Ground-based Infrared Sounders: A New Look at Their Capabilities for Operational Meteorologists

Despite many improvements in operational U.S. upper air observing systems over the last 50 years, the planetary boundary layer remains a vastly under observed portion of the atmosphere. Currently, no operational boundary layer observing networks exist in the U.S., and any instrumentation deployed to monitor the boundary layer has primarily been the result of research campaigns. This deficit highlights a generally underexplored avenue towards improving the U.S.'s abilities in weather prediction.

From 1999 to 2003, the Atmospheric Radiation Measurement (ARM) program maintained a research network of high-temporal resolution boundary layer profilers across five sites in Oklahoma and Kansas. Each site hosted an infrared thermodynamic sounder named the Atmospheric Emitted Radiance Interferometer (AERI) in addition to a radar wind profiler and in situ surface meteorological instruments. Together, these instruments produced continuous observations of temperature, moisture, and wind profiles through the depth of the boundary layer at a spatial density higher than the current operational radiosonde network and a temporal resolution (approx. 8 minutes) comparable to the existing NEXRAD Doppler radar network. Prior research using this observing network demonstrated its utility for severe storm forecasting, but work was limited as AERI thermodynamic retrieval algorithms were restricted to clear-sky observations only. A newly developed algorithm, the AERI Optimal Estimation (AERIoe) retrieval, overcomes this restriction and offers the ability to retrieve thermodynamic profiles from AERI data in cloudy conditions as well as clear ones. This new retrieval greatly improves the utility of this demonstration network by enabling the AERI to be used in a much wider variety of meteorological situations.

We believe that this ability to profile the atmosphere at a high temporal resolution in both cloudy and clear conditions is a significant aid to operational forecasters. To help demonstrate this, data collected by this network from two significant weather events in Oklahoma: the 8 May 2003 Oklahoma City tornado and the 25-26 December 2000 Great Plains ice storm, will be presented to show how a network of these instruments can provide critical support to forecasters and nowcasters through its ability to observe rapid changes in thermodynamic and kinematic structures. These cases provide a fresh look into the capabilities of the AERI, make an argument for an updated network of AERI instruments, and demonstrate how such a network can help fill gaps in our current understanding of synoptic scale and mesoscale events.