10 0 MANUAL OBSERVATION 21 1 OPTICAL SCATTER SYSTEM COMBINED WITH PRECIPITATION OCCURRENCE SENSING SYSTEM 32 2 FORWARD AND/OR BACKSCATTER SYSTEM OF VISIBLE LIGHT 43 3 FORWARD AND/OR BACKSCATTER SYSTEM OF INFRARED LIGHT 54 4 INFRARED LIGHT EMITTING DIODE (IRED) SYSTEM 65 5 DOPPLER RADAR SYSTEM 714 14 OTHERS 815 15 MISSING VALUE 9