Breakout Summary Report


ARM/ASR User and PI Meeting

10 - 13 June 2019

LASSO Update and Discussion: Expansion Beyond Shallow Convection
11 June 2019
1:30 PM - 3:30 PM
William I. Gustafson Jr., Andrew M. Vogelmann, and James H. Mather

Breakout Description

The Large-Eddy Simulation (LES) Atmospheric Radiation Measurement (ARM) Symbiotic Simulation and Observation (LASSO) workflow provides high-resolution simulations of shallow convection at ARM’s Southern Great Plains (SGP) atmospheric observatory to complement the large suite of observations at the site. The goals of this breakout session were to convey an update of LASSO releases since the prior PI Meeting, and to involve the ARM/ASR community in the decision process for LASSO expansion. This session served as the final group setting for open discussion on LASSO expansion prior to providing a report to management to facilitate their decision process.

Main Discussion

The update on LASSO activities highlighted the 30 new cases to be released this summer from the 2018 shallow convection season. Two new products have been added to LASSO this year. The first is a new LCL VAP that is produced daily and includes time series of LCL for the SGP and Oklahoma Mesonet surface stations. The second is a data set containing high-frequency observations for the LASSO case dates. This latter file is produced just for LASSO days and contains the input observations used within the LASSO data bundle, but with high time sampling instead of the hourly sampling used for the model evaluation. A new data product included in this file provides cloud-base heights retrieved from the five Doppler lidars around the SGP.

Most of the breakout was devoted to discussion about LASSO expansion ideas. The group was informed that community members submitted white papers with LASSO expansion ideas in March 2019, and a workshop in May discussed the various proposed scenarios for expanding LASSO beyond shallow convection at the Southern Great Plains. Results from the LASSO Expansion Workshop were presented for each of the following scenarios, which were each defined based on white papers written in preparation for the workshop, followed by an opportunity for community members to provide feedback and offer additional insight. Four scenarios were presented: clear-air turbulence with a focus on diurnal transitions and the stable boundary layer, arctic clouds, maritime clouds at the East North Atlantic (ENA) site, and deep convection during the CACTI field campaign.

  1. Clear-air turbulence

    • The science drivers for this scenario focus around transitions in the boundary-layer state associated with the day-to-night transition and the subsequent stable conditions. Discussion brought up questions about the importance of surface heterogeneity and a desire for using a nested configuration with detailed handling of the soil/surface. The use of the tethersonde to obtain profiles of meteorological state was suggested. Concern was noted of the ultra-high resolution that would be needed to capture the smaller eddies present during the decay process.

  2. Deep convection scenario

    • The science drivers for this scenario focus on convective dynamics and microphysics-dynamics interactions. The primary focus would be on convective initiation and the early stages of the convective life cycle. The model configuration would be for CACTI with an initial ensemble of mesoscale simulations performed to ultimately choose boundary conditions for LES run(s) for each case. A suggestion was made to include an inline radar simulator to reduce output requirements, but it is unclear how much this would help.

  3. Maritime scenario

    • The science drivers for this scenario focus on precipitation processes in shallow maritime clouds with additional interest in aerosol-cloud interactions in these conditions. The model would be configured using an an ocean-only domain at the East North Atlantic site.

  4. Arctic scenario

    • The science drivers for this scenario are arctic cloud processes and interactions between the surface, boundary layer, and clouds. The simulations would focus on the MOSAiC field campaign period to further benefit from the added attention in this region from the Year of Polar Prediction. Questions were raised regarding the option of using interactive ice-surface modeling, but it was noted that this would not be likely. Questions were also raised about uncertain ice microphysics and how this would be handled.

Overall discussion included questions about the use of ensembles and how this would be appropriate for the different scenarios. It was also noted how LASSO integrates many aspects of ARM and helps focus attention of both users and the infrastructure staff.

Key Findings

There was some discussion about how much LASSO has been used. Some statistics were presented but this may be something that ARM needs to illustrate better. A suggestion for another use of LASSO was to take advantage of the many simulations that have been done to assess how well the model has done in simulating shallow convection. This could be a useful science paper.

It was also noted that an important element of LASSO is the set of diagnostics that have been created and that it would be a service to the community if these diagnostics could be applied to models more broadly (beyond the LASSO WRF simulations).


Need to determine the ability of the measurements to quantify the smallest scales of motion for the clear-air scenario.

There is a need for profiles of temperature and moisture fluxes, which could be computed from combining multiple lidar instruments. Multiple researchers have done this, but no operational product is currently available. Also, the uncertainty from these products would need to be quantified in order to reliably use them. This would benefit multiple scenario types with a priority for the clear-air scenario.

It was noted that the ENA does not currently include operational measurements of sea salt particles. This would be highly desirable for defining conditions around the proposed maritime scenario.

Reliable radar coverage and products for regional precipitation are needed to successfully execute the maritime and deep convection scenarios. This limits some options, such as doing the maritime scenario at the ENA outside of the ACE-ENA field campaign period until the XSAPR-2 is back online. C-band coverage also prevents doing deep convection at the SGP.

For the arctic case in particular, it will be important to test the microphysics up front before doing extensive simulations.


See “issues.”



Future Plans

It is hoped that all four scenarios will be implemented over time with the shallow convection scenario operating for one to two more years. There is value in all four scenarios, and the current decision process will be strongly determined by availability of observations and the time needed to design and test each scenario. Each one has its own set of unique data products and model configuration questions.

Action Items

The LASSO Expansion Workshop report will be released later this summer. Likewise the 2018 LASSO cases will be released this summer.