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After 30 years of collecting data, ARM is still in the business of bettering the performance of global climate models.

ARM’s Uniquely Continuous Climate Observations

In 1989, the U.S. Department of Energy (DOE) established the Atmospheric Radiation Measurement (ARM) user facility. From its home within DOE’s Biological and Environmental Research Program, ARM organized around a task that was both big and new: To establish, over time, a series of instrumented platforms that would provide an observational basis for studying the Earth’s climate.

ARM’s mission, still being executed and refined today, was outlined back then in crisp operational language: “to advance a robust predictive understanding of Earth’s climate and environmental systems and to inform the development of sustainable solutions to the Nation’s energy and environmental challenges.”

How ARM came to be: After 30 years in action, ARM is still in the business of bettering the performance of the climate sciences’ general circulation models. Largely, it has done that by improving how those models deal with radiative energy transfer and the impact of clouds and aerosols.

ARM collects, processes, quality-checks, stores, and distributes continuous climate measurements gathered 24 hours a day in climate-critical locations. Decades ago, ARM seemed to arrive just in time. By the 1970s, concern was mounting over increasing carbon dioxide in the atmosphere. DOE and the scientific community at large were also alarmed at apparent uncertainties within global climate models.

Between 1982 and 1990, a number of federal agencies commissioned intercomparison studies of radiation models in clouds. The biggest conclusion, as one report stated, was that “cloud radiative feedback is the single most important effect determining the magnitude of possible climatic responses to human activity.” That led to ARM.

What ARM meant: To unravel the uncertainties in cloud feedbacks, it was necessary to obtain simultaneous measurements of a broad range of parameters relative to clouds and their impact on the radiative energy balance.

The key was to establish well-instrumented ground research sites in the world’s most important climate regions, including its equatorial and polar extremes. Other needs: make cloud and radiation measurements; perform experiments at appropriately short physical and temporal scales; and amass relevant data any climate researcher could use.

Performing these measurements over a long period of time further provided the unique opportunity to get away from idealized case studies and to investigate the wide range of conditions that occur in nature.

Since beginning operations, ARM has made significant contributions to improving climate prediction models as they represent radiative heat transfer, aerosol processes, and cloud processes. Scientists use data gathered from ARM’s fixed, mobile, and aerial facilities worldwide to address these issues and compare the observations with their models.

ARM was the first climate research program to deploy such a comprehensive suite of cutting-edge instrumentation for obtaining continuous measurements of cloud and aerosol properties.  This strategy revolutionized scientists’ ability to collect long-term statistics of detailed cloud properties and now serves as a model for programs around the world.

How ARM grew: By 1992, ARM’s first fixed research site was deployed. Today, the Southern Great Plains is the largest climate research field site in the world. It has seven radar sites and more than 20 instrument clusters arrayed across 9,000 square miles.

Over the next 30 years of data collection, an expanding ARM flourished in many ways. It opened (and closed) more fixed observation sites worldwide, coordinated dozens of intensive field campaigns domestically and internationally, established mobile instrument platforms, continuously fine-tuned its data flow systems, started an aerial instrumentation program, greatly expanded its toolbox of instruments, widened access to its data, joined in wider collaborations, and became a national science user facility.

In 2022, ARM continues to strengthen ties between observations and models, including an accelerated application of its data to modeling simulations.

Meanwhile, the ARM continuous data machine continues to churn and churn. So far, it has archived more than 3 petabytes of data.

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