Shareware lidar: an entry level network system to enable boundary layer and cloud studies for the lower troposphere

Ground-based networks of lidars have long been recognized as important to establish atmospheric observations of aerosols and clouds. Most of these lidar networks are now participating in the Global Atmospheric Watch Atmospheric Lidar Network (GALION), recently formed by the World Meteorological Organization. In the US, both NASA (MPLNET) and DOE (ARM program) have invested significant resources to establish their own global lidar networks based on a commercial product called a Micro-Pulse Lidar (MPL). These existing networks are attractive because a common-style lidar is used suitable for unattended operation enabling continuous 24/7 measurements, uniformity, and consistency to network-wide data. However, these systems are significant in cost (>$100,000 USD) and are also complicated by near-field calibration corrections inherent with the MPL approach. These difficulties have limited the production of calibrated data to those programs with sufficient resources and infrastructure to handle the calibration complexities and sensitive optical alignments. For the larger community to participate fully in profiling the aerosol structure, it is obvious from the evolution of existing networks that cost and complexity are going to be major factors. In the National Research Council Report on Mesoscale Observational Capabilities to Meet Multiple Needs (NRC, 2008), this observational gap was highlighted by noting that 400 lidars are needed to be strategically placed across the US to adequately understand the mesoscale structure of the lower troposphere.

In this study, we explore the performance of simple visible-wavelength “eye-safe” lidar system as a means to address near-field calibration issues for MPLs and as a low-cost stand-alone lidar system for entry-level research participants interested in lower troposphere studies. Modeling studies and measurements indicate that visible-wavelength “eye-safe” transmitter with a wide field-of-view (WFOV) receiver are capable of yielding useful measurements in the planetary boundary layer while simultaneously eliminating key near-field calibration problems. Results will be presented using an example portable WFOV receiver with “eye-safe” transmission energies to illustrate daytime and nighttime performance over a range of atmospheric conditions. Data collected to date demonstrate the ability to capture boundary layer heights and mixing dynamics, even during daytime when solar background levels are high. Representative measurements will be presented for different aerosol loading conditions, along with a discussion on expected performance, and example data products that can be obtained. The instrument development is intended to result in a public-domain device, with emphasis on a modular design using commercial off-the-shelf components, interchangeable sub-components, and ease of assembly. The ideal prototype system would be based on several factors to make it desirable for long-term use in a lidar network setting. All aspects of the system, including components list, software, assembly and alignment procedures would be publicly available to research groups to replicate the system. The goal would be to enable university groups that do not have expertise in lidar systems or cannot afford to purchase a full-cost commercial lidar to participate in network activities with a standardized instrument, enabling a broader scale of networking activity for the community at-large. Interested groups are invited to participate in this effort and help with the development, test and evaluation, networking, data analysis, and education aspects of this effort.