Assimilation of ice and water observations from SAR imagery to improve estimates of sea ice concentration

In this paper, the assimilation of binary observations calculated from synthetic aperture radar (SAR) images of sea ice is investigated. Ice and water observations are obtained from a set of SAR images by thresholding ice and water probabilities calculated using a supervised maximum likelihood estim...

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Bibliographic Details
Published in:Tellus A: Dynamic Meteorology and Oceanography
Main Authors: K. Andrea Scott, Zahra Ashouri, Mark Buehner, Lynn Pogson, Tom Carrieres
Format: Article in Journal/Newspaper
Language:English
Published: Stockholm University Press 2015
Subjects:
sea ice
data assimilation
synthetic aperture radar
binary
Bayesian
probability
forward model
Oceanography
GC1-1581
Meteorology. Climatology
QC851-999
Sea ice
Online Access:https://doi.org/10.3402/tellusa.v67.27218
https://doaj.org/article/1da3780bdd7b4d228423b73191cc0993
Description
Summary:In this paper, the assimilation of binary observations calculated from synthetic aperture radar (SAR) images of sea ice is investigated. Ice and water observations are obtained from a set of SAR images by thresholding ice and water probabilities calculated using a supervised maximum likelihood estimator (MLE). These ice and water observations are then assimilated in combination with ice concentration from passive microwave imagery for the purpose of estimating sea ice concentration. Due to the fact that the observations are binary, consisting of zeros and ones, while the state vector is a continuous variable (ice concentration), the forward model used to map the state vector to the observation space requires special consideration. Both linear and non-linear forward models were investigated. In both cases, the assimilation of SAR data was able to produce ice concentration analyses in closer agreement with image analysis charts than when assimilating passive microwave data only. When both passive microwave and SAR data are assimilated, the bias between the ice concentration analyses and the ice concentration from ice charts is 19.78%, as compared to 26.72% when only passive microwave data are assimilated. The method presented here for the assimilation of SAR data could be applied to other binary observations, such as ice/water information from visual/infrared sensors.

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