Sensors 2007, 7(10), 2028-2048; doi:10.3390/s7102028
Article

A Wetness Index Using Terrain-Corrected Surface Temperature and Normalized Difference Vegetation Index Derived from Standard MODIS Products: An Evaluation of Its Use in a Humid Forest-Dominated Region of Eastern Canada

1 Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 6C2 2 Lanzhou Regional Climate Centre, 2070 Donggang East Road, Lanzhou, 730020, Gansu, P.R. China 3 Natural Resources Canada - Canadian Forest Service, Atlantic Forestry Centre, Fredericton, New Brunswick, Canada E3B 5L7
* Author to whom correspondence should be addressed.
Received: 6 September 2007; Accepted: 26 September 2007 / Published: 1 October 2007
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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Abstract: In this paper we develop a method to estimate land-surface water content in amostly forest-dominated (humid) and topographically-varied region of eastern Canada. Theapproach is centered on a temperature-vegetation wetness index (TVWI) that uses standard 8-day MODIS-based image composites of land surface temperature (TS) and surface reflectanceas primary input. In an attempt to improve estimates of TVWI in high elevation areas, terrain-induced variations in TS are removed by applying grid, digital elevation model-basedcalculations of vertical atmospheric pressure to calculations of surface potential temperature(θS). Here, θS corrects TS to the temperature value to what it would be at mean sea level (i.e.,~101.3 kPa) in a neutral atmosphere. The vegetation component of the TVWI uses 8-daycomposites of surface reflectance in the calculation of normalized difference vegetation index(NDVI) values. TVWI and corresponding wet and dry edges are based on an interpretation ofscatterplots generated by plotting θS as a function of NDVI. A comparison of spatially-averaged field measurements of volumetric soil water content (VSWC) and TVWI for the 2003-2005 period revealed that variation with time to both was similar in magnitudes. Growing season, point mean measurements of VSWC and TVWI were 31.0% and 28.8% for 2003, 28.6% and 29.4% for 2004, and 40.0% and 38.4% for 2005, respectively. An evaluation of the long-term spatial distribution of land-surface wetness generated with the new θS-NDVI function and a process-based model of soil water content showed a strong relationship (i.e., r2 = 95.7%).
Keywords: MODIS standard products; normalized difference vegetation index; surface; potential temperature; soils; temperature-vegetation wetness index; vegetation; water content.

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MDPI and ACS Style

Hassan, Q.K.; Bourque, C.P.-A.; Meng, F.-R.; Cox, R.M. A Wetness Index Using Terrain-Corrected Surface Temperature and Normalized Difference Vegetation Index Derived from Standard MODIS Products: An Evaluation of Its Use in a Humid Forest-Dominated Region of Eastern Canada. Sensors 2007, 7, 2028-2048.

AMA Style

Hassan QK, Bourque CP-A, Meng F-R, Cox RM. A Wetness Index Using Terrain-Corrected Surface Temperature and Normalized Difference Vegetation Index Derived from Standard MODIS Products: An Evaluation of Its Use in a Humid Forest-Dominated Region of Eastern Canada. Sensors. 2007; 7(10):2028-2048.

Chicago/Turabian Style

Hassan, Quazi K.; Bourque, Charles P.-A.; Meng, Fan-Rui; Cox, Roger M. 2007. "A Wetness Index Using Terrain-Corrected Surface Temperature and Normalized Difference Vegetation Index Derived from Standard MODIS Products: An Evaluation of Its Use in a Humid Forest-Dominated Region of Eastern Canada." Sensors 7, no. 10: 2028-2048.

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