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
 Water Management and Conservation Research: Maricopa, AZ
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                                    Software
                People

                    Staff Listing
                                    Careers


        


                    Research Units
                        Main Page - ALARC
                                    Pest Management and Biocontrol Unit
                                    Plant Physiology and Genetics Unit
                                    Western Regional Biomass Research Center
                    About UsSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Pacific West Area Maricopa, Arizona U.S. Arid Land Agricultural Research Center Water Management and Conservation Research 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
                                            French, Andrewitem
                                            Alfieri, Josephitem
                                            Kustas, William

                                                         - *Bill*item
                                            Prueger, Johnitem
                                            HIPPS, LAWRENCE - Utah State Universityitem
                                            Chavez Eguez, Joseitem
                                            Evett, Steven

                                                         - *Steve*item
                                            Howell, Terryitem
                                            Gowda, Prasannaitem
                                            Hunsaker, Douglas

                                                         - *Doug*item
                                            Thorp, Kelly
  Submitted to: Advances in Water Resources
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 7/6/2012
                                    Publication  Date: 7/7/2012
                                    Citation: French, A.N., Alfieri, J.G., Kustas, W.P., Prueger, J.H., Hipps, L.E., Chavez Eguez, J.L., Evett, S.R., Howell, T.A., Gowda, P., Hunsaker, D.J., Thorp, K.R. 2012. Estimation of surface energy fluxes using surface renewal and flux variance techniques over an advective irrigated agricultural site. Advances in Water Resources. 50:91-105. doi:10.1016/j.advwatres.2012.07.007.Interpretive Summary: Estimating the surface energy balance over irrigated lands is important for monitoring and managing the amount of water used for crops. The energy balance is especially important for windy regions where crop water use can sometimes greatly exceed average requirements. One way to accurately measure this surface energy is with an eddy-covariance system, which is a collection of instruments that combines precise observations of energy fluxes in the air, plants and soil. However, these systems are expensive and complex, hindering their deployment beyond more than a few sites. One way that could reduce this obstacle is to deploy monitoring systems that collect air temperature data that can be used to emulate energy flux information obtained in more costly ways. These systems are based on data from fine-wire thermocouples that are combined with models known as ‘surface renewal’ and ‘flux variance’. The accuracies of these models were tested in a field experiment, BEAREX 2008, conducted at Bushland, Texas. Both methods produced good results at midday, and acceptable estimates at other times of day. These outcomes will be important for investigators seeking effective, low-cost ways to measure crop water use in windy environments.
                                Technical Abstract: Estimation of surface energy fluxes over irrigated agriculture is needed to monitor crop water use. Estimates are commonly done using well-established techniques such as eddy covariance (EC) and weighing lysimetry, but implementing these to collect spatially distributed observations is complex and costly. Two techniques that could simplify flux observations are the surface renewal and flux variance approaches. These methods infer sensible heat fluxes from high frequency observations of near surface air temperatures using low cost thermocouples. In combination with net radiation and soil heat flux observations, surface renewal and flux variance observations produce latent heat fluxes as a residual of the surface energy balance. The viability of these techniques was tested in a strongly advective irrigated agricultural setting as part of the Bushland Evapotranspiration and Remote Sensing Experiment in 2008 (BEAREX08). Using 20Hz air temperature data collected between 12 June and 13 August from two cotton field sites and one senescent grass site, sensible heat flux estimates were generated. Surface flux conditions ranged widely and include episodes of latent heat fluxes exceeding net radiation. Flux estimates from surface renewal and flux variance were similar with respect to simultaneous eddy covariance observations on most days. At midday the flux variance had better peformance than surface renewal estimates, although the reverse was true for early morning and late afternoon transition times. During advection neither approach was accurate, although the surface renewal fluxes did a better job estimating the correct sign of sensible heat fluxes . Both techniques were found to offer flux estimates comparable to EC data with the additional potential benefit of reduced fetch requirements. These outcomes indicate that flux data with accuracies approaching EC capabilities is feasible with a potential for reduced deployment complexity and  cost.


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