The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation for the Integration of a Virtual Evapotranspiration Sensor Based on VIIRS and Passive Microwave Sensors into the Annualized Agricultural Non-Point Source (AnnAGNPS) Pollution Model Greg Easson, H. G. Momm The University of Mississippi Ronald Bingner USDA – ARS – National Sedimentation Laboratory

The University of Mississippi Geoinformatics Center NASA RPC – March, Project Objectives To investigate the feasibility of using existing NASA results as source of ET estimates for AnnAGNPS pollution model To evaluate the continuity of the NASA-based remotely sensed ET estimates by the future missions

The University of Mississippi Geoinformatics Center NASA RPC – March, Project Rationale Evapotranspiration (ET) plays an important role for modeling surface- lower atmospheric flux processes ET estimates in a continuous and spatially distributed fashion represents a challenge for scientists Remote sensing-based techniques are sought as an possible alternative

The University of Mississippi Geoinformatics Center NASA RPC – March, Background: AnnAGNPS The Annualized Agricultural Non-Point Source Pollution model is a continuous watershed-scale computer simulation tool used to generate loading estimates for some constituents of agricultural non-point source pollution

The University of Mississippi Geoinformatics Center NASA RPC – March, Background: AnnAGNPS (continued) Developed by USDA-NRCS Event driven model Simulates –Surface flow –Sediment –Nutrients –Pesticides Used to evaluate Best Management Practices

The University of Mississippi Geoinformatics Center NASA RPC – March, Background: AnnAGNPS (continued) Watershed is divided into cells Each of these cells requires 22 parameters Climate data is derived from field weather stations located within or nearby the watershed Thiessen polygon method

The University of Mississippi Geoinformatics Center NASA RPC – March, Background: AnnAGNPS (continued) Problem when field weather stations are sparse or even non-existing

The University of Mississippi Geoinformatics Center NASA RPC – March, Project Objectives To investigate the feasibility of using existing NASA results as source of ET estimates for AnnAGNPS pollution model To evaluate the continuity of the NASA-based remotely sensed ET estimates by the future missions

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS Modifications to AnnAGNPS Concept of “Virtual” field weather stations

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Modifications to AnnAGNPS

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Study Site Long history of hydrologic work Extensive infrastructure USDA-ARS NSL past and ongoing projects

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) MOD16 daily images for 2004 Provided by scientists at The University of Montana (Nishida et al., 2003, Cleugh et al., 2007, and Mu et al., 2007). Ground sampling distance (GSD) of approximately 5,000 meters

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Two AnnAGNPS simulations –ET computed using the Penman equation –ET provided proxy-MOD16

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Results: –Average watershed ET

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Results: –Daily runoff

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Results: –Spatial distribution of the 2004 annual percent difference between ET from AnnAGNPS and from MODIS

The University of Mississippi Geoinformatics Center NASA RPC – March, Evaluation of the Integration of NASA Results into AnnAGNPS (continued) Results: –Spatial distribution of the 2004 annual percent difference between runoff from AnnAGNPS and from MODIS

The University of Mississippi Geoinformatics Center NASA RPC – March, Project Objectives To investigate the feasibility of using existing NASA results as source of ET estimates for AnnAGNPS pollution model To evaluate the continuity of the NASA-based remotely sensed ET estimates by the future missions

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results Due to the lack of published methodology describing the generation of ET estimates from VIIRS data, a different approach was considered Using the relationship between ET, VI, and LST, daily ET maps were generated from models created using multivariate linear regression techniques

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Lambin and Ehrlich’s feature space

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Daily images from April 01, 2004 to July 31, 2004 Re-sampled to 5,000 GSD 250 meter MODIS NDVI pixels 400 meter proxy- VIIRS NDVI pixels 1,000 meter MODIS LST pixels 750 meter proxy- VIIRS LST pixels

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) “Virtual” stations Field “Virtual”

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Simplified representation DOY DOY DOY DOY 4 Stations DOY

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Simplified representation

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Model development –Stations 127 to 136 (physical stations) –Stepwise backward elimination (P-value associated with Pearson’s Chi-Squared). –One model per day for each of the sensors considered

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Adjusted R 2 > 0.25

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Results –Variability of models performance –Adjusted R 2 –Predictors

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued)

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued) Simplified representation

The University of Mississippi Geoinformatics Center NASA RPC – March, Comparison of Existing and Future NASA Results (continued)

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions Linking MODIS ET with AnnAGNPS was successfully performed. The use of MODIS ET can reduce the need to collect/generate dew point, wind speed, and cloud coverage.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) Reducing uncertainty in input parameters will reduce the uncertainty in the model results. In addition, these values usually have temporal and spatial variability that are not easily taken into consideration when computing ET values.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) MODIS-ET produced 35% less ET then AnnAGNPS-ET and resulted in a 10% increase in runoff. Large watershed system, climate parameters can be highly variable.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) MODIS-ET provided a more comprehensive spatial variability capability than is not often available from measured climate stations. Additional remotely sensed data: precipitation and temperature.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) The second objective of this research project was to investigate the continuity of future NASA missions in providing ET estimates to AnnAGNPS simulation model. Daily NDVI and LST maps from MODIS and proxy-VIIRS data were used to create two sets of daily ET maps.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) Direct comparison between these two sets of daily ET maps indicates that the next generation of moderate resolution sensor will continue to be a potential source of ET estimates to simulation models such as AnnAGNPS. The VIIRS’s physical design features, such as improved signal to noise ratio and the attenuation of the “bowtie-shaped” footprint at large scan angles were not considered.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) The spatial variability demonstrated by the VIIRS-based LST map can be in part attributed to the downscaling technique used in the simulation process. Further investigation should be conducted to estimate ET for different land use/land cover classes.

The University of Mississippi Geoinformatics Center NASA RPC – March, Conclusions (continued) There are situations were the ET maps generated from VIIRS and from MODIS agreed. This demonstrates the potential of VIIRS to be used as the continuity mission, in providing ET estimates for AnnAGNPS pollution model.

The University of Mississippi Geoinformatics Center NASA RPC – March, Acknowledgements Institute for Technology Development National Sedimentation Laboratory The University of Montana NASA and the University of Southern Mississippi