Identification

Title

A land surface soil moisture data assimilation system based on the dual-UKF method and the Community Land Model

Abstract

Many studies have shown the deficiencies of the extended Kalman filter (EKF), even though it has become a standard technique used in nonlinear estimation. In the EKF method, the state distribution is propagated analytically through the first-order linearization of the nonlinear system, which can introduce large errors in variable estimation and may lead to suboptimal performance and sometimes divergence of the filter. The unscented Kalman filter (UKF) addresses these problems using a deterministic sampling approach to capture the posterior mean and covariance accurate to the third order for any nonlinearity, while the dual-UKF method uses two UKF filters (one for state variables and one for parameters, in contrast to only one filter in the usual UKF) to simultaneously optimize the model states and parameters using observational data. In this paper, we employ the dual-UKF method to account for the effects of land surface subgrid-scale heterogeneity and soil water thawing and freezing and implement it into the NCAR Community Land Model version 2.0 to build a data assimilation system for assimilating satellite observations of soil moisture. Experiments for two sites in north and south China show that this dual-UKF-based assimilation system outperforms the usual UKF- and EKF-based methods in reproducing the temporal evolution of daily soil moisture, especially under freezing conditions. Furthermore, the improvement also propagates, albeit to a lesser extent, to lower layers where observations are unavailable.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7g1624q

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2008-07-29T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact