%0 Journal Article
%T 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
%A Quazi K. Hassan
%A Charles P.-A. Bourque
%A Fan-Rui Meng
%A Roger M. Cox
%J Sensors
%D 2007
%I MDPI AG
%R 10.3390/s7102028
%X 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(¦ÈS). Here, ¦ÈS 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 ¦ÈS 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 ¦ÈS-NDVI function and a process-based model of soil water content showed a strong relationship (i.e., r2 = 95.7%).
%K MODIS standard products
%K normalized difference vegetation index
%K surface
%K potential temperature
%K soils
%K temperature-vegetation wetness index
%K vegetation
%K water content.
%U http://www.mdpi.com/1424-8220/7/10/2028