Open AccessInfluence of meter-scale wind-formed features on the variability of the microwave brightness temperature around Dome C in Antarctica
Author(s) -
Ghislain Picard,
A. Royer,
Laurent Arnaud,
Michel Fily
Publication year - 2014
Publication title -
the cryosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.574
H-Index - 82
eISSN - 1994-0424
pISSN - 1994-0416
DOI - 10.5194/tc-8-1105-2014
Subject(s) - brightness temperature , brightness , snow , radiometer , transect , remote sensing , geology , special sensor microwave/imager , microwave radiometer , atmospheric sciences , environmental science , optics , physics , geomorphology , oceanography
Space-borne passive microwave radiometers are widely used to retrieveinformation in snowy regions by exploiting the high sensitivity of microwaveemission to snow properties. For the Antarctic Plateau, many studiespresenting retrieval algorithms or numerical simulations have assumed,explicitly or not, that the subpixel-scale heterogeneity is negligible andthat the retrieved properties were representative of whole pixels. In thispaper, we investigate the spatial variations of brightness temperature over arange of a few kilometers in the Dome C area. Using ground-based radiometerstowed by a vehicle, we collected brightness temperature at 11, 19 and 37 GHzat horizontal and vertical polarizations along transects with meterresolution. The most remarkable observation was a series of regularundulations of the signal with a significant amplitude reaching 10 K at37 GHz and a quasi-period of 30–50 m. In contrast, the variability atlonger length scales seemed to be weak in the investigated area, and the meanbrightness temperature was close to SSM/I and WindSat satellite observationsfor all the frequencies and polarizations. To establish a link between thesnow characteristics and the microwave emission undulations, we collecteddetailed snow grain size and density profiles at two points where oppositeextrema of brightness temperature were observed. Numerical simulations withthe DMRT-ML microwave emission model revealed that the difference in densityin the upper first meter explained most of the brightness temperaturevariations. In addition, we found that these variations of density near thesurface were linked to snow hardness. Patches of hard snow – probably formedby wind compaction – were clearly visible and covered as much as 39% ofthe investigated area. Their brightness temperature was higher than in normalareas. This result implies that the microwave emission measured by satellitesover Dome C is more complex than expected and very likely depends on theyear-to-year areal proportion of the two different types of snow