HYDROLOGIC REMOTE SENSING AND APPLICATIONS
Our research group uses remote sensing products to develop high resolution land surface and atmospheric products. These products are critical for characterizing and understanding spatial and temporal heterogeneity in watershed systems and for validating hydrologic models in regions where ground-based data are not readily available. Ongoing studies investigate solely satellite-derived net radiation and evapotranspiration with regional application. We utilize satellite imagery such as MODIS (Moderate Resolution Imaging Spectroradiometer), Landsat, and GOES (Geostationary Operational Environmental Satellite). Products of interest include land surface temperature, albedo, vegetation indices, and radiation, among many others. These remotely sensed products are used to spatially and temporally improve prediction and management of hydrological variables and vegetation in ungauged areas or disturbed systems.
- MODIS triangle-based evapotranspiration (ET) algorithm (2013) for semi-arid regions (Kim and Hogue, 2013)
- Triangle method, relying on remotely sensed inputs and a previously developed net radiation model.
- Solely MODIS-based products for estimation of ET at the daily timestep for clear and cloudy days
- Model assumption of a linear variation in evaporative fraction across the triangular domain (LST/EVI space) results in more uncertainty under water-stressed conditions such as those found at the upland sites.
Overall, the proposed MODIS-based algorithm provides reasonable estimates of riparian and upland plant water use and unique spatial and temporal information.
- Downscaling AMSR-E Soil Moisture method using Passive Microwave observations and finer resolution Visible/Near Infrared observations (Kim and Hogue, 2011)
- Various key factors (i.e., surface temperature, vegetation indexes, and albedo) derived from MODIS provide information on relative variations in surface wetness conditions and contribute weighting parameters for downscaling the larger AMSR-E soil moisture footprint
- Development of MODIS-Based Potential Evapotranspiration, which is a continuous, daily time series of potential evapotranspiration (PET) MODIS (Kim and Hogue, 2008)
- Priestley–Taylor equation, incorporating a daily net radiation model during cloudless days
- “Theoretical clear-sky” net radiation and PET is used to estimate net radiation and PET under cloudy conditions
- Requires minimal ground-based observations for initial calibration of regional radiation algorithm coefficients
In general, the MODIS-based daily PET estimates derived in this study are promising and show the potential for use in theoretical and operational water resource studies in both gauged and ungauged basins.