The M-AERI (Marine-Atmosphere Emitted Radiance Interferometer) is a development of the AERI, built at the Space Science and Engineering Center, University of Wisconsin-Madison, in collaboration with the Rosenstiel School of Marine and Atmospheric Science, University of Miami, with funding from NASA. It is intended to be used as the primary validation instrument for skin sea-surface temperature (SST) retrievals from the Moderate Resolution Imaging Radiometer (MODIS) on the EOS AM- 1 satellite of the Earth Observing System.
The M-AERI is a Fourier-Transform Interferometric Spectro-Radiometer which operates in the range of infrared wavelengths from ~3 to ~18µm and measures spectra with a resolution of ~0.5 cm-1. It uses a sandwich of two infrared detectors (Indium Antimonide and Mercury Cadmium Telluride) to achieve the wide spectral range, and these are cooled to ~78oK by a Stirling cycle mechanical cooler to reduce the noise equivalent temperature difference to levels below 0.1K. The M-AERI includes two internal black-body targets for accurate real-time calibration. A scan mirror directs the field of view from the interferometer to either of the black-body calibration targets or to the environment from nadir to zenith. The mirror is programmed to step through a pre-selected range of angles. When the mirror is angled below the horizon the instrument measures the spectra of radiation emitted by the sea-surface, and when it is directed above the horizon it measures the radiation emitted by the atmosphere. The M-AERI is equipped with pitch and roll sensors so that the influence of the ship’s motion on the measurements can be determined.
The prototype M_AERI was used in a short cruise in the Gulf of Mexico in early 1995 and these measurements demonstrated the ability to measure skin SSTs to accuracies useful not only for satellite validation, but also to study the oceanic thermal skin effect in the field. Furthermore the infrared spectra can be used to derive spectra of the infrared emissivity of seawater (Smith et al., 1996).
A M-AERI was used on the Combined Sensor Cruise on the Tropical Western Pacific Ocean (Post et al., 1997). It was mounted on the port side of the ship. Long sections, greater than 3000km, across the Pacific at ~2oS going west and ~1oS going east both showed a thermal skin effect of about 0.2K with respect to in situ measurements at a depth of 5m, with a diurnal signal superimposed. When conditions were favorable, the diurnal warming caused the skin temperature to become warmer than the 5m temperature. However, when on station off Papua New Guinea and a surface float was used, and these measurements show that the skin temperature remained consistently colder than bulk measurements made at a depth of a few centimeters. The diurnal modulation of the skin-bulk temperature difference shows a strong dependence on wind surface wind speed.
The size of the skin effect and superimposed diurnal signal was found on another transect from Hawaii to New Zealand in late 1997 on the R/V Roger Revelle. (For more details of the ship, click here).
For further details, please contact Peter Minnett
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