mgrib(grib_field_position = 1, grib_input_file_name = "t850.grb") -20.00, -10.00,...,20.00, 50.00, contour_level_list = [-20.00, -10.00, -5.00, -2.50, -1.00, -0.50, 0.00, 0.50, 1.00, 2.50, 5.00, 10.00, 20.00, 50.00], contour_line_colour = "grey", contour_shade_colour_direction = "clockwise", contour_line_thickness = 2, contour_highlight = "off", contour_label = "off", contour_shade_max_level_colour = "red", legend = "on", contour_shade_min_level_colour = "blue")