Recent Advances in Automated Temperature and Humidity Lidar

We will give an update of our recent activities regarding automated high-resolution temperature and humidity lidar.

The Raman lidar ARTHUS (Atmospheric Raman Temperature and HUmidity Sounder) of University of Hohenheim is an automated instrument with continuous operation (Lange et al., 2019; Wulfmeyer and Behrendt, 2022). Besides being operated during several field campaigns elsewhere, ARTHUS is usually located at the LAFO (Land Atmospheric Feedback Observatory) near the agricultural research fields of our university. Here, in addition, three scanning Doppler lidars, a Doppler cloud radar, two meteorological 10-m towers with eddy-covariance stations, as well as surface and sub-surface sensors are collecting routinely data. These data are combined with detailed vegetation analyses.

ARTHUS is an eyesafe Raman lidar using a diode-pumped Nd:YAG laser as transmitter. Only the third-harmonic radiation at 355 nm is – after beam expansion – transmitted into the atmosphere. The laser power is about 20 W at 200 Hz repetition rate. The receiving telescope has a diameter of 40 cm. A polychromator extracts the elastic backscatter signal and four inelastic signals, namely the vibrational Raman signal of water vapor and CO₂ molecules, and two pure rotational Raman signals. The raw data is stored with a resolution of 7.5 m and typically 1 to 10 s. All five signals are simultaneously analyzed and stored in both photon-counting (PC) mode and voltage (so-called “analog” mode) in order to make optimum use of the large intensity range of the backscatter signals covering several orders of magnitude. Primary data products are temperature, water vapor mixing ratio, carbon dioxide mixing ratio, particle backscatter coefficient, and particle extinction coefficient. The high resolution allows studies of boundary layer turbulence (Behrendt et al, 2015) and - in combination with the vertical pointing Doppler lidar - sensible and latent heat fluxes (Behrendt et al, 2020).

Further refined lidars like ARTHUS are offered by the company Purple Pulse Lidar Systems (www.purplepulselidar.com). Meanwhile three more systems have been built and are operating.

At the conference, we will present the recent advances in these powerful automated temperature and humidity lidars and show highlights of the measurements.

 

References:

Behrendt et al. 2015, https://doi.org/10.5194/acp-15-5485-2015

Behrendt et al. 2020, https://doi.org/10.5194/amt-13-3221-2020

Lange et al. 2019, https://doi.org/10.1029/2019GL085774

Wulfmeyer and Behrendt 2022, https://doi.org/10.1007/978-3-030-52171-4_25