Laser concept of the mobile ATMONSYS-lidar and its application during CHEESEHEAD

Water vapor is the most important greenhouse gas and dominates weather patterns, the atmospheric energy budget and radiative balance. For analysing
dynamic processes of planetary boundary layer we developed the ATMONSYS lidar for measuring water vapor, aerosols and temperature. In summer 2019 the application of the ATMONSYS lidar was part of the CHEESEHEAD campaign in Northern Wisconsin (USA). Former investigations showed the very high spatio-temporal short term variability of tropospheric water vapor in a three dimensional study [1]. From a technical point of view this also depicted the general requirement of short integration times while recording water-vapor profiles with lidar. For this purpose,  the differential absorption lidar (DIAL) working in the near-infrared (NIR) spectral region is a suitable technique. For measuring the light absorption by single spectral lines in the 817nm band of water vapor, the laser emission is predominated for the use of Ti:Sapphire as laser medium. We present a new concept of transversely pumping a Ti:Sapphire crystal to generate high power NIR laser emission directly from a laser resonator without amplification stage. This setup allows for a high output power at repetitions rates up to 100Hz or even more due to the enhanced cooling situation for the laser rod. It is, because of its compactness, also suitable for mobile applications. We also show a concept, how this resonator can be locked to two seeding DIAL wavelengths at the same time.

[1] Vogelmann, H., Sussmann, R., Trickl, T., and Reichert, A.: Spatiotemporal variability of water vapor investigated using lidar and FTIR vertical soundings above the Zugspitze, Atmos. Chem. Phys., 15, 3135-3148, 2015.