In July, the SGP site hosted an instrument intercomparison between the AERI and the new ASSIST instrument, shown above.

One instrument scientists use to obtain measurements important for climate studies is an atmospherically emitted radiance interferometer, or AERI. This sophisticated instrument measures the absolute infrared spectral radiance of the sky directly above the instrument. In July, the ACRF Southern Great Plains (SGP) site hosted a new instrument for measuring these spectra, called the Atmospheric Sounder Spectrometer for Infrared Spectral Technology, or ASSIST. It operated for 10 days side-by-side with the AERI to obtain comparative data that will help scientists to validate new instrumentation and data processing algorithms, as well as improve research performed using AERI-like measurements. Data from the AERI can be used to evaluate radiative transfer codes in models, detect and quantify cloud effects on ground-based radiance measurements, and calculate vertical atmospheric profiles of temperature and water vapor and the detection of trace gases.

For the instrument intercomparison, operations staff at the SGP helped to situate the ASSIST next to the AERI, and also carved out space for the control computer and data display at the SGP Guest Instrument Facility. On relatively cloud-free days, SGP staff also supplemented their routine radiosonde launch schedule with additional launches to coincide with the MetOp satellite overpasses in the morning and evening. Scientists sponsored by the Department of Energy’s Remote Sensing Laboratory will compare radiance measurements from the ASSIST with those from the AERI and radiances calculated from the radiosonde observations to determine systematic and random differences from a statistical ensemble of these comparisons.