Instrument: Marine-Atmospheric Emitted Radiance Interferometer

The the Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) is a Fourier Transform Infrared (FTIR) sprectoradiometer with calibrations traceable to NIST standards. The M-AERI measures spectra in the infrared (about 3 to 18 micrometers) range with a resolution of about 0.5 cm-1. It uses two infrared detectors cooled to 78 K by a Stirling cycle cooler to reduce the noise equivalent temperature difference to levels well below 0.1 K.

The radiometric calibration of the M-AERI is done continuously using two internal black-body cavities, each with an effective emissivity of greater than 0.998. The mirror scan sequence includes measurements of the reference cavities before and after each set of spectra from the ocean and atmosphere. The absolute accuracy of the M-AERI calibration is monitored by episodic use in the laboratory of a NIST-certified water-bath black-body calibration target and residual errors in the M-AERI spectral brightness temperature measurements at temperatures typical of the ocean surface and lower troposphere are typically less than 0.03K.

The interferometer integrates measurements over a pre-selected time interval, usually a few tens of seconds, to obtain a satisfactory signal to noise ratio, and a typical cycle of measurements including two view angles to the atmosphere, one to the ocean, and calibration measurements, takes about ten minutes. The absolute accuracy of the spectral measurements (when expressed as a brightness temperature) is 20-30 mK. The measured spectra are processed in real-time to generate measurements of the skin SST and air temperature at the height of the instrument to accuracies much better than 0.1K.

Reference:

Minnett, P. J., R. O. Knuteson, F. A. Best, B. J. Osborne, J. A. Hanafin and O. B. Brown, 2001. The Marine-Atmospheric Emitted Radiance Interferometer (M-AERI), a high-accuracy, sea-going infrared spectroradiometer. Journal of Atmospheric and Oceanic Technology, 18: 994-1013.