Snow thickness retrieval over thick Arctic sea ice using SMOS satellite data 1Institute of Oceanography, University of Hamburg, Bundesstraße 53, 20146 Hamburg, Germany
20 Dec 2013
2European Space Agency, ESA-ESTEC, 2200 AG Noordwijk, the Netherlands
Received: 30 Jun 2013 – Published in The Cryosphere Discuss.: 23 Jul 2013 Abstract. The microwave interferometric radiometer of the European Space
Agency's Soil Moisture and Ocean Salinity (SMOS) mission measures at
a frequency of 1.4 GHz in the L-band. In contrast to other
microwave satellites, low frequency measurements in L-band have
a large penetration depth in sea ice and thus contain information on
the ice thickness. Previous ice thickness retrievals have neglected
a snow layer on top of the ice. Here, we implement a snow layer in
our emission model and investigate how snow influences L-band
brightness temperatures and whether it is possible to retrieve snow
thickness over thick Arctic sea ice from SMOS data.
Revised: 14 Nov 2013 – Accepted: 26 Nov 2013 – Published: 20 Dec 2013
We find that the brightness temperatures above snow-covered sea ice
are higher than above bare sea ice and that horizontal polarisation
is more affected by the snow layer than vertical polarisation. In
accordance with our theoretical investigations, the root mean square
deviation between simulated and observed horizontally polarised
brightness temperatures decreases from 20.9 K to
4.7 K, when we include the snow layer in the
simulations. Although dry snow is almost transparent in L-band, we
find brightness temperatures to increase with increasing snow
thickness under cold Arctic conditions. The brightness temperatures'
dependence on snow thickness can be explained by the thermal
insulation of snow and its dependence on the snow layer thickness.
This temperature effect allows us to retrieve snow thickness over
thick sea ice. For the best simulation scenario and snow thicknesses
up to 35 cm, the average snow thickness retrieved from
horizontally polarised SMOS brightness temperatures agrees within
0.1 cm with the average snow thickness measured during the
IceBridge flight campaign in the Arctic in spring 2012. The
corresponding root mean square deviation is 5.5 cm, and the
coefficient of determination is r2 = 0.58.
Citation: Maaß, N., Kaleschke, L., Tian-Kunze, X., and Drusch, M.: Snow thickness retrieval over thick Arctic sea ice using SMOS satellite data, The Cryosphere, 7, 1971-1989, doi:10.5194/tc-7-1971-2013, 2013.