The timings of daily were derived from the ERA40 6-hourly surface air temperature data for the 1990 to 2001 period using the fitting of parabolas by Ke Zhang at NTSG, The University of Montana. The data are saved as singly-precision floating-point binary images in a global lat/lon grid. The grid has 360*180 grid cells with 1-degree resoluation. The coordinate of the center of the upper left corner is (-179.5Deg,89.5Deg).