 28th, 2019.

All the data present in this archive are presented in the paper "Katabatic winds over steep slopes: overview of a field experiment designed to investigate slope-normal velocity and near surface turbulence"
by CHARRONDIÈRE, C., BRUN, C., COHARD, J.M., SICART, J.E., OBLIGADO, M., BIRON, R., COULAUD, C. & GUYARD, H. (2022), Boundary-Layer Meteorol. 187, 29–54.

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Site A : 
GPS coordinates : N 45.16273°, E 5.91396°
Altitude : 1788m
Local slope angle = 30°, based on a Digital Elevation Model (DEM, BD ALTI IGN) of the region with 25-m horizontal resolution.
 *Turbulence mast :
	 - 7 3D sonic anemometers at an acquisition frequency of 20Hz : 1 CSAT3B (Campbell Scientific), 5 CSAT3 and 1 WindMaster Pro (Gill Instruments)
	 - 4 2D sonic anemometers at an acquisition frequency of 0.2Hz : Wind Sonics (Gill Instruments)
	 - 10 thermocouples at an acquisition frequency of 20Hz : FW3 type E (Campbell Scientific)
 *Meteorological mast (1 measurement / 10 min)
	 - Barometer : CS100 (Campbell Scientific)
	 - Radiometer : CNR1 (Campbell Scientific)
	 - Thermohygrometer : CS215 (Campbell Scientific)
	 - Distance sensor : SR50 (Campbell Scientific)

Site B : 
GPS coordinates : N 45.17811°, E 5.90172°
Altitude : 1175m
Flat clearing (1 measurement / 10 min)
	 - Barometer : CS100 (Campbell Scientific)
	 - 2D sonic anemometer : WMT700 (Vaisala)
	 - Thermohygrometer : CS215 (Campbell Scientific)

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Data are stored in netCDF files.

Height of the sensors are provided in the slope-coordinate system, taking into account the evolution of the snow cover (SR50 sensor).

All CSAT3 sensors are intercalibrated with respect to the CSAT3B sensor, based on measurements acquired in a wind tunnel.

For the Wind Sonic sensors (2D), the wind direction is provided with an error of +/-5°.

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Whole field experiment

This folder includes temporal series of the all the sensors.
*Site A :
 - Turbulence mast : one folder per sensor, and one file per day. 
All sensors are placed as parallel to the slope as possible during the installation.
CSAT3 and CSAT3B sensors are re-oriented with an angle of 30° (+/- 1°) with respect to horizontal to match the slope angle.
 - Meteorological mast : one file per sensor

*Site B : one file per sensor.
We observe a brief decrease of the solar radiation flux received by the surface at the beginning of the afternoon, due to the shadow of the mast on the sensor.

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Katabatic events

In this folder, you will find data from 13 katabatic events extracted from the whole field experiment dataset (Table 3 of Charrondière et al., 2022).
Data from the CSAT are rotated in the slope-coordinate system, with an angle of 30° with respect to horizontal, and such that mean spanwise (transverse) velocity is zero.
Data for the other sonic anemometers (Wind Master and Wind Sonics) are rotated in the streamline coordinate system.

For the 7b event, the 6 measurements levels from the 3D pitot probe are added, in the streamline coordinate system. The sensor height, and the time of the measurements are included in the name of the file.
Each time-series lasted 1 minute.


*Note that the Wind Master Pro sonic anemometer, placed at the top of the mast behaves strangely in terms of mean temperatre. We observe clear shifts in the mean temperature by nights (when the shortwave radiation is negligible). This behavior does not seems to impact the turbulence.
We do not have any explanation for this, and we are open to discussion if you have already encountered this problem.