Graduate Thesis Or Dissertation
 

Land surface energy balance and surface soil moisture variation in HAPEX-MOBILHY

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9019s593n

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  • The HAPEX-MOBILHY regional experiment provided an significant opportunity to analyze the partition of energy and distribution of water over land surfaces. The combination of remotely sensed data and ground instrument networks over the large-scale in situ experiment allowed investigation of spatial and temporal variation of such hydrologic parameters as the latent heat flux and surface soil moisture. A literature review provided the fundamental physical theory for remote sensing detection of surface energy balance components and surface soil moisture. In instances where ground-based instruments were incorporated into the remote sensing approach, or were specifically of interest in the study, the appropriate theoretical background was also presented. The review identifies the approaches necessary for future attempts to model evaporative flux directly with combined remote-based and ground-based data collection systems. Sensors and equipment used in the HAPEX-MOBILHY Program to monitor land surface hydrologic processes are identified and described. Algorithms were developed for use in computer processing of data collected by a passive microwave sensor, the Push Broom Microwave Radiometer. The variation of the surface energy balance was examined through the use of the evaporative fraction, a ratio found to be relatively stable for daylight periods. The behavior of the evaporative fraction was examined with respect to location and meteorological conditions to determine its suitability for remote sensing applications. Surface soil moisture variation was examined for two intensely instrumented ground sites in the HAPEX-MOBILHY experiment grid using passive microwave remote sensing. The relationship between passive microwave measurements and ground truth data was examined to attempt to calibrate the remote sensor. Factors which resulted in a weak relationship were examined. The association between surface energy balance and soil moisture was examined using several soil moisture measurement techniques. This resulted in an understanding of the limitations of passive microwave remote sensing for use in measuring a state variable, moisture, as it pertains to evaporative flux estimation by remote-sensing techniques. Several suggestions for additional research priorities in this field were made with future large-scale in situ experiments in mind. Opportunities to combine these research efforts with ongoing or planned projects are noted.
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