Breakout Summary Report
ARM/ASR User and PI Meeting
10 - 13 June 2019
Lidar Applications Breakout
10 June 2019
1:30 PM - 3:30 PM
60
Rob Newsom, Larry Berg, Dave Turner
10 June 2019
1:30 PM - 3:30 PM
60
Rob Newsom, Larry Berg, Dave Turner
Breakout Description
The ARM lidar systems are powerful tools for understanding a wide variety of atmospheric processes that are being used in a number of science projects. The goal of this session is to provide an opportunity for scientists to describe how lidar data are being used in their research, and to highlight the issues and challenges associated with the use of these data. The intent is to provide a forum for data users to share results and lessons learned, and to provide feedbac kto the ARM user facility. The focus in this session is on the science applications of the Doppler, Raman, and high-spectral-resolution lidar systems deployed at either the ARM fixed sites or with the AMFs.Main Discussion
During the first part of the lidar breakout session, the focus was on new developments in lidar remote sensing of water vapor and temperature, with an emphasis on small compact systems that may be good candidates for deployment in large networks. Three presentations were given during this part of the session. These include:
- Rob Newsom talked about a new and fairly novel broadband DIAL system developed by Vaisala for water vapor profiling. The Vaisala DIAL demonstrates good accuracy and near-range performance (<50 m minimum range), but limited maximum range (<1.5 km), and no capability for doing temperature profiling.
- Dave Turner talked about the micropulse DIAL (MPD) system developed by NCAR and Montana State. NSF recently funded NCAR/MSU to build five of these systems, and they are currently being tested at SGP (mid-April through mid-July 2019).The MPD exhibits better range performance than the Vaisala DIAL but with a higher minimum range of ~500m. The MPD can also be configured to do temperature profiling, but that capability has not yet been demonstrated and they are likely years away from having a hardened system that can do both water vapor and temperature.
- Volker Wulfmeyer talked about a compact Raman lidar (RL) system for water vapor and temperature profiling developed at the University of Hoehenheim. Volker showed that this system is able to achieve a temperature uncertainty of ~1K for z>5km, and water vapor uncertainty of ~5% for z>3.5 km. The water vapor profiling capability of this system is roughly comparable to the current SGP RL, although the Hoehenheim system is far more compact. By contrast, the temperature profiling capability is much better than the SGP RL.
Following the water vapor and temperature lidar talks, we had two talks that were more focused on improvements to aerosol profiling by the ARM RL and HSRL systems. These include:
- Ray Bambha gave an update on the ARM RLs as well as planned upgrades for the NSA HSRL. Basically, the plan is to take the NSA HSRL offline in mid-July 2019 and send the system to Ed Eloranta at the University of the Wisconsin. There the system will be modified to add a 1064 nm channel, a wide field of view to the molecular channel and possibly the combined channel, and an elevation scanner. The current plan is for these modifications to be completed by January 2020, at which time the system will be temporarily deployed at SGP until it can be moved back to its permanent home at NSA in the summer of 2020. During the temporary deployment at SGP the system will be collocated with the SGP RL. This will afford another opportunity to perform multi-wavelength retrievals of aerosol properties at SGP. Furthermore, once the system is back at NSA, it will be collocated next to the ARM RL, which would enable the possibility of doing the multi-wavelength retrievals on a routine basis.
- Duli Chand talked about the new RL aerosol optical properties VAP, i.e., the Feature detection and EXtinction (FEX) VAP. This VAP provides estimates of aerosol backscatter, extinction, scattering ratio, lidar ratio, and depolarization ratio. The VAP incorporates feature masks that can be used to identify regions containing aerosol, liquid clouds, ice clouds, rain, and horizontally oriented ice crystals. The VAP is currently running on the SGP and ENA RLs. Efforts are currently underway to get it running on the Oliktok RL.
There were also several presentations that were more focused on science applications of lidar. This included the following presentations:
- Dave Turner discussed testing new water vapor similarity relationships using Raman lidar and radar wind profiler observations.
- Larry Berg talked about using Doppler lidar to evaluate simulations of the evening transition. In this talk he showed comparisons between lidar-derived and LES-derived estimates of zi that suggest there are times when the ARM Doppler lidars are not able to see all the way to the top of the convective boundary layer.
- Satoshi Endo discussed reconciling differences between LES-predicted and Doppler lidar-observed cloud-base vertical velocities. At last year’s ASR meeting Andy Vogelmann showed substantial differences between lidar-observed and LES-predicted PDFs of w at cloud base. Satoshi showed that you can improve the agreement by incorporating spectral-bin microphysics and horizontal longwave radiation into the LES runs.
- Neil Lareau presented efforts to retrieve sub-cloud and cloud-base latent heat fluxes from Raman and Doppler lidar observations.
- Kyle Dawson talked about the retrieval of aerosol humidification factors during CHARMS. He showed that the lidar f(RH) aloft is greater than f(RH) derived from surface nephelometer measurements. He also points out the need to improved temperature profiling by the ARM RLs.