Use of multi-annual MODIS Land Surface Temperature data for the characterization of the heat requirements for grapevine varieties

Heat requirements for grapevine varieties have been widely used to characterize potential growing regions for viticulture. One of the most important indices is the Winkler Index (WI) defined as the total summation of daily average air temperature above 10°C from 1^st of April to 31^th of October in the Northern hemisphere. Mapping of the WI is commonly based on temperature data from meteorological stations. However, in complex terrain such as the European Alps, these are usually irregularly and sparsely distributed or unavailable. This renders traditional geospatial interpolation approaches difficult to become reliable. As an alternative, thermal remote sensing data, which are intrinsically spatialised, can be used. The aim of this work was to provide time series of Winkler Index maps from 2003 to 2010, by means of the MODIS Land Surface Temperature (LST) data and to validate the maps using ground truth data, collected by two weather station networks.