The Atmospheric Radiation Measurement (ARM) Facility: Recent Advances and Plans Supporting Cloud Property Characterization

The ARM Climate Research Facility (www.arm.gov) is a user facility operated under the U.S. Department of Energy for the purpose of providing measurements of clouds, aerosols and their interaction with the Earth’s energy budget to support the international atmospheric research community. ARM operates a network of six continuously operating comprehensive atmospheric observatories located in diverse meteorological regimes. The purpose of this presentation is to describe current activities related to cloud property measurements and associated data products. These activities include substantial effort related to the ARM radar network and associated data products, a growing suite of supporting aerial measurements, and an effort to better link measurements of shallow convection at the ARM Southern Great Plains (SGP) site.

ARM has developed a new coordinated approach to maintain and characterize the elements of its radar network. Recent work has included field characterization of cloud radars at the Graciosa Island and Oliktok sites, substantial upgrades to the scanning X-band network at the SGP site and implementation of an X-band scanning radar on Graciosa Island. To enhance the usability of measurements from ARM radars and other remote sensing instruments a variety of cloud-oriented data products have been developed. To advance beyond the current ARM standard cloud retrieval, MICROBASE, which relates water content to radar reflectivity, a new cloud property retrieval framework is being developed that will enable evaluation and implementation of multiple cloud property retrievals.

To augment and evaluate ground-based cloud measurements, ARM operates a suite of aerial platforms that provide measurements of cloud and aerosol properties and the background atmospheric state over ARM sites on an episodic basis. The aerial platforms include the Gulfstream G-1 and a growing set of Unmanned Aerial Systems (UAS) and Tethered Balloon Systems (TBS). The G-1 instrument suite includes an extensive set of cloud probes and recently flew a pair of missions over the Graciosa Island ARM site. The UAS and TBS fill an important niche and are being developed to provide additional in situ measurements of aerosol and cloud properties over ARM sites.

To better link ARM observations, including cloud properties, with global-scale models, ARM has implemented a framework for running a Large Eddy Simulation (LES) model over the SGP site. This framework is currently being used to provide LES simulations of shallow convection events over the Southern Great Plains site and integrates LES simulations with ARM observations including cloud parameters such as cloud base height and liquid water path. This effort has included not only the implementation of the LES model but additional observations to constrain and evaluate the model simulations. As an example, cloud top observations are challenging in this environment because cloud radars often cannot detect very small cloud droplets in continental shallow convection. In part to address this issue for the SGP shallow convection work, ARM has recently installed three pairs of cameras around the Southern Great Plains central facility. These cameras are providing stereo images and cloud boundary maps. A project is currently underway to derive full three-dimensional cloud fields from the cloud boundary maps for broken cloud conditions.