Upper tropospheric water vapor profiles derived from Raman lidar over France territories for contrail investigations

Accurate water vapor measurements in the upper troposphere at cruise altitude are required to investigate contrails formation. We present 4 Raman lidars having these capabilities in France. Water vapor mixing ratio is proportional to the ratio of H2O and N2 Raman signals for the same altitude by a scale factor called calibration factor. Coaxial systems can be calibrated with independent measurement of water vapor total column. A more universal external method able to calibrate any lidar (co/non-axial system) is adopted, using co-located ERA5 hourly water vapor profiles. Full night calibration factor is estimated as the mean of hourly coefficients, daily calibrations are inspected to detect any instrumental changes. Final coefficients are then considered for quasi stationary periods. Calibrated profiles are validated against available radiosondes ones. This new software can be used to force models to better understand contrails contribution in future air traffic regulation as part of European project BeCoM.