Temporal evolution of remote water vapour (humidity) - UTC time. LR111-D300 LIDAR systems are capable of retrieving remote humidity data during nighttime up to a range of ~6 km. PBL height is also identifiable at ~2 km. *
Humidity is an area in which remote data is particularly lacking in meteorological studies. Radiosondes cannot provide constant data due to the high expense and logistical difficulty of sending up large numbers of weather balloons. Therefore aerosol LIDARs can be of use through augmenting radiosonde data.
* The water vapour mixing ratio is defined as the ratio of the mass of water vapour to the mass of dry air in a sample of the atmosphere. The water vapour profile, in mixing ratio units (g/kg), is determined by inverting the ratio of the LIDAR signals corresponding to the 355 nm-Raman shifted laser beam that is backscattered by H2O (at 408 nm) and by N2 atmospheric molecules (at 387 nm). Each vertical profile corresponds to an integration time of 3 minutes and a vertical resolution of 30 m. Calibration constant is equal to 75 (lidar returns and radiosonde data were used as the calibration method).
LR111-D300 model aerosol LIDARs are capable of being upgraded with a detection channel at 408 nm, enabling retrieval of water vapour profiles. The image below shows an example of the time evolution and vertical variability of the water vapour mixing ratio.
Comparison of historical Raymetrics LIDAR data with radiosonde data