Exploiting a decadal time-series of spectrally resolved downwelling infrared radiances at Dome C, Antarctica to assess the occurrence of advective warming events

On the East Antarctic Plateau, in winter, rapid warming events originated by the advection of warm, moist air from lower latitudes, cause the disruption of the stable thermal structure of the atmosphere, and can be linked to the warming of the Plateau region itself. Continuous monitoring of these events can shed light on temperature trends in East Antarctica, trends which are still not clearly defined in terms of origin and amount.

Since the main mechanism acting in the warming events is the strong increase in cloud cover linked to the higher water content of the advected air, for a systematic monitoring of warming phenomena a simultaneous detection of water vapor vertical profile and cloud properties is needed. These two tasks can be both performed through the analysis of spectrally resolved atmospheric downwelling emitted radiances.

The REFIR (Radiation Explorer in the Far Infrared) Fourier transform spectroradiometer was installed at Concordia station, in the Dome C region of the Antarctic Plateau, in December 2011, and it has been performing continuous measurement since then. REFIR measures the downwelling atmospheric radiance in the 100-1500 cm^-1 (6.7-100 µm) spectral interval, with a resolution of 0.4 cm^-1, and with a repetition rate of about 10 minutes. The measured spectral interval extends from the far infrared, which includes the water vapor rotational band, to the atmospheric window region (8-14 µm), which provides information about the radiative effects of clouds.

A dedicated inversion code was developed to retrieve vertical profiles of water vapor and temperature from the measured emission spectra. The retrieved profiles allow for the monitoring of the evolution of the vertical structure of the troposphere on a 10 minutes timescale, whereas the spectral radiance itself provides, in a more direct way, information on the cloud cover. Therefore, the dataset produced by the REFIR instrument allow us to detect and obtain statistics about warming events in the Dome C region.