mgrib(grib_field_position = 1, grib_input_file_name = "t850.grb") mcont(contour_grid_value_plot = "on", contour_level_selection_type = "level_list", contour_grid_value_height = 0.30, contour_level_list = [-20.00, -10.00,...,10.00, 20.00], contour_grid_value_plot_type = "both", contour_line_colour = "grey", contour_grid_value_marker_height = 0.20, contour_line_thickness = 2, contour_highlight = "off", contour_label = "off", contour_grid_value_lon_frequency = 10, contour_grid_value_lat_frequency = 10, legend = "off")