Study on surface moisture content, vegetation cover and air temperature based on NOAA/AVHRR surface temperatures and field measurements

Abstract

Split window technique has been applied in this study to extract Land Surface Temperature (Ts) as a step leading to the retrieval of surface soil moisture and evapotranspiration over five study areas in Perak Tengah& Manjong, where the areas were selected according to the difference in surface cover type. Multiple NOAA/AVHRR images throughout June-August (2009) were acquired over the study area and processed; measured ground air temperature data (Ta) for the targeted areas were collected as well. Normalized Difference Vegetation Index (NDVI) and land surface Emissivity (ε) were calculated from image visible bands 1&2. The brightness temperature from bands 4&5 was then used with ε to derive Ts using three different split window algorithms. The results show a good correlation between satellite estimated Ts and measured Ta especially when Uliveri et al. (1994) algorithm was applied over the agricultural area with R2 reaching 87%. Moreover, the work handled the analysis of Soil moisture content Mc acquired from in-situ measurements and Surface temperature. Mc was measured using soil moisture probe for Sitiawan and the oven method for UTP; verification values of Ts and Mc were measured in three variables near surface depths 5 cm, 10 cm and 15 cm then plotted against each other in graphical representation to study the behavior of wet soil under surface temperature impact. A reasonable negative relationship was noticed among the Mc - Ts representation. NDVI-Ts relationship has been studied and negative representation also was found between NDVI and Ts over the uniform vegetation covers, indicating the applicability/suitability of the so called “Triangle method”.