Talks and Poster Presentations (with Proceedings-Entry):

C. Paulik, S. Zwieback, V. Naeimi, W. Wagner, R. Kidd:
"Comparison of 2 approaches for freeze/thaw detection from ASCAT data.";
Talk: EUMETSAT Meteorological Satellite Conference, Sopot, Poland; 2012-09-03 - 2012-09-07; in: "Proceedings", (2012), 19 pages.

English abstract:
The Freeze/Thaw state of the soil has comprehensive influence on, among others, surface and subsurface hydrology, surface energy and water balance and ecosystem processes. A robust determination of the freeze/thaw state is also very important for the estimation of soil moisture from ASCAT backscatter observations. Soil moisture values observed under frozen conditions lack physical meaning and if not correctly picked out also influence the estimation of the model parameters which in turn will reduce the accuracy of all soil moisture estimates. This makes the correct identification of the freeze/thaw state a crucial component for robust soil moisture retrieval with active microwave sensors.

The first approach, the Surface State Flag, was developed within the framework of the GMES project geoland2 and and aims at flagging soil moisture estimates from ASCAT for the near real time generation of the Soil Water Index (SWI). It uses ASCAT backscatter information as well as ancillary data like the probability of negative temperatures and snowcover and is based on a empirical-threshold analysis algorithm. The second approach uses a probabilistic time series model (Hidden Markov Model) in which ASCAT backscatter and ERA Interim air temperature data are combined to estimate the freeze/thaw state.

In the framework of the FP7 program CCI Soil Moisture this work tries to assess how the results produced by the different approaches differ and which one is better suited for freeze/thaw flagging during soil moisture retrieval.

Electronic version of the publication:

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