U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 close



Research
                Research Home
                            National Programs
                            Research Projects
                            Scientific Manuscripts
                            International Engagement
                            Scientific Software/Models
                            Databases and Datasets
                            Office of Scientific Quality Review
            Media
                News & Features
                            Multimedia
                            Briefing Room
                            Down on the Farm
                            Press Room
                            Science in Your Shopping Cart
                            Scientific Discoveries
                            Tellus
                            Under the Microscope
            About ARS
                About ARS Home
                            Staff Directory
                            Labs and Research Centers (Map)
                            Headquarter Offices
                            Organizational Chart
                            Employee Services (REE Employees Only)
                            Office of Outreach, Diversity, and Equal Opportunity
            Work With Us
                Work With Us Home
                            ARS Vacancies at USAJOBS
                            Careers at ARS Information
                            Scientific Collaborations
                            Extramural Agreements
                            1890 Faculty Research Sabbatical ProgramSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Fitzmaurice, Jeanitem
                                            Crow, Wade
  Submitted to: American Meteorological Society
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 2/1/2011
                                    Publication  Date: 3/10/2011
                                    Citation: Fitzmaurice, J.A., Crow, W.T. 2011. Online vegetation parameter estimation using passive microwave observations for soil moisture estimation [abstract]. American Meteorological Society. 2011 CDROM.Interpretive Summary:
                                Technical Abstract: Vegetation affects the ability to estimate soil moisture from passive microwave observations by attenuating the surface soil moisture signal. To use radiobrightness observations in land data assimilation a vegetation opacity parameter is required as input to a radiative transfer model, which maps surface soil moisture to radiobrightness temperature. Ancillary vegetation data options, for example visible/NIR remote sensing data or monthly climatology, are external and uncertain. Other approaches which rely on dual incidence angles are not feasible for the proposed NASA SMAP (Soil Moisture Active Passive) mission which has a fixed incidence angle instrument.

We propose to estimate the vegetation opacity parameter online using an ensemble Kalman filter. The parameter is part of the observation operator, the radiative transfer model. A state augmentation approach is used where the vegetation parameter is added to the soil moisture vector. The filter consists of a two-layer soil hydrology model and the radiative transfer model and is tested using simulated passive microwave observations. We study both time-invariant and time-varying parameter cases. The novel time-varying parameter case yields satisfactory parameter estimation results. The time-varying vegetation opacity case is derived from field leaf area index observations from
a field site of corn crop during a growing season. Adding small variance mean zero Gaussian noise is required in the time-varying case to converge to the true parameter, consistent with theory. Vegetation information could be extracted from passive microwave observations using the data assimilation system itself. This online approach differs from physical methods which require dual frequency, dual polarization or dual incidence angle observations.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov