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Water & Energy Cycles

I propose to validate and improve the Surface Energy Balance Algorithm for Land (SEBAL) and the NASA Land Information System (LIS) to improve evapotranspiration (ET) mapping in the semi-arid drought-prone south-western US. SEBAL uses Landsat and MODIS satellite imagery to solve the energy balance equation at the land surface to calculate ET as the residual. The satellite radiometric surface temperature is mapped to H by subjective user selection of a pixel which is fully evaporating (e.g. irrigated alfalfa) and a pixel without water availability (ET=0). If H over the pixel scale was known from ground truth measurements, an automatic calibration would be possible. However, the assimilation of sensible and latent heat fluxes into hydrologic models is complicated by the scale gap between footprints of existing surface flux measurements (lysimeter, eddy covariance) and the pixel or gridcell area of SEBAL, LIS, and other models. Large Aperture Scintillometer (LAS) measurements of H over transect lengths of up to 4 km, a scale commensurate with model grid or pixel sizes will improve the accuracy of these models and algorithms through data assimilation and calibration. To leverage existing NASA work, we will evaluate LIS and SEBAL using a unique database of over 10 ground flux measurements sites, high resolution LIS model runs, and SEBAL results collected in 2007 in the Middle Rio Grande riparian area of New Mexico. Spatial and temporal evolution of the differences between measurements and models will be examined. A particular emphasis will be the relationship between radiometric surface temperature and heat flux to evaluate strategies for automated calibration of SEBAL imagery. A second focus is the quality of downscaling methods from coarse thermal imagery data using higher resolution visible channels, as this is critical in riparian areas. Scaling and subpixel variability will also be the focus of a field campaign in year 2. Through the use of unmanned aerial vehicles collocated with LAS measurements, I will conduct detailed spatiotemporal mapping of radiometric surface temperatures. This analysis will provide bounds to the spatio-temporal variability of surface temperature around the time of the satellite overpass. This project will result in progress in expanding and accelerating the realization of societal benefits from NASA's earth science work. From calibrated SEBAL - ET maps of the Imperial Valley, CA, created during the experiment in year 2, we will analyze fallow land ET. Temporal and spatial distribution of the fallow land ET will be analyzed to obtain policy relevant recommendations for land fallowing practices. We also anticipate that we can demonstrate successfully how scintillometer data can be integrated into remote sensing algorithms to develop more accurate spatio-temporal maps of ET. In this way the research products are useful to activities sponsored by the Applied Sciences Program, in particular, the applications area of Water Resources. The results from this project should demonstrate the utility of such a remote sensing product to optimize crop irrigation in near real-time and result in significant water conservation. Besides these outreach efforts to water agencies, the education and public outreach will be significant. The PI has already engaged in outreach activities through the organization of a nationwide workshop on scintillometry in September 2009 in New Mexico. Kleissl also works with the UC Extension Service in Imperial on evaluating water conservation strategies and has presented in a workshop on climate change impacts on ET at the California Dept of Water Resources. Strongly anchored in the university and local K12 setting where water conservation has risen to great prominence, Kleissl will organize water conservation competitions and disseminate water cycle teaching modules in teaching together with the California Space Grant Consortium.

Project PI: Jan Kleissl/UC San Diego

9500 Gilman Dr, EBUII - 580 University of California, San Diego La Jolla, CA, 92093-0411

Phone: (858) 534-8087

Fax: (858) 534-7599

Email: jkleissl@ ucsd.edu

http://maeresearch.ucsd.edu/kleissl/

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Started: Sep 29, 2010

Last Activity: Jan 05, 2011

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